DD297456A5 - PROCESS FOR THE PROCESSING OF RENEWED METALES CONTAINING RARE METALS - Google Patents

Abstract

The invention relates to a process for the digestion of a rare earth-containing ore. The process consists of sulfuric acid digestion of an ore in reactor 1, subsequent picking by a calcium nitrate solution in 3, then removal of the insoluble constituents in 5 and recovery of the rare earth metals by a liquid / liquid extraction process in batteries 6a and 6b.

Description

description The invention relates to a process for the treatment of a rare earth-containing ore.

At present, the major mined rare earth ores are those containing carrier minerals of the rare earth metals such as monazite, bastnasite and xenotime. In addition, there are many other ores whose extraction and processing are currently not profitable.

When the ore has a low or moderate content of rare earth metals, it is necessary to subject it to physical processing such as mechanical separation by gravity, flotation or magnetic separation. Such a method, which is added to a necessary chemical treatment for the extraction of rare earth metals, can prove to be costly and the efficiency of the process burdensome. One of the objects of the invention is to provide an economical method of recovering the rare earths from the mineral containing them by a method which is particularly suitable for preventing or limiting the previous accumulation of this mineral.

Another object of the present invention is to provide a method suitable for processing all kinds of ores or residues containing rare earth metals, regardless of their concentration. The invention also has for its object to provide a process which is particularly suitable for the treatment of ores comprising rare earth fluorine compounds such as Bastnäsite's containing fluorocarbonates of rare earth metals and permitting the removal of fluorine without the need for high temperature thermal treatments ,

To this end, the invention proposes a process for the treatment of ores containing rare earth compounds, which comprises the following steps: (i) ore digestion with sulfuric acid, (ii) addition of a compound comprising an insoluble anion and an anion with the sulfate anion, that with the

(Iii) recovering the rare earth metals by liquid / liquid extraction between the aqueous phase containing the rare earth metal salts and an organic phase containing a water insoluble extractant for solene earth metals, and then reextracting the rare earth metals Rare earth metals from the organic phase.

Advantageously, the insoluble constituents of the aqueous phase are separated prior to the liquid / liquid extraction of the rare earth metals.

The rare earth metals are dissolved by exchanging the sulfate anion with another anion such as nitrate, halide, acetate and perchlorate anion. According to another feature of the invention, the compound added in step (ii) is advantageously a nitrate or a chloride such as a nitrate or a chloride of an alkaline earth metal or an analog.

The preferred compound according to the invention, especially from the economic point of view, is calcium nitrate or chloride.

The compound is used in an amount sufficient to obtain complete dissolution of the rare earth metals.

The rare earth metal solution can be separated from the insoluble components by any conventional solid-liquid separation process such as decantation, filtration or centrifugation.

The separation of the rare earth metals is carried out by liquid / liquid extraction between the aqueous phase containing the rare earth metal salts and an organic phase containing a water-insoluble extractant, followed by re-extraction of the rare earth metals from the organic phase.

The extractant used in the process according to the invention may be selected from all extractants which have a selectivity for rare earth metals.

The extractant employed may be selected from the class of anionic extractants, the solvating extract tonic or cationic extract tonic or a mixture thereof. The anionic extractants used are, in particular, the inorganic compounds with a long, amino-functional chain.

The hydrocarbon chains of these compounds preferably have between about 5 and 20 carbon atoms. This can be mentioned as an example:

tertiary amines and in particular the products marketed under the trade names Alamine 336 and Adogen 364, which are built up from tertiary amines of the formula R ₃ N in which the hydrocarbon radical R has 8 to 10 carbon atoms,

quaternary ammonium nitrates and, in particular, the products sold under the trademarks Adogen 464 and Aliquat 336 which are obtained from quaternary ammonium salts of the formula

(R ₃ N-CH ₃ I ⁺ Cl "are constructed, wherein the hydrocarbon radical R has 8 to 10 carbon atoms, derived products.

The cationic extractants used are, in particular, organophosphorus acids, carboxylic acids and β-diketones. These include:

- The organophosphorus acids of the general formulas

OR, OR ₁ R ₁

R ₀ O -P = O or R ₀ - P = O or R ₀ - P = O,

OH OH OH

wherein Ri and R _{2 are} aliphatic or aromatic hydrocarbon radicals whose total number of carbon atoms is at least equal to 10. The use of di- (2-ethylhexyl) -phosphoric acid and

Bis (2-ethylhexyl) phosphonic acid

the carboxylic acids marketed by SHELL Chemicals under the trademark "VERSATIC" which are of the general formula

₂ COOH

in which R ₁ and R _{2 are} optionally substituted hydrocarbon radicals and in particular the acid derived by the SHELL process for the carbonylation of C ₈ olefins "VERSATIC 10", wherein R ₁ and R _{2 are} hydrocarbon radicals whose carbon atom sum is equal to 7.

The anionic or cationic extractants may be used to extract and separate the rare earth metals from the aqueous solution derived from the receiving step (ii). In this case, however, it is necessary to carry out a pre-neutralization by means of a base and preferably a base whose cation is identical to that of the compound added in step (ii).

The solvating extractants used are in particular neutral, substantially water-insoluble organophosphorus compounds and selected from the following four classes:

R ₁ - Ο _χ phosphates ^R 2 ~ ° - P = O (I)

^R 3 "°

Phosphonates R - O - ^ P = O (II)

Phosphinates R ₀ - ^ P = O (III)

Phosphine Oxides R ₀ - P = O (IV)

In the formulas (I! To (IV), R ₁ , R ₂ and R _{3 are} hydrocarbon radicals such as aliphatic, cycloaliphatic and / or

aromatic radicals.

These radicals may contain from 1 to 18 carbon atoms, but preferably at least one of these radicals must be at least

4 carbon atoms aufweison.

The extractants of formula (I) to (IV) can be used individually or in admixture. According to the invention, especially those compounds which are industrially available, such as tri-n-butylphosphate, are used

(TBP), triisobutyl phosphate (TIBP), debutylbutylphosphonate (DBBP), di- (2-ethylhexvl) -2-hexylhexylphosphonate (DEHEHP) and

Tri-n-octylphosphine oxide (TOPO). Tributyl phosphate or dibutyl butyl phosphonate should preferably be mentioned for the process according to the invention. The solvating extractants may be used to extract and separate the rare earth metals from the Step (ii) obtained aqueous solution can be used. In this case, this solution must contain the nitration as an anion. Therefore, the compound added in this step (ii) to take up the digested amount is a nitrate, for example Calcium nitrate. Preferably, the aqueous solution derived from step (ii) has a nitrate ion concentration between 4 N and 9 N. The organic phase according to the invention optionally contains, in addition to the extraction agent, an organic Diluent. Suitable suitable diluents may be those which are commonly used for Implementation of liquid / liquid extraction method can be used. Of these, the aliphatic hydrocarbons

for example, dodecane, kerosene type petroleum cuts and aromatic hydrocarbons, for example, petroleum cuts consisting of an alkylbenzene mixture, in particular cuts of the Solvesso type marketed by the company EXXON.

Likewise one can use a mixture of these diluents. Preference is given to petroleum cuts of the kerosene type. The proportion of the extractant in the organic phase varies according to the extractant within wide limits. Its concentration can range from 5VoI .-%, when the extractant is dissolved in a diluent, up to 100%, if

the agent is used purely, vary.

When tributylphosphate or dibutylbutylphosphonate is used as the preferred extraction agent according to the invention, is Share between 50 and 80Vol .-% advantageous. The organic phase of the invention may also contain various modifiers, one of which is essential Purpose to improve the hydrodynamic properties of the system without altering the complexing Properties of the extractant is. Of the well-suited compounds, one can especially use the compounds with

an alcohol function and in particular dig heavy alcohols whose carbon atom number is between 4 and 15 call.

In general, a proportion which can reach 20% by volume, based on the organic phase, is preferred. The separation of the rare earth element or metals is carried out by countercurrent in several theoretical extraction stages

, wherein each stage consists of the mixing-shaving process step.

The aqueous phase is brought into contact with the organic phase at an uncritical temperature; it generally becomes

chosen between 15 ° C and 65 ⁰ C and usually between 20 ⁰ C and 50 ⁰ C.

The separation step leads on the one hand to obtain an aqueous, freed from rare earth metals solution that or not

extracted element (s) of the digestion solution and, on the other hand, to an organic rare earth-containing phase.

Subsequently, a reextraction stage of the rare earth metals contained in the organic phase is carried out. Separating the extracted rare earth metals of the organic phase by contacting the latter with water or

optionally, a nitric acid solution diluted to less than about 0.3N.

It is based on the aqueous solution containing rare earth nitrate obtained in the re-extraction stage

possible to precipitate the rare earth metals in the form of their hydroxides by means of a basic solution having a pH of about 8.

The extracted after extraction by the organic solvent, rare earth-free aqueous solution is

advantageously recycled after step (ii) as a solution for performing the inclusion of the digested amount in the circulation. In fact, this solution contains the anion forming a soluble salt with the rare earth metals. Therefore, it will be sufficient to adjust the cation content of, for example, calcium in this recycle solution by adding, for example, lime to obtain a solution for receiving the proper digested amount.

This procedure provides a significant advantage from both the economic point of view and the Wastewater discharge. In fact, recirculation allows for the recovery of the rare earth metals in stage (iii)

obtained solution, the liquid waste products and in particular the Nitrateabwässer to reduce or even avoid. Thus, in the case of the use of lime and calcium nitrate, the effluents will consist essentially of calcium sulfate and the spent starting materials will be essentially lime and sulfuric acid.

Another advantage of the invention lies in the fact that the process the preparation of all Rare earth metal-containing ores or residues permitted. The inventive method can be applied to all types of ore and in particular ores with a low content of Rare earth metals are applied. It is to be understood that the scope of the present invention should not be abandoned when dealing with ore concentrates

working, for example enrichment by means of physical methods, grinding and floating and / or concentration by gravity on vibrating tables and / or magnetic separation and / or any other physical or chemical method.

It is also possible to use an ore which has undergone a thermal pretreatment. In the case of rare earth metals of poor ores, preference is given to an ore which is partly insoluble in sulfuric acid Gait has and you can enumerate quartz and the silicates, magnetite, anatase, rutile, ilmenite, grenade and zircons. As ores that are well suited for use in the invention, you can call the ores, their rare earth metal carrier Phosphates, fluorocarbonates, carbonates or silicates are. As examples of ores, the following may be mentioned, the average weight content of rare earth metals,

expressed as rare earth metal oxides, is given:

- Phosphate-type ores such as apatites, wherein the rare-earth metals are incorporated into the calcium phosphate lattice

Ca ₆ (PO ₄ I ₃ (F, Cl, OH) (10%); Rhabdophanite TRPO ₄ , H ₂ O (60%); Monazite TRPO ₄ (65%) (TR = rare earth metal). Churchit TRPO ₄ , HjO (50%), the rare earth metals are essentially yttered metals; the family of the grandallite

for example, Florenzite TRAL ₃ (POJ ₂ (OH) ₆ (30%).

- Fluorocarbonate-type ores, for example BastnMsit TRCO ₃ F (75%), Synchisite TRCa (COj) ₂ F (52%);

- ores of the carbonate type, in particular lanthanite TR] (CO ₃ I ₃ , 8 H ₂ O (55%);

Ores of the silicate type, in particular Alhnit (TRCa) ₂ (FeAIMg) ₃ (SiO ₄ I ₃ OH (60%), Britholite (TR ₆ Ca ₄ ) Si ₆ O ₂₄ (OH) ₂ and Eudialyte (Na, Ca) ₆ ( Zn, Fe, Mh} Si »0, _?% 0.0: -i, CI).

The process according to the invention is completely suitable for the treatment of ores of the fluorocarbonate type. In fact, we J released the fluorine content of the ore during sulfuric acid digestion in the form of, in particular, hydrofluoric acid.

The process according to the invention also makes it possible to prepare any form of residue, be it solid or liquid.

Residues containing salted rare earth metals (phosphates, carbonates or sulphates) or residues (powders, chips, pieces, blocks or dusts) may be used, mostly from the production of TR-Co type magnets, where the rare earth metal is essentially Samarium is or of the TR / Fe / B type, wherein the rare earth element is essentially neodymium, and the atomic percentage of the elements is generally 8 to 30% rare earth metal, 2 to 28% boron and the remainder iron.

As mentioned above, it is also possible by the method according to the invention, processing digestion residues from iron mines, which still contain iron oxides and apatite. In the same case, before carrying out the process of the invention, it is desirable to remove the magnetite by magnetic separation, a process well known in the art.

The process is also suitable for the treatment of residues of gypsum dissolution, in particular of gypsum derived from the sulfuric acid digestion of the phosphate ores and of slurries obtained in the concentration stage of the crude phosphoric acids.

The list of ores and residues mentioned above is by no means limiting. In this description of the invention, "ore" refers to both a rare earth-containing ore and a residue.

In accordance with the process according to the invention, in step (i) ore digestion is carried out by means of sulfuric acid, for example by thickening or slurrying of the ore.

Prior to acid digestion, one operation of crushing and / or milling to release the carrier mineral species of the rare earth metals may prove interesting. The grain size depends on the mesh size, which is between a few micrometers, generally! to 5 microns, and 2 mm may vary. However, if one wishes to have a fairly rapid digestion, it is advantageous to use particles with a diameter smaller than 1 mm.

The operations of crushing and grinding can be carried out in a classical manner, for example in a jaw crusher and / or a ball mill or hammer mill.

In addition to the carrier minerals of rare earth metals certain mineral impurities are also digested by the sulfuric acid. However, these impurities can be removed during the process or in a subsequent step.

The ore digestion is carried out by means of sulfuric acid. The sulfuric acid concentration for this is not critical. So you can use oleum as a sulfuric acid solution. In this case, the concentration of the sulfuric acid solutions is preferably between 45 and 100% by weight.

The amount of sulfuric acid used depends on the content of the sulfuric acid digestible species (rare earth metals and impurities). Their amount is preferably equal to the stoichiometric amount required to digest the digestible elements.

Advantageously, this amount will be greater than the required stoichiometric and the excess will preferably be on the order of 20%.

To improve the yield and in particular the kinetics of sulfuric acid digestion, it is advantageous to carry it out at a temperature greater than 10O ⁰ C, preferably between 100 ⁰ C and 400 ⁰ C, to remove the water present and thus to shift the equilibrium.

Further advantages, details and results of the invention will become apparent from the following examples and the detailed description of a preferred embodiment of the invention with reference to the figure, which is a schematic diagram of a preferred embodiment of the invention. The inventive method according to a preferred embodiment consists of the sulfuric acid thickening of a rare earth metal ore in a reactor 1 by adding a sulfuric acid solution by 2.

After reaction and sulfuric acid digestion, a solution of a salt comprising a cation comprising an insoluble sulfate and an anion which forms a soluble salt with the rare earth metals, for example a calcium nitrate solution, is added to reactor 3. This addition is made by 4

 Thus, the rare earth metals are dissolved in the reactor 3.

The insoluble components are separated in 5, for example by filtration, and the aqueous phase is then fed into a liquid / liquid extraction battery 6. This battery comprises a plurality of countercurrent mixer-separator stages and consists of an extraction section 6a and a reextraction section 6b for the rare earth metals extracted by the organic phase.

The organic phase is introduced into the extraction section through 7 and then into the reextraction section through 8 and recycled through the return line 9.

The aqueous phase filled in the extraction section by 10 is returned to the reactor 3 through the return line 11.

This recirculation line 11 comprises a feed 12 allowing, for example, to adjust the content of calcium and nitrate, and a filtration step for removing the insoluble matter in FIG.

example 1

Containing 10 kg ore with an average grain size less than or equal to 100 \ in which (expressed as TR ₂ O ₃₎ 32.8% rare earth metals, sulfuric acid is digested at 200 ⁰ C for 2 h with 10 kg 62%.

After mincing the disrupted Menye, it is taken up with 200 I of a 4 M calcium nitrate solution. The resulting mixture is filtered. The filtered solution is poured into a working countercurrent liquid / Filled with liquid extraction battery. The organic extraction phase is a 50% solution of dibutyl butyl phosphonate

(DBBP) in kerosene. The contained rare earth metals are completely extracted by the organic phase, then reextracted from this and gew nnen by means of a 0.05 N nitric acid solution.

The obtained purified rare earth metal solution contains 44 g / l of rare earth metals (expressed as TR ₂ O ₃ ). Example 2

1COg ore containing 32.8% rare earth metals (expressed as TR ₂ O ₃ ) is digested with 100 g of 62% sulfuric acid at 200 ⁰ C for ₂ hours.

After crushing the digested amount, this is a leaching by means of a liter of a

200g / l calcium chloride solution. After stirring, the pH of the reaction mass is adjusted to 4.5. Thereafter, the insoluble matters are removed by filtration, the resulting solution containing 30g / l of rare earth metals.

This solution is poured into a liquid / liquid extraction battery in countercurrent with a solution of HDEHP (di- (2-ethylhexyl) -

phosphoric acid) in kerosene as an organic extraction phase.

The entire content of rare earth metals is extracted by the organic phase. The rare earth metals are then reextracted and passed through a 2N nitric acid or 6N hydrochloric acid solution

won.

Claims (21)

1. A process for the preparation of ores containing rare earth metal compounds, characterized by (i) ore digestion with sulfuric acid, (ii) adding a compound comprising an insoluble sulfate-forming cation and a the rare earth metals a soluble salt-forming anion, the digested mass in the presence of water, (iii) recovering the rare earth metals by liquid / liquid extraction between the aqueous phase containing the rare earth metal salts and an organic phase containing a water-insoluble extractive agent for rare earth metals, and then re-extracting the rare earth metals from the organic phase. 2. The method according to claim 1, characterized in that the insoluble constituents are separated from the aqueous phase before the aforementioned step (iii). 3. The method according to claim 1 or 2, characterized in that the compound added in step (ii) is a nitrate or a chloride. 4. The method according to any one of claims 1,2 or 3, characterized in that the compound added in step (ii) is an alkaline earth nitrate or chloride such as calcium nitrate or chloride. A process according to any one of the preceding claims, characterized in that the amount added in step (ii) to obtain a ratio cation of the compound / sulphate ion containing in the leachate is at least equal to the stoichiometry. 6. The method according to any one of the preceding claims, characterized in that the digestion stage (:) at a temperature greater than 100 ° C, and preferably between 100 ⁰ C and 400 ⁰ C durated by jhgeführt. 7. The method according to any one of the preceding claims, characterized in that the sulfuric acid used in step (i) is a sulfuric acid solution of concentration between 45% and 100%. 8. The method according to any one of claims 1 to 7, characterized in that in the digestion step (i) used sulfuric acid is an oleum. 9. The method according to any one of the preceding claims, characterized in that the amount of sulfuric acid used in step (i) is at least equal to the theoretical amount required for the digestion of the digestible elements of the ore. 10. The method according to claim 9, characterized in that the aforementioned amount of sulfuric acid is 20% above the theoretical amount. 11. The method according to any one of the preceding claims, characterized in that the ore is an ore whose carrier for the rare earth metals are phosphates, fluorocarbonates, carbonates or silicates, or any rare earth metals in metallic or salt-containing residue. 12. The method according to any one of the preceding claims, characterized in that the ore used is apatite or Bastnäsit containing ore. 13. The method according to any one of the preceding claims, characterized in that the ore used is a residue from the production of magnets of the samarium-cobalt or neodymium-iron boron type. 14. The method according to any one of the preceding claims, characterized in that the ore digestion is carried out by thickening the ore with sulfuric acid. 15. The method according to any one of claims 1 to 14, characterized in that the ore digestion is carried out by transfer of the ore in Breifo'rm with sulfuric acid. 16. The method according to any one of the preceding claims, characterized in that the extractant used in step (iii) is an anionic, solvating or cationic extractant. 17. The method according to claim 16, characterized in that the extractant is a selected from the phosphates, phosphonates, phosphinates and phosphine oxides neutral organophosphorus compound. 18. The method according to claim 17, characterized in that the extraction agent Tributvlphosphat or Dibutylbutylphosphonat is. 19. The method according to any one of claims 16 to 18, characterized in that the organic phase contains a diluent which is a petroleum cut of the kerosene type or an alkylbenzene mixture. 20. The method according to any one of claims 16 to 19, characterized in that one carries out the reextraction of the rare earth metals from the organic phase with water. 21. The method according to any one of the preceding claims, characterized in that the liberated from rare earth metals aqueous phase in stage (ii) is recycled. For this 1 page drawing