A method for preparing magnesium sulfate crystal by using cobalt raffinate

Abstract

The application discloses a method for preparing magnesium sulfate crystal by using cobalt raffinate, which comprises the processes of precipitation reaction, dissolution reaction, resin adsorption, crystallization and the like, and the cobalt-nickel-magnesium precipitate generated by using the chemical precipitation method can be completely dissolved by adding acid after washing the residue, and no residue is discharged, so that the pollution to the environment is reduced, and the method is more in line with the requirements of green chemistry. In the method, the resin can be directly used for the next adsorption after being resolved, and the alkali regeneration operation is not needed, so that the sodium impurity is avoided to be introduced into the magnesium sulfate solution, the cost is reduced, and the purity of the magnesium sulfate crystal obtained is improved. The magnesium sulfate crystal produced by using the method has high purity, and the purity can reach 99.8%. By using the method, the magnesium in the cobalt raffinate can be recovered, the sodium-containing filtrate and the residue washing water obtained can be transported to a sodium wastewater section to produce sodium sulfate, and the overall metal recovery rate of the method can reach more than 99.5%.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a method for preparing magnesium sulfate crystals using cobalt extraction residue. Background Technology

[0002] In the process of producing high-purity cobalt sulfate using intermediates from cobalt-nickel hydrometallurgical processes as raw materials, a certain amount of magnesium sulfate solution containing low levels of cobalt and nickel and high levels of sodium (i.e., cobalt raffinate) is generated. In the metallurgical industry, magnesium sulfate wastewater containing low levels of cobalt and nickel and high levels of sodium is typically treated by resin adsorption, oxidation precipitation, or sulfide precipitation to remove nickel and cobalt. However, these methods cannot effectively separate sodium and magnesium from the wastewater, cannot produce pure sodium sulfate and magnesium sulfate to increase added value, have poor economic benefits, and the impurities also pollute the environment. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a method for preparing magnesium sulfate crystals using cobalt extraction residue, specifically including the following:

[0004] A method for preparing magnesium sulfate crystals using cobalt extraction residue includes the following steps:

[0005] (1) Precipitation reaction: Add an alkaline solution to the cobalt extraction residue, adjust the pH to 10-11, carry out the precipitation reaction, and the reaction time is 0.5-2h. After the reaction is completed, perform solid-liquid separation and wash the filter residue to obtain sodium-containing filtrate, washing water and magnesium-containing filter residue.

[0006] (2) Dissolution reaction: Add pure water and sulfuric acid solution to magnesium-containing filter residue to dissolve the magnesium-containing filter residue and obtain a solution;

[0007] (3) Resin adsorption: First, wash the resin with 1.5-2.5 BV of pure water, then wash it with 1.5-2.5 BV of sulfuric acid solution with a mass concentration of 4-6%; finally wash it with pure water until the pH of the wash water reaches 3-5; then use the washed resin to adsorb cobalt and nickel impurities in the solution to obtain crude magnesium sulfate solution.

[0008] (4) Crystallization: After evaporating and concentrating the crude magnesium sulfate solution, cool it to 25-28℃ for crystallization, and let it stay for 2-3 hours to obtain the crystallization mother liquor and magnesium sulfate crystals.

[0009] Preferably, the nickel and cobalt content in the sodium-containing filtrate and washing residue water in step (1) is less than 1 mg / L.

[0010] Preferably, the resin in step (3) is LSC930 resin.

[0011] Preferably, in step (3), the flow rates of pure water and sulfuric acid solution during the washing process are controlled to be 1-2 BV / h.

[0012] Preferably, step (3) further includes resin analysis: first, the adsorbed resin is washed with 2-4 BV of pure water, and the flow rate of pure water is controlled at 2-3 BV / h; then, the resin is washed with 2-4 BV of sulfuric acid solution with a mass concentration of 12%-18%, and the flow rate of sulfuric acid solution is controlled at 1-2 BV / h; then, it is washed with pure water, and the flow rate is controlled at 2-3 BV / h, until the pH of the washing solution reaches 3-5.

[0013] Preferably, in step (3) during the resin adsorption of the solution, the amount of Mg2+ adsorbed does not exceed 0.1% of the total amount.

[0014] Preferably, step (4) further includes returning the crystallization mother liquor to the crude magnesium sulfate solution, evaporating and concentrating it together with the crude magnesium sulfate solution, and then cooling and crystallizing.

[0015] Preferably, in step (4), the primary crystallization rate of magnesium sulfate is ≥50%, and the purity of the magnesium sulfate crystals is ≥99.8%.

[0016] Preferably, the composition and content of the cobalt extraction residue include: Co 60-100 mg / L, Ni 450-600 mg / L, Mg 2-4 g / L, and Na 30-50 g / L.

[0017] The beneficial effects of this invention are:

[0018] (1) The method for preparing magnesium sulfate crystals using cobalt extraction residue disclosed in this invention includes precipitation reaction, dissolution reaction, resin adsorption, crystallization and other processes. The cobalt-nickel-magnesium precipitate generated by chemical precipitation method can be completely dissolved by adding acid after washing the residue. There is no external slag discharge, which reduces the pollution to the environment and is more in line with the requirements of green chemistry.

[0019] (2) In the method for preparing magnesium sulfate crystals using cobalt extraction residue disclosed in this invention, the resin can be directly used for the next adsorption after analysis, without the need for alkali regeneration, thus avoiding the introduction of sodium impurities into the magnesium sulfate solution. This reduces costs and improves the purity of the final magnesium sulfate crystals.

[0020] (2) The magnesium sulfate crystals produced by the method of preparing magnesium sulfate crystals from cobalt leaching residue disclosed in this invention have high purity, reaching ≥99.8%. Moreover, by using the method disclosed in this invention, not only can magnesium in cobalt leaching residue be recovered, but the sodium-containing filtrate and washing water obtained can also be transported to the sodium wastewater section to produce sodium sulfate. The overall metal recovery rate of this method can reach more than 99.5%. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process flow of the method disclosed in this invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments shown below do not limit the scope of the invention as described in the claims. Furthermore, the complete contents of the configurations illustrated in the following embodiments are not limited to those necessary for the solution of the invention as described in the claims.

[0023] A method for preparing magnesium sulfate crystals using cobalt raffinate, wherein the cobalt raffinate comprises: Co 60-100 mg / L, Ni 450-600 mg / L, Mg 2-4 g / L, and Na 30-50 g / L, and includes the following steps:

[0024] (1) Precipitation reaction: Add an alkaline solution to the cobalt extraction residue, adjust the pH to 10-11, and carry out the precipitation reaction for 0.5-2 hours (e.g., 0.8 hours, 1.0 hours, 1.5 hours, 1.8 hours, etc.). After the reaction is completed, perform solid-liquid separation and wash the filter residue to obtain sodium-containing filtrate, washing water, and magnesium-containing filter residue; the nickel and cobalt contents of the sodium-containing filtrate and washing water are both less than 1 mg / L.

[0025] (2) Dissolution reaction: Add pure water and sulfuric acid solution to magnesium-containing filter residue to dissolve the magnesium-containing filter residue and obtain a solution;

[0026] (3) Resin adsorption: First, wash the LSC930 resin with 1.5-2.5 BV (e.g., 1.6 BV, 1.8 BV, 2.0 BV, 2.2 BV, 2.4 BV, etc.), then wash it with 1.5-2.5 BV (e.g., 1.6 BV, 1.8 BV, 2.0 BV, 2.2 BV, 2.4 BV, etc.) sulfuric acid solution with a mass concentration of 4-6% (e.g., 4.5%, 5%, 5.5%, 5.8%, etc.). The solution is then washed with pure water until the pH of the wash water reaches 3-5 (e.g., 3, 3.5, 4, 4.5, 5, etc.). The washed LSC930 resin is then used to adsorb cobalt and nickel impurities from the solution, yielding a crude magnesium sulfate solution. The flow rates of both pure water and sulfuric acid solution during the washing process are controlled at 1-2 BV / h (e.g., 1.2 BV, 1.4 BV, 1.6 BV, 1.8 BV, 2 BV, etc.). During this process, the adsorbed Mg... 2+The amount should not exceed 0.1% of the total amount; finally, resin analysis is performed: first, the adsorbed resin is washed with 2-4 BV (e.g., 2.5 BV, 3 BV, 3.4 BV, 3.8 BV, 4 BV, etc.) of pure water, controlling the pure water flow rate at 2-3 BV / h (e.g., 2 BV, 2.2 BV, 2.4 BV, 2.6 BV, 2.8 BV, etc.); then, the resin is washed with 2-4 BV (e.g., 2.5 BV, 3 BV, 3.4 BV, 3.8 BV, 4 BV, etc.) at a mass concentration of 12%-18%. Wash the resin with sulfuric acid solution of 1% (e.g., 13%, 14%, 15%, 16%, 17%, etc.), controlling the flow rate of the sulfuric acid solution at 1-2 BV / h (e.g., 1.2 BV, 1.4 BV, 1.6 BV, 1.8 BV, 2 BV, etc.); then wash with pure water, controlling the flow rate at 2-3 BV / h (e.g., 2 BV, 2.2 BV, 2.4 BV, 2.6 BV, 2.8 BV, etc.), until the pH of the washing solution reaches 3-5 (e.g., 3.5, 4, 4.5, 5, etc.).

[0027] (4) Crystallization: After evaporating and concentrating the crude magnesium sulfate solution, cool it to 25-28℃ (e.g., 25.5℃, 26℃, 26.5℃, 27℃, 27.5℃, etc.) for crystallization, and hold for 2-3 hours (e.g., 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, etc.) to obtain crystallization mother liquor and magnesium sulfate crystals. The primary crystallization rate of magnesium sulfate is ≥50%, and the purity of the magnesium sulfate crystals is ≥99.8%. Return the crystallization mother liquor to the crude magnesium sulfate solution, and evaporate and concentrate it together with the crude magnesium sulfate solution before cooling and crystallizing.

[0028] Example 1

[0029] In this embodiment, the cobalt wire raffinate contains 90.8 mg / L Co, 586 mg / L Ni, 2.84 g / L Mg, and 35.8 g / L Na.

[0030] A method for preparing magnesium sulfate crystals using cobalt raffinate residue involves first slowly adding liquid alkali to 500 liters of cobalt raffinate residue to adjust the pH to 10.54. After stabilizing the reaction for 60 minutes, the mixture is filtered to obtain a filtrate and a filter residue. The filter residue is washed three times countercurrently with a solid-liquid ratio of 1:3, and then filtered again to obtain a washing residue. The washing residue is then dissolved in water and acid to obtain a 25 liter back-dissolved solution, which is then passed through an LSC930 wet resin column to adsorb cobalt and nickel, yielding a crude magnesium sulfate solution. Finally, the crude magnesium sulfate solution is concentrated and transferred to a crystallization apparatus. Crystallization is carried out at 25°C for 2 hours, with the cooling rate decreasing rapidly. At this point, magnesium sulfate crystals with a main content of 99.9% and a primary crystallization rate of 53.4% ​​are obtained.

[0031] Example 2

[0032] In this embodiment, the cobalt wire raffinate contains 76.5 mg / L Co, 458 mg / L Ni, 3.05 g / L Mg, and 40.37 g / L Na.

[0033] A method for preparing magnesium sulfate crystals using cobalt raffinate residue involves first slowly adding liquid alkali to 500 liters of cobalt raffinate residue to adjust the pH to 10.71, stabilizing the reaction for 30 minutes, and then filtering to obtain filtrate and filter residue. The filter residue is washed three times countercurrently with a solid-liquid ratio of 1:3, and then filtered again to obtain washing residue. The washing residue is then dissolved in water and acid to obtain 25 liters of resolution solution, which is then passed through an LSC930 wet resin column to adsorb cobalt and nickel, yielding a crude magnesium sulfate solution. Finally, the crude magnesium sulfate solution is concentrated and then transferred to a crystallization apparatus for cooling and crystallization at 28°C for 3 hours, with the cooling rate decreasing rapidly. At this point, magnesium sulfate crystals with a main content of 99.85% and a primary crystallization rate of 51.2% are obtained.

[0034] Example 3

[0035] A method for preparing magnesium sulfate crystals using cobalt raffinate, wherein the cobalt raffinate comprises the following components and contents: Co 90 mg / L, Ni 585 mg / L, Mg 3.5 g / L, and Na 45 g / L, comprising the following steps:

[0036] (1) Precipitation reaction: Add alkaline solution to cobalt extraction residue, adjust pH to 10.5-11, carry out precipitation reaction, reaction time 2h, after the reaction is completed, perform solid-liquid separation and wash the filter residue to obtain sodium-containing filtrate, washing water and magnesium-containing filter residue; the nickel and cobalt contents of the sodium-containing filtrate and washing water are both less than 1mg / L;

[0037] (2) Dissolution reaction: Add pure water and sulfuric acid solution to magnesium-containing filter residue to dissolve the magnesium-containing filter residue and obtain a solution;

[0038] (3) Resin adsorption: First, LSC930 resin was washed with 2.4 BV of pure water, then with 1.8 BV of 4.5% sulfuric acid solution; finally, it was washed with pure water until the pH of the wash water reached 4.5; then, the washed LSC930 resin was used to adsorb cobalt and nickel impurities in the solution to obtain crude magnesium sulfate solution; the flow rates of pure water and sulfuric acid solution during the washing process were controlled at 1.5 BV / h; during this process, the adsorbed Mg 2+ The amount of [unspecified substance] should not exceed 0.1% of the total amount; finally, resin analysis is performed: first, the adsorbed resin is washed with 3.5 BV of pure water, with the pure water flow rate controlled at 2.8 BV / h; then, the resin is washed with 3.5 BV of 16% sulfuric acid solution, with the sulfuric acid solution flow rate controlled at 1.8 BV / h; then, it is washed with pure water, with the flow rate controlled at 2.8 BV / h, until the pH of the washing solution reaches 4.5;

[0039] (4) Crystallization: After evaporating and concentrating the crude magnesium sulfate solution, it is cooled to 27°C for crystallization, and the residence time is 2.8h to obtain the crystallization mother liquor and magnesium sulfate crystals. The primary crystallization rate of magnesium sulfate is 60%, and the purity of the magnesium sulfate crystals is 99.95%. The crystallization mother liquor is returned to the crude magnesium sulfate solution, and after evaporating and concentrating together with the crude magnesium sulfate solution, it is cooled and crystallized.

[0040] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing magnesium sulfate crystal using cobalt raffinate, characterized by, The method comprises the following steps: (1) Precipitation reaction: adding an alkaline solution to the cobalt raffinate, adjusting the pH to 10-11, and performing a precipitation reaction for 0.5-2 hours, wherein the cobalt raffinate comprises Co 60-100 mg / L, Ni 450-600 mg / L, Mg 2-4 g / L, and Na 30-50 g / L; after the reaction is completed, solid-liquid separation is performed, and the filter residue is washed to obtain a sodium-containing filtrate, residue washing water, and a magnesium-containing filter residue, wherein the content of nickel and cobalt in the sodium-containing filtrate and the residue washing water is less than 1 mg / L; (2) Dissolution reaction: adding pure water and a sulfuric acid solution to the magnesium-containing filter residue to dissolve the magnesium-containing filter residue to obtain a dissolution solution; (3) Resin adsorption: first, the resin is washed with 1.5-2.5 BV of pure water, and then washed with 1.5-2.5 BV of a sulfuric acid solution with a mass concentration of 4-6%; finally, the resin is washed with pure water until the pH of the washing water reaches 3-5; then, the washed resin is used to adsorb cobalt and nickel impurities in the dissolution solution to obtain a crude magnesium sulfate solution; (4) Crystallization: after the crude magnesium sulfate solution is evaporated and concentrated, it is cooled to 25-28°C for crystallization for 2-3 hours to obtain a crystallization mother liquor and magnesium sulfate crystals, and the crystallization mother liquor is returned to the crude magnesium sulfate solution, which is evaporated and concentrated and then cooled and crystallized. The resin in step (3) is LSC930 resin.

2. The method for preparing magnesium sulfate crystal using cobalt raffinate according to claim 1, characterized in that, In step (3), the flow rate of the pure water and the sulfuric acid solution during the washing process is 1-2 BV / h.

3. The method of claim 1, wherein the method is characterized by, Step (3) further comprises resin elution: first, the adsorbed resin is washed with 2-4 BV of pure water at a flow rate of 2-3 BV / h; then, the resin is washed with 2-4 BV of a sulfuric acid solution with a mass concentration of 12%-18% at a flow rate of 1-2 BV / h; and finally, the resin is washed with pure water at a flow rate of 2-3 BV / h until the pH of the washing liquid reaches 3-5.

4. The method for preparing magnesium sulfate crystal using cobalt raffinate according to claim 1, characterized in that, In step (4), the primary crystallization rate of magnesium sulfate is ≥50%, and the purity of the magnesium sulfate crystals is ≥99.8%.

5. The method of claim 1, wherein the method is characterized by, Step (3) The amount of Mg 2+ adsorbed in the resin adsorption of the dissolved solution does not exceed 0.1% of the total amount.

6. The method for preparing magnesium sulfate crystal using cobalt raffinate according to any one of claims 1-5, characterized in that, ​

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