Method for removing sulfate radicals through rare earth saponification extraction

Abstract

The invention discloses a rare earth saponification extraction sulfate radical removal method, which comprises: carrying out a saponification reaction on an extraction agent and a calcium salt to obtain a calcium-loaded saponification extraction agent; the method comprises the following steps: reacting rare earth ions with a supported calcium saponification extractant to obtain a supported rare earth ion saponification extractant and a solution A; a rare earth ion-loaded saponification extraction agent is used for purifying and separating rare earth feed liquid, and a sulfate radical separation step is carried out to obtain a rare earth ion solution which does not contain or contains a small amount of sulfate radicals. In the process, the lanthanum ion-loaded saponification extraction agent enters the extraction production process to exchange with the feed liquid containing the sulfate ions, so that the problems of emulsification, difficult phase separation and the like in the extraction process due to the fact that fine calcium sulfate suspensions or precipitates are formed after the sulfate ions are in contact with calcium entering the extraction process are greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for removing sulfate radicals by saponification extraction of rare earth. Background Art

[0002] The cascade continuous extraction process is the most mature preparation process for the industrial preparation of high-purity rare earth products. It utilizes the differences in the binding abilities of different rare earth elements with rare earth extractants such as P507 and P204, and continuously distributes and exchanges them in the aqueous phase and the oil phase, thereby achieving pairwise separation of rare earth elements, and ultimately obtaining 3N-5N grade high-purity rare earths.

[0003] There are certain differences in the sources of rare earth raw materials used in rare earth extraction. For example, northern fluorocarbon cerium ore is usually prepared by sulfuric acid roasting, and then transformed to obtain rare earth chloride raw materials. Southern ionic rare earth ores mainly use ammonium sulfate, magnesium sulfate and other leaching agents to exchange with rare earth ions and then precipitate to obtain rare earth salts. However, these processes all introduce sulfate ions to varying degrees. At present, some domestic companies still use calcium saponification technology to avoid ammonia nitrogen pollution. After sulfate ions enter the extraction process and come into contact with calcium, they will form fine calcium sulfate suspension or precipitation, causing problems such as emulsification and phase separation difficulties in the extraction process, which in turn has an adverse effect on the quality of rare earth products.

[0004] Among the existing technical solutions, the most effective method is to add barium salts to the rare earth acid solution and use the formation of barium sulfate precipitates to remove sulfate. However, not only are barium salts highly toxic, but the precipitates generated during the reaction can only be disposed of as hazardous waste. At the same time, the barium sulfate precipitates generated by the reaction are small in size and difficult to filter. At the same time, they will also cause entrainment losses of rare earth elements during solid-liquid separation, which brings many disadvantages to the existing production process.

[0005] The patent document with the announcement number CN102443699A discloses a method for separating a single rare earth by combining non-saponifiable transformation pre-purification and linkage extraction. The water extract of the northern Baotou ore after high-temperature roasting with sulfuric acid and water immersion is used as the raw material. After three steps of non-saponifiable extraction, transformation pre-purification extraction and linkage extraction in a hydrochloric acid system with P204 and P507 as extractants, the non-rare earth impurities such as iron, calcium and sulfate in the product are removed. However, this process is mainly for wastewater treatment and is not suitable for use in extraction processes. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for removing sulfate by saponification extraction of rare earth.

[0007] The present invention is achieved through the following technical solutions.

[0008] The present invention provides a method for removing sulfate by saponification extraction of rare earth, comprising the following steps:

[0009] S1: using a rare earth extractant to prepare a saponification extractant in a rare earth saponification extraction, and performing a saponification reaction between the saponification extractant and a calcium salt to obtain a calcium-loaded saponification extractant;

[0010] S2: using rare earth ions to react with a loaded calcium saponification extractant to obtain a loaded rare earth ion saponification extractant and solution A;

[0011] S3: purifying and separating the rare earth liquid by using a loaded rare earth ion saponification extractant, performing a sulfate separation step, and obtaining a rare earth ion solution.

[0012] Preferably, the calcium salt in step S1 is one or both of calcium hydroxide and calcium carbonate.

[0013] Preferably, the extractant in step S1 is P507.

[0014] Preferably, the step of preparing the saponification extractant comprises: adding calcium hydroxide solution to the P507 extractant, and obtaining a saponification extractant loaded with calcium ions and having a saponification rate of 33-35% after sufficient reaction.

[0015] Preferably, the rare earth ion solution in step S2 does not contain sulfate ions, and the rare earth ions include one or more of La, Ce, Pr, and Nd.

[0016] Preferably, the rare earth ions are La or a mixture of La and Ce, Pr and Nd.

[0017] Preferably, the sulfate separation in step S3 comprises the following steps:

[0018] S4: extracting and separating the rare earth ions from the rare earth liquid using a saponified extractant loaded with rare earth ions, and obtaining rare earth ions in the aqueous phase again after exchange;

[0019] S5: The rare earth ions obtained in step S4 are mixed with the solution A obtained in step S1 to obtain a mixed solution;

[0020] S6: filtering the mixed solution to obtain a rare earth ion solution and a solid precipitate, wherein the sulfate content in the rare earth ion solution is less than 0.05 g / L.

[0021] Preferably, the solution A is a calcium chloride solution.

[0022] Preferably, the solid precipitate is a calcium sulfate precipitate.

[0023] The beneficial effects of the present invention are:

[0024] In the process of the present invention, an equal amount or an excess amount of lanthanum chloride solution is added to a saponified extractant loaded with calcium ions, and after sufficient reaction, the lanthanum ions replace the calcium ions to obtain a saponified extractant loaded with lanthanum ions and a calcium chloride solution. The saponified extractant loaded with lanthanum ions enters the extraction production process to exchange with a feed liquid containing sulfate ions, thereby greatly reducing the formation of fine calcium sulfate suspension or precipitation after the sulfate ions contact the calcium entering the extraction process, causing emulsification, difficult phase separation and other problems in the extraction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a process flow chart of the present invention; DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0027] Embodiment 1:

[0028] like Figure 1 As shown, a method for removing sulfate by saponification extraction of rare earth comprises the following steps:

[0029] S1: Rare earth extractant is used in rare earth saponification extraction to prepare saponification extractant, by Saponification The extractant undergoes saponification reaction with the calcium salt to obtain a calcium-loaded saponified extractant;

[0030] S2: After the rare earth saponification extraction is mixed, it takes 3-5 minutes for oil-water separation to separate the phases. After the organic phase and the aqueous phase are separated, an equal amount or excess of rare earth ions is used to react with the loaded calcium saponification extractant to replace the calcium ions from the organic phase to obtain a loaded rare earth ion saponification extractant with a saponification rate of 33% and a calcium chloride solution;

[0031] S3: purifying and separating the rare earth liquid by using a loaded rare earth ion saponification extractant, and performing a sulfate separation step to obtain a rare earth ion solution and a calcium sulfate solid, wherein the sulfate content in the rare earth ion solution is <0.01 g / L.

[0032] The calcium salt in step S1 is calcium hydroxide.

[0033] The extractant in step S1 is P507.

[0034] The step of preparing the saponification extractant comprises: in a reaction kettle, adding calcium hydroxide solution to the P507 extractant, and obtaining the saponification extractant loaded with calcium ions and having a saponification rate of 33% after sufficient reaction.

[0035] The rare earth ion solution in step S2 does not contain sulfate ions, and the rare earth ions are La.

[0036] The sulfate separation in step S3 comprises the following steps:

[0037] S4: using a rare earth ion loaded saponification extractant and a rare earth liquid to purify and separate, and after exchange, obtaining rare earth ions in the aqueous phase again;

[0038] S5: mixing the rare earth ions obtained in step S4 with the calcium chloride obtained in step S1 to obtain a mixed solution;

[0039] S6: filtering the mixed solution to obtain a rare earth ion solution and a calcium sulfate solid precipitate, wherein the sulfate content in the rare earth ion solution is less than 0.01 g / L.

[0040] The aqueous phase in step S4: P507 organic phase is mixed with calcium carbonate slurry, Ca 2+ Extracted by organic phase (P507-Ca 2 + ), the aqueous phase is discharged from wastewater treatment, and the loaded organic phase continues to react with LaCl3, La 3+ The Ca in the organic phase 2+ Replaced into the aqueous phase (the aqueous phase is CaCl2), the organic phase (P507-La 3+ ) into the extraction tank, after extraction exchange, the rare earth in the original water phase of the extraction tank is exchanged to the organic phase (P507-RE 3+ ) and La in the organic phase 3+ The effluent from the extraction tank is a mixture of lanthanum chloride (containing sulfate) (LaCl3+SO4 2- ). Calcium chloride solution is added thereto to generate calcium sulfate precipitate, which is filtered to obtain lanthanum chloride solution and calcium sulfate precipitate.

[0041] Embodiment 2:

[0042] like Figure 1 As shown, a method for removing sulfate by saponification extraction of rare earth comprises the following steps:

[0043] S1: using a rare earth extractant to prepare a saponification extractant in a rare earth saponification extraction, and performing a saponification reaction between the saponification extractant and a calcium salt to obtain a calcium-loaded saponification extractant;

[0044] S2: After the rare earth saponification extraction is mixed, it takes 3-5 minutes for oil-water separation to separate the phases. After the organic phase and the aqueous phase are separated, an equal amount or excess of rare earth ions is used to react with the loaded calcium saponification extractant to replace the calcium ions from the organic phase to obtain a loaded rare earth ion saponification extractant with a saponification rate of 35% and a calcium chloride solution;

[0045] S3: purifying and separating the rare earth liquid by using a rare earth ion loaded saponification extractant, and performing a sulfate separation step to obtain a rare earth ion solution and a calcium sulfate solid, wherein the sulfate content in the rare earth ion solution is <0.05 g / L.

[0046] In step S1, the calcium salt is calcium carbonate.

[0047] The extractant in step S1 is P507.

[0048] The steps of preparing the saponification extractant include: adding calcium hydroxide solution to the P507 extractant in a continuous extraction tank, and obtaining the saponification extractant loaded with calcium ions and having a saponification rate of 35% after sufficient reaction.

[0049] The rare earth ions in step S2 do not contain sulfate ions, and the rare earth ions are a mixture of La, Ce, Pr, and Nd.

[0050] The sulfate separation in step S3 comprises the following steps:

[0051] S4: using a rare earth ion loaded saponification extractant and a rare earth liquid to purify and separate, and after exchange, obtaining rare earth ions in the aqueous phase again;

[0052] S5: mixing the rare earth ions obtained in step S4 with the calcium chloride obtained in step S1 to obtain a mixed solution;

[0053] S6: filtering the mixed solution to obtain a rare earth ion solution and a calcium sulfate solid precipitate, wherein the rare earth ion solution contains less than 0.01% sulfate.

[0054] The aqueous phase in step S4: P507 organic phase is mixed with calcium carbonate slurry, Ca 2+ Extracted by organic phase (P507-Ca 2 + ), the aqueous phase is discharged from wastewater treatment, and the loaded organic phase continues to react with LaCl3, La 3+ The Ca in the organic phase 2+ Replaced into the aqueous phase (the aqueous phase is CaCl2), the organic phase (P507-La 3+ ) into the extraction tank, after extraction exchange, the rare earth in the original water phase of the extraction tank is exchanged to the organic phase (P507-RE 3+ ) and La in the organic phase 3+ The effluent from the extraction tank is a mixture of lanthanum chloride (containing sulfate) (LaCl3+SO4 2- ). Calcium chloride solution is added thereto to generate calcium sulfate precipitate, which is filtered to obtain lanthanum chloride solution and calcium sulfate precipitate.

[0055] Embodiment 3:

[0056] like Figure 1 As shown, a method for removing sulfate by saponification extraction of rare earth comprises the following steps:

[0057] S1: using a rare earth extractant to prepare a saponification extractant in a rare earth saponification extraction, and performing a saponification reaction between the saponification extractant and a calcium salt to obtain a calcium-loaded saponification extractant;

[0058] S2: After the rare earth saponification extraction is mixed, it takes 3-5 minutes for oil-water separation to separate the phases. After the organic phase and the aqueous phase are separated, an equal amount or excess of rare earth ions is used to react with the loaded calcium saponification extractant to replace the calcium ions from the organic phase to obtain a loaded rare earth ion saponification extractant with a saponification rate of 34% and a calcium chloride solution;

[0059] S3: purifying and separating the rare earth liquid by using a loaded rare earth ion saponification extractant, and performing a sulfate separation step to obtain a rare earth ion solution and a calcium sulfate solid, wherein the sulfate content in the rare earth ion solution is <0.01 g / L.

[0060] The calcium salt in step S1 is calcium hydroxide.

[0061] The extractant in step S1 is P507.

[0062] The step of preparing the saponification extractant comprises: in a reaction kettle, adding calcium hydroxide solution to the P507 extractant, and obtaining the saponification extractant loaded with calcium ions and having a saponification rate of 34% after sufficient reaction.

[0063] The rare earth ion solution in step S2 does not contain sulfate ions, and the rare earth ions are La.

[0064] The sulfate separation in step S3 comprises the following steps:

[0065] S4: using a rare earth ion loaded saponification extractant and a rare earth liquid to purify and separate, and after exchange, obtaining rare earth ions in the aqueous phase again;

[0066] S5: mixing the rare earth ions obtained in step S4 with the calcium chloride obtained in step S1 to obtain a mixed solution;

[0067] S6: filtering the mixed solution to obtain a rare earth ion solution and a calcium sulfate solid precipitate, wherein the sulfate content in the rare earth ion solution is less than 0.01 g / L.

[0068] The aqueous phase in step S4: P507 organic phase is mixed with calcium carbonate slurry, Ca 2+ Extracted by organic phase (P507-Ca 2 + ), the aqueous phase is discharged from wastewater treatment, and the loaded organic phase continues to react with LaCl3, La 3+The Ca in the organic phase 2+ Replaced into the aqueous phase (the aqueous phase is CaCl2), the organic phase (P507-La 3+ ) into the extraction tank, after extraction exchange, the rare earth in the original water phase of the extraction tank is exchanged to the organic phase (P507-RE 3+ ) and La in the organic phase 3+ The effluent from the extraction tank is a mixture of lanthanum chloride (containing sulfate) (LaCl3+SO4 2- ). Calcium chloride solution is added thereto to generate calcium sulfate precipitate, which is filtered to obtain lanthanum chloride solution and calcium sulfate precipitate.

[0069] The rare earth-containing feed solutions of Examples 1-3 were tested before the sulfate separation step and after the sulfate removal step, and the results are shown in the following table.

[0070]

[0071] As can be seen from the above table, the removal rate of sulfate radical = 98.33%. The method of the present application has a good effect on the removal of sulfate radical and can significantly reduce the sulfate radical content.

Claims

1. A method for removing sulfate by saponification extraction of rare earth, characterized in that: The following steps are involved: S1: using a rare earth extractant to prepare a saponification extractant in a rare earth saponification extraction, and performing a saponification reaction between the saponification extractant and a calcium salt to obtain a calcium-loaded saponification extractant; S2: using rare earth ions to react with a loaded calcium saponification extractant to obtain a loaded rare earth ion saponification extractant and solution A; S3: purifying and separating the rare earth liquid by using a loaded rare earth ion saponification extractant, performing a sulfate separation step, and obtaining a rare earth ion solution.

2. The method for removing sulfate by saponification extraction of rare earth as claimed in claim 1, characterized in that: In step S1, the calcium salt is one or both of calcium hydroxide and calcium carbonate.

3. The method for removing sulfate by saponification extraction of rare earth as claimed in claim 1, characterized in that: The extractant in step S1 is P507.

4. A method for removing sulfate by saponification extraction of rare earth as claimed in claim 1 or 3, characterized in that: The step of preparing the saponification extractant comprises: adding calcium hydroxide solution to the P507 extractant, and obtaining the saponification extractant loaded with calcium ions and having a saponification rate of 33-35% after sufficient reaction.

5. The method for removing sulfate by saponification extraction of rare earth as claimed in claim 1, characterized in that: The rare earth ion solution in step S2 does not contain sulfate ions, and the rare earth ions include one or more of La, Ce, Pr, and Nd.

6. The method for removing sulfate by saponification extraction of rare earth as claimed in claim 5, characterized in that: The rare earth ions are La or a mixture of La, Ce, Pr and Nd.

7. The method for removing sulfate by saponification extraction of rare earth as claimed in claim 1, characterized in that: In step S3, sulfate separation The following steps are involved: S4: using a rare earth ion loaded saponification extractant and a rare earth liquid to purify and separate, and after exchange, lanthanum ions are obtained again in the aqueous phase; S5: The rare earth ions obtained in step S4 are mixed with the solution A obtained in step S1 to obtain a mixed solution; S6: filtering the mixed solution to obtain a rare earth ion solution and a solid precipitate, wherein the sulfate content in the rare earth ion solution is less than 0.05 g / L.

8. A method for removing sulfate by saponification extraction of rare earth as claimed in claim 1 or 7, characterized in that: The solution A is a calcium chloride solution.

9. The method for removing sulfate by saponification extraction of rare earth as claimed in claim 7, characterized in that: The solid precipitate is a calcium sulfate precipitate.

Images