CN117604240A - Method for recovering rare earth, zirconium and ferric phosphate by decomposing xenotime through high-temperature roasting of concentrated sulfuric acid - Google Patents

Abstract

The application relates to a method for recovering rare earth, zirconium and ferric phosphate by roasting and decomposing xenotime with concentrated sulfuric acid at high temperature, which comprises the following steps: mixing xenotime, iron powder and sulfuric acid for roasting to obtain a roasting material, wherein the roasting temperature is 500-750 ℃; leaching the roasting material, and carrying out solid-liquid separation to obtain solid and leaching liquid, wherein the concentration of hydrogen ions in a leaching treatment system is 0.5 mol/L-1.5 mol/L; carrying out acid dissolution treatment on the solid, and then carrying out crystallization treatment on a solution obtained by the acid dissolution treatment to prepare zirconium sulfate, wherein the concentration of hydrogen ions in an acid dissolution treatment system is 4-8 mol/L; and preparing the rare earth element compound by leaching the solution. The method has the advantages that the steps are synergistic, the recovery rate of rare earth elements is effectively improved, and meanwhile, the recovery and utilization of zirconium elements are realized.

Description

Method for recovering rare earth, zirconium and ferric phosphate by decomposing xenotime through high-temperature roasting of concentrated sulfuric acid

Technical Field

The application relates to the technical field of metallurgy, in particular to a method for recovering rare earth, zirconium and ferric phosphate by decomposing xenotime through high-temperature roasting of concentrated sulfuric acid.

Background

Xenotime is a phosphate rare earth ore commonly assigned to multi-metal complex deposits or non-metal deposits and is produced as a byproduct of the separation of other minerals by intergrowth with quartz, feldspar, tourmaline, ilmenite, and the like. The prior art processes xenotime by acid processes such as sulfuric acid roasting decomposition or alkali processes such as liquid alkali pressurizing decomposition, alkali melting decomposition and sodium carbonate roasting decomposition, wherein the alkali processes mainly recover rare earth elements and phosphorus elements in the xenotime and the phosphorus elements are mainly recovered in the form of trisodium phosphate, the acid processes usually mix the xenotime with inorganic acid to decompose the xenotime and then recover the rare earth elements in the roasting material through subsequent treatment.

Therefore, it would be desirable to provide a process that is capable of recovering zirconium element from xenotime with high recovery of rare earth elements.

Disclosure of Invention

Based on this, there is a need for a method for recovering rare earth, zirconium and iron phosphate by decomposing xenotime by high temperature roasting with concentrated sulfuric acid, which can recover zirconium element and iron phosphate in the xenotime, and which has a high recovery rate of rare earth element.

The present application provides a method for recovering rare earth, zirconium and iron phosphate by high temperature roasting and decomposing xenotime with concentrated sulfuric acid, comprising the steps of:

mixing xenotime, iron powder and sulfuric acid for roasting to obtain a roasting material, wherein the roasting temperature is 500-750 ℃;

leaching the roasting material, and carrying out solid-liquid separation to obtain solid and leaching liquid, wherein the concentration of hydrogen ions in a leaching treatment system is 0.5 mol/L-1.5 mol/L;

carrying out acid dissolution treatment on the solid, and then carrying out crystallization treatment on a solution obtained by the acid dissolution treatment to prepare zirconium sulfate, wherein the concentration of hydrogen ions in an acid dissolution treatment system is 4-8 mol/L;

and preparing a rare earth element compound by the leaching solution.

The method comprises the steps of mixing and roasting xenotime, iron powder and sulfuric acid at a specific temperature, and fully reacting the three raw materials at a relatively high roasting temperature to obtain a roasting material containing rare earth element sulfate, zirconium sulfate and ferric phosphate; leaching the roasted material to dissolve soluble rare earth element sulfate to obtain leaching solution containing rare earth element ions, and controlling the concentration of hydrogen ions in the leaching treatment to hardly decompose zirconium sulfate by utilizing the characteristic that zirconium sulfate is not easy to hydrolyze under low acidity, so as to obtain a solid containing zirconium sulfate and ferric phosphate; then, the solid is subjected to acid dissolution treatment under the specific hydrogen ion concentration, under the condition, the solubility of zirconium sulfate is larger than that of ferric phosphate, so that the zirconium sulfate can be dissolved, and the ferric phosphate is hardly dissolved, thereby realizing the separation of the zirconium sulfate and the ferric phosphate, and then, the solution obtained by the acid dissolution treatment is subjected to crystallization treatment, so that the zirconium sulfate solid can be obtained. And meanwhile, carrying out corresponding post-treatment on the leaching solution, and extracting rare earth elements from the leaching solution to prepare the rare earth element compound. The method has the advantages that the steps are synergistic, the recovery rate of rare earth elements is effectively improved, and meanwhile, the recovery and the utilization of zirconium element and ferric phosphate are realized.

In addition, the method has simple process flow, small consumption of sulfuric acid raw materials and easy mass production.

In some embodiments, the firing temperature is 650 ℃ to 700 ℃.

In some embodiments, the concentration of hydrogen ions in the leaching treatment system is 0.8 mol/L to 1.5 mol/L.

In some embodiments, the concentration of hydrogen ions in the acid-soluble treatment system is 5mol/L to 7.5 mol/L.

In some of these embodiments, the method satisfies at least one of the following (1) - (5):

(1) P in the iron powder and xenotime ₂ O ₅ The mass ratio of (1-0.5): 1, a step of;

(2) The mass ratio of the sulfuric acid to the xenotime is (1-2): 1, a step of;

(3) The sulfuric acid is concentrated sulfuric acid;

(4) The roasting time is 1.5-3 hours;

(5) The calcination is performed in an oxygen-containing atmosphere.

In some of these embodiments, the method satisfies at least one of the following (1) - (3):

(1) The liquid-solid ratio of the liquid adding amount of the leaching treatment to the roasting material is (4-8) L:1 Kg;

(2) The leaching treatment time is 4-6 hours;

(3) And regulating and controlling the concentration of hydrogen ions in the leaching treatment system by adopting inorganic alkali.

In some of these embodiments, the method satisfies at least one of the following (1) - (3):

(1) The liquid adding amount of the acid dissolution treatment and the liquid-solid ratio of the solid are (1-4) L:1 Kg;

(2) The temperature of the acid dissolution treatment is 70-90 ℃;

(3) The acid dissolution treatment time is 2-4 hours.

In some of these embodiments, the acid solution used for the acid-dissolving treatment comprises an aqueous sulfuric acid solution.

In some of these embodiments, the crystallization process comprises:

concentrating the solution obtained by acid dissolution, controlling the concentration of hydrogen ions in a reaction end point system to be more than 5mol/L, and carrying out solid-liquid separation to obtain zirconium sulfate.

In some of these embodiments, the step of preparing a rare earth element compound from the leachate comprises:

adjusting the pH value of the leaching solution to 3.5-4.5, adding oxalic acid for precipitation treatment, and carrying out solid-liquid separation to obtain rare earth element oxalate;

or extracting the leaching solution by using an extracting agent to prepare the rare earth element compound.

Detailed Description

In order to facilitate an understanding of the present application, a more complete description of the present application will follow. This application may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

In the description of the present application, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" is at least two, such as two, three, etc., unless explicitly defined otherwise.

The weights of the relevant components mentioned in the embodiments of the present application may refer not only to specific contents of the components, but also to the proportional relationship between the weights of the components, and thus, any ratio of the contents of the relevant components according to the embodiments of the present application may be enlarged or reduced within the scope disclosed in the embodiments of the present application. Specifically, the weight described in the specification of the examples of the present application may be a mass unit known in the chemical industry such as μ g, mg, g, kg.

The application provides a method for recycling rare earth, zirconium and ferric phosphate by decomposing xenotime through high-temperature roasting of concentrated sulfuric acid, which comprises the following steps S10-S40.

S10, mixing xenotime, iron powder and sulfuric acid for roasting to obtain a roasting material, wherein the roasting temperature is 500-750 ℃.

It is understood that during the calcination process the rare earth oxides in the xenotime react with sulfuric acid to form rare earth sulfates and the phosphorus in the xenotime reacts with the iron powder to form iron phosphate. It should be noted that, the iron phosphate formed by roasting in the subsequent step can still exist in a solid form, so that the recycling rate of the iron phosphate can be improved, and the value of the iron phosphate is higher compared with trisodium phosphate recovered by the traditional alkali method. Further, compared with other rare earth element oxides, the decomposition temperature of the zirconium oxide is higher, and most of the conventional technologies adopt a middle-low temperature roasting method or pressure cooking method, and the zirconium oxide cannot be fully decomposed under the temperature condition, so that the conventional technologies rarely recycle the zirconium element, and the conventional low temperature roasting method is difficult to effectively recycle the phosphorus element. The inventor of the application researches and discovers that when the roasting temperature is regulated to 500-750 ℃, zirconium oxide in xenotime can be fully decomposed and reacts with sulfuric acid to form zirconium sulfate which is not easy to hydrolyze under low acidity, and a foundation is provided for subsequent recovery of zirconium sulfate with higher purity. Specifically, when the roasting temperature is lower than 500 ℃, the zirconium oxide in xenotime is difficult to decompose, and the recovery rate of zirconium element is affected; when the roasting temperature is higher than 750 ℃, overburning can occur, so that the roasting material is formed into hard blocks, the effect of subsequent acid leaching treatment is affected, and the recovery rate of rare earth elements is reduced.

Alternatively, the baking temperature may be 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃, 620 ℃, 640 ℃, 660 ℃, 680 ℃, 700 ℃, 720 ℃, 740 ℃, or 750 ℃, and the baking temperature may be selected in the range of 500 ℃ to 750 ℃ as appropriate, for example, 500 ℃ to 600 ℃, 620 ℃ to 750 ℃, or 650 ℃ to 750 ℃.

In some of these embodiments, the xenotime composition comprises, in mass percent, 20% -60% rare earth oxide, 5% -20% zirconia, and 10% -30% phosphorus pentoxide.

In some of these embodiments, the firing temperature is 650 ℃ to 700 ℃. When the roasting temperature is within the range, not only can the zirconium oxide in xenotime be fully decomposed and the recovery rate of zirconium sulfate be improved and the recovery rate of rare earth elements be ensured, but also the reaction of iron powder and the xenotime can be promoted, the effective separation of the rare earth elements and phosphorus elements can be realized, and the recovery rate of zirconium sulfate is further improved. In addition, when the firing temperature is too high, the firing material may be agglomerated, increasing the production cost.

In some of these embodiments, the iron powder is mixed with P in xenotime ₂ O ₅ The mass ratio of (1-0.5): 1. when the mass ratio is used, the phosphorus element in xenotime can fully react with iron powder, and the separation efficiency of the phosphorus element and the rare earth element is improved. Alternatively, iron powder and P in xenotime ₂ O ₅ The mass ratio of (2) may be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, and the mass ratio may be (0.5-1): other suitable choices are made within the scope of 1. Note that P in xenotime ₂ O ₅ The mass of (2) can be based on the mass of xenotime and P ₂ O ₅ Is calculated by the mass content of (2).

In some of these embodiments, the mass ratio of concentrated sulfuric acid to xenotime is (1-2): 1. when the mass ratio is used, the rare earth elements in xenotime can be fully reacted with concentrated sulfuric acid, so that the recovery rate of the rare earth elements is improved. Optionally, the mass ratio of concentrated sulfuric acid to xenotime can be 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1 or 2:1, which can also be in (1-2): other suitable choices are made within the scope of 1.

In one specific example, the sulfuric acid is concentrated sulfuric acid.

In some embodiments, the calcination time is 1.5 h to 3 h. Alternatively, the roasting time may be 1.5 h, 2 h, 2.5 h or 3 h, and the roasting time may be selected from the range of 1.5 h to 3 h.

In some of these embodiments, the firing is performed in an oxygen-containing atmosphere.

In a specific example, the firing atmosphere includes at least one of oxygen and air.

S20, leaching the roasting material, and carrying out solid-liquid separation to obtain solid and leaching liquid, wherein the concentration of hydrogen ions in a leaching treatment system is 0.5 mol/L-1.5 mol/L.

It will be appreciated that leaching the roast allows the rare earth sulphate to be dissolved which is more soluble, while the relatively poorly soluble iron phosphate remains in the solid phase. Meanwhile, the concentration of hydrogen ions in the leaching treatment system is regulated and controlled within the range of 0.5 mol/L to 1.5 mol/L, so that rare earth element sulfate can be fully dissolved, the recovery rate of rare earth elements is further improved, and under the concentration of the hydrogen ions, the characteristic that zirconium sulfate is not easy to hydrolyze under low acidity can be utilized, so that the zirconium sulfate is hardly decomposed, the zirconium sulfate is kept in solids, and the purity of the recovered rare earth element compound is ensured. Further, in the leaching treatment process, unreacted sulfuric acid is dissolved in water, so that the hydrogen ion concentration of the system is increased, and the hydrogen ion concentration of the system can be reduced by regulating and controlling the adding amount of roasting materials and leaching treatment and/or adding a proper amount of inorganic alkali into the system, so that the hydrogen ion concentration in the system is controlled to be 0.5-1.5 mol/L.

Alternatively, the concentration of hydrogen ions in the leaching treatment system may be 0.5 mol/L, 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, 0.9 mol/L, 1.0 mol/L, 1.1 mol/L, 1.2 mol/L, 1.3 mol/L, 1.4 mol/L or 1.5 mol/L, and the concentration of hydrogen ions in the leaching treatment system may be selected within the range of 0.5 mol/L to 1.5 mol/L. When the concentration of hydrogen ions in the system is less than 0.5 mol/L, or when the concentration of hydrogen ions in the system is more than 1.5 mol/L, the recovery rate of rare earth elements is affected.

In some embodiments, the concentration of hydrogen ions in the leaching treatment system is 0.8 mol/L to 1.5 mol/L. When the concentration of hydrogen ions in the leaching treatment is in the range, rare earth sulfate in the roasting material can be fully dissolved, and the rare earth sulfate and ferric phosphate can be hardly decomposed, so that the recovery rate of rare earth elements is further improved.

In some embodiments, the liquid-solid ratio of the liquid adding amount of the leaching treatment to the roasting material is (4-8) L:1 Kg. The soluble rare earth sulfate in the roasting material can be fully dissolved in the liquid-solid ratio. Alternatively, the liquid-to-solid ratio of the liquid charge to the roast material of the leaching treatment may be 4L: 1 Kg, 5L: 1 Kg, 6L: 1 Kg, 7L: 1 Kg or 8L:1 Kg, the above-mentioned liquid-solid ratio may be (4 to 8) L: other suitable choices are made within the scope of 1 Kg.

In some of these embodiments, an inorganic base is used to regulate the hydrogen ion concentration in the leaching treatment system. Optionally, the inorganic base comprises at least one of magnesium oxide, ammonia, ammonium carbonate, and ammonium bicarbonate. Understandably, the type and the addition amount of the inorganic base can be determined by a person skilled in the art according to actual needs, so as to control the concentration of hydrogen ions in the leaching treatment system to be 0.5 mol/L-1.5 mol/L.

In some embodiments, the leaching process is performed for 4-6 hours. Optionally, the leaching time may be 4 h, 4.5 h, 5 h, 5.5 h or 6 h, and the leaching time may be selected within a range of 4-6 h.

In some of these embodiments, the leaching process is performed at ambient temperature. Illustratively, the normal temperature is 25 ℃ + -5 ℃.

S30, carrying out acid dissolution treatment on the solid, and then carrying out crystallization treatment on the solution obtained by the acid dissolution treatment to prepare zirconium sulfate, wherein the concentration of hydrogen ions in an acid dissolution treatment system is 4-8 mol/L.

It is understood that the acid-dissolution treatment of the solid can dissolve the zirconium sulfate which is easily dissolved in the acid and remain in the solution in the form of ions, while the iron phosphate which is relatively insoluble in the acid remains in the solid phase, and the solid phase containing the iron phosphate and the solution containing sulfate ions and zirconium ions can be obtained by the solid-liquid separation treatment. In the acid dissolution treatment, impurities such as excessive iron powder contained in the solid react with hydrogen ions, so that the concentration of the hydrogen ions is reduced, namely, if the concentration of the hydrogen ions in the acid dissolution treatment system is not regulated and controlled, the concentration of the hydrogen ions in a solution obtained by the acid dissolution treatment is less than 4 mol/L, and the separation effect of zirconium sulfate and ferric phosphate is affected.

Further, the concentration of hydrogen ions in the acid dissolution treatment system is controlled within the range of 4 mol/L to 8 mol/L, so that zirconium sulfate can be fully dissolved, and meanwhile, the iron phosphate is ensured to be insoluble. Alternatively, the concentration of hydrogen ions in the acid-soluble treatment system may be 4 mol/L, 4.5 mol/L, 5mol/L, 5.5 mol/L, 6 mol/L, 6.5 mol/L, 7 mol/L, 7.5 mol/L or 8 mol/L, and the concentration of hydrogen ions in the acid-soluble treatment system may be selected from the range of 4 mol/L to 8 mol/L. When the concentration of hydrogen ions in the acid-soluble treatment system is less than 4 mol/L, zirconium sulfate in the solid cannot be completely dissolved, so that the recovery rate of the zirconium sulfate is affected; when the concentration of hydrogen ions in the acid-soluble treatment system is more than 8 mol/L, the ferric phosphate can be dissolved, and the purity of the recovered zirconium sulfate is influenced. Furthermore, the concentration of hydrogen ions in the acid dissolution treatment can be regulated and controlled by the content and concentration of inorganic acid adopted in the acid dissolution treatment, for example, if strong acid such as sulfuric acid is adopted to regulate and control the concentration of hydrogen ions, the strong acid is completely dissociated in water, so that an acid dissolution treatment environment with the concentration of hydrogen ions of 4-8 mol/L can be obtained by adopting 2-4 mol/L sulfuric acid aqueous solution.

In some embodiments, the concentration of hydrogen ions in the acid-soluble treatment system is 5mol/L to 7.5 mol/L. When the concentration of hydrogen ions is in this range, the recovery rate of zirconium sulfate and iron phosphate can be further improved by the acid-dissolution treatment.

In some embodiments, the ratio of the liquid adding amount of the acid dissolution treatment to the solid is (1-4) L:1 Kg. For this liquid-solid ratio, zirconium sulfate in the solid can be sufficiently dissolved. Alternatively, the liquid-solid ratio of the amount of the acid-soluble treatment to the solid may be 1: 1. 1: 2. 1:3 or 1:4, the liquid-solid ratio may be (1 to 4) L: other suitable choices are made within the scope of 1 Kg.

In some embodiments, the temperature of the acid dissolution treatment is 70 ℃ to 90 ℃. Alternatively, the temperature of the acid-dissolving treatment may be 70 ℃, 72 ℃, 74 ℃, 76 ℃, 80 ℃, 82 ℃, 84 ℃, 86 ℃, 88 ℃ or 90 ℃, and the temperature of the acid-dissolving treatment may be selected from the range of 70 ℃ to 90 ℃ as appropriate.

In some embodiments, the acid dissolution treatment is performed for 2-4 hours. Alternatively, the acid-dissolving treatment time may be 2 h, 2.5 h, 3 h, 3.5 h or 4 h, and the acid-dissolving treatment time may be selected from the range of 2 h to 4 h.

In some of these embodiments, the acid solution used for the acid dissolution treatment comprises an aqueous sulfuric acid solution. It is understood that the use of aqueous sulfuric acid can dissolve zirconium sulfate without introducing other impurity ions. Further, the concentration of hydrogen ions in the acid dissolution treatment system can be regulated to 4-8 mol/L by a person skilled in the art through regulating and controlling the concentration of the sulfuric acid aqueous solution and the liquid-solid ratio of the sulfuric acid aqueous solution to the solid.

In one specific implementation, the acid dissolution treatment is performed with 2.5 mol/L to 3.75 mol/L sulfuric acid aqueous solution.

In some of these embodiments, the crystallization process comprises:

concentrating the solution obtained by acid dissolution treatment, controlling the concentration of hydrogen ions in a reaction end point system to be more than 5mol/L, and carrying out solid-liquid separation to obtain zirconium sulfate.

It is understood that iron powder remaining in the solids during the acid-dissolution treatment reacts with hydrogen ions to consume part of the hydrogen ions, resulting in a decrease in the hydrogen ion concentration of the solution obtained by the acid-dissolution treatment. In order to ensure the yield of crystallization treatment, the concentration of hydrogen ions at the end point of crystallization concentration reaction is controlled to be more than 5mol/L in the embodiment, so that zirconium sulfate with higher yield and purity can be obtained. Specifically, as the crystallization concentration reaction proceeds, the concentration of zirconium ions in the system increases and the concentration of hydrogen ions decreases, so that the acidity of the system decreases, which leads to hydrolysis of zirconium, and therefore, the concentration of hydrogen ions at the reaction end point needs to be controlled within a range of more than 5mol/L to improve the yield of zirconium sulfate.

In some embodiments, the method further comprises:

washing the solid obtained by acid dissolution treatment to prepare the ferric phosphate.

It will be appreciated that washing the solids resulting from the acid dissolution treatment may remove impurities therein, such as calcium and magnesium.

In some implementations, the solid obtained by acid dissolution treatment is washed by dilute acid, and optionally sulfuric acid with the concentration of 0.5 mol/L-1 mol/L is used for washing the solid obtained by acid dissolution treatment, wherein the liquid-solid ratio of the sulfuric acid to the solid obtained by acid dissolution treatment is (3-4) L:1 Kg.

S40, preparing rare earth element compounds through leaching liquid.

The steps S40 and S30 may be performed simultaneously, or may be performed first, then S40, and then S30.

In some of these embodiments, step S40 includes: and adjusting the pH value of the leaching solution to 3.5-4.5, adding oxalic acid for precipitation treatment, and carrying out solid-liquid separation to obtain rare earth element oxalate.

Understandably, al can be removed by controlling the pH of the leachate ³⁺ 、Fe ³⁺ Ca and Ca ²⁺ And (3) adding oxalic acid into the impurity ions to enable the rare earth element ions to form oxalate precipitates, so that rare earth element oxalate products can be obtained. Further, the pH of the leachate may be adjusted to 3.5 to 4.5 by adding an appropriate amount of an inorganic base, which illustratively includes at least one of magnesium oxide, ammonia, ammonium carbonate and ammonium bicarbonate.

In some embodiments, the precipitation process is at a temperature of 60 ℃ to 75 ℃. Alternatively, the temperature of the precipitation treatment may be 60 ℃, 61 ℃, 62 ℃, 63 ℃, 64 ℃, 65 ℃, 66 ℃, 67 ℃, 68 ℃, 69 ℃, 70 ℃, 71 ℃, 72 ℃, 73 ℃, 74 ℃ or 75 ℃, and the temperature of the precipitation treatment may be selected from the range of 60 ℃ to 75 ℃ as appropriate.

In some of these embodiments, step S40 includes:

extracting the leaching solution by using an extracting agent to prepare the rare earth element compound.

Optionally, the extractant includes at least one of a P204 extractant, a P507 extractant, and an epoxy acid extractant. It is understood that rare earth ions in the leachate can be extracted by an extraction treatment, whereby a rare earth compound can be produced.

The method comprises the steps of mixing and roasting xenotime, iron powder and sulfuric acid at a specific temperature, and fully reacting the three raw materials at a relatively high roasting temperature to obtain a roasting material containing rare earth element sulfate, zirconium sulfate and ferric phosphate; leaching the roasted material to dissolve soluble rare earth element sulfate to obtain leaching solution containing rare earth element ions, and controlling the concentration of hydrogen ions in the leaching treatment to hardly decompose zirconium sulfate by utilizing the characteristic that zirconium sulfate is not easy to hydrolyze under low acidity, so as to obtain a solid containing zirconium sulfate and ferric phosphate; then, the solid is subjected to acid dissolution treatment under the specific hydrogen ion concentration, under the condition, the solubility of zirconium sulfate is larger than that of ferric phosphate, so that the zirconium sulfate can be dissolved, and the ferric phosphate is hardly dissolved, thereby realizing the separation of the zirconium sulfate and the ferric phosphate, and then, the solution obtained by the acid dissolution treatment is subjected to crystallization treatment, so that the zirconium sulfate solid can be obtained. And meanwhile, carrying out corresponding post-treatment on the leaching solution, and extracting rare earth elements from the leaching solution to prepare the rare earth element compound. The xenotime method has synergistic effect between the steps, effectively improves the recovery rate of rare earth elements, and simultaneously realizes the recovery and utilization of zirconium elements.

In addition, the method has simple process flow, small consumption of sulfuric acid raw materials and easy mass production.

The following are specific examples.

Example 1

(1) Roasting

500 g xenotime, 66 g iron powder and 550 g sulfuric acid are mixed, and after being uniformly mixed, the mixture is roasted in an air atmosphere at 600 ℃ for 3 h, so as to obtain a roasted material. The xenotime of this example comprises, among other things, 42 wt% rare earth oxide, 15 wt% zirconia and 22 wt% phosphorus pentoxide with sulfuric acid being a 98 vol% aqueous sulfuric acid solution. The rare earth element oxide does not include zirconia.

(2) Leaching treatment

Adding water into the roasting material, and leaching at normal temperature, wherein the ratio of the water adding amount to the liquid-solid ratio of the roasting material is 4L to 1 Kg, so that the hydrogen ion concentration of the system can be controlled to be 1 mol/L, and the leaching time is 4 h. And filtering to obtain solid and leachate.

(3) Preparation of zirconium sulfate

Mixing and stirring the solid and the sulfuric acid aqueous solution, carrying out acid dissolution treatment at 80 ℃, carrying out stirring reaction for 3 h, and filtering to obtain an acid dissolution treatment solution and solid, wherein the concentration of the sulfuric acid aqueous solution is 2.75 mol/L, and the liquid-solid ratio of the sulfuric acid aqueous solution to the solid is 2L/1 Kg, so that an acid dissolution treatment environment with the hydrogen ion concentration of 5.5 mol/L can be constructed.

Concentrating the solution obtained by acid dissolution, controlling the concentration of hydrogen ions in a reaction end point system to be 5.5 mol/L, and obtaining zirconium sulfate crystals after the crystals are fully separated out.

(4) Preparation of ferric phosphate

Washing the solid obtained by acid dissolution treatment by adopting 0.5 mol/L sulfuric acid aqueous solution to obtain an iron phosphate product, wherein the liquid-solid ratio of the 0.5 mol/L sulfuric acid aqueous solution to the solid obtained by acid dissolution treatment is 3L to 1 Kg.

(5) Preparation of rare earth element oxalate

Adjusting pH of the leaching solution to 3.5 with ammonia water, filtering, and collecting filtrate. Adding 400 g oxalic acid into the filtrate, carrying out precipitation treatment at 65 ℃, and obtaining rare earth element oxalate after complete precipitation.

Example 2

(1) Roasting

1000 g xenotime, 224 g iron powder and 1800 g sulfuric acid were mixed and after uniform mixing, baked in an air atmosphere at 700 ℃ for 2.5 h to obtain a baked material. The xenotime of this example comprises 55 wt% rare earth oxide, 11 wt% zirconia and 28 wt% phosphorus pentoxide, and sulfuric acid is 98 vol% sulfuric acid in water, except that the rare earth oxide does not comprise zirconia.

(2) Leaching treatment

Adding water into the roasting material, and carrying out water leaching treatment at normal temperature, wherein the ratio of the water addition amount to the liquid-solid ratio of the roasting material is 4.5L to 1 Kg, so that the concentration of hydrogen ions in the system can be controlled to be 1.5 mol/L, and the leaching treatment time is 3 h. And filtering to obtain solid and leachate.

(3) Preparation of zirconium sulfate

Mixing and stirring the solid and the sulfuric acid aqueous solution, carrying out acid dissolution treatment at the temperature of 85 ℃, carrying out stirring reaction for 3.5 and h, and filtering to obtain the solid of the solution obtained by the acid dissolution treatment, wherein the concentration of the sulfuric acid aqueous solution is 3.6 mol/L, and the liquid-solid ratio of the sulfuric acid aqueous solution to the solid is 3 L:1 Kg, thereby constructing the acid dissolution treatment environment with the hydrogen ion concentration of 7.2 mol/L.

Concentrating the solution obtained by acid dissolution, controlling the concentration of hydrogen ions in a reaction end point system to be 5.8 mol/L, and obtaining zirconium sulfate crystals after the crystals are fully separated out.

(4) Preparation of ferric phosphate

Washing the solid obtained by acid dissolution treatment by adopting 0.8 mol/L sulfuric acid aqueous solution to obtain an iron phosphate product, wherein the liquid-solid ratio of the 0.8 mol/L sulfuric acid aqueous solution to the solid obtained by acid dissolution treatment is 3.5L/1 Kg.

(5) Preparation of rare earth element oxalate

Adjusting pH of the leaching solution to 4 with ammonia water, filtering, and collecting filtrate. Adding 1100 g oxalic acid into the filtrate, precipitating at 70deg.C, and obtaining rare earth element oxalate after precipitation.

Example 3

The preparation of example 3 and the xenotime composition are essentially the same as in example 2 except that: the calcination temperature in step (1) was 500 ℃.

Example 4

The preparation of example 4 and the xenotime composition are essentially the same as in example 2 except that: the firing temperature in step (1) was 750 ℃.

Example 5

The preparation of example 5 and the xenotime composition are essentially the same as in example 2 except that: in the leaching treatment process of the step (2), the liquid-solid ratio of the water addition amount to the roasting material is 7.5L to 1 Kg, so that the hydrogen ion concentration of the system can be controlled to be 0.5 mol/L.

Example 6

The preparation of example 6 and the xenotime composition are essentially the same as in example 2 except that: in the leaching treatment process of the step (2), the liquid-solid ratio of the water addition amount to the roasting material is 5.4L to 1 Kg, so that the hydrogen ion concentration of the system can be controlled to be 1.2 mol/L.

Example 7

The preparation of example 7 and the xenotime composition are essentially the same as in example 2 except that: in the acid dissolution treatment process of the step (3), the concentration of the sulfuric acid aqueous solution is 2 mol/L, and the liquid-solid ratio of the sulfuric acid aqueous solution to the solid is 3.8L/1 Kg, so that an acid dissolution treatment environment with the hydrogen ion concentration of 5mol/L can be constructed.

Example 8

The preparation of example 8 and the xenotime composition are essentially the same as in example 2 except that: in the acid dissolution treatment process of the step (3), the concentration of the sulfuric acid aqueous solution is 3 mol/L, and the liquid-solid ratio of the sulfuric acid aqueous solution to the solid is 4L to 1 Kg, so that an acid dissolution treatment environment with the hydrogen ion concentration of 8 mol/L can be constructed.

Comparative example 1

The preparation of comparative example 1 and the xenotime composition were essentially the same as in example 2, except that: the calcination temperature in step (1) was 400 ℃.

Comparative example 2

The preparation of comparative example 2 and the xenotime composition were essentially the same as in example 2, except that: in the leaching treatment process of the step (2), the liquid-solid ratio of the water addition amount to the roasting material is 8.4L/1 Kg, and the liquid-solid ratio of the water addition amount to the roasting material is 2L/1 Kg, so that the hydrogen ion concentration of the system can be controlled to be 0.2 mol/L.

Comparative example 3

The preparation of comparative example 3 and the xenotime composition were essentially the same as in example 2, except that: in the leaching treatment process of the step (2), the liquid-solid ratio of the water addition amount to the roasting material is 3L to 1 Kg, and the liquid-solid ratio of the water addition amount to the roasting material is 4.2L to 1 Kg, so that the concentration of hydrogen ions in the system can be controlled to be 2 mol/L.

Comparative example 4

The preparation of comparative example 4 and the xenotime composition were essentially the same as in example 2, except that: in the acid dissolution treatment process of the step (3), the concentration of the sulfuric acid aqueous solution is 1 mol/L, and the liquid-solid ratio of the sulfuric acid aqueous solution to the solid is 6L to 1 Kg, so that an acid dissolution treatment environment with the concentration of hydrogen ions of 2 mol/L can be constructed.

Comparative example 5

The preparation of comparative example 5 and the xenotime composition were essentially the same as in example 2, except that: in the acid dissolution treatment process of the step (3), the concentration of the sulfuric acid aqueous solution is 5mol/L, and the liquid-solid ratio of the sulfuric acid aqueous solution to the solid is 3L to 1 Kg, so that an acid dissolution treatment environment with the hydrogen ion concentration of 10 mol/L can be constructed.

The roasting temperature, the leaching hydrogen ion concentration and the acid-soluble hydrogen ion concentration in the methods of examples 1 to 8 and comparative examples 1 to 5 are shown in the following table 1:

TABLE 1

The rare earth element recovery rates, zirconium element recovery rates, and phosphorus element recovery rates of examples 1 to 8 and comparative examples 1 to 5 are shown in table 2, and the recovery rates are calculated according to the following formulas:

rare earth recovery = (rare earth oxalate weight x total rare earth weight percentage)/(xenotime weight x total rare earth weight percentage in xenotime) ×100%;

zirconium element recovery = (weight of zirconium sulfate x weight percent of zirconium)/(weight of xenotime x weight percent of zirconium in xenotime) ×100%;

phosphorus recovery = (weight of iron phosphate x weight percent of phosphorus)/(weight of xenotime x weight percent of phosphorus in xenotime) ×100%.

TABLE 2

From table 2 above, the recovery rate of rare earth in examples 1 to 8 is not lower than 95%, the recovery rate of zirconium is not lower than 90%, and the recovery rate of phosphorus is not lower than 91%, which indicates that the recovery method of the present application can effectively improve the recovery rate of rare earth element, and simultaneously realize the recovery of zirconium and phosphorus.

Compared with the embodiment 2, the roasting temperature of the comparative example 1 is too low, and the recovery rates of rare earth, zirconium and phosphorus are obviously reduced, which shows that the roasting temperature of 500-750 ℃ is adopted in the method for fully reacting the three raw materials, so that the rare earth and zirconium in xenotime are effectively converted into corresponding sulfate, and the recovery rate is ensured. Further, the firing temperature of example 4 is higher than that of example 3, and the recovery rate of rare earth and zirconium element is slightly lower than that of example 2, but the recovery rate of rare earth and zirconium element of example 4 is slightly higher than that of example 3, but the production cost is increased due to the relatively higher firing temperature, that is, the firing temperature of 650 ℃ to 700 ℃ is adopted, so that the relationship between the recovery rate and the production cost can be balanced better.

Compared with example 2, the concentration of hydrogen ions in the leaching treatment of comparative example 2 is too low, the concentration of hydrogen ions in the leaching treatment of comparative example 3 is too high, and the recovery rates of comparative example 2 and comparative example 3 are both reduced, which shows that the recovery rate of rare earth can be effectively improved by controlling the concentration of hydrogen ions in the leaching treatment in the range of 0.5 mol/L to 1.5 mol/L, and the recovery rate of zirconium element and phosphorus element can also be improved. Further, compared with examples 2 and 6, the concentration of hydrogen ions in the leaching treatment in example 5 is lower, and the rare earth recovery rate is slightly reduced, which means that the recovery rate of rare earth can be further improved by controlling the concentration of hydrogen ions in the leaching treatment to 0.8 mol/L to 1.5 mol/L.

The too low concentration of acid-dissolved hydrogen ions in comparative example 4 and the too high concentration of acid-dissolved hydrogen ions in comparative example 5, as compared with example 2, showed a decrease in recovery of both zirconium and phosphorus elements in comparative example 4 and comparative example 5, indicating that the concentration of acid-dissolved hydrogen ions has an effect on the zirconium recycling effect of xenotime. Further, the concentration of hydrogen ions in the acid-soluble treatment of example 7 was lower than that of example 2, zirconium sulfate in the solid was not sufficiently dissolved, so that the recovery rate of zirconium element was slightly lowered, and the recovery rate of phosphorus element was also lowered; the higher concentration of hydrogen ions in the acid dissolution treatment in example 8 causes the decomposition of ferric phosphate, so the recovery rate of phosphorus element is slightly reduced, which shows that the recovery rate of zirconium element and phosphorus element can be further improved by controlling the concentration of hydrogen ions in the acid dissolution treatment to 5.5 mol/L-7.5 mol/L.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.

Claims (10)

1. A process for the recovery of rare earth, zirconium and iron phosphate from the high temperature roasting of concentrated sulfuric acid to break up xenotime comprising the steps of:

mixing xenotime, iron powder and sulfuric acid for roasting to obtain a roasting material, wherein the roasting temperature is 500-750 ℃;

leaching the roasting material, and carrying out solid-liquid separation to obtain solid and leaching liquid, wherein the concentration of hydrogen ions in a leaching treatment system is 0.5 mol/L-1.5 mol/L;

carrying out acid dissolution treatment on the solid, and then carrying out crystallization treatment on a solution obtained by the acid dissolution treatment to prepare zirconium sulfate, wherein the concentration of hydrogen ions in an acid dissolution treatment system is 4-8 mol/L;

and preparing a rare earth element compound by the leaching solution.

2. The method of claim 1, wherein the firing temperature is 650 ℃ to 700 ℃.

3. The method of claim 1, wherein the concentration of hydrogen ions in the leaching treatment system is 0.8 mol/L to 1.5 mol/L.

4. The method of claim 1, wherein the concentration of hydrogen ions in the acid-soluble treatment system is 5mol/L to 7.5 mol/L.

5. The method according to any one of claims 1 to 4, wherein the method satisfies at least one of the following (1) - (5):

(1) P in the iron powder and xenotime ₂ O ₅ The mass ratio of (1-0.5): 1, a step of;

(2) The mass ratio of the sulfuric acid to the xenotime is (1-2): 1, a step of;

(3) The sulfuric acid is concentrated sulfuric acid;

(4) The roasting time is 1.5-3 hours;

(5) The calcination is performed in an oxygen-containing atmosphere.

6. The method according to any one of claims 1 to 4, wherein the method satisfies at least one of the following (1) - (3):

(1) The liquid-solid ratio of the liquid adding amount of the leaching treatment to the roasting material is (4-8) L:1 Kg;

(2) The leaching treatment time is 4-6 hours;

(3) And regulating and controlling the concentration of hydrogen ions in the leaching treatment system by adopting inorganic alkali.

7. The method according to any one of claims 1 to 4, wherein the method satisfies at least one of the following (1) - (3):

(1) The liquid adding amount of the acid dissolution treatment and the liquid-solid ratio of the solid are (1-4) L:1 Kg;

(2) The temperature of the acid dissolution treatment is 70-90 ℃;

(3) The acid dissolution treatment time is 2-4 hours.

8. The method of any one of claims 1-4, wherein the acid solution used for the acid dissolution treatment comprises an aqueous sulfuric acid solution.

9. The method according to any one of claims 1 to 4, wherein the crystallization treatment comprises:

concentrating the solution obtained by acid dissolution, controlling the concentration of hydrogen ions in a reaction end point system to be more than 5mol/L, and carrying out solid-liquid separation to obtain zirconium sulfate.

10. The method of any one of claims 1 to 4, wherein the step of preparing the rare earth element compound from the leachate comprises:

adjusting the pH value of the leaching solution to 3.5-4.5, adding oxalic acid for precipitation treatment, and carrying out solid-liquid separation to obtain rare earth element oxalate;

or extracting the leaching solution by using an extracting agent to prepare the rare earth element compound.