Method for removing impurities from rare earth sulfate leaching solution

Abstract

The present invention discloses a method for removing impurities from a rare earth sulfate leaching solution. The method comprises the following steps: (1) adding an ammonium bicarbonate solution having a concentration of 2 to 3.6 mol / L to the rare earth sulfate leaching solution at a flow rate of 3 to 5.5 mL / min until the pH of the reaction system is 3.7 to 4.5 to form a first mixed solution; (2) adding magnesium oxide to the first mixed solution to form a second mixed solution; reacting the second mixed solution to obtain a leaching solution after impurities are removed. The method can effectively reduce the content of iron and aluminum elements in the rare earth sulfate leaching solution.

Description

Technical Field

[0001] The invention relates to a method for removing impurities from rare earth sulfate leaching solution, in particular to a method for reducing the contents of iron and aluminum in the rare earth sulfate leaching solution. Background Art

[0002] In the rare earth hydrometallurgy process, rare earth concentrate is usually added with concentrated sulfuric acid and a small amount of iron powder for high temperature roasting to form rare earth roasted ore; the rare earth roasted ore is water-leached and filtered to obtain rare earth sulfate leaching solution. The rare earth sulfate leaching solution contains impurities such as iron and aluminum, which affect the quality of the products in the subsequent processes. Therefore, it is necessary to remove impurities in the rare earth sulfate leaching solution.

[0003] CN112281003B discloses a method for removing impurities from low-grade rare earth sulfate leaching solution. Lime powder is added to the rare earth sulfate leaching solution to make the pH of the leaching solution reach 1.5-2.5, and then magnesium oxide slurry is added to make the pH of the rare earth sulfate leaching solution reach 4.5-5.5, and then the solution is allowed to stand for clarification to obtain a precipitate. This method is suitable for low-grade rare earth sulfate leaching solution, but the impurity removal effect on iron and aluminum elements in the rare earth sulfate leaching solution is not high.

[0004] CN114293012A discloses a method for reducing the iron and aluminum content in rare earth sulfate leaching solution. Lime milk is passed into rare earth sulfuric acid leaching solution containing iron and aluminum elements to obtain a first mixed solution; magnesium oxide slurry is passed into the first mixed solution to obtain a second mixed solution; the second mixed solution is reacted, and then solid-liquid separation is performed to obtain a rare earth sulfate solution. The impurity removal effect of this method on iron and aluminum elements needs to be improved. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for removing impurities from rare earth sulfate leaching solution, which can effectively reduce the content of iron and aluminum elements in rare earth sulfate leaching solution. Further, it can reduce the loss of rare earth elements in rare earth sulfate leaching solution. The above object is achieved by the following technical solution.

[0006] The present invention provides a method for removing impurities from a rare earth sulfate leaching solution, comprising the following steps:

[0007] (1) adding an ammonium bicarbonate solution having a concentration of 2 to 3.6 mol / L into the rare earth sulfate leaching solution at a flow rate of 3 to 5.5 mL / min until the pH of the reaction system is 3.7 to 4.5, thereby forming a first mixed solution;

[0008] (2) adding magnesium oxide to the first mixed solution to form a second mixed solution; reacting the second mixed solution to obtain a decontaminated leaching solution.

[0009] According to the method of the present invention, preferably, the ammonium bicarbonate solution is added to the rare earth sulfate leaching solution at 15-30°C.

[0010] According to the method of the present invention, preferably, the magnesium oxide is added to the first mixed liquid in the form of powder or slurry.

[0011] According to the method of the present invention, preferably, magnesium oxide is added to the first mixed solution in the form of slurry, and the flow rate of the magnesium oxide slurry is 0.2-2.0 mL / min.

[0012] According to the method of the present invention, preferably, the magnesium oxide slurry is formed by magnesium oxide and water in a mass volume ratio of 1:(3-5) kg / L.

[0013] According to the method of the present invention, preferably, magnesium oxide is added to the first mixed solution until the pH value is 4.8 to 5.5 to form a second mixed solution.

[0014] According to the method of the present invention, preferably, the pH of the rare earth sulfate leaching solution is 0.5-2.5.

[0015] According to the method of the present invention, preferably, in the rare earth sulfate leaching solution, the content of rare earth elements is 30-37 g / L, the content of iron elements is 10-12 g / L, and the content of aluminum elements is 1-2 g / L;

[0016] The content of rare earth elements is calculated as rare earth oxides, the content of iron elements is calculated as Fe2O3, and the content of aluminum elements is calculated as Al2O3.

[0017] According to the method of the present invention, preferably, in the leaching solution after impurities removal, the iron content is ≤0.0013 g / L, and the aluminum content is ≤0.0012 g / L.

[0018] According to the method of the present invention, preferably, the reaction time of the second mixed solution is 1 to 5 hours.

[0019] The method of the present invention can effectively reduce the content of iron and aluminum in the rare earth sulfate leaching solution. Further, the method can reduce the loss of rare earth elements in the rare earth sulfate leaching solution. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0021] The present invention first adds an ammonium bicarbonate solution of a specific concentration into a rare earth sulfuric acid leaching solution at a certain flow rate to form a first mixed solution of a specific pH, and then adds magnesium oxide to the first mixed solution. In this way, the contents of iron and aluminum elements in the rare earth sulfuric acid leaching solution can be effectively reduced, and the loss rate of rare earth elements is small.

[0022] The method for removing impurities from rare earth sulfate leaching solution of the present invention comprises: (1) the step of adding ammonium bicarbonate solution; and (2) the step of adding magnesium oxide and reacting. The following is a detailed description.

[0023] Steps for adding ammonium bicarbonate solution

[0024] The ammonium bicarbonate solution is added into the rare earth sulfate leaching solution to form a first mixed solution.

[0025] Rare earth sulfate leaching solution is a liquid substance obtained by leaching and filtering rare earth roasted ore formed by high-temperature roasting of rare earth concentrate, concentrated sulfuric acid and iron powder. The method of forming rare earth sulfate leaching solution is a conventional method in the art. For example, rare earth concentrate, concentrated sulfuric acid and iron powder are fully mixed, added to a rotary kiln, and roasted at 700-900°C to obtain rare earth roasted ore. The rare earth roasted ore is leached in water to obtain a rare earth roasted ore slurry having a rare earth element content (in terms of rare earth oxides) of 30-40 g / L. The rare earth roasted ore slurry is filtered through a plate filter to obtain a rare earth sulfate leaching solution.

[0026] The pH of the rare earth sulfate leaching solution may be 0.5 to 2.5, preferably 0.5 to 2.0, and more preferably 1.0 to 2.0.

[0027] The rare earth element content in the rare earth sulfate leaching solution is 30 to 37 g / L, preferably 30 to 36 g / L, and more preferably 32 to 36 g / L. The rare earth element content is calculated as rare earth oxide.

[0028] The content of iron in the rare earth sulfate leaching solution is 10 to 12 g / L, preferably 10.5 to 12 g / L, and more preferably 10.5 to 11.6 g / L. The content of iron is calculated as Fe2O3.

[0029] The content of aluminum in the rare earth sulfate leaching solution is 1 to 2 g / L, preferably 1 to 1.8 g / L, and more preferably 1 to 1.5 g / L. The content of aluminum is calculated as Al2O3.

[0030] The concentration of the ammonium bicarbonate solution is 2-3.6 mol / L, preferably 2.1-3.55 mol / L, and more preferably 2.2-3.5 mol / L. This can reduce the content of iron and aluminum in the leaching solution after impurity removal, and can reduce the loss rate of rare earth elements.

[0031] The flow rate of adding the ammonium bicarbonate solution to the rare earth sulfate leaching solution is 3-5.5 mL / min, preferably 3-5 mL / min, and more preferably 3.3-4 mL / min. This helps to reduce the content of iron and aluminum elements in the leaching solution after impurity removal, and helps to reduce the loss rate of rare earth elements.

[0032] The ammonium bicarbonate solution is added to the rare earth sulfate leaching solution at 15-30° C. Preferably, the ammonium bicarbonate solution is added to the rare earth sulfate leaching solution at 20-25° C.

[0033] In the present invention, an ammonium bicarbonate solution is added to the rare earth sulfate leaching solution until the pH is 3.7 to 4.5 to form a first mixed solution. Preferably, the pH is 3.8 to 4.2. More preferably, the pH is 3.8 to 4. This helps to reduce the content of iron and aluminum elements in the leaching solution after impurity removal, and helps to reduce the loss rate of rare earth elements.

[0034] Steps of adding magnesium oxide and reacting

[0035] The magnesium oxide is added to the first mixed solution to form a second mixed solution, and the second mixed solution is reacted to obtain a leaching solution after impurities are removed. Preferably, the magnesium oxide is added to the first mixed solution under stirring.

[0036] Magnesium oxide can be used in the form of powder or slurry. In some embodiments, magnesium oxide powder is added to the first mixed solution. In other embodiments, magnesium oxide slurry is added to the first mixed solution.

[0037] The magnesium oxide slurry can be formed by reacting magnesium oxide and water. The mass volume ratio of magnesium oxide to water is 1: (3-5) kg / L, preferably 1: (3.3-4.8) kg / L, and more preferably 1: (3.5-4.5) kg / L.

[0038] The flow rate of adding the magnesium oxide slurry into the first mixed solution is 0.2 to 2.0 mL / min, preferably 0.5 to 1.5 mL / min, and more preferably 0.8 to 1 mL / min.

[0039] In the present invention, magnesium oxide is added to the first mixed solution until the pH value is 4.8 to 5.5 to form a second mixed solution. Preferably, the pH value is 5 to 5.5. More preferably, the pH value is 5.3 to 5.4.

[0040] The reaction time of the second mixed solution is 1 to 5 hours, preferably 1.5 to 4 hours, and more preferably 2 to 3 hours.

[0041] The reaction product obtained by the reaction of the second mixed solution is subjected to solid-liquid separation to obtain a leaching solution after impurities are removed.

[0042] In the leaching solution after impurity removal, the content of iron is ≤0.0013 g / L; preferably, the content of iron is ≤0.0011 g / L. The content of iron is calculated as Fe2O3.

[0043] In the leaching solution after impurity removal, the content of aluminum element is ≤0.0012 g / L; preferably, the content of aluminum element is ≤0.0009 g / L. The content of aluminum element is calculated as Al2O3.

[0044] The loss rate of rare earth elements is less than or equal to 1.5%; preferably, the loss rate of rare earth elements is less than or equal to 1.2%; more preferably, the loss rate of rare earth elements is 0.8-1.1%.

[0045] Here is the test method:

[0046] The iron content was determined by atomic absorption spectrometry.

[0047] The aluminum content was determined by plasma spectrometry.

[0048] The content of rare earth elements was determined by EDTA titration method.

[0049] In the following embodiments and comparative examples, the pH of the rare earth sulfate leaching solution is 1.5, the rare earth content (calculated as rare earth oxide) is 35.3 g / L, the iron content (calculated as Fe2O3) is 11.58 g / L, and the aluminum content (calculated as Al2O3) is 1.06 g / L.

[0050] In the following examples and comparative examples, the magnesium oxide slurry is formed by reacting magnesium oxide and water in a mass volume ratio of 1:4 kg / L.

[0051] Example 1

[0052] (1) At 25° C., a 2.5 mol / L ammonium bicarbonate solution was added to the rare earth sulfate leaching solution at a flow rate of 3.3 mL / min until the pH value was 3.8, thereby forming a first mixed solution.

[0053] (2) Under stirring conditions, magnesium oxide slurry was added to the first mixed solution at a flow rate of 0.8 mL / min until the pH value was 5.3 to form a second mixed solution. The second mixed solution was reacted for 2 h, and then solid-liquid separation was performed to obtain a leaching solution after impurity removal.

[0054] The contents of some elements in the leaching solution after impurity removal are shown in Table 1.

[0055] Comparative Example 1

[0056] Except that the concentration of the ammonium bicarbonate solution is 1.5 mol / L, the rest is the same as in Example 1. The contents of some elements in the leaching solution after impurity removal are shown in Table 1.

[0057] Comparative Example 2

[0058] Except that the flow rate of the ammonium bicarbonate solution is 7 mL / min, the rest is the same as in Example 1. The contents of some elements in the leaching solution after impurity removal are shown in Table 1.

[0059] Comparative Example 3

[0060] Except that step (1) is different from that in Example 1, the rest is the same as in Example 1. Step (1) is specifically as follows:

[0061] (1) At 25° C., a 2.5 mol / L ammonium bicarbonate solution was added to the rare earth sulfate leaching solution at a flow rate of 3.3 mL / min until the pH value was 3.5, thereby forming a first mixed solution.

[0062] The contents of some elements in the leaching solution after impurity removal are shown in Table 1.

[0063] Comparative Example 4

[0064] Except that the ammonium bicarbonate solution is replaced by lime milk, the rest is the same as in Example 1. The lime milk is composed of a mass volume ratio of 1:8 t / m 3 The contents of some elements in the leaching solution after impurity removal are shown in Table 1.

[0065] Table 1

[0066]

[0067] Note: Aluminum content is calculated as Al2O3, iron content is calculated as Fe2O3, and rare earth element content is calculated as rare earth oxides.

[0068] As can be seen from the above table, the concentration and flow rate of the ammonium bicarbonate solution and the pH value of the reaction system have an important influence on the iron and aluminum content in the leaching solution after impurity removal, and also have a certain influence on the loss rate of rare earth elements, so it is not a conventional choice in this field. In addition, there are great differences in the chemical composition of ammonium bicarbonate solution and lime milk, and the use of ammonium bicarbonate solution instead of lime milk can significantly reduce the iron and aluminum content in the leaching solution after impurity removal, so it is not a conventional choice in this field.

[0069] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for removing impurities from rare earth sulfate leaching solution, characterized in that: The steps include: (1) adding an ammonium bicarbonate solution having a concentration of 2 to 3.6 mol / L into the rare earth sulfate leaching solution at a flow rate of 3 to 5.5 mL / min until the pH of the reaction system is 3.7 to 4.5, thereby forming a first mixed solution; (2) adding magnesium oxide slurry to the first mixed solution at a flow rate of 0.2 to 2.0 mL / min to form a second mixed solution; reacting the second mixed solution to obtain a decontaminated leaching solution; the magnesium oxide slurry is formed by magnesium oxide and water in a mass volume ratio of 1:(3 to 5) kg / L; The pH of the rare earth sulfate leaching solution is 0.5-2.5; the rare earth element content in the rare earth sulfate leaching solution is 30-37 g / L, the iron element content is 10-12 g / L, and the aluminum element content is 1-2 g / L; the rare earth element content is calculated as rare earth oxide, the iron element content is calculated as Fe2O3, and the aluminum element content is calculated as Al2O3; Among them, in the leaching solution after impurity removal, the iron content is ≤0.0013g / L, the aluminum content is ≤0.0012g / L, the iron content is calculated as Fe2O3, and the aluminum content is calculated as Al2O3; the loss rate of rare earth elements is less than or equal to 1.5%.

2. The method according to claim 1, characterized in that: Add ammonium bicarbonate solution into the rare earth sulfate leaching solution at 15-30°C.

3. The method according to claim 1, characterized in that Magnesium oxide is added to the first mixed solution until the pH value is 4.8 to 5.5 to form a second mixed solution.

4. The method according to any one of claims 1 to 3, characterized in that: The reaction time of the second mixed solution is 1 to 5 hours.

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