WO1996000698A1

WO1996000698A1 - Rare earth recovery process

Info

Publication number: WO1996000698A1
Application number: PCT/US1995/007965
Authority: WO
Inventors: Bernard Greenberg
Original assignee: Pure Etch Co.
Priority date: 1994-06-28
Filing date: 1995-06-23
Publication date: 1996-01-11

Abstract

A method and apparatus for recovery of rare earths from rare earth transition metal alloys involving in one embodiment the steps of (a) completely oxidizing all rare earths and transition metals contained in the alloy; (b) partially dissolving the oxidized rare earth transition metal alloy with a mineral acid to selectively dissolve the rare earth oxide but leave the transition metal oxide undissolved; and (c) precipitating the liquid rare earth compound with a precipitating agent, which can be (d) further processed into a rare earth fluoride or (e) re-burnt to produce a rare earth oxide.

Description

RARE EARTH RECOVERY PROCESS

BACKGROUND OF THE INVENTION

1. Field of The Invention

The present invention generally relates to the field of the recovery of valuable material from industrial waste. Particularly, the present invention relates to the field of the recovery of rare earths from waste by-products, surplus materials, mining ore and spent materials containing at least one rare earth and at least one transition metal. More particularly, the present invention relates to the field of the recovery of (1 ) neodymium (Nd) from various rare earth-transition metal alloys, (2) cobalt (Co) and samarium (Sm) from rare earth-transition metal alloys, and (3) various rare earth and transition metal alloys from nickel metal hydride and lanthanide batteries.

2. Description of The Prior Art

There are many waste materials which are by-products from the use of rare earth-containing alloys. An example would be iron (Fe) and neodymium (Nd), in the form of Nd₂Fe₁₄B magnet-making scrap, where B is boron. This material is often in the form of furnace sweepings, grinding swarf, or a nodular metallic slag or chunky scraps. These neodymium (Nd) containing waste by-products from magnet manufacture are often referred to as NdFeB alloys or feedstocks.

In the prior art, the process of recovery of neodymium (Nd) from the by-products of rare earth magnet production are not satisfactorily developed and implemented on an industrial scale. There are several major problems in the development of a feasible process for the recovery of neodymium (Nd). One problem is the high cost of chemical raw materials necessary to process the constituent iron. Another problem is the disposal of the considerable mass of the iron by-product. In addition, the prior art processes often fail in formation of quality uncontaminated crystals of the rare earth compound. Furthermore, the prior art processes often require costly procedures to remove inorganic or organic impurities contained in the rare earth by-product.

The difficulty which persists in the prior art for neodymium (Nd) recovery is both theoretical and practical. As a practical difficulty, the iron is intimately dispersed within the alloy and the entire waste mass must be solubilized to separate neodymium (Nd). The prior art fails to adequately provide a commercial means to address this. As a theoretical difficulty, it has been conventionally believed in prior art rare earth chemistry that the lanthanide metals would liberate hydrogen from water and be attacked by acids, but not by alkalis. This belief has effectively foreclosed any attempt in utilizing alkalization in a neodymium (Nd) recovery process. As a result, prior art neodymium recovery processes are almost exclusively based on acid dissolution at the initial stage of the recovery process.

The final steps in the production of neodymium trifluoride (NdF₃) in the prior art is also problematic at a commercial scale. The prior art relies on the treatment of a double salt of the rare earth with hydrofluoric acid (HF) which allows for contamination of the resulting material with other fluoride salts, such as sodium fluoride (NaF). Additionally, the converted neodymium trifluoride (NdF₃) contains a significant amount of moisture and must be dried. In the prior art the drying step is normally carried out by heating the neodymium trifluoride (NdF₃) in the atmosphere of hydrogen fluoride (HF) gas. This presents considerable work place hazard, and an air-pollution control problem as well. Another prior art drying method is thermal-drying. However, the thermal-drying method tends to eliminate the hydrogen fluoride (HF) gas with the formation of neodymium oxyfluoride (NdFO), which is unacceptable as a feed material to the calciothermic metal winning method. An alternative prior art drying method is air-drying. Unfortunately, air-dried neodymium trifluoride (NdF₃) contains at least 3% moisture, which is not quite acceptable since the calciothermic process in which it is used to make industrial neodymium metal is highly sensitive to moisture.

The following prior art references are also found to be pertinent to the field of the present invention: 1 . United States Patent No. 2,783,125 issued to Rohden et al. on February 26, 1957 for "Treatment of Monazite" (hereafter "the Rohden Patent").

2. United States Patent No. 3,619,128 issued to Angstadt on November 9, 1971 for "Method for Processing Rare Earth Fluorocarbonate Ores"

(hereafter "the Angstadt Patent").

3. United States Patent No. 3,763,050 issued to Dikhoff et al. on October 2, 1973 for "Method of Recovering A Rare Earth Phosphor" (hereafter "the Dikhoff Patent").

4. United States Patent No. 4,906,290 issued to Worner on

March 6, 1990 for "Microwave Irradiation of Composites" (hereafter "the Worner Patent").

5. United States Patent No. 5,129,945 issued to Lyman et al. on July 14, 1992 for "Scrap Treatment Method for Rare Earth Transition Metal Alloys" (hereafter "the Lyman Patent").

6. An Article by J.W. Morrison and G.R. Palmer, entitled "Recovery of Metal Values From NdFeB Magnet Scrap" (hereafter "the Morrison article").

7. An article by J.W. Lyman and G.R. Palmer, entitled "Recycling of Rare Earths and Iron NdFeB Magnet Scrap" (hereafter "the Lyman NdFeB Article").

8. An article by J.W. Lyman and G.R. Palmer, entitled "Investigating the Recycling of Nickel Hydride Scrap" (hereafter "the Lyman NiCd Article").

9. European Patent No. 216,688 (hereafter "the European

Patent"). 10. Japanese Document No. JO 1021 -022 (hereafter "the '022 Japanese document").

1 1 . Japanese Document No. J6 1 127-621 (hereafter "the '621 Japanese document").

12. Japanese Document No. J6 2132-731 (hereafter "the '731

Japanese document").

13. Japanese Document No. J6 2187-1 12 (hereafter "the '1 12 Japanese document").

The Rohden Patent discloses a treatment of monazite. After an attachment of the monazite at a temperature near the boiling point of the reacting medium by sodium hydroxide (NaOH), the substance is retreated with hot water to separate the insoluble hydroxides and the soluble sodium phosphate, and the hydroxides then undergoing a process of separation of the rare earths from the Thorium (Th) and Uranium (U).

The Angstadt Patent discloses a method for processing rare earth fluorocarbonate ores. The rare earth fluorocarbonate ores can be effectively processed by digesting the ore in a concentrated aqueous alkaline solution at a temperature within the range of about 100 degree C to about 150 degree C. The ore is effectively processed in a nonsputtering reaction below the boiling temperature of the mixture and there is no requirement that additional water be added during the digestion period. After the digestion, the mineral values can be separated from the digestion solution in the form of rare earth hydrous oxides.

The Dikhoff Patent discloses a method of recovering a rare earth phosphor from a mixture which contains the phosphor and at least one sulphide and/or selenite of Zinc (Zn) and/or Cadmium (Cd). The mixture is treated in an aqueous alkaline solution which contains a hypohalogenite and whose pH is larger than 12. The rare earth phosphor is subsequently separated from the liquid and washed with water. The Worner Patent discloses a leaching or smelting precursor method of drying and heating paniculate ores or concentrates which have been previously intimately admixed with either an already active form of carbon or with some other carbon containing material which can be readily dried and heated to charring temperatures by microwave energy. The irradiation is continued after drying to heat the composite to in excess of 300 degree C and initiate reduction reactions within the mixture.

The Morrison article mentions several prior art methods of neodymium recovery, such as magnetic and leaching procedures, but discards them because "the extremely fine grain size of the oxidized scrap prevented recovery by either technique" (page 1 , Abstract). It disclosed a recovery process of using sulfuric acid (H₂SO₄) dissolution followed by precipitation of neodymium-sodium-sulfate double salts having formulas such as Nd₂(S0₄)₃ • Na₂S0₄ • 6H₂0, Nd₂(S0₄)₃ • 3Na₂S0₄ • 126H₂0, or NaNd(S0₄)₂ • nH₂0, where n is 0 or 1 (page 14, lines 1 1 through 13). The neodymium-sodium-sulfate double salts were then treated with hydrofluoric acid (HF) to produce neodymium trifluoride (NdF₃). Several major problems exist with this type of sulfuric acid based process including the excessive raw material costs, the production of large volume of transition metal by-products and that the neodymium-sodium-sulfate salts do not yield a pure neodymium trifluoride product because of contamination by the alkali element (e.g. sodium fluoride (NaF).

The Lyman Patent discloses a scrap treatment method for rare earth transition metal alloys. The method is comprised of forming an acid sulfate solution having the rare earth and the transition metal of the scrap dissolved therein, adding to the solution a salt of an alkali element or ammonium and establishing a solution pH effective to selectively precipitate a double sulfate salt of the rare earth and the alkali element or ammonium, and separating the precipitated double sulfate salt from the solution. This process presents the same problems as those cited above for that described in the Morrison Article.

The Lyman NdFeB Article mentions several methods to recover valuable rare-earth materials from NdFeB magnet scrap. It states that the best way to separate rare earths from the NdFeB magnet scrap was obtained by sulfuric acid dissolution followed by precipitation of recyclable rare-earth salts. The iron-rich effluent following the rare earth recovery was treated to produce sodium and ammonium iron jarosites that can be converted to hematite or disposed of. This process presents the same problems as those described in the Morrison Article.

The Lyman NiCd Article discusses a preliminary investigation of the recycling of nickel hydride battery scrap. Various mineral acids, such as sulfuric acid (H₂S0₄), nitric acid (HN0₃) and hydrochloric acid (HCl) were used to treat the nickel hydride battery scrap.

The European Patent discloses a method of leaching a rare earth mineral with a concentrated alkali metal hydroxide solution to recover the rare earths as their hydroxides by using a controlled amount of alkali metal hydroxide.

The '022 Japanese document discloses a neodymium (Nd) recovery process. The neodymium (Nd) is recovered from neodymium (Nd) containing scrap by dissolving Nd-Fe containing alloy scrap directly in a strong acid.

The '621 Japanese document discloses a process for decomposing rare earth element ore by an alkali in which the reaction of the decomposition is carried out while hydroxide product produced on the surface of the ore is ground off.

The '731 Japanese document discloses rare earth metal oxides which are produced by heating corresponding hydroxides using microwaves. The heating is carried out continuously or suitably in a batch-wise process.

The '1 12 Japanese document discloses a rare earth metal recovery from rare earth metal iron magnetic material. The rare earth metal is collected from an iron magnetic material by dissolving in a mineral acid solution; adding a solution containing hydrofluoric acid ion into the solution to form fluoride precipitate, and separating the precipitate. Most waste by-products spent materials and surplus chemicals generated for the use of rare earth metals contain one or more transition metals, one or more rare earth metals, and several other constituents. The transition metals typically include iron (Fe), Cobalt (Co), Nickel (Ni), Manganese (Mn), Zinc (Zn), Zirconium (Zr), Vanadium (V), Titanium (Ti), Chromium (Cr) and Aluminum (Al). The rare earth metals typically include Cerium (Ce), Cadmium (Cd), Dysprosium (Dy), Erbium (Er), Europium (Eu), Gadolinium (Gd), Holmium (Ho), Lanthanum (La), Lutetium (Lu), Neodymium (Nd), Praseodymium (Pr), Samarium (Sm), Scandium (Sc), Terbium (Tb), Thulium (Tm), Ytterbium (Yb) and Yttrium (Y). The other constituents typically include Aluminum (Al), Boron (B), Gallium (Ga) and Niobium (Nb).

Rare earth metals may be found in many materials, including mined or naturally occurring material, surplus chemicals, co-products, waste by-products, usable and reusable materials, spent materials, and other commercially generated materials. Typical rare earth containing materials includes furnace sweepings, grinding swarf, chunk metallic slag or scraps of Ne-Fe-B and Co-Sm magnet scraps, metal hydride battery scraps such as nickel hydride battery scraps, lanthanide battery scraps, lithium battery scraps, mining ore, mining waste, mining tailings etc.

It is highly desirable to provide an improved rare earth recovery process for industrial scale operation, to produce an optimum rare earth recovery yield of uncontaminated material while conforming with very high environmental and work place safety standards at an acceptable production cost.

It is specifically highly desirable to provide a rare earth recovery process which (1 ) reduces the consumption of raw materials, such as mineral acid, (2) prevents the generation of massive volumes of waste by-products such as iron waste by-products, (3) consistently produces uncontaminated quality rare earth crystals, and (4) removes all inorganic or organic impurities from the rare earth materials. SUMMARY OF THE INVENTION

The present invention is a series of novel methods of recovering rare earths from rare earth containing materials.

A general object of the present invention is to provide a new method for the recovery of rare earths from mining sources, surplus chemicals, waste by-products or other commercially generated materials which contain rare earth metals.

An aspect of the present invention rare earth recovery process is to utilize a chemical scheme that requires minimal input of raw materials and produces minimal output of chemical waste.

A further aspect of the present invention is to employ a chemical scheme that is as safe as possible to the workplace and to the environment.

An additional aspect of the present invention rare earth recovery process is to provide a manufacturing method that consistently produces quality, impurity-free rare earth compounds on a commercial scale.

1. Summary of the Present Invention "Caustic Soda" Method

It is known that rare earths may be recovered from the by-products of rare earth containing scrap. It is also known that the major waste by-products from rare earth magnet manufacture are NdFeB furnace sweepings, grinding swarf, metallic slag or chunky scraps. However, prior art neodymium

(Nd) recovery processes have been mainly limited to using acids, such as sulfuric acid (H₂S0₄) or hydrochloric acid (HCl), at the initial stage of treating such waste materials.

It has been discovered, according to the present invention, that contrary to the conventional wisdom in rare earth chemistry that the lanthanide metals will liberate hydrogen from water and are attacked by acids but not by alkalis, the lanthanide metals are in fact attacked by aqueous alkali superficially and are converted to oxides at the surface.

It has also been discovered, according to the present invention, that it is important to use a weak acid in the digestion process of the crude material obtained from the initial alkali treatment stage, so that only rare earth oxides are dissolved, e.g. neodymium oxide (Nd₂0₃) contained in the crude is dissolved, but the ferric oxide (Fe₂0₃) remains largely undissolved, which effectively separates neodymium oxide (Nd₂0₃) from ferric oxide (Fe₂0₃).

It has further been discovered, according to the present invention, that the most effective and hazardless method of drying rare earth recovered fluoride salts is by using microwave radiation, e.g. moist neodymium trifluoride (NdF₃) is using microwave radiation, which only excites the water molecules and dries the moist neodymium trifluoride (NdF₃) without generating toxic hydrofluoric (HF) gas.

It is therefore a primary aspect of the present invention to provide a new method for the recovery of rare earths from commercial surplus materials, waste products and mining ores such as neodymium (Nd) from NdFeB furnace sweepings which is one of the major waste by-products of Nd-Fe-B magnet manufacture.

It is also an aspect of the present invention to provide a new method for the recovery of rare earths from commercial surplus materials, waste products and mining ores such as neodymium (Nd) from NdFeB furnace sweepings, wherein sodium hydroxide (NaOH) is used for treating the NdFeB furnace sweepings at the initial stage to produce neodymium oxide (Nd₂0₃).

It is a further aspect of the present invention to provide a new method for the recovery of rare earths from commercial surplus materials, waste products and mining ores such as neodymium (Nd) from NdFeB furnace sweepings, wherein acetic acid (HC₂H₃0₂) is used in the digestion process of the crude obtained from the initial alkali treatment stage, so that only neodymium oxide (Nd₂0₃) contained in the crude is dissolved, but the ferric oxide (Fe₂0₃) remains largely undissolved, which effectively separates neodymium oxide (Nd₂0₃) from ferric oxide (Fe₂0₃).

It is an additional aspect of the present invention to provide a new method for the recovery of rare earths from commercial surplus materials, waste products and mining ores such as neodymium (Nd) from NdFeB furnace sweepings, including a novel, effective and hazardless method of drying the neodymium trifluoride (NdF₃). The new effective and hazardless drying method is using microwave radiation to dry the rare earth recovered fluoride salts is by using microwave radiation, e.g., moist neodymium trifluoride (NdF₃), which only excites the water molecules and dries the moist neodymium trifluoride (NdF₃) without generating toxic hydrofluoride (HF) gas.

It is a further aspect of the present invention to provide a method for the separation of Samarium-Cobalt scrap wherein the foregoing processes are utilized to separate the rare earth, samarium, from the transition metal, cobalt.

It is a further aspect of the present invention to provide a method for the separation of the rare earths from the transition metals in a nickel-metal-hydride batteries, wherein the foregoing processes are utilized to generate the rare earths, including praseodymium, neodymium, lanthanum and cerium from the transition metals, including iron, nickel, zirconium, titanium, cobalt and vanadium.

The basic process of one embodiment of the present invention can be illustrated using it to recover NdF₃ from NdFeB furnace sweepings recovery method may include the following steps:

1. mixing an adequate amount of aqueous sodium hydroxide (NaOH) into the furnace sweeping which yields a mixture, and grinding the mixture so that the neodymium (Nd) reacts at fresh surface of the sodium hydroxide (NaOH) to produce neodymium oxide (Nd₂0₃) contained in a crude that also contains iron powder (Fe), ferric oxide (Fe₂0₃) and aqueous sodium hydroxide (NaOH); 2. applying magnetic restrainers to the crude to remove the iron powder (Fe);

3. filtrating the crude and recycling the aqueous sodium hydroxide (NaOH) back to step 1 so that it can be reused;

5 4. digesting the crude with acetic acid (HC₂H₃0₂) having a pK value of approximately 4.7, such that it can dissolve neodymium oxide (Nd₂0₃) but not ferric oxide (Fe₂0₃), to produce a digested solution containing undissolved ferric oxide (Fe₂0₃), neodymium acetate (Nd(C₂H₃0₂)₃) which has

10 a solubility between approximately 260 grams per liter at ambient temperature and contains approximately 42% metal by weight, and ferric acetate

(Fe₃(CH₃COO)₆(CH₃COO)₃) which has a solubility higher than that of neodymium acetate (Nd(C₂H₃0₂)₃);

1 5 5. discharging the undissolved ferric oxide (Fe₂0₃) from the digested solution;

6. evaporating the digested solution to produce neodymium acetate (Nd(C₂H₃0₂)₃) crystals, and dislodging a concentrated liquor which contains ferric acetate

20 (Fe₃(CH₃COO)₆(CH₃COO)₃) and residual neodymium acetate

(Nd(C₂H₃0₂)₃);

7. adding hydrofluoric acid (HF) to the neodymium acetate (Nd(C₂H₃0₂)₃) crystals to produce neodymium trifluoride (NdF₃), which also regenerates acetic acid (HC₂H₃0₂);

25 8. separating the neodymium trifluoride (NdF₃) from the acetic acid (HC₂H₃0₂), and recycling the acetic acid (HC₂H₃0₂) back to step 4 so that it can be reused;

9. drying the neodymium trifluoride (NdF₃) by using microwave radiation to produce dry neodymium trifluoride (NdF₃) which

30 contains less than approximately 3% moisture;

10. precipitating the concentrated liquor from step 6 with oxalic acid (H₂C₂0₄) to convert the residual neodymium acetate (Nd(C₂H₃0₂)₃) into neodymium oxalate (Nd₂(C₂0₃)₃);

1 1 . removing the ferric acetate (Fe₃(CH₃COO)₆(CH₃COO)₃); and 12. treating the neodymium oxalate (Nd₂(C₂0₃)₃) with steps 7 through 9 to produce dry neodymium trifluoride (NdF₃), and regenerating and recycling said oxalic acid (H₂C₂0₄) back to step 10 so that it can be reused.

2. Summary of the Present Invention "Electrolysis" Method

In addition, it is also known that plating barrels can be utilized in fine metal manufacturing processes. Conventionally in plating operations, the plating barrel is connected to the negative terminal of a direct current (DC) power source and deposition on the barrel contents is effected.

It has been discovered, however, according to the present invention, that the rare earth metals, such as neodymium (Nd), cannot be electrodeposited from aqueous solution by connecting the plating barrel to the negative terminal of a DC power source. A modified digestion tank with plating barrel must be used for the electrolysis process, where the plating barrel contains the rare earth-containing materials, such as NdFeB slag, and is connected to the positive terminal of the DC power source, and the tank contains the electrolytic bath and is connected to the negative terminal of the DC power supply, so that the NdFeB slag is anodized into solution and iron (Fe) is deposited on the cathode plates.

It has also been discovered, according to the present invention, that the pH value in the electrolyte rises as the operation proceeds because the deficit of metal irons that are deposable at the cathodes, and such pH value must be periodically adjusted downwardly to facilitate the precipitation of the neodymium accumulation in the bath.

Therefore, it is also a primary aspect of the present invention to provide a new method for the recovery of rare earths, such as neodymium (Nd) from NdFeB slag, major waste by-product material of rare earth magnet manufacture. It is a further aspect of the present invention to provide a new method for the recovery of rare earths, such as neodymium (Nd) from NdFeB slag, where an electrolysis process can be effected by utilizing a modified plating barrel tank which includes a plating barrel connected to the positive terminal of the DC power source for containing the NdFeB slag, and an electrolytic bath contained in the tank which is connected to the negative terminal of the DC power supply, so that the NdFeB slag can be anodized into solution while iron (Fe) is deposited on the cathode plates.

It is also an aspect of the present invention to provide a new method for the recovery of rare earths, such as neodymium (Nd) from NdFeB slag, where the pH value of the electrolytic bath is periodically adjusted downwardly to facilitate the precipitation of the neodymium accumulation in the bath.

The basic process of one embodiment of the present invention can be illustrated by applying it to the recovery of NdF₃ from NdFeB slag in the following steps:

1 . effectuating an electrolysis process by utilizing a modified electrolyte tank which includes a plating barrel serving as an anode and a circumscribing sheet serving as a cathode, filling the plating barrel with the metallic slag and filling the tank with an electrolyte bath containing sulfamic acid (NH₂S0₃H) and having a pH value of approximately 2.7, connecting the plating barrel to a positive terminal of a direct current (DC) power source and the cathode sheet to a negative terminal of the DC power source, so that the metallic slag is anodized into solution as the neodymium (Nd) accumulates in the electrolyte bath while iron (Fe) is deposited on the cathode sheet, and maintaining a current density of approximately 50 ampere per square foot on the cathode until the pH value of the electrolyte bath rises to approximately 3.2;

2. pumping and filtrating approximately one-third of the electrolyte bath into an acidification precipitation tank; 3. adding hydrofluoric acid (HF) to the filtrated electrolyte bath until its pH value drops back to 2.7 to produce neodymium trifluoride (NdF₃);

4. separating the neodymium trifluoride (NdF₃) and recycling the electrolyte bath back to step 1 so that it can be reused; and

5. drying the neodymium trifluoride (NdF₃) by using microwave radiation to produce dry neodymium trifluoride (NdF₃) which contains less than approximately 3% moisture.

3. Summary of the Present Invention Improved Method

In addition, it is known that rare earths can be recovered from metallic scrap containing rare earths, if it is treated by acid dissolution as the first step. For example, as taught by the Morrison article, the Lyman NdFeB Article and the Lyman Patent, the waste rare earth-transition metal alloy is first treated with an acid dissolution process.

However, it has been discovered, according to the present invention, that there are several significant problems associated with the prior art acid dissolution method. First, acid dissolution keeps all the nuisance materials (such as grinding compounds, magnet coatings and binders, the carbon content of any feedstock iron, and other inorganic and organic impurities) in the solution, which have to be dealt with later in a more involved fashion. Second, and more importantly, immediate acid dissolution leaves any iron (Fe) or other transition metals in their lower oxidation states (e.g., iron (Fe) in its divalent state), which does not allow preferential leaching over the rare earth element in a later stage. Third, the reaction of the dissolved solution with an alkali hydroxide (e.g. NaOH or KON) or ammonium hydroxide to selectively precipitate a double sulphate salt of the rare earth and the alkali element or ammonium, results in a material that presents problems if converted into a rare earth fluoride. The rare earth alkali double sulphate salt necessitates the formation of alkali-fluoride impurities, such as sodium fluoride (NaF) with the rare earth fluoride. The rare earth-ammonium double sulphate salt does not render a commercially acceptable yield of rare earth fluoride material. It has also been discovered, according to the present invention, that various rare earth containing materials, including mined or naturally occurring material, surplus chemicals, co-products, waste by-products, usable and reusable materials, spent materials, and other commercially generated materials, whether in the form of furnace sweepings, grinding swarf, chunk metallic slag or scraps, cobalt samarium magnet scraps, metal hydride battery scraps, lanthanide battery scraps, or lithium battery scraps, etc., can be treated to recover the rare earth in one simple process which starts by completely oxidizing all metals (including rare earths and transition metals) within the rare earth containing material.

It has been further discovered, according to the present invention, that if such rare earth containing material is completely oxidized by burning at the very beginning stage of the recovery process the nuisance materials of the rare earth by-product (grinding compounds, coatings, binders, etc.) can be burnt off before the rare earth containing material undergoes further treatment procedures.

It has been additionally discovered, according to the present invention, that if the rare earth containing material is completely oxidized at the initial stage, then any iron (Fe) or other transition metals are converted into their trivalent or highest oxidation state, which allows preferential leaching of the rare earth oxide, [e.g. neodymium oxide (Nd₂0₃) over ferric oxide (Fe₂0₃)l because the higher oxidation state of a given metals oxide, the more acidic its properties.

It has been further discovered, according to the present invention, that if a rare earth compound in solution is first precipitated into an interim solid rare earth compound by reacting it with an anion present in an acid or salt that can produce a solid rare earth compound with a strong crystal field effect, it will slow down the formation of crystals. Thus, the precipitation rate in producing the fluoride of a rare earth, such as neodymium trifluoride (NdF₃) from a rare earth compound solution and a fluoride compound solution is controlled, which yields commercially usable crystals.

In the prior art described in the Morrison Article, Lyman Patent and the Lyman NdFeB Article, such interim solid was generated using a cation or ammonium to produce a double salt of the rare earth. This will result in cation contamination in the resulting rare earth fluoride, such as sodium fluoride or, in the case of ammonium, an unacceptably low yield of the rare earth fluoride. The present invention addresses this problem.

It is therefore an additional aspect of the present invention to provide an improved method for recovery of rare earth compounds from rare earth-containing materials, wherein the rare earth-containing materials are completely oxidized by burning at the very beginning stage of the recovery process, so that all rare earth and transition metals are oxidized and any nuisance contents are burnt off before the material undergoes further treatment procedures, and any iron (Fe) or other transition metals in the material are converted into their trivalent or highest oxidation state, which allows preferential leaching of the rare earth over the transition metal oxide because the higher oxidate state of a given metal's oxide, the more acidic its properties.

It is a further aspect of the present invention to provide an improved method for recovery of rare earths from rare earth compounds in solution wherein such rare earth compound is first precipitated into a rare earth solid compound by using an anion present in an acid or salt that can produce a solid rare earth compound with a strong crystal field effect for the purposes of controlling the formation of rare earth fluoride crystals. For example, the precipitation rate in producing neodymium trifluoride (NdF₃) from a neodymium compound in solution (e.g. NdCI) and a fluoride compound in solution (e.g. HF) is controlled by first converting the neodymium chloride (NdCI) solution into neodymium oxalate (Nd₂(C₂0₄)₃) utilizing the oxalate union from oxalic acid (H₂C₂0₄). This yields commercially usable neodymium fluoride crystal without the problems associated with the alkaline ammonium double salts used in the prior art.

The basic process of one embodiment of the present invention for recovery of rare earth from rare earth-containing materials can be illustrated by the following application to the recovery of neodymium (Nd) and any other rare earths from furnace sweepings, grinding swarf and chunk metallic scraps generated in the manufacture and use of NdFeB powders and magnets:

1 . grinding the neodymium (Nd) containing material; 2. completely oxidizing all rare earth and transition metals contained in the material by burning it to the extent necessary to complete such oxidation and also burn off all nuisance contents, such as epoxy coatings and grinding compounds. This will occur in an approximate temperature range of from approximately 400 degree F to approximately 2,000 degree F to oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃ ), the iron (Fe) into ferric oxide (Fe₂0₃) and all other rare earths and transition metals into their respective oxides;

3. partially dissolving said fully oxidized material with an acid, such as hydrochloric acid (HCl), sulfuric acid (H₂S0₄) or nitric acid (HN0₃), to selectively dissolve the neodymium oxide (Nd₂0₃)and other rare earths into a compound in solution based on the selected acid but leave the ferric oxide

(Fe₂0₃)and other transition metal oxides undissolved;

4. filtrating out the dissolved neodymium and rare earth compounds, such as neodymium chloride (NdCI₃);

5. precipitating the filtrated neodymium compounds with any one of a category of chemical compounds, such as oxalic acid (H₂C₂0₄), to precipitate a solid neodymium compound, e.g., neodymium oxalate (Nd₂(C₂0₄)₃), with a strong crystal field effect which will slow down the absorption rate of fluoride; 6. filtrating out the neodymium compound precipitate;

7. treating the neodymium solid precipitate with a liquid fluoride compound, such as hydrofluoric acid (HF), to produce neodymium trifluoride (NdF₃);

8. filtrating out the neodymium trifluoride (NdF₃); and 9. drying the neodymium trifluoride (NdF₃) by using microwave radiation to produce commercially usable neodymium trifluoride (NdF₃) powder; or 10. as an alternative to Steps 7 through 9, reburning the neodymium oxalate to produce commercially usable neodymium oxide (Nd₂0₃). 4. Summary of the Present Invention Further Improved Method

Furthermore, it is known that hydrofluoric acid (HF) can be used in the final precipitation stage of the rare earth recovery process to convert the rare earth salt, such as a neodymium double salt, into rare earth trifluoride, such as neodymium trifluoride (NdF₃). However, hydrofluoric acid (HF) is highly toxic and is a serious hazard to both the workers in the plant and to the environment, and the implementation of toxic control processes and installation of toxic control equipment can involve very high costs.

It has been further discovered, according to the present invention, that if the neodymium (Nd) compound in solution, such as neodymium chloride (NdCI₃) is precipitated with a solid fluoride salt to produce neodymium fluoride crystals, then it is not necessary to have the neodymium (Nd) compound first precipitated to create a rare earth solid with strong crystal field effects because the absorption rate of the fluoride is controlled by the characteristics of the fluoride salt. Thus, the neodymium compound solution can be directly crystallized into a solid neodymium fluoride with the fluoride salt.

Accordingly, it is also an aspect of the present invention to provide a further improved method for recovery of rare earth fluorides, wherein no hazardous hydrofluoric acid (HF) is used in the final precipitation stage of the rare earth fluoride recovery process. Rather, a solid non-hazardous fluoride salt is used directly following the leaching stage described above.

The basic process of one embodiment of the present invention for recovery of rare earth fluorides from rare earth-containing materials can be summarized by the following application to the recovery of neodymium trifluoride (NdF₃) from neodymium (Nd) contained furnace sweepings, grinding swarf and chunk metallic scraps generated in the manufacture and use of NdFeB powder and magnets:

1 . grinding the neodymium (Nd) containing material; 2. completely oxidizing all rare earth and transition metals contained in the material by burning it to the extent necessary to complete such oxidation and also burn off all nuisance contents, such as epoxy coatings and grinding compounds. This will occur in an approximate temperature range of from approximately 400 degree F to approximately 2,000 degree F to oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃), the iron (Fe) into ferric oxide

(Fe₂0₃), and all other rare earths and transition metals into their respective oxides;

3. partially dissolving said fully oxidized material with an acid, such as hydrochloric acid (HCl), sulfuric acid (H₂S0₄) or nitric acid (HN0₃), to selectively dissolve the neodymium oxide (Nd₂0₃) and other rare earths into a compound in solution based on the selected acid but leave the ferric oxide (Fe₂0₃) and other transition metal oxides undissolved;

4. filtrating out the dissolved neodymium compounds, such as neodymium chloride (NdCI₃);

5. precipitating the filtrated neodymium compound with any one of a category of solid fluoride compounds, such as calcium fluoride (CaF₂) to produce neodymium trifluoride (NdF₃); 6. filtrating out the neodymium trifluoride (NdF₃); and

7. drying the neodymium trifluoride (NdF₃) by using microwave radiation to produce commercially usable neodymium trifluoride (NdF₃) powders.

5. Major Novelties of the Improved and Further Improved Methods

The above described present invention improved and further improved methods have many novel features. However, the fundamental novelties of the present invention improved and further improved methods focus on the following two aspects: first, complete oxidation of the rare earth containing material as an initial step in treatment; and second, control of the final crystal formation of the rare earth fluoride compounds by either first forming one of a category of solid rare earth compounds or utilizing one of a category of solid fluoride salts. 5a. Complete Oxidation

One of the primary difficulties in rare earth recovery processes is the separation of rare earths on the one hand from transition metals and other impurities on the other. In the prior art, the primary approach is to dissolve the rare earth containing materials in a mineral acid to produce a salt of rare earth metal and salt of transition metal, and apply further treatment to separate the rare earth salt and the transition metal salt. This prior art process consumes a huge volume of mineral acid because the acid must react and dissolve both the rare earths and the transition metals; where much of the acid is consumed to dissolve the massive transition metal contents. The process also necessarily retains in solution all other nuisance contents such as epoxy coatings and grinding compounds. It further necessitates the generation of large volumes of transition metal salts in solution which must be further managed or disposed of.

In the present invention improved and further improved methods, the very first essential step of treatment is not acid digestion, but rather a complete oxidation of all rare earths and transition metals in the material. This step achieves two important purposes: first, both the rare earths and the transition metals are completely oxidized; and second, if the preferred oxidation method of burning is utilized, inorganic and organic nuisance contents carried with the material are burnt off.

Since the oxide of any transition metal is more acidic than its partially oxidized or unoxidized status, it is less capable of reacting with a mineral acid. This allows preferential leaching of the rare earth oxide over the transition metal oxide with a mineral acid. Since the mineral acid now only reacts with and dissolves the rare earth oxide, this allows for separation of the rare earth from the transition metal with a minimal consumption of acid and without the creation of transition metal solutions.

In fact, once both the rare earths and the transition metals are completely oxidized, the oxides of the rare earth and the oxides of the transition metal are readily separable by a number of methods. Using strong mineral acid is one of the preferred methods. However, the present invention is not limited to using mineral acids only.

5b. Control the Formation of Rare Earth Fluoride Crystals

Another one of the primary difficulties in rare earth recovery processes is the formation of rare earth crystals at the final stages of the recovery process. The prior art has failed to teach how to effectively control the speed or rate of formation of rare earth fluoride crystals so that the final product is a commercially usable crystal compound of rare earth, free of other fluoride salt contaminants.

In the present invention improved and further improved methods, the speed or rate of formation of rare earth crystal is controlled by generating a chemical compound with strong crystal field effects which will effectively slow down the rate of formation of the rare earth fluoride crystal. This goal is further achieved by effectuating a solid-liquid or liquid-solid reaction in the final stage of rare earth crystal formation.

In the final stage of rare earth fluoride crystal formation, a rare earth compound and a fluoride acid or salt are mixed together to form rare earth fluoride crystals. The present invention improved and further improved methods designed two different approaches to effectuate a solid-liquid or liquid-solid reaction between the rare earth compound and fluoride acid or salt.

In the first approach, the rare earth compound is first converted into a solid compound by utilizing a chemical compound with an anion that will create a solid rare earth compound that exhibits strong crystal field effects, such as oxalic acid (H₂C₂0₄), and a liquid fluoride agent such as hydrofluoric acid is added to the solid rare earth compound to form rare earth fluoride crystals in a controlled fashion.

In the second approach, the rare earth compound is left in solution, but a solid precipitating agent, such as calcium fluoride (CaF₂), is added to the rare earth compound solution to again form rare earth crystal in a controlled fashion. This second approach has the benefit of eliminating the use of extremely hazardous hydrofluoric acid (HF).

Further novel features and other objects of the present invention will become apparent from the following detailed description, discussion and the appended claims, taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring particularly to the drawings for the purpose of illustration only and not limitation, there is illustrated:

FIG. 1 is a schematic diagram showing the apparatus implementing the present invention "Caustic Soda" method.

FIG. 2 is a flow chart showing the operation sequence of the present invention "Caustic Soda" method.

FIG. 3 is a schematic diagram showing the apparatus implementing the present invention "Electrolysis" method.

FIG. 4 is a schematic diagram showing the detailed arrangement of the modified plating barrel electrolyte tank used in the present invention "Electrolysis" method.

FIG. 5 is a flow chart showing the operation sequence of the present invention "Electrolysis" method.

FIG. 6 is a flow chart showing the overall operation of the present invention "Caustic Soda" and "Electrolysis" methods.

FIG. 7 is a schematic diagram showing the apparatus implementing the present invention improved method for recovery of neodymium trifluoride (NdF₃) from NdFeB furnace sweepings, grinding swarf and chunk metallic scraps, wherein the furnace sweepings, grinding swarf and chunk metallic scraps are first completely oxidized by burning, and then selectively leached with mineral acid.

FIG. 8 is a flow chart showing the operation sequence of the present invention improved method for recovery of neodymium trifluoride (NdF₃) or neodymium oxide (Nd0₃) from furnace sweepings, grinding swarf and chunk metallic scraps, wherein the furnace sweepings, grinding swarf and chunk metallic scraps are first completely oxidized by burning, selectively leached then either precipitated with oxalic acid and then either burned to form neodymium oxide or treated to generate neodymium fluoride.

FIG. 9 is a flow chart showing the essential steps of the present invention improved method for recovery of rare earths from a material containing at least one rare earth and at least one transition metal, wherein the rare earth containing material is completely oxidized by burning at the initial stage, selectively leached, then further treated to either generate a rare earth oxide or fluoride.

FIG. 10 is a schematic diagram showing the apparatus implementing the further improved method of the present invention for recovery of neodymium trifluoride from furnace sweepings, grinding swarf and chunk metallic scraps, wherein non-hazardous solid fluoride salt is used to replace hazardous hydrofluoric acid (HF) in the final precipitation stage of the rare earth recovery process to convert neodymium salt solution into neodymium trifluoride.

FIG. 1 1 is a flow chart showing the operation sequence of the further improved method of the present invention for recovery of neodymium trifluoride from furnace sweepings, grinding swarf and chunk metallic scraps, wherein a non-hazardous solid fluoride salt is used to replace hazardous hydrofluoric acid (HF) in the final precipitation stage of the rare earth recovery process to convert the neodymium salt solution into neodymium trifluoride.

FIG. 1 2 is a flow chart showing the essential steps of the further improved method of the present invention for recovery of rare earths from materials containing at least one rare earth and at least one transition metal, wherein a non-hazardous solid fluoride salt is used to replace hazardous hydrofluoric acid (HF) in the final precipitation stage of the rare earth recovery process to convert the rare earth salt solution into rare earth trifluoride.

FIG. 13 is a schematic diagram showing the apparatus implementing the complete oxidation and selective rare earth dissolution process of the present invention method (showing neodymium (Nd) recovery as an example).

FIG. 14 is a flow chart showing the complete oxidation and selective rare earth dissolution process of the present invention method.

FIG. 1 5 is a schematic diagram showing the apparatus implementing the "solid-liquid" approach to generating a rare earth fluoride of the present invention method (showing neodymium (Nd) recovery as an example).

FIG. 16 is a flow chart showing the "solid-liquid" approach to generating a rare earth fluoride of the present invention method.

FIG. 17 is a schematic diagram showing the apparatus implementing the alternative "liquid-solid" approach to penetrating a rare earth fluoride of the present invention method (showing neodymium (Nd) recovery as an example).

FIG. 18 is a flow chart showing the alternative "liquid-solid" approach to penetrating a rare earth fluoride of the present invention method.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Although specific embodiments of the present invention will now be described with reference to the drawings, it should be understood that such embodiments are by way of example only and merely illustrative of but a small number of the many possible specific embodiments which can represent applications of the principles of the present invention. Various changes and modifications obvious to one skilled in the art to which the present invention pertains are deemed to be within the spirit, scope and contemplation of the present invention as further defined in the appended claims.

The present invention is a novel method of recovering neodymium (Nd) from waste by-products of rare earth magnet manufacture. There are three primary concerns which are also the objects of the present invention. First, the present invention is aimed at a new method for the recovery of neodymium (Nd) from both of the two major waste by-products of rare earth magnet manufacture, namely the NdFeB furnace sweepings and the NdFeB slag. Second, the present invention is aimed at a chemical scheme that requires minimal input of chemical compounds and produces no output of chemical waste. Third, the present invention is aimed at eliminating any hazard to the work place or the environment.

The present invention includes two distinct but related processes to deal with the recovery of neodymium (Nd) from the NdFeB furnace sweepings and NdFeB slag, respectively.

1. The NdFeB Furnace Sweepings Recovery Process

Referring to Figures 1 and 2, the present invention NdFeB furnace sweepings recovery process includes essentially twelve (1 2) steps. The whole process can be repeated until all furnace sweeping is processed.

a. Step 1 : Caustic Grinding

The first step involves mixing an adequate amount of aqueous sodium hydroxide (NaOH) into the furnace sweeping which yields a mixture, and grinding the mixture so that the neodymium (Nd) reacts at fresh surface of the sodium hydroxide (NaOH) to produce neodymium oxide (Nd₂0₃) contained in a crude that also contains iron powder (Fe), ferric oxide (Fe₂0₃) and aqueous sodium hydroxide (NaOH).

The first step takes place in Tank-1 which has a rotary grinding mill. The chemical equation for this step is as follows: 2Nd + 3H₂0 = Nd₂0₃ + 3H 2(g) in

This reaction takes place in the presence of caustic alkali. However, no alkali is consumed by the process and no new waste is generated. The neodymium (Nd) only reacts at the surface with the sodium hydroxide (NaOH) to give hydrogen gas (H_2(ol) and neodymium oxide (Nd₂0₃). The grinding process exposes fresh surface continually and allows the oxidation to go to completion.

Step 1 represents one of the many novel characteristics of the present invention NdFeB furnace sweepings recovery process. It involves mixing an adequate amount of aqueous sodium hydroxide (NaOH) with the furnace sweeping in Tank-1 , and grinding the mixture with the rotary mill so that the neodymium (Nd) reacts at the fresh surface of the sodium hydroxide (NaOH). The result of this step is a crude containing neodymium oxide (Nd₂O₃), iron powder (Fe), ferric oxide (Fe₂0₃) and aqueous sodium hydroxide (NaOH).

b. Step 2: Magnetic Restraining

The second step involves applying magnetic restrainers to the crude to remove the iron powder (Fe).

The residual iron powder (Fe) from Step 1 is ferromagnetic, but the neodymium oxide (Nd₂0₃) and ferric oxide (Fe₂0₃) are not. Placement of magnets about the exit pipe from Tank-1 is made so as to prevent the sweepings out of the iron powder (Fe) along with the oxide slurry. The presence of the ferric oxide (Fe₂0₃) in the slurry results from the atmosphere reacting with the furnace sweeping prior to the caustic grinding.

c. Step 3: Filtration

The third step involves filtrating the crude and recycling the aqueous sodium hydroxide (NaOH) back to step 1 so that it can be reused. This step is carried out by Filter Press-1 . In the filtration of the mixed oxide slurry the caustic liquor (NaOH) is recycled back to Tank-1 . It can be reused 5 or 6 cycles with only small augmentation to make up for handling losses.

d. Step 4: Acetic Acid Digestion

The fourth step involves digesting the crude with acetic acid (HC₂H₃0₂) having a pK value of approximately 4.7, such that it can dissolve neodymium oxide (Nd₂0₃) but not ferric oxide (Fe₂0₃), to produce a digested solution containing undissolved ferric oxide (Fe₂0₃), neodymium acetate (Nd(C₂H₃0₂)₃) which has a solubility between approximately 260 grams per liter at ambient temperature and contains approximately 42% metal by weight, and ferric acetate (Fe₃(CH₃COO)₆(CH₃COO)₃) which has a solubility higher than that of neodymium acetate (Nd(C₂H₃0₂)₃).

This step takes place in Tank-2. The chemical equation for this step is as follows:

Nd₂0₃ + 6HC₂H₃0₂ = 2Nd(C₂H₃0₂)₃ ^« H₂0 + H₂0 [2]

Step 4 represents another one of the many novel characteristics of the present invention NdFeB furnace sweepings recovery process. It is the most important step of the NdFeB furnace sweepings recovery process. The use of the weak acid, acetic acid (HC₂H₃0₂), which has a pK value of 4.7, is to dissolve the neodymium oxide (Nd₂0₃) but to leave the ferric oxide (Fe₂0₃) largely undissolved. Ferric oxide (Fe₂0₃) is more acidic than the strongly basic neodymium oxide (Nd₂0₃) and will not dissolve appreciably in weak acid. It will largely be left as a residue to be separated from the neodymium acetate (Nd(C₂H₃0₂)₃) solution by filtration.

A small amount of iron will be converted to ferric acetate (Fe₃(CH₃C00)₆(CH₃C00)₃), but the acetate of trivalent iron is fundamentally different than that of neodymium, and necessarily will have different chemical properties. Neodymium acetate (Nd(C₂H₃0₂)₃) is a simple ionic salt, whereas ferric acetate (Fe₃(CH₃COO)₆(CH₃COO)₃) is a complex salt. This fundamental difference sets up a huge difference in solubilities. The solubility of neodymium acetate (Nd(C₂H₃0₂)₃) is limited, while that of the ferric acetate (Fe₃(CH₃COO)₆(CH₃COO)₃) is virtually unlimited.

The neodymium acetate (Nd(C₂H₃0₂)₃) has a solubility of 260 gram/liter at room temperature, which allows the operational volumes to be kept at reasonable levels, while it is still far lower than that of ferric acetate (Fe₃(CH₃COO)₆(CH₃COO)₃). The neodymium acetate (Nd(C₂H₃0₂)₃) is approximately 42% metal by weight.

e. Step 5: Filtration

The fifth step involves discharging the undissolved ferric oxide

(Fe₂0₃) from the digested solution.

This step is carried out by Filter-1 which is a simple filter. Step 5 is a simple filtration of the acetate acid (HC₂H₃0₂) digested solution obtained from step 4.

f. Step 6: Evaporation

The sixth step involves evaporating the digested solution to produce neodymium acetate (Nd(C₂H₃0₂)₃) crystals, and dislodging a concentrated liquor which contains ferric acetate (Fe₃(CH₃C00)₆(CH₃C00)₃) and residual neodymium acetate (Nd(C₂H₃0₂)₃).

This step takes place in evaporator Tank-E. Water is evaporated and neodymium acetate (Nd(C₂H₃0₂)₃) collects at the bottom of the tank. The remaining iron-rich acetate liquor is pumped off, which will be treated later in steps 10 through 12.

Since ferric acetate (Fe₃(CH₃C00)₆(CH₃C00)₃) and neodymium acetate (Nd(C₂H₃0₂)₃) have a vast difference in solubilities, that of neodymium acetate (Nd(C₂H₃0₂)₃) being limited while that of the ferric acetate (Fe₃(CH₃COO)₆(CH₃COO)₃) being virtually unlimited, evaporation of the liquor gives neodymium acetate (Nd(C₂H₃0₂)₃) monohydrate in highly pure, lilac-colored crystals of remarkable beauty. In prior art recovery processes, the neodymium-sulfate salts cannot be crystallized from aqueous solution with such high purity.

g. Step 7: Acetic Acid Precipitation

The seventh step involves adding hydrofluoric acid (HF) to the neodymium acetate (Nd(C₂H₃0₂)₃) crystals to produce neodymium trifluoride (NdF₃), which also regenerates acetic acid (HC₂H₃0₂).

This step takes place in Tank-3. The collected neodymium acetate (Nd(C₂H₃0₂)₃) crystals are dropped into Tank-3, wherein hydrofluoric acid (HF) is added while simultaneously stirred by the stirrer. Neodymium trifluoride (NdF₃) is formed, and acetic acid (HC₂H₃0₂) remains in the solution as neodymium trifluoride (NdF₃) is highly insoluble. The chemical equation for this step is as follows: Nd(C₂H₃0₂)₃ - H₂0 + 3HF = NdF₃ + 3HC₂H₃0₂ [3]

h. Step 8: Filtration

The eighth step involves separating the neodymium trifluoride (NdF₃) from the acetic acid (HC₂H₃0₂), and recycling the acetic acid (HC₂H₃O₂) back to step 4 so that it can be reused.

This step is carried out by Filter Press-2. The neodymium trifluoride (NdF₃) separated by Filter Press-3 contains a considerable amount of moisture and needs to be dried.

i. Step 9: Drying

The ninth step involves drying the neodymium trifluoride (NdF₃) by using microwave radiation to produce dry neodymium trifluoride (NdF₃) which contains less than approximately 3% moisture. Step 9 represents an additional one of the many novel characteristics of the present invention NdFeB furnace sweepings recovery process. Prior art drying methods such as air or thermal drying or heating have presented all sorts of problems as previously discussed. The present invention utilizes microwave radiation which only excites the water molecules, and thereby dries the neodymium trifluoride (NdF₃) without creating the problems encountered by prior art drying methods.

j. Step 10: Oxalic Acid Precipitation

The tenth step involves precipitating the concentrated liquor from step 6 with oxalic acid (H₂C₂0₄) to convert the residual neodymium acetate (Nd(C₂H₃0₂)₃) into neodymium oxalate (Nd₂(C₂0₃)₃).

This step takes place in Tank-4. The residual liquor from the evaporation step, step 6, contains all the iron that has leaked into the process through the barriers to iron inclusion. The liquor in its concentrated form will begin to cling to the additionally formed neodymium acetate (Nd(C₂H₃0₂)₃) crystals at about 90% neodymium (Nd) recovery level. To avoid the loss of the remaining 10% neodymium (Nd), precipitation of the remaining neodymium with oxalic acid (H₂C₂0₄) is effected. The chemical equation for this step is as follows: 2Nd(C₂H₃0₂)₃ + 3H₂C₂0₄ = Nd₂(C₂0₄)₃ + 6HC₂H₃0₂ [4]

Since the oxalic acid (H₂C₂0₄) is regenerated in the subprocess, there is no additional chemical cost.

k. Step 1 1 : Filtration

The eleventh step involves removing the ferric acetate (Fe₃(CH₃COO)₆(CH₃COO)₃).

This step is carried out by the Filter Press-3. The ferric acetate (Fe₃(CH₃COO)₆(CH₃COO)₃) solution can easily be converted to basic ferric acetate which is an article of commerce in the textile manufacturing business. This would eliminate the need to treat this small iron containing stream.

I. Step 12: Acetic Acid Precipitation

The twelfth step involves treating the neodymium oxalate (Nd₂(C₂0₃)₃) with steps 7 through 9 to produce dry neodymium trifluoride (NdF₃), and regenerating and recycling the oxalic acid (H₂C₂0₄) back to step 10 so that it can be reused.

The chemical equation for this step is as follows:

2Nd₂(C₂0₄)₃ + 6HF = 2NdF₃ + 3H₂C₂0₄ [51

It is noted that steps 10 through 1 2 are severable from steps 1 through 9. Since the volume of the evaporate liquor is so much smaller than the starting volumes, the concentrated liquor out of evaporation may be stored and treated only once for each 8 to 10 cycles of steps 1 through 9. Much of the existing equipment can be used, for example Tank-3 and Filter Press-2 used in steps 7 and 8 respectively.

2. NdFeB Slag Recovery Process

Referring to Figures 3 through 5, the present invention NdFeB slag recovery process includes essentially five (5) steps. The whole process can be repeated until all metallic slag is processed.

a. Step 1 : Electrolysis

The first step involves effectuating an electrolysis process by utilizing a modified electrolyte tank which includes a plating barrel serving as an anode and a circumscribing sheet serving as a cathode, filling the plating barrel with the metallic slag and filling the tank with an electrolyte bath containing sulfamic acid (NH₂S0₃H) and having a pH value of approximately 2.7, connecting the plating barrel to a positive terminal of a direct current (DC) power source and the cathode sheet to a negative terminal of the DC power source, so that the metallic slag is anodized into solution as the neodymium (Nd) accumulates in the electrolyte bath while iron (Fe) is deposited on the cathode sheet, and maintaining a current density of approximately 50 ampere per square foot on the cathode until the pH value of the electrolyte bath rises to approximately 3.2.

This step takes place in modified electrolysis Tank-5. Since the plating barrel is connected to the positive terminal of the DC power source, the NdFeB slag is anodized into solution. The chemical half-reaction equation of this step is as follows:

Nd → Nd³⁺ + 3e^' [6] Fe → Fe²⁺ + 2e^' [71

Simultaneously, Neodymium (Nd) is accumulated in the electrolyte bath while the iron (Fe) dissolved at the anode is deposited on the cathode sheet:

2e⁺ + Fe²⁺ = Fe_w [8]

The pH in the electrolyte bath rises as hydrogen (H) is deposited: 2e ^• + 2H₂0 → 20H^" + H_2(fl, [9]

That is, water is reduced, producing hydroxyl ion (OH ) and hydrogen gas (H₂).

Step 1 represents one of the many novel characteristics of the present invention NdFeB slag recovery process. The composition of the electrolyte bath has been the subject of more than two-hundred (200) experiments by the inventor. To constitute the electrolyte bath from scratch, a solution of 1 50 gram/liter of sulfamic acid (NH₂S0₃H) is mixed with the NdFeB slag with agitation until, by the consumption of some of the acid, the pH value rises to 2.7. The solution is then filtered into electrolysis Tank-5. Additional NdFeB slag is filled into the plating barrel and electrolysis begins. A current density of 50 ampere/ft² at the cathode sheet is maintained until the pH rises to 3.2. At this point the electrolysis is interrupted.

It is noted that the iron deposited on the cathode sheet is pure iron metal, which can be collected for use in the manufacturing industries. b. Step 2: Filtration

The second step involves pumping and filtrating approximately one-third of the electrolyte bath into an acidification precipitation tank.

This step is carried out by Filter-2. When the pH value of the electrolyte bath in Tank-5 rises to 3.2, the electrolysis is interrupted and one-third of the electrolyte bath is pumped out and filtrated through Filter-2 into Tank-6.

c. Step 3: Hydrofluoric Acid Precipitation

The third step involves adding hydrofluoric acid (HF) to the filtrated electrolyte bath until its pH value drops back to 2.7 to produce neodymium trifluoride (NdF₃).

This step takes place in Tank-6. Hydrofluoric acid (HF) is added therein until the pH reaches 2.7 again. The pH value is constantly detected by a pH monitor. Neodymium trifluoride (NdF₃) precipitates in Tank-6, and it is allowed to settle.

d. Step 4: Filtration

The fourth step involves separating the neodymium trifluoride (NdF₃) and recycling the electrolyte bath back to step 1 so that it can be reused.

This step is carried out by Filter Press-4. The slurry from Tank-6 is pumped through Filter Press-4, where the precipitate of neodymium trifluoride (NdF₃) is retained and the filtrate containing sulfamic acid (NH₂S0₃H) is recycled back to Tank-5.

It is noted that the sulfamic acid (NH₂S0₃H) is not consumed in the process and therefore presents no environmental hazard.

e. Step 5: Drying The fifth step involves drying the neodymium trifluoride (NdF₃) by using microwave radiation to produce dry neodymium trifluoride (NdF₃) which contains less than approximately 3% moisture. This step is the same as step 9 of the NdFeB furnace sweepings recovery process.

3. The Complete Operation of Neodymium Recovery

Referring to Figure 6, there is shown a flow chart of the complete recovery operation. The waste by-products, NdFeB furnace sweepings and NdFeB slag, from the rare earth magnetic manufacture are treated by two respective chemical schemes as described above. However, the only major consumption of chemical compound is hydrofluoric acid (HF). The moist neodymium trifluoride (NdF₃) produced by both schemes can be dried by using the same microwave radiation technique to produce dry neodymium trifluoride (NdF₃) which contains less than 3% moisture.

The present invention method for the recovery of neodymium (Nd) from NdFeB furnace sweepings and slag has many advantageous features. It achieves a very high efficiency of neodymium (Nd) recovery: over 95% of neodymium (Nd) in the magnet manufacture wastes is recovered. It also incurs only minimal chemical and energy costs: only Hydrofluoric Acid (HF) is consumed and all steps are carried out at ambient temperature. It further conforms with high safety standard: minimal waste generation, no hazardous waste, and minimal work place hazards. In addition, it requires a very low capital cost for industrial scale operation; standard chemical plant equipment can be easily modified to suit the need of the present invention process. Moreover, it yields a high product purity. Finally, it also produces many other valuable by-products, such as pure iron metal, which can be utilized in the manufacturing industries.

4. The Improved Method for Rare Earth Recovery

Referring to Figures 7 through 9, there is shown the present invention improved method and apparatus for recovery of rare earth metal from rare earth containing materials, including mined or naturally occurring material, surplus chemicals, co-products, waste by-products, usable and reusable materials, spent materials, and other commercially generated materials. Typical rare earth containing materials includes furnace sweepings, grinding swarf, chunk metallic slag or scraps from NdFeB and Samarium-Cobalt magnet scraps, nickel hydride battery scraps, lanthanide battery scraps, etc. The rare earth metals which may be recovered by the present invention contained in other industrial by-product materials typically include Cerium (Ce), Dysprosium (Dy), Erbium (Er), Europium (Eu), Gadolinium (Gd), Holmium (Ho), Lanthanum (La), Lutetium (Lu), Neodymium (Nd), Praseodymium (Pr), Samarium (Sm), Scandium (Sc), Terbium (Tb), Thulium (Tm), Ytterbium (Yb) and Yttrium (Y). The transition metals which may be contained in such industrial by-product materials typically include iron (Fe), Cobalt (Co), Nickel (Ni), Manganese (Mn), Zinc (Zn), Zirconium (Zr), Vanadium (V), Titanium (Ti), Chromium (Cr) and Aluminum (Al). The present invention improved method and apparatus are described here by the example of recovering neodymium (Nd) from furnace sweepings, grinding swarf and chunk metallic scraps generated in manufacturing and using NdFeB magnets. The complete process includes the following nine (9) steps.

a. Step 1 : Mechanical Grinding

The first step is optional. The feedstock furnace sweepings of grinding swarf and chunk metallic scraps of the rare earth waste by-product should be mechanically ground under water to produce a finely divided powder to create a uniform feedstock for further treatment.

b. Step 2: Complete Oxidation

Step 2 is an essential step of the present invention improved rare earth recovery process. The furnace sweepings are only partially oxidized from superficially reacting with air. The grinding swarf and chunk metallic scraps are essentially unoxidized. Therefore, the resulting mixture of NdFeB material after grinding in step 1 is a substantially unoxidized feedstock.

The substantially unoxidized ground mixture of furnace sweepings, grinding swarf and metallic scraps is oxidized. The preferred oxidation method is by burning. It is burnt in air in a controlled manner. The temperature range may be from 400 degree F to 2,000 degree F, with the preferred range being from 800 degree F to 1 ,200 degree F. The neodymium (Nd) and all other rare earths and the iron (Fe) and all other transition metals are oxidized to their highest valence. The chemical equation for this step is as follows: 4Nd + 30₂ = 2Nd₂0₃ [10]

4Fe + 30₂ = 2Fe₂0₃ [1 1 ]

Step 2 represents one of the many novel characteristics of the present invention improved rare earth recovery process. First, the nuisance contents of the rare earth waste by-product, such as grinding compounds, magnet coatings and binders, and the carbon content of the feedstock iron, are burnt off before the rare earth containing material undergoes further treatment procedures. This saves the costs of further removal of the nuisance contents. Second, the iron (Fe) and all other transition metals in the material are converted into a higher oxidation state, e.g. iron to its trivalent state. This allows subsequent preferential leaching by a strong mineral acid to dissolve only the rare earth oxide, e.g. neodymium oxide (Nd₂0₃) because the higher the oxidation state of a transition metal, the more acidic its properties.

c. Step 3: Partial Dissolving

Step 3 is also an essential step of the present invention improved rare earth recovery process. This step involves dissolving the oxidized mixture with a mineral acid. The preferred mineral acid is hydrochloric acid (HCl). However, other mineral acids such as sulfuric acid (H₂S0₄) or nitric acid (HN0₃) can be used.

As discussed above, the complete oxidation of the rare earth mixture by burning converts all metals to their highest oxidation state, e.g. iron (Fe) to its trivalent state. As a general rule, the acidity of the oxides of any element increases by increasing its oxidation state. This allows the rare earth, e.g. neodymium (Nd), to be extracted from the burnt mixture with a mineral acid; the more acidic ferric oxide (Fe₂0₃) not being solubilized preferentially under this condition of enhanced acidity. Therefore, this step is a partial dissolution step, where only the rare earth oxide is dissolved, but the transition metal oxide is left undissolved.

In the previously described processes, divalent iron oxide (FeO) was present. Since divalent iron oxide (FeO) is more basic than trivalent iron oxide (Fe₂0₃), to avoid co-extraction of iron (Fe) with neodymium (Nd), an expensive weak acid, acetic acid (HC₂H₃0₂), was needed. In the present improved process, since iron (Fe) is completely oxidized into its trivalent state, a mineral acid can be used which enhances the rate and efficiency of the neodymium (Nd) extraction, allowing it to be completed in a single step.

This step takes place in Tank-7. The chemical equation for this step is as follows:

Nd₂0₃ + 6HCI = 2NdCI₃ + 3H₂0 [12]

More generally, this step of the present invention can be utilized to treat completely oxidized materials containing rare earth metals and transition metals. After the last step which is complete oxidation, both rare earth metals and transition metals are completely oxidized. However, by treating with mineral acid, only the rare earth oxides are dissolved, but the transition metal oxides are left undissolved. This effectively achieves the result of partial dissolution which selectively dissolves the rare earth oxides only.

d. Step 4: Filtration

The fourth step involves separating the dissolved rare earth and the undissolved transition metals. For example, undissolved ferric oxide (Fe₂0₃) is filtrated from dissolved neodymium compounds, such as neodymium chloride (NdCI₃) solution. This step is carried out by Filter-3 which is a simple filter. e. Step 5: Rare Earth Compound Precipitation

The fifth step is the precipitation of rare earth compounds such as neodymium solid compound utilizing certain acids or salts containing an anion which is capable of forming a rare earth compound of a required crystal field effect, such as oxalate, by adding oxalic acid (H₂C₂0₄) to neodymium chloride (NdCI₃) solution to form Nd₂(C₂0₄)₃. This is also an essential step of the present invention improved recovery method.

It is noted that direct addition of aqueous hydrofluoric acid (HF) or other liquid fluoride compound to the rare earth solution, such as neodymium chloride (NdCI₃) extract, could be practiced. However, the neodymium trifluoride (NdF₃) so generated is a gelatinous material. The filtration and washing of this gelatinous material is a daunting matter, and the generation of dense, crystalline solids is very difficult from the direct mixing of solutions containing the constituents.

Therefore, the neodymium filtrate extract is first treated with a compound, such as an oxalic salt (e.g. sodium oxalate (Na₂C₂0₄)) or oxalic acid (H₂C₂0₄), which contains an anion that is capable of forming a neodymium solid, such as neodymium oxalate (Nd₂(C₂0₄)₃), with strong crystal field effect. Other acids, such glycollic, citric and formic acids, may also be used. However, oxalic acid is preferred because it has been discovered that the crystal field effects exhibited by the oxalate anion dramatically affects the nature and rates of formation of most of the metal salts it takes.

This step takes place in Tank-8. The chemical equation for this step is as follows: 2NdCI₃ + 3H₂C₂0₄ = Nd₂(C₂0₄)₃ + 6HCI [13]

As a general proposition, this step is designed to precipitate rare earth compounds, such as oxalates, which when treated with hydrofluoric acid (HF) in a later step will render better formed rare earth trifluoride (NdF₃). Examples of oxalic salts which may be used in this step include sodium oxalate (Na₂C₂0₄) and sodium hydrogen oxalate (NaHC₂0₄), where the relevant chemical equations may be as follows:

2NdCI₃ + 3Na₂C₂0₄ = Nd₂(C₂0₄)₃ + 6NaCI [14] 2NdCI₃ + 3NaHC₂0₄ = Nd₂(C₂0₄)₃ + 3NaCI + 3HCI [15]

f. Step 6: Filtration

The sixth step involves separating the rare earth solid compound, such as neodymium oxalate (Nd₂(C₂0₄)₃), from the mineral acid, such as hydrochloric acid (HCl).

g. Step 7: Neodymium Trifluoride (NdF.) Precipitation

The seventh step involves adding a soluble form of fluoride compound or acid, such as hydrofluoric acid (HF), to the solid rare earth compound, such as neodymium oxalate (Nd₂(C₂0₄)₃), to precipitate a rare earth fluoride, such as neodymium trifluoride (NdF₃). The neodymium oxalate (Nd₂(C₂0₄)₃) is washed and reslurried in water, and aqueous hydrofluoric acid (HF) is added. This step is also an essential step of the present invention improved recovery method.

This step takes place in Tank-9. The chemical equation for this step is as follows: Nd₂(C₂0₄)₃ + 6HF = 2NdF₃ + 3H₂C₂0₄ [16]

As a general proposition, the hydrofluoric acid (HF) used in this step can be considered as a crystallizing agent which can effect the formation of quality rare earth crystals.

Alternatively, as an optional step 7a, the solid rare earth compound such as neodymium oxalate (Nd₂(C₂0₄)₃) may be completely oxidized through burning to recover a rare earth oxide such as neodymium oxide (Nd₂0₃). The chemical equation for this step is as follows:

2Nd₂(C₂0₄)₃ + 30_2(g, = 2Nd₂0₃ + 1 2C0_2(α) [17] h. Step 8: Filtration

The eighth step involves filtrating out the rare earth fluoride, such as neodymium trifluoride (NdF₃). This step is carried out by Filter Press-7. The neodymium trifluoride (NdF₃) separated by Filter Press-7 contains a considerable amount of moisture and needs to be dried.

i. Step 9: Drying

The ninth step involves drying the rare earth fluoride such as neodymium trifluoride (NdF₃) by using microwave radiation to produce dry neodymium trifluoride (NdF₃) which contains less than approximately 3% moisture. As described earlier in this specification, this drying step utilizes microwave radiation which only excites the water molecules, and thereby dries the neodymium trifluoride (NdF₃) without creating the problems encountered by prior art drying methods.

In general, the purpose of steps 7-9 is to provide further treatment to the rare earth precipitation to yield commercially usable rare earth salts such as dried rare earth trifluoride.

5. The Further Improved Method for Rare Earth Metal Recovery

Referring to Figures 10 through 12, there is shown the further improved method and apparatus of the present invention for recovery of rare earth metal from rare earth containing materials, including the materials referenced in the improved method described above. The present invention further improved method and apparatus are described here by the example of the application of recovering neodymium (Nd) from NdFeB furnace sweepings, grinding swarf and chunk metallic scraps. The complete process includes the following seven (7) steps.

The main object of the further improved method of the present invention is to completely eliminate the use of hazardous hydrofluoric acid (HF) and to further cut down the costs in the rare earth recovery process. The first four (4) steps (grinding, oxidizing, leaching, and filtrating) and the last two

(2) steps (filtrating and drying) of this further improved method is the same as those of the improved method described above. However, the three

(3) intermediate steps of the above described improved method have been replaced by only one (1 ) step in this further improved method. Therefore, the complete process of this further improved method includes only seven (7) steps. In the following descriptions, steps 1 through 4, 6 and 7 will be described briefly as they are the same as previously described.

a. Step 1 : Mechanical Grinding

Again, the first step is optional. The feedstock of scraps of the rare earth waste by-product should be mechanically ground under water to produce a finely divided powder to form a uniform feedstock for further treatment.

b. Step 2: Complete Oxidation

Step 2 is also an essential step of the present invention further improved rare earth recovery process. The furnace sweepings is only partially oxidized from superficially reacting with air. The grinding swarf and chunk metallic scraps are essentially unoxidized. Therefore, the resulting mixture of NdFeB material after grinding in step 1 is a substantially unoxidized feedstock.

The substantially unoxidized ground mixture is oxidized by burning.

It is burnt in air in a controlled manner. The temperature range may be from 400 degree F to 2,000 degree F, with the preferred range being from 800 degree F to 1 ,200 degree F. For example, the chemical equation for this step is as follows:

4Nd + 30₂ = 2Nd₂0₃ [18] 4Fe + 30₂ = 2Fe₂0₃ [19]

Step 2 again represents one of the many novel characteristics of the present invention further improved rare earth recovery process. First, the nuisance contents of the rare earth waste by-product, such as grinding compounds, magnet coatings and binders, and the carbon content of the feedstock iron, are burnt off before the rare earth waste by-product undergoes further treatment procedures. This saves the costs of further removal of the nuisance contents. Second, the transition metals, such as iron (Fe), in the material is converted into its highest oxidation state. This allows subsequent preferential leaching by a strong mineral acid to dissolve only the rare earth oxide.

c. Step 3: Partial Dissolving

Step 3 is again an essential step of the present invention further improved rare earth recovery process. This step involves dissolving the oxidized mixture with a mineral acid. The preferred mineral acid is hydrochloric acid (HCl). However, other mineral acid such as sulfuric acid (H₂S0₄) or nitric acid (HN0₃) can be used.

This step takes place in Tank-10. The chemical equation for this step is illustrated as follows: Nd₂0₃ + 6HCI = 2NdCI₃ + 3H₂0 [20]

d. Step 4: Filtration

The fourth step involves separating the dissolved rare earth and the undissolved transition metals. The undissolved transition metal oxide is filtrated out from the dissolved rare earth compound, such as neodymium chloride (NdCI₃) solution. This step is carried out by Filter-4 which is also a simple filter.

e. Step 5: Fluoride salt Precipitation

This fifth step is the heart of the present invention further improved method for rare earth recovery. It has been discovered, according to the present invention, that another method to permit the rare earth fluoride to form in an environment of strong crystal field effect for slowing rare earth crystal formation of rare earth fluoride crystal is to require the fluoride compound be a solid with strong crystal field effect. This permits direct precipitation of the rare earth fluoride from the rare earth compound in solution generated in step 4. Therefore, the use of hazardous hydrofluoric acid (HF) is completely eliminated.

This new step involves adding, for example, calcium fluoride (CaF₂) to the rare earth solution, such as neodymium chloride (NdCI₃) solution. Other fluoride salts such as sodium fluoride (NaF), ammonium fluoride (NH₄F), or other fluoride salts of the Group-IIA alkaline-earth metals (Beryllium (Be), Magnesium (Mg), Strontium (Sr), Barium (Ba) and Radium (Ra)) can be used.

This step takes place in Tank-1 1 . The examples of the relevant chemical equation for this step are as follows: 2NdCI₃ + 3CaF₂ = 2NdF₃ + 3CaCI₂ [21 ]

NdCI₃ + 3NaF = NdF₃ + 3NaCI [22]

NdCI₃ + 3NH₄F = NdF₃ + 3NH₄CI [23]

f. Step 6: Filtration

The sixth step involves filtrating out the rare earth fluoride, such as neodymium trifluoride (NdF₃). This step is carried out by Filter Press-8.

g. Step 7: Drying

The seventh step involves drying the rare earth fluoride, such as neodymium trifluoride (NdF₃), by using microwave radiation to produce dry neodymium trifluoride (NdF₃). Other methods of drying may also be utilized.

Comparing this further improved method to the improved method which is described previously, it can be seen that this further improved method also reduces the amount of operation equipment. Particularly, the further improved method uses one (1 ) less precipitation tank and one (1 ) less filter press.

6. The Complete Oxidation Process

Referring to Figures 13 and 14, there is shown the complete oxidation process and apparatus of the present invention method. Generally, this process comprises the steps of: (a) completely oxidizing said material by burning. Such complete oxidation will take place in an approximate temperature range of from approximately 400 degree F to approximately 2,000 degree F to completely oxidize said at least one rare earth metal into at least one rare earth oxide and said at least one transition metal into at least one transition metal oxide; and (b) partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said at least one rare earth oxide into a rare earth containing solution, but leave said at least one transition metal oxide undissolved.

7. The Interim Solid-Liquid Approach of the Present Invention

Referring to Figures 1 5 and 1 6, there is shown the interim solid-liquid approach of the present invention method and apparatus. This approach comprises the steps of: (a) precipitating said rare earth solution with at least one precipitating agent to produce an interim solid rare earth compound; and (b) treating said interim solid rare earth compound with at least one fluoride agent; said interim solid rare earth compound effects slow formation of rare earth fluoride when it reacts with the at least one fluoride agent, to produce commercially usable rare earth crystal.

8. The Direct Liouid-Solid Approach of the Present Invention

Referring to Figures 1 7 and 18, there is shown the direct liquid-solid approach of the present invention method and apparatus. This approach comprises the step of precipitating said solution with at least one solid precipitating agent which effects slow formation of rare earth fluoride when it reacts with the rare earth containing solution, to produce commercially usable rare earth fluoride.

Defined in detail, the present invention is a method for recovering a neodymium trifluoride (NdF₃) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising the steps of: (a) completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃) and the iron (Fe) into ferric oxide (Fe₂0₃); (b) partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave the ferric oxide (Fe₂0₃) undissolved; (c) precipitating the neodymium (Nd) containing solution with at least one precipitating agent to produce an interim solid neodymium (Nd) compound; and (d) treating the interim solid neodymium (Nd) compound with at least one fluoride compound, such that the interim solid neodymium (Nd) compound effects slow formation of neodymium trifluoride (NdF₃) crystal when it reacts with the at least one fluoride compound, to produce commercially usable neodymium trifluoride (NdF₃).

Also defined in detail, the present invention is neodymium trifluoride (NdF₃) compound recovered by the method as described immediately above.

Additionally defined in detail, the present invention is an apparatus for recovering a neodymium trifluoride (NdF₃) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising: (a) a burner for completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃) and the iron (Fe) into ferric oxide (Fe₂0₃); (b) a leaching tank for partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave the ferric oxide (Fe₂O₃) undissolved; (c) a precipitation tank for precipitating the neodymium (Nd) containing solution with at least one precipitating agent to produce an interim solid neodymium (Nd) compound; and (d) a treatment tank for treating the interim solid neodymium (Nd) compound with at least one fluoride compound, such that the interim solid neodymium (Nd) compound effects slow formation of neodymium fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable neodymium trifluoride (NdF₃).

Alternatively defined in detail, the present invention is a method for recovering a neodymium oxide (Nd₂0₃) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising the steps of: (a) completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃) and the iron (Fe) into ferric oxide (Fe₂0₃); (b) partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave the ferric oxide (Fe₂0₃) undissolved; (c) precipitating the neodymium (Nd) containing solution with an oxalic compound to produce neodymium oxalate (Nd₂(C₂0₄)₃); and (d) oxidizing the neodymium oxalate (Nd₂(C₂0₄)₃) to produce commercially usable neodymium oxide (Nd₂0₃).

Also alternatively defined in detail, the present invention is a neodymium oxide (Nd₂0₃) compound recovered by the method as described immediately above.

Additionally alternatively defined in detail, the present invention is an apparatus for recovering a neodymium oxide (Nd₂0₃) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising: (a) a burner for completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃) and the iron (Fe) into ferric oxide (Fe₂0₃); (b) a leaching tank for partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave the ferric oxide (Fe₂0₃) undissolved; (c) a precipitation tank for precipitating the neodymium (Nd) containing solution with at least one oxalic compound to produce neodymium oxalate (Nd₂(C₂0₄)₃); and (d) means for oxidizing the neodymium oxalate (Nd₂(C₂0₄)₃) to produce commercially usable neodymium oxide (Nd₂0₃).

Further defined in detail, the present invention is a method for recovering a neodymium trifluoride (NdF₃) from a material containing neodymium (Nd) and massive iron (Fe), comprising the steps of: (a) completely oxidizing the material by burning the material at a sufficient temperature to completely oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃) and the iron (Fe) into ferric oxide (Fe₂0₃); (b) partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave the ferric oxide (Fe₂0₃) undissolved; and (c) precipitating the neodymium (Nd) containing solution with at least one solid fluoride compound which effects slow formation of neodymium trifluoride (NdF₃) crystal when it reacts with the neodymium (Nd) containing solution, to produce commercially usable neodymium trifluoride (NdF₃).

Also further defined in detail, the present invention is a neodymium trifluoride (NdF₃) compound recovered by the method as described immediately above.

Additionally further defined in detail, the present invention is an apparatus for recovering neodymium trifluoride (NdF₃) from a material containing neodymium (Nd) and massive iron (Fe), comprising: (a) a burner for completely oxidizing the material by burning the material at a sufficient temperature to completely oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃) and the iron (Fe) into ferric oxide (Fe₂0₃); (b) a leaching tank for partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave the ferric oxide (Fe₂0₃) undissolved; and (c) a precipitating tank for precipitating the neodymium (Nd) containing solution with at least one solid fluoride compound which effects slow formation of neodymium trifluoride (NdF₃) crystal when it reacts with the neodymium (Nd) containing solution, to produce commercially usable neodymium trifluoride (NdF₃).

Defined broadly, the present invention is a method for recovering a neodymium (Nd) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising the steps of: (a) completely oxidizing the material to completely oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃) and the iron (Fe) into ferric oxide (Fe₂0₃); and (b) partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave the ferric oxide (Fe₂0₃) undissolved. Also defined broadly, the present invention is a neodymium (Nd) compound recovered by the method as described immediately above.

Additionally defined broadly, the present invention is an apparatus for recovering a neodymium (Nd) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising: (a) a burner for completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the neodymium (Nd) into neodymium oxide (Nd₂0₃) and the iron (Fe) into ferric oxide (Fe₂0₃); and (b) a leaching tank for partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave the ferric oxide (Fe₂0₃) undissolved.

Alternatively defined broadly, the present invention is a method for recovering a neodymium (Nd) compound from a neodymium (Nd) containing solution, comprising the steps of: (a) precipitating the solution with at least one precipitating agent to produce an interim solid neodymium (Nd) compound; and (b) treating the interim solid neodymium (Nd) compound with at least one fluoride compound, such that the interim solid neodymium (Nd) compound effects slow formation of neodymium trifluoride (NdF₃) crystals when it reacts with the at least one fluoride compound, to produce commercially usable neodymium trifluoride (NdF₃).

Also alternatively defined broadly, the present invention is a neodymium (Nd) compound recovered by the method as described immediately above.

Additionally alternatively defined broadly, the present invention is an apparatus for recovering a neodymium (Nd) compound from a neodymium (Nd) containing solution, comprising: (a) a precipitation tank for precipitating the solution with at least one precipitating agent to produce an interim solid neodymium (Nd) compound; and (b) a treatment tank for treating the interim solid neodymium (Nd) compound with at least one fluoride compound, such that the interim solid neodymium (Nd) compound effects slow formation of neodymium fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable neodymium trifluoride (NdF₃).

Further defined broadly, the present invention is a method for recovering a neodymium (Nd) compound from a neodymium (Nd) containing solution, comprising the step of precipitating the solution with at least one solid fluoride compound which effects slow formation of neodymium fluoride crystal when it reacts with the neodymium (Nd) containing solution, to produce commercially usable neodymium trifluoride (NdF₃).

Also further defined broadly, the present invention is a neodymium (Nd) compound recovered by the method as described immediately above.

Additionally further defined broadly, the present invention is an apparatus for recovering a neodymium (Nd) compound from a neodymium (Nd) containing solution, comprising a precipitation tank for precipitating the solution with at least one solid fluoride compound which effects slow formation of neodymium fluoride crystal when it reacts with the neodymium (Nd) containing solution, to produce commercially usable neodymium trifluoride (NdF₃).

Defined more broadly, the present invention is a method for recovering a rare earth fluoride compound from a material containing at least one rare earth and at least one transition metal, comprising the steps of: (a) completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the at least one rare earth into at lease one rare earth oxide and the at least one transition metal into at least one transition metal oxide; (b) partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the at least one rare earth oxide into a rare earth compound solution, but leave the at least one transition metal oxide undissolved; (c) precipitating the rare earth compound solution with at least one precipitating agent to produce an interim solid rare earth compound; and (d) treating the interim solid rare earth compound with at least one fluoride compound, such that the interim solid rare earth compound effects slow formation of rare earth fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable rare earth fluoride. Also defined more broadly, the present invention is a rare earth fluoride compound recovered by the method as described immediately above.

Additionally defined more broadly, the present invention is an apparatus for recovering a rare earth fluoride compound from a material containing at least one rare earth and at least one transition metal, comprising: (a) a burner for completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the at least one rare earth into at least one rare earth oxide and the at least one transition metal into at least one transition metal oxide; (b) a leaching tank for partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the at least one rare earth oxide into a rare earth compound solution, but leave the at least one transition metal oxide undissolved; (c) a precipitation tank for precipitating the rare earth compound solution with at least one precipitating agent to produce an interim solid rare earth compound; and (d) a treatment tank for treating the interim solid rare earth compound with at least one fluoride compound, such that the interim solid rare earth compound effects slow formation of neodymium fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable rare earth fluoride.

Alternatively defined more broadly, the present invention is a method for recovering a rare earth oxide compound from a material containing at least one rare earth and at least one transition metal, comprising the steps of: (a) completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the at least one rare earth into at least one rare earth oxide and the at least one transition metal into at least one transition metal oxide; (b) partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the at least one rare earth oxide into a rare earth compound solution, but leave the at least one transition metal oxide undissolved; (c) precipitating the rare earth compound solution with an oxalic compound to produce a rare earth oxalate; and (d) oxidizing the a rare earth oxalate to produce commercially usable at least one rare earth oxide. Also alternatively defined more broadly, the present invention is a rare earth oxide compound recovered by the method as described immediately above.

Additionally alternatively defined more broadly, the present invention is an apparatus for recovering a rare earth oxide compound from a material containing at least one rare earth and at least one transition metal, comprising: (a) a burner for completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the at least one rare earth into at least one rare earth oxide and the at least one transition metal into at least one transition metal oxide; (b) a leaching tank for partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the at least one rare earth oxide into a rare earth compound solution, but leave the at least one transition metal oxide undissolved; (c) a precipitation tank for precipitating the rare earth compound solution with at least one oxalic compound to produce a rare earth oxalate; and (d) means for oxidizing the a rare earth oxalate to produce commercially usable at least one rare earth oxide.

Further defined more broadly, the present invention is a method for recovering a rare earth fluoride from a material containing at least one rare earth and at least one transition metal, comprising the steps of: (a) completely oxidizing the material by burning the material at a sufficient temperature to completely oxidize the at least one rare earth into at least one rare earth oxide and the at least one transition metal into at least one transition metal oxide; (b) partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the at least one rare earth oxide into a rare earth compound solution, but leave the at least one transition metal oxide undissolved; and (c) precipitating the rare earth compound solution with at least one solid fluoride compound which effects slow formation of rare earth fluoride crystal when it reacts with the rare earth compound solution, to produce commercially usable rare earth fluoride.

Also further defined more broadly, the present invention is a rare earth fluoride compound recovered by the method as described immediately above. Additionally further defined more broadly, the present invention is an apparatus for recovering rare earth fluoride from a material containing at least one rare earth and at least one transition metal, comprising: (a) a burner for completely oxidizing the material by burning the material at a sufficient temperature to completely oxidize the at least one rare earth into at least one rare earth oxide and the at least one transition metal into at least one transition metal oxide; (b) a leaching tank for partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the at least one rare earth oxide into a rare earth compound solution, but leave the at least one transition metal oxide undissolved; and (c) a precipitating tank for precipitating the rare earth compound solution with at least one solid fluoride compound which effects slow formation of rare earth fluoride crystal when it reacts with the rare earth compound solution, to produce commercially usable rare earth fluoride.

Defined even more broadly, the present invention is a method for recovering a rare earth compound from a material containing at least one rare earth and at least one transition metal, comprising the steps of: (a) completely oxidizing the material to completely oxidize the at least one rare earth into at least one rare earth oxide and the at least one transition metal into at least one transition metal oxide; and (b) partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the at least one rare earth oxide into a rare earth compound solution, but leave the at least one transition metal oxide undissolved.

Also defined even more broadly, the present invention is a rare earth compound recovered by the method as described immediately above.

Additionally defined even more broadly, the present invention is an apparatus for recovering a rare earth compound from a material containing at least one rare earth and at least one transition metal, comprising: (a) a burner for completely oxidizing the material by burning the material at a temperature sufficient to completely oxidize the at least one rare earth into at least one rare earth oxide and the at least one transition metal into at least one transition metal oxide; and (b) a leaching tank for partially dissolving the completely oxidized material with at least one dissolving agent to selectively dissolve the at least one rare earth oxide into a rare earth compound solution, but leave the at least one transition metal oxide undissolved.

Alternatively defined even more broadly, the present invention is a method for recovering a rare earth compound from a rare earth compound solution, comprising the steps of: (a) precipitating the solution with at least one precipitating agent to produce an interim solid rare earth compound; and (b) treating the interim solid rare earth compound with at least one fluoride compound, such that the interim solid rare earth compound effects slow formation of rare earth fluoride crystals when it reacts with the at least one fluoride compound, to produce commercially usable rare earth fluoride.

Also alternatively defined even more broadly, the present invention is a rare earth compound recovered by the method as described immediately above.

Additionally alternatively defined even more broadly, the present invention is an apparatus for recovering a rare earth compound from a rare earth compound solution, comprising: (a) a precipitation tank for precipitating the solution with at least one precipitating agent to produce an interim solid rare earth compound; and (b) a treatment tank for treating the interim solid rare earth compound with at least one fluoride compound, such that the interim solid rare earth compound effects slow formation of neodymium fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable rare earth fluoride.

Further defined even more broadly, the present invention is a method for recovering a rare earth compound from a rare earth compound solution, comprising the step of precipitating the solution with at least one solid fluoride compound which effects slow formation of neodymium fluoride crystal when it reacts with the rare earth compound solution, to produce commercially usable rare earth fluoride.

Also further defined even more broadly, the present invention is a rare earth compound recovered by the method as described immediately above. Additionally further defined even more broadly, the present invention is an apparatus for recovering a rare earth compound from a rare earth compound solution, comprising a precipitation tank for precipitating the solution with at least one solid fluoride compound which effects slow formation of neodymium fluoride crystal when it reacts with the rare earth compound solution, to produce commercially usable rare earth fluoride.

Of course the present invention is not intended to be restricted to any particular form or arrangement, or any specific embodiment disclosed herein, or any specific use, since the same may be modified in various particulars or relations without departing from the spirit or scope of the claimed invention hereinabove shown and described of which the apparatus shown is intended only for illustration and for disclosure of an operative embodiment and not to show all of the various forms or modification in which the present invention might be embodied or operated.

The present invention has been described in considerable detail in order to comply with the patent laws by providing full public disclosure of at least one of its forms. However, such detailed description is not intended in any way to limit the broad features or principles of the present invention, or the scope of patent monopoly to be granted.

Claims

1. A method for recovering a neodymium (Nd) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising the steps of: a. completely oxidizing said material to completely oxidize said neodymium (Nd) into neodymium oxide (Nd₂0₃) and said iron (Fe) into ferric oxide (Fe₂0₃); and b. partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave said ferric oxide (Fe₂0₃) undissolved.

2. The method as defined in Claim 1 wherein said oxidizing step includes burning said material at a temperature sufficient to completely oxidize said neodymium (Nd) and said iron (Fe).

3. The method as defined in Claim 2 wherein said temperature is within the range of from approximately 400 degree F to approximately 2,000 degree F.

4. The method as defined in Claim 3 wherein said at least one dissolving agent is a mineral acid.

5. The method as defined in Claim 4 wherein said mineral acid is hydrochloric acid (HCl).

6. The method as defined in Claim 4 wherein said mineral acid is sulfuric acid (H₂S0₄).

7. The method as defined in Claim 4 wherein said mineral acid is nitric acid (HN0₃).

8. The method as defined in Claim 3 further comprising the step of grinding said material before the step of complete oxidation.

9. The method as defined in Claim 3 further comprising the step of filtrating said neodymium (Nd) containing solution after the step of dissolving to separate it from said ferric oxide (Fe₂0₃).

10. A neodymium (Nd) compound recovered by the method as claimed in Claim 1 .

1 1 . An apparatus for recovering a neodymium (Nd) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising: a. a burner for completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said neodymium (Nd) into neodymium oxide (Nd₂0₃) and said iron (Fe) into ferric oxide (Fe₂0₃); and b. a leaching tank for partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave said ferric oxide (Fe₂0₃) undissolved.

1 2. The apparatus as defined in Claim 1 1 further comprising a grinder for grinding said material before oxidation.

13. The apparatus as defined in Claim 1 1 further comprising a filter for filtrating said neodymium (Nd) containing solution after dissolving to separate it from said ferric oxide (Fe₂0₃).

14. A method for recovering a neodymium (Nd) compound from a neodymium (Nd) containing solution, comprising the steps of: a. precipitating said solution with at least one precipitating agent to produce an interim solid neodymium

(Nd) compound; and b. treating said interim solid neodymium (Nd) compound with at least one fluoride compound, such that said interim solid neodymium (Nd) compound effects slow formation of neodymium trifluoride (NdF₃) crystals when it reacts with the at least one fluoride compound, to produce commercially usable neodymium trifluoride (NdF₃).

15. The method as defined in Claim 14 wherein said at least one precipitating agent is an oxalic compound.

16. The method as defined in Claim 1 5 wherein said oxalic compound is oxalic acid (H₂C₂0₄).

17. The method as defined in Claim 1 5 wherein said oxalic compound is an oxalic salt.

18. The method as defined in Claim 15 wherein said interim solid neodymium (Nd) compound is neodymium oxalate (Nd₂(C₂0₄)₃).

19. The method as defined in Claim 14 wherein said at least one precipitating agent is an acid selected from the group of acids consisting of glycollic acids, citric acids and formic acids.

20. The method as defined in Claim 14 wherein said at least one fluoride compound is hydrofluoric acid (HF).

21 . The method as defined in Claim 14 wherein said at least one fluoride compound is a fluoride salt solution.

22. The method as defined in Claim 14 further comprising the step of filtrating said interim solid neodymium (Nd) compound after the step of precipitation.

23. The method as defined in Claim 14 further comprising the step of filtrating said neodymium trifluoride (NdF₃) after the step of treatment.

24. The method as defined in Claim 23 further comprising the step of drying said neodymium trifluoride (NdF₃) after the step of filtration.

25. The method as defined in Claim 24 wherein said drying step includes using microwave radiation to dry said neodymium trifluoride (NdF₃).

26. A neodymium (Nd) compound recovered by the method as claimed in Claim 14.

27. An apparatus for recovering a neodymium (Nd) compound from a neodymium (Nd) containing solution, comprising: a. a precipitation tank for precipitating said solution with at least one precipitating agent to produce an interim solid neodymium (Nd) compound; and b. a treatment tank for treating said interim solid neodymium (Nd) compound with at least one fluoride compound, such that said interim solid neodymium (Nd) compound effects slow formation of neodymium fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable neodymium trifluoride (NdF₃).

28. The apparatus as defined in Claim 27 further comprising a first filter press for filtrating said interim solid neodymium (Nd) compound after precipitation.

29. The apparatus as defined in Claim 27 further comprising a second filter press for filtrating said neodymium trifluoride (NdF₃) after treatment.

30. The apparatus as defined in Claim 27 further comprising a micro wave device for drying said neodymium trifluoride (NdF₃) after filtration.

31 . A method for recovering a neodymium (Nd) compound from a neodymium (Nd) containing solution, comprising the step of precipitating said solution with at least one solid fluoride compound which effects slow formation of neodymium fluoride crystal when it reacts with said neodymium (Nd) containing solution, to produce commercially usable neodymium trifluoride (NdF₃).

32. The method as defined in Claim 31 wherein said at least one solid fluoride compound is a fluoride salt.

33. The method as defined in Claim 32 wherein said fluoride salt is calcium fluoride (CaF₂).

34. The method as defined in Claim 32 wherein said fluoride salt is sodium fluoride (NaF).

35. The method as defined in Claim 32 wherein said fluoride salt is ammonium fluoride (NH₄F).

36. The method as defined in Claim 31 wherein said at least one solid fluoride compound is a fluoride salt of a Group-IIA alkaline-earth metal.

37. The method as defined in Claim 31 further comprising the step of filtrating said neodymium trifluoride (NdF₃).

38. The method as defined in Claim 37 further comprising the step of drying said neodymium trifluoride (NdF₃) after the step of filtration.

39. The method as defined in Claim 38 wherein said drying step includes using microwave radiation to dry said neodymium trifluoride (NdF₃).

40. A neodymium (Nd) compound recovered by the method as claimed in Claim 31 .

41 . An apparatus for recovering a neodymium (Nd) compound from a neodymium (Nd) containing solution, comprising a precipitation tank for precipitating said solution with at least one solid fluoride compound which effects slow formation of neodymium fluoride crystal when it reacts with said neodymium (Nd) containing solution, to produce commercially usable neodymium trifluoride (NdF₃).

42. The apparatus as defined in Claim 41 further comprising a filter press for filtrating said neodymium trifluoride (NdF₃).

43. The apparatus as defined in Claim 42 further comprising a microwave device for drying said neodymium trifluoride (NdF₃) after filtration.

44. A method for recovering a neodymium trifluoride (NdF₃) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising the steps of: a. completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said neodymium (Nd) into neodymium oxide (Nd₂0₃) and said iron (Fe) into ferric oxide (Fe₂0₃); b. partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave said ferric oxide (Fe₂0₃) undissolved; c. precipitating said neodymium (Nd) containing solution with at least one precipitating agent to produce an interim solid neodymium (Nd) compound; and d. treating said interim solid neodymium (Nd) compound with at least one fluoride compound, such that said interim solid neodymium (Nd) compound effects slow formation of neodymium trifluoride (NdF₃) crystal when it reacts with the at least one fluoride compound, to produce commercially usable neodymium trifluoride (NdF₃).

45. The method as defined in Claim 44 wherein said temperature is within the range of from approximately 400 degree F to approximately 2,000 degree F.

46. The method as defined in Claim 44 wherein said at least one dissolving agent is a mineral acid.

47. The method as defined in Claim 46 wherein said mineral acid is hydrochloric acid (HCl).

48. The method as defined in Claim 46 wherein said mineral acid is sulfuric acid (H₂S0₄).

49. The method as defined in Claim 46 wherein said mineral acid is nitric acid (HN0₃).

50. The method as defined in Claim 44 wherein said at least one precipitating agent is an oxalic compound.

51 . The method as defined in Claim 50 wherein said interim oxalic compound is oxalic acid (H₂C₂0₄).

52. The method as defined in Claim 30 wherein said oxalic compound is an oxalic salt.

53. The method as defined in Claim 44 wherein said interim solid neodymium (Nd) compound is neodymium oxalate (Nd₂(C₂0₄)₃).

54. The method as defined in Claim 44 wherein said at least one precipitating agent is an acid selected from the group of acids consisting of glycollic acids, citric acids and formic acids.

55. The method as defined in Claim 44 wherein said at least one fluoride compound is hydrofluoric acid (HF).

56. The method as defined in Claim 44 wherein said at least one fluoride compound is a fluoride salt solution.

57. The method as defined in Claim 44 further comprising the step of grinding said material before the step of complete oxidation.

58. The method as defined in Claim 44 further comprising the step of filtrating said neodymium (Nd) containing solution after the step of dissolving to separate it from said ferric oxide (Fe₂0₃).

59. The method as defined in Claim 44 further comprising the step of filtrating said interim solid neodymium (Nd) compound after the step of precipitation.

60. The method as defined in Claim 44 further comprising the step of filtrating said neodymium trifluoride (NdF₃) after the step of treatment.

61 . The method as defined in Claim 60 further comprising the step of drying said neodymium trifluoride (NdF₃) after the step of filtration.

62. The method as defined in Claim 61 wherein said drying step includes using microwave radiation to dry said neodymium trifluoride (NdF₃).

63. A neodymium trifluoride (NdF₃) compound recovered by the method as claimed in Claim 44.

64. An apparatus for recovering a neodymium trifluoride

(NdF₃) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising: a. a burner for completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said neodymium (Nd) into neodymium oxide (Nd₂0₃) and said iron (Fe) into ferric oxide (Fe₂0₃); b. a leaching tank for partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave said ferric oxide (Fe₂0₃) undissolved; c. a precipitation tank for precipitating said neodymium

(Nd) containing solution with at least one precipitating agent to produce an interim solid neodymium (Nd) compound; and d. a treatment tank for treating said interim solid neodymium (Nd) compound with at least one fluoride compound, such that said interim solid neodymium (Nd) compound effects slow formation of neodymium fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable neodymium trifluoride (NdF₃).

65. The apparatus as defined in Claim 64 further comprising a grinder for grinding said material before oxidation.

66. The apparatus as defined in Claim 64 further comprising a filter for filtrating said neodymium (Nd) containing solution after dissolving to separate it from said ferric oxide (Fe₂0₃).

67. The apparatus as defined in Claim 64 further comprising a first filter press for filtrating said interim solid neodymium (Nd) compound after precipitation.

68. The apparatus as defined in Claim 64 further comprising a second filter press for filtrating said neodymium trifluoride (NdF₃) after treatment.

69. The apparatus as defined in Claim 68 further comprising means for drying said neodymium trifluoride (NdF₃) after filtration.

70. The apparatus as defined in Claim 69 wherein said drying means is a microwave device.

71 . A method for recovering a neodymium oxide (Nd₂0₃) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising the steps of: a. completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said neodymium (Nd) into neodymium oxide (Nd₂0₃) and said iron (Fe) into ferric oxide (Fe₂0₃); b. partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave said ferric oxide (Fe₂0₃) undissolved; c. precipitating said neodymium (Nd) containing solution with an oxalic compound to produce neodymium oxalate (Nd₂(C₂0₄)₃); and d. oxidizing said neodymium oxalate (Nd₂(C₂0₄)₃) to produce commercially usable neodymium oxide (Nd₂0₃).

72. The method as defined in Claim 71 wherein said temperature is within the range of from approximately 400 degree F to approximately 2,000 degree F.

73. The method as defined in Claim 71 wherein said last oxidizing step includes burning said neodymium oxalate (Nd₂(C₂0₄)₃) at a temperature sufficient to oxidize said neodymium oxalate (Nd₂(C₂0₄)₃) into said neodymium oxide (Nd₂0₃).

74. The method as defined in Claim 71 wherein said at least one dissolving agent is a mineral acid.

75. The method as defined in Claim 74 wherein said mineral acid is hydrochloric acid (HCl).

76. The method as defined in Claim 74 wherein said mineral acid is sulfuric acid (H₂S0₄).

77. The method as defined in Claim 74 wherein said mineral acid is nitric acid (HN0₃).

78. The method as defined in Claim 71 wherein said oxalic compound is oxalic acid (H₂C₂0₄).

79. The method as defined in Claim 71 wherein said oxalic compound is an oxalic salt.

80. The method as defined in Claim 71 further comprising the step of grinding said material before the step of complete oxidation.

81 . The method as defined in Claim 71 further comprising the step of filtrating said neodymium (Nd) containing solution after the step of dissolving to separate it from said ferric oxide (Fe₂0₃).

82. The method as defined in Claim 71 further comprising the step of filtrating said neodymium (Nd) oxalate (Nd₂(C₂0₄)₃) after the step of precipitation.

83. A neodymium oxide (Nd₂0₃) compound recovered by the method as claimed in Claim 71 .

84. An apparatus for recovering a neodymium oxide (Nd₂0₃) compound from a material containing neodymium (Nd) and massive iron (Fe), comprising: a. a burner for completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said neodymium (Nd) into neodymium oxide (Nd₂0₃) and said iron (Fe) into ferric oxide (Fe₂0₃); b. a leaching tank for partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said neodymium oxide (Nd₂O₃) into a

" neodymium (Nd) containing solution, but leave said ferric oxide (Fe₂0₃) undissolved; c. a precipitation tank for precipitating said neodymium

(Nd) containing solution with at least one oxalic compound to produce neodymium oxalate (Nd₂(C₂0₄)₃); and d. means for oxidizing said neodymium oxalate (Nd₂(C₂0₄)₃) to produce commercially usable neodymium oxide (Nd₂0₃).

85. The apparatus as defined in Claim 84 wherein said means for oxidizing said neodymium oxalate (Nd₂(C₂0₄)₃) includes an additional burner for burning said neodymium oxalate (Nd₂(C₂0₄)₃) at a temperature sufficient to oxidize said neodymium oxalate (Nd₂(C₂0₄)₃) into said neodymium oxide (Nd₂0₃).

86. The apparatus as defined in Claim 84 further comprising a grinder for grinding said material before oxidation.

87. The apparatus as defined in Claim 84 further comprising a filter for filtrating said neodymium (Nd) containing solution after dissolving to separate it from said ferric oxide (Fe₂0₃).

88. The apparatus as defined in Claim 84 further comprising a first filter press for filtrating said neodymium (Nd) oxalate (Nd₂(C₂0₄)₃) after precipitation.

89. A method for recovering a neodymium trifluoride (NdF₃) from a material containing neodymium (Nd) and massive iron (Fe), comprising the steps of: a. completely oxidizing said material by burning said material at a sufficient temperature to completely oxidize said neodymium (Nd) into neodymium oxide (Nd₂0₃) and said iron (Fe) into ferric oxide (Fe₂0₃); b. partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave said ferric oxide (Fe₂0₃) undissolved; and c. precipitating said neodymium (Nd) containing solution with at least one solid fluoride compound which effects slow formation of neodymium trifluoride (NdF₃) crystal when it reacts with said neodymium (Nd) containing solution, to produce commercially usable neodymium trifluoride (NdF₃).

90. The method as defined in Claim 89 wherein said temperature is within the range of from approximately 400 degree F to approximately 2,000 degree F.

91 . The method as defined in Claim 89 wherein said at least one dissolving agent is a mineral acid.

92. The method as defined in Claim 91 wherein said mineral acid is hydrochloric acid (HCl).

93. The method as defined in Claim 91 wherein said mineral acid is sulfuric acid (H₂S0₄).

94. The method as defined in Claim 91 wherein said mineral acid is nitric acid (HN0₃).

95. The method as defined in Claim 89 wherein said at least one solid fluoride compound is a fluoride salt.

96. The method as defined in Claim 95 wherein said fluoride salt is calcium fluoride (CaF₂).

97. The method as defined in Claim 95 wherein said fluoride salt is sodium fluoride (NaF).

98. The method as defined in Claim 95 wherein said fluoride salt is ammonium fluoride (NH₄F).

99. The method as defined in Claim 89 wherein said at least one solid fluoride compound is a fluoride salt of a Group-IIA alkaline-earth metal.

100. The method as defined in Claim 89 further comprising the step of grinding said material before the step of complete oxidation.

101 . The method as defined in Claim 89 further comprising the step of filtrating said neodymium (Nd) containing solution after the step of dissolving to separate said ferric oxide (Fe₂0₃).

102. The method as defined in Claim 89 further comprising the step of filtrating said neodymium trifluoride (NdF₃).

103. The method as defined in Claim 102 further comprising the step of drying said neodymium trifluoride (NdF₃) after the step of filtration.

104. The method as defined in Claim 103 wherein said drying step includes using microwave radiation to dry said neodymium trifluoride (NdF₃).

105. A neodymium trifluoride (NdF₃) compound recovered by the method as claimed in Claim 44.

106. An apparatus for recovering neodymium trifluoride (NdF₃) from a material containing neodymium (Nd) and massive iron (Fe), comprising: a. a burner for completely oxidizing said material by burning said material at a sufficient temperature to completely oxidize said neodymium (Nd) into neodymium oxide (Nd₂0₃) and said iron (Fe) into ferric oxide (Fe₂0₃); b. a leaching tank for partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said neodymium oxide (Nd₂0₃) into a neodymium (Nd) containing solution, but leave said ferric oxide (Fe₂0₃) undissolved; and c. a precipitating tank for precipitating said neodymium

(Nd) containing solution with at least one solid fluoride compound which effects slow formation of neodymium trifluoride (NdF₃) crystal when it reacts with said neodymium (Nd) containing solution, to produce commercially usable neodymium trifluoride (NdF₃).

107. The apparatus as defined in Claim 106 further comprising the step of grinding said material before oxidation.

108. The apparatus as defined in Claim 106 further comprising a filter for filtrating said neodymium (Nd) containing solution after dissolving.

109. The apparatus as defined in Claim 106 further comprising a filter press for filtrating said neodymium trifluoride (NdF₃).

1 10. The apparatus as defined in Claim 106 further comprising a microwave for drying said neodymium trifluoride (NdF₃) after filtration.

1 1 1 . A method for recovering a rare earth compound from a material containing at least one rare earth and at least one transition metal, comprising the steps of: a. completely oxidizing said material to completely oxidize said at least one rare earth into at least one rare earth oxide and said at least one transition metal into at least one transition metal oxide; and b. partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said at least one rare earth oxide into a rare earth compound solution, but leave said at least one transition metal oxide undissolved.

1 2. The method as defined in Claim 1 1 1 wherein said at least one rare earth is neodymium (Nd) and said at least one transition metal is iron (Fe).

13. The method as defined in Claim 1 1 1 wherein said material is samarium-cobalt battery scrap in which said at least one rare earth is samarium (Sm) and said at least one transition metal is cobalt (Co).

14. The method as defined in Claim 1 1 1 wherein said material is nickel hydride battery scrap which contains rare earth including Cerium (Ce), Lanthanum (La), Neodymium (Nd) and Praseodymium (Pr), and contains transition metals including iron (Fe), Zinc (Zn), Nickel (Ni), Zirconium (Zr), Vanadium (V), Titanium (Ti) and Cobalt (Co).

1 5. The method as defined in Claim 1 1 1 wherein said oxidizing step includes burning said material at a temperature sufficient to completely oxidize said at least one rare earth and said at least one transition metal.

16. The method as defined in Claim 1 1 5 wherein said temperature is within the range of from approximately 400 degree F to approximately 2,000 degree F.

17. The method as defined in Claim 1 15 wherein said at least one dissolving agent is a mineral acid.

18. The method as defined in Claim 1 17 wherein said mineral acid is hydrochloric acid (HCl).

19. The method as defined in Claim 1 17 wherein said mineral acid is sulfuric acid (H₂S0₄).

20. The method as defined in Claim 1 17 wherein said mineral acid is nitric acid (HN0₃).

121 . The method as defined in Claim 1 1 1 further comprising the step of grinding said material before the step of complete oxidation.

122. The method as defined in Claim 1 1 1 further comprising the step of filtrating said rare earth compound solution after the step of dissolving to separate it from said at least one transition metal oxide.

123. A rare earth compound recovered by the method as claimed in Claim 1 1 1 .

124. An apparatus for recovering a rare earth compound from a material containing at least one rare earth and at least one transition metal, comprising: a. a burner for completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said at least one rare earth into at least one rare earth oxide and said at least one transition metal into at least one transition metal oxide; and b. a leaching tank for partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said at least one rare earth oxide into a rare earth compound solution, but leave said at least one transition metal oxide undissolved.

125. The apparatus as defined in Claim 1 24 further comprising a grinder for grinding said material before oxidation.

126. The apparatus as defined in Claim 124 further comprising a filter for filtrating said rare earth compound solution after dissolving to separate it from said at least one transition metal oxide.

127. A method for recovering a rare earth compound from a rare earth compound solution, comprising the steps of: a. precipitating said solution with at least one precipitating agent to produce an interim solid rare earth compound; and b. treating said interim solid rare earth compound with at least one fluoride compound, such that said interim solid rare earth compound effects slow formation of rare earth fluoride crystals when it reacts with the at least one fluoride compound, to produce commercially usable rare earth fluoride.

128. The method as defined in Claim 127 wherein said at least one precipitating agent is an oxalic compound.

1 29. The method as defined in Claim 1 28 wherein said oxalic compound is oxalic acid (H₂C₂0₄).

130. The method as defined in Claim 128 wherein said oxalic compound is an oxalic salt.

131 . The method as defined in Claim 128 wherein said interim solid rare earth compound is a rare earth oxalate.

132. The method as defined in Claim 127 wherein said at least one precipitating agent is an acid selected from the group of acids consisting of glycollic acids, citric acids and formic acids.

133. The method as defined in Claim 127 wherein said at least one fluoride compound is hydrofluoric acid (HF).

134. The method as defined in Claim 127 wherein said at least one fluoride compound is a fluoride salt solution.

135. The method as defined in Claim 127 further comprising the step of filtrating said interim solid rare earth compound after the step of precipitation.

136. The method as defined in Claim 1 27 further comprising the step of filtrating said rare earth fluoride after the step of treatment.

137. The method as defined in Claim 136 further comprising the step of drying said rare earth fluoride after the step of filtration.

138. The method as defined in Claim 137 wherein said drying step includes using microwave radiation to dry said rare earth fluoride.

139. A rare earth compound recovered by the method as claimed in Claim 127.

140. An apparatus for recovering a rare earth compound from a rare earth compound solution, comprising: a. a precipitation tank for precipitating said solution with at least one precipitating agent to produce an interim solid rare earth compound; and b. a treatment tank for treating said interim solid rare earth compound with at least one fluoride compound, such that said interim solid rare earth compound effects slow formation of neodymium fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable rare earth fluoride.

141 . The apparatus as defined in Claim 140 further comprising a first filter press for filtrating said interim solid rare earth compound after precipitation.

142. The apparatus as defined in Claim 140 further comprising a second filter press for filtrating said rare earth fluoride after treatment.

143. The apparatus as defined in Claim 142 further comprising a micro wave device for drying said rare earth fluoride after filtration.

144. A method for recovering a rare earth compound from a rare earth compound solution, comprising the step of precipitating said solution with at least one solid fluoride compound which effects slow formation of neodymium fluoride crystal when it reacts with said rare earth compound solution, to produce commercially usable rare earth fluoride.

145. The method as defined in Claim 144 wherein said at least one solid fluoride compound is a fluoride salt.

146. The method as defined in Claim 145 wherein said fluoride salt is calcium fluoride (CaF₂).

147. The method as defined in Claim 145 wherein said fluoride salt is sodium fluoride (NaF).

148. The method as defined in Claim 145 wherein said fluoride salt is ammonium fluoride (NH₄F).

149. The method as defined in Claim 144 wherein said at least one solid fluoride compound is a fluoride salt of a Group-IIA alkaline-earth metal.

1 50. The method as defined in Claim 144 further comprising the step of filtrating said rare earth fluoride.

1 51 . The method as defined in Claim 1 50 further comprising the step of drying said rare earth fluoride after the step of filtration.

1 52. The method as defined in Claim 1 51 wherein said drying step includes using microwave radiation to dry said rare earth fluoride.

1 53. A rare earth compound recovered by the method as claimed in Claim 144.

154. An apparatus for recovering a rare earth compound from a rare earth compound solution, comprising a precipitation tank for precipitating said solution with at least one solid fluoride compound which effects slow formation of neodymium fluoride crystal when it reacts with said rare earth compound solution, to produce commercially usable rare earth fluoride.

1 55. The apparatus as defined in Claim 1 54 further comprising a filter press for filtrating said rare earth fluoride.

156. The apparatus as defined in Claim 1 55 further comprising a microwave device for drying said rare earth fluoride after filtration.

157. A method for recovering a rare earth fluoride compound from a material containing at least one rare earth and at least one transition metal, comprising the steps of: a. completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said at least one rare earth into at least one rare earth oxide and said at least one transition metal into at least one transition metal oxide; b. partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said at least one rare earth oxide into a rare earth compound solution, but leave said at least one transition metal oxide undissolved; c. precipitating said rare earth compound solution with at least one precipitating agent to produce an interim solid rare earth compound; and d. treating said interim solid rare earth compound with at least one fluoride compound, such that said interim solid rare earth compound effects slow formation of rare earth fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable rare earth fluoride.

1 58. The method as defined in Claim 1 57 wherein said at least one rare earth is neodymium (Nd) and said at least one transition metal is iron (Fe).

159. The method as defined in Claim 1 57 wherein said material is samarium-cobalt battery scrap in which said at least one rare earth is samarium (Sm) and said at least one transition metal is cobalt (Co).

1 60. The method as defined in Claim 1 57 wherein said material is nickel hydride battery scrap which contains rare earth including Cerium (Ce), Lanthanum (La), Neodymium (Nd) and Praseodymium (Pr), and contains transition metals including iron (Fe), Zinc (Zn), Nickel (Ni), Zirconium (Zr), Vanadium (V), Titanium (Ti) and Cobalt (Co).

161 . The method as defined in Claim 1 57 wherein said temperature is within the range of from approximately 400 degree F to approximately 2,000 degree F.

1 62. The method as defined in Claim 1 57 wherein said at least one dissolving agent is a mineral acid.

163. The method as defined in Claim 1 62 wherein said mineral acid is hydrochloric acid (HCl).

164. The method as defined in Claim 162 wherein said mineral acid is sulfuric acid (H₂S0₄).

1 65. The method as defined in Claim 1 62 wherein said mineral acid is nitric acid (HN0₃).

166. The method as defined in Claim 1 57 wherein said at least one precipitating agent is an oxalic compound.

167. The method as defined in Claim 1 66 wherein said interim oxalic compound is oxalic acid (H₂C₂0₄).

168. The method as defined in Claim 166 wherein said oxalic compound is an oxalic salt.

169. The method as defined in Claim 1 57 wherein said interim solid rare earth compound is a rare earth oxalate.

170. The method as defined in Claim 1 57 wherein said at least one precipitating agent is an acid selected from the group of acids consisting of glycollic acids, citric acids and formic acids.

171 . The method as defined in Claim 1 57 wherein said at least one fluoride compound is hydrofluoric acid (HF).

172. The method as defined in Claim 157 wherein said at least one fluoride compound is a fluoride salt solution.

173. The method as defined in Claim 1 57 further comprising the step of grinding said material before the step of complete oxidation.

174. The method as defined in Claim 1 57 further comprising the step of filtrating said rare earth compound solution after the step of dissolving to separate it from said at least one transition metal oxide.

175. The method as defined in Claim 1 57 further comprising the step of filtrating said interim solid rare earth compound after the step of precipitation.

176. The method as defined in Claim 1 57 further comprising the step of filtrating said rare earth fluoride after the step of treatment.

177. The method as defined in Claim 176 further comprising the step of drying said rare earth fluoride after the step of filtration.

178. The method as defined in Claim 177 wherein said drying step includes using microwave radiation to dry said rare earth fluoride.

179. A rare earth fluoride compound recovered by the method as claimed in Claim 1 57.

180. An apparatus for recovering a rare earth fluoride compound from a material containing at least one rare earth and at least one transition metal, comprising: a. a burner for completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said at least one rare earth into at least one rare earth oxide and said at least one transition metal into at least one transition metal oxide; b. a leaching tank for partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said at least one rare earth oxide into a rare earth compound solution, but leave said at least one transition metal oxide undissolved; c. a precipitation tank for precipitating said rare earth compound solution with at least one precipitating agent to produce an interim solid rare earth compound; and d. a treatment tank for treating said interim solid rare earth compound with at least one fluoride compound, such that said interim solid rare earth compound effects slow formation of neodymium fluoride crystal when it reacts with the at least one fluoride compound, to produce commercially usable rare earth fluoride.

181 . The apparatus as defined in Claim 180 further comprising a grinder for grinding said material before oxidation.

182. The apparatus as defined in Claim 180 further comprising a filter for filtrating said rare earth compound solution after dissolving to separate it from said at least one transition metal oxide.

183. The apparatus as defined in Claim 180 further comprising a first filter press for filtrating said interim solid rare earth compound after precipitation.

184. The apparatus as defined in Claim 180 further comprising a second filter press for filtrating said rare earth fluoride after treatment.

185. The apparatus as defined in Claim 184 further comprising means for drying said rare earth fluoride after filtration.

186. The apparatus as defined in Claim 185 wherein said drying means is a microwave device.

187. A method for recovering a rare earth oxide compound from a material containing at least one rare earth and at least one transition metal, comprising the steps of: a. completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said at least one rare earth into at least one rare earth oxide and said at least one transition metal into at least one transition metal oxide; b. partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said at least one rare earth oxide into a rare earth compound solution, but leave said at least one transition metal oxide undissolved; c. precipitating said rare earth compound solution with an oxalic compound to produce a rare earth oxalate; and d. oxidizing said a rare earth oxalate to produce commercially usable at least one rare earth oxide.

188. The method as defined in Claim 187 wherein said at least one rare earth is neodymium (Nd) and said at least one transition metal is iron (Fe).

189. The method as defined in Claim 187 wherein said material is samarium-cobalt battery scrap in which said at least one rare earth is samarium (Sm) and said at least one transition metal is cobalt (Co).

190. The method as defined in Claim 187 wherein said material is nickel hydride battery scrap which contains rare earth including Cerium (Ce), Lanthanum (La), Neodymium (Nd) and Praseodymium (Pr), and contains transition metals including iron (Fe), Zinc (Zn), Nickel (Ni), Zirconium (Zr), Vanadium (V), Titanium (Ti) and Cobalt (Co).

191 . The method as defined in Claim 187 wherein said temperature is within the range of from approximately 400 degree F to approximately 2,000 degree F.

192. The method as defined in Claim 187 wherein said last oxidizing step includes burning said a rare earth oxalate at a temperature sufficient to oxidize said a rare earth oxalate into said at least one rare earth oxide.

193. The method as defined in Claim 187 wherein said at least one dissolving agent is a mineral acid.

194. The method as defined in Claim 193 wherein said mineral acid is hydrochloric acid (HCl).

195. The method as defined in Claim 193 wherein said mineral acid is sulfuric acid (H₂S0₄).

196. The method as defined in Claim 193 wherein said mineral acid is nitric acid (HN0₃).

197. The method as defined in Claim 187 wherein said oxalic compound is oxalic acid (H₂C₂0₄).

198. The method as defined in Claim 187 wherein said oxalic compound is an oxalic salt.

199. The method as defined in Claim 187 further comprising the step of grinding said material before the step of complete oxidation.

200. The method as defined in Claim 187 further comprising the step of filtrating said rare earth compound solution after the step of dissolving to separate it from said at least one transition metal oxide.

201 . The method as defined in Claim 187 further comprising the step of filtrating said rare earth oxalate (Nd₂(C₂0₄)₃) after the step of precipitation.

202. A rare earth oxide compound recovered by the method as claimed in Claim 187.

203. An apparatus for recovering a rare earth oxide compound from a material containing at least one rare earth and at least one transition metal, comprising: a. a burner for completely oxidizing said material by burning said material at a temperature sufficient to completely oxidize said at least one rare earth into at least one rare earth oxide and said at least one transition metal into at least one transition metal oxide; b. a leaching tank for partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said at least one rare earth oxide into a rare earth compound solution, but leave said at least one transition metal oxide undissolved; c. a precipitation tank for precipitating said rare earth compound solution with at least one oxalic compound to produce a rare earth oxalate; and d. means for oxidizing said a rare earth oxalate to produce commercially usable at least one rare earth oxide.

204. The apparatus as defined in Claim 203 wherein said means for oxidizing said a rare earth oxalate includes an additional burner for burning said a rare earth oxalate at a temperature sufficient to oxidize said a rare earth oxalate into said at least one rare earth oxide.

205. The apparatus as defined in Claim 203 further comprising a grinder for grinding said material before oxidation.

206. The apparatus as defined in Claim 203 further comprising a filter for filtrating said rare earth compound solution after dissolving to separate it from said at least one transition metal oxide.

207. The apparatus as defined in Claim 203 further comprising a first filter press for filtrating said rare earth oxalate (Nd₂(C₂0₄)₃) after precipitation.

208. A method for recovering a rare earth fluoride from a material containing at least one rare earth and at least one transition metal, comprising the steps of: a. completely oxidizing said material by burning said material at a sufficient temperature to completely oxidize said at least one rare earth into at least one rare earth oxide and said at least one transition metal into at least one transition metal oxide; b. partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said at least one rare earth oxide into a rare earth compound solution, but leave said at least one transition metal oxide undissolved; and c. precipitating said rare earth compound solution with at least one solid fluoride compound which effects slow formation of rare earth fluoride crystal when it reacts with said rare earth compound solution, to produce commercially usable rare earth fluoride.

209. The method as defined in Claim 208 wherein said at least one rare earth is neodymium (Nd) and said at least one transition metal is iron (Fe).

210. The method as defined in Claim 208 wherein said material is samarium-cobalt battery scrap in which said at least one rare earth is samarium (Sm) and said at least one transition metal is cobalt (Co).

21 1 . The method as defined in Claim 208 wherein said material is nickel hydride battery scrap which contains rare earth including Cerium (Ce), Lanthanum (La), Neodymium (Nd) and Praseodymium (Pr), and contains transition metals including iron (Fe), Zinc (Zn), Nickel (Ni), Zirconium (Zr), Vanadium (V), Titanium (Ti) and Cobalt (Co).

212. The method as defined in Claim 208 wherein said temperature is within the range of from approximately 400 degree F to approximately 2,000 degree F.

213. The method as defined in Claim 208 wherein said at least one dissolving agent is a mineral acid.

214. The method as defined in Claim 213 wherein said mineral acid is hydrochloric acid (HCl).

21 5. The method as defined in Claim 213 wherein said mineral acid is sulfuric acid (H₂S0₄).

216. The method as defined in Claim 213 wherein said mineral acid is nitric acid (HN0₃).

217. The method as defined in Claim 208 wherein said at least one solid fluoride compound is a fluoride salt.

218. The method as defined in Claim 21 7 wherein said fluoride salt is calcium fluoride (CaF₂).

219. The method as defined in Claim 217 wherein said fluoride salt is sodium fluoride (NaF).

220. The method as defined in Claim 217 wherein said fluoride salt is ammonium fluoride (NH₄F).

221 . The method as defined in Claim 208 wherein said at least one solid fluoride compound is a fluoride salt of a Group-IIA alkaline-earth metal.

222. The method as defined in Claim 208 further comprising the step of grinding said material before the step of complete oxidation.

223. The method as defined in Claim 208 further comprising the step of filtrating said rare earth compound solution after the step of dissolving to separate said at least one transition metal oxide.

224. The method as defined in Claim 208 further comprising the step of filtrating said rare earth fluoride.

225. The method as defined in Claim 224 further comprising the step of drying said rare earth fluoride after the step of filtration.

226. The method as defined in Claim 225 wherein said drying step includes using microwave radiation to dry said rare earth fluoride.

227. A rare earth fluoride compound recovered by the method as claimed in Claim 208.

228. An apparatus for recovering rare earth fluoride from a material containing at least one rare earth and at least one transition metal, comprising: a. a burner for completely oxidizing said material by burning said material at a sufficient temperature to completely oxidize said at least one rare earth into at least one rare earth oxide and said at least one transition metal into at least one transition metal oxide; b. a leaching tank for partially dissolving said completely oxidized material with at least one dissolving agent to selectively dissolve said at least one rare earth oxide into a rare earth compound solution, but leave said at least one transition metal oxide undissolved; and c. a precipitating tank for precipitating said rare earth compound solution with at least one solid fluoride compound which effects slow formation of rare earth fluoride crystal when it reacts with said rare earth compound solution, to produce commercially usable rare earth fluoride.

229. The apparatus as defined in Claim 228 further comprising the step of grinding said material before oxidation.

230. The apparatus as defined in Claim 228 further comprising a filter for filtrating said rare earth compound solution after dissolving.

231 . The apparatus as defined in Claim 228 further comprising a filter press for filtrating said rare earth fluoride.

232. The apparatus as defined in Claim 228 further comprising a microwave for drying said rare earth fluoride after filtration.