A method for recycling laterite nickel ore hydrometallurgy wastewater

Abstract

This application discloses a method for recycling wastewater from the hydrometallurgical process of laterite nickel ore, comprising the following steps: high-pressure acid leaching of laterite nickel ore is subjected to circulating leaching, CCD washing, iron and aluminum removal, and MHP precipitation treatment, followed by filtration to obtain a post-MHP precipitation liquid; alkali is added to this liquid to remove manganese, and filtration is performed to obtain post-MHP precipitation and manganese removal wastewater; the post-MHP precipitation and manganese removal wastewater is subjected to ion exchange to recover nickel and cobalt, yielding an ion-exchange liquid and a enriched nickel-cobalt solution, which is reused in the CCD washing process; the ion-exchange liquid is treated by extraction or ion-selective membrane treatment to obtain a magnesium-rich solution and a magnesium-poor solution; part of the magnesium-rich solution is reused in the MHP precipitation process, and the remaining portion is evaporated and crystallized to obtain magnesium sulfate; the magnesium-poor solution is subjected to bipolar membrane electrolysis, and the resulting sodium hydroxide solution is reused in the iron and aluminum removal and MHP precipitation processes, while the sulfuric acid solution is reused in the high-pressure acid leaching process. This application improves the recycling rate of wastewater from the hydrometallurgical process of laterite nickel ore, and the recovered intermediate products can be further purified or directly reused in previous processes.

Description

Technical Field

[0001] This application belongs to the field of hydrometallurgy, and in particular relates to a method for recycling wastewater from hydrometallurgical treatment of laterite nickel ore. Background Technology

[0002] The hydrometallurgical process for laterite nickel ore inevitably generates wastewater containing complex metal ions, such as Ni, Co, Mn, Mg, Fe, Zn, and Al, during the refining of valuable metals like nickel and cobalt. This wastewater not only contains potential resources but can also become a source of environmental pollution. Therefore, its effective recycling and utilization is not only a matter of economic benefit but also an urgent need for environmental protection.

[0003] In the hydrometallurgical preparation of MHP (nickel-cobalt hydroxide) intermediates from laterite nickel ore, commonly used precipitants include sodium hydroxide and magnesium oxide. However, the use of sodium hydroxide in industrial production leads to localized over-alkalinity in the reaction system. This not only increases the manganese content in MHP but also correspondingly reduces the nickel and cobalt content. Increased manganese content increases the cost of subsequent refining steps. Furthermore, the over-alkalinity environment accelerates the nucleation rate of MHP, producing smaller and unevenly distributed particles. This makes effective sedimentation and filtration of MHP difficult, resulting in a higher moisture content in the filter cake and increased transportation costs. Additionally, in existing processes, after complete precipitation and separation of nickel and cobalt, the filtrate from this stage mainly contains Mn and Mg. In wastewater treatment, specific precipitants are typically used to precipitate manganese, and the resulting manganese slag is then filtered and landfilled. The filtrate after manganese slag filtration mainly contains Mg. Due to its alkalinity, it is generally neutralized with sulfuric acid before being discharged into the ocean.

[0004] It is evident that existing wastewater treatment technologies for laterite nickel ore hydrometallurgical processes still have shortcomings. New pollutants are often generated during wastewater treatment, leading to adverse environmental impacts. Although various technologies and methods have been applied to the treatment and recycling of such wastewater, challenges remain, such as high treatment costs, compatibility issues between technologies, and the risk of secondary pollution. Therefore, improving wastewater recycling rates and reducing environmental impact is a research topic worthy of in-depth exploration. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide a method for recycling wastewater from laterite nickel ore hydrometallurgical processes, aiming to solve the problems of low treatment efficiency and secondary pollution associated with existing technologies for laterite nickel ore hydrometallurgical wastewater.

[0006] This application is specifically implemented through the following technical solutions:

[0007] A method for recycling wastewater from hydrometallurgical processes in laterite nickel ore production includes the following steps:

[0008] (1) Take the high-pressure acid leaching solution of laterite nickel ore and perform circulating leaching, CCD washing, iron and aluminum removal and MHP precipitation treatment, filter to obtain MHP precipitation liquid; add alkali to the MHP precipitation liquid to remove manganese, filter to obtain MHP precipitation and manganese removal wastewater.

[0009] (2) The wastewater after manganese removal by MHP is subjected to ion exchange to obtain ion-exchanged liquid and enriched nickel-cobalt solution. The enriched nickel-cobalt solution is reused in the CCD washing process.

[0010] (3) After ion exchange, the liquid is treated by extraction or ion-selective membrane to obtain magnesium-rich liquid and magnesium-poor liquid; part of the magnesium-rich liquid is recycled for the precipitation of MHP, and the remaining part is evaporated and crystallized to obtain magnesium sulfate.

[0011] (4) The magnesium-poor solution is electrolyzed by bipolar membrane, and the resulting sodium hydroxide solution is reused in the iron and aluminum removal and MHP precipitation process, while the sulfuric acid solution is reused in the high-pressure acid leaching process.

[0012] This application utilizes ion exchange to recover nickel and cobalt from wastewater after manganese removal via MHP (Metallurgical Hydrometallurgical Processing). This not only reduces the nickel and cobalt content in the wastewater, better meeting environmental protection requirements, but also improves the utilization rate of nickel and cobalt by returning the recovered nickel and cobalt to CCD washing. Magnesium and sodium salts are separated using extraction or ion-selective membrane technology. The sodium salt is converted into sodium hydroxide solution and sulfuric acid solution via bipolar membrane electrolysis. Part of the sodium hydroxide solution is reused in the iron and aluminum removal process (as a neutralizing agent), and part is used with the magnesium salt in the manganese precipitation process (as a precipitant). The sulfuric acid solution is reused in the high-pressure acid leaching process, and the remaining magnesium salt is recovered as magnesium sulfate through evaporation and crystallization. The intermediate products recovered by this recycling method can be further purified or extracted to obtain corresponding products, or directly reused in the upstream processes of hydrometallurgy, reducing SO4 in the wastewater. 2- Na + Mg 2+ OH - Ni 2+ Co 2+ It can be directly reused, resulting in high atom utilization. Furthermore, this application utilizes the above method to recover and reuse OH- from wastewater. - Na + Mg 2+ It is used in the MHP precipitation process, and the final MHP product has performance comparable to or even better than that of the product prepared using industrial-grade sodium hydroxide and magnesium oxide, while significantly reducing production costs.

[0013] Preferably, the pH value of the iron and aluminum removal process in step (1) is set to 3.8~5.5.

[0014] Preferably, the pH value of the MHP precipitation process in step (1) is set to 6.3~8.5.

[0015] Preferably, the method of removing manganese by adding alkali to the MHP precipitate in step (1) is to adjust the pH of the solution to 9.5~11 by adding alkali.

[0016] Preferably, the specific operation of step (2) of ion-exchanging the wastewater after manganese removal by MHP precipitation to obtain the ion-exchanged liquid and the enriched nickel-cobalt solution includes: sending the wastewater after manganese removal by MHP precipitation to a resin adsorption column to obtain nickel-cobalt adsorption resin and ion-exchanged liquid, and using a desorbent to desorb the nickel-cobalt adsorption resin to obtain the enriched nickel-cobalt solution.

[0017] Preferably, the resin adsorption column is a cation exchange resin or a chelating resin; more preferably, the cation exchange resin is a strongly acidic cation exchange resin, and the chelating resin is an M4195 chelating ion exchange resin or an IRC-748 chelating ion exchange resin.

[0018] Preferably, the desorbent is an inorganic acid, and the desorbent contains H... + The concentration is ≥0.01mol / L; more preferably, the inorganic acid is at least one of sulfuric acid, hydrochloric acid and nitric acid.

[0019] Preferably, the specific operation of obtaining magnesium-rich solution and magnesium-poor solution by extraction of the ion-exchange liquid in step (3) includes: firstly, extracting the ion-exchange liquid with an extractant to separate the organic phase and raffinate; then, acid washing the organic phase; and finally, back-extraction with a back-extraction agent. The resulting back-extraction solution is the magnesium-rich solution, and the raffinate is the magnesium-poor solution.

[0020] Preferably, the extractant is BC196 extractant, the diluent is kerosene, the saponification rate is 25-40%, the O / A ratio is 1-3, and the number of extraction stages is 3-8.

[0021] Preferably, the specific operation of acid washing the organic phase includes: washing with an inorganic acid with a concentration of 0.1 to 0.8 mol / L, and the number of washing stages is 6 to 10; the inorganic acid is at least one of hydrochloric acid and sulfuric acid.

[0022] Preferably, the specific operation of back-extraction with the back-extraction agent includes: back-extraction with an inorganic acid at a concentration of 3.0 to 6.5 mol / L, and the number of back-extraction stages is 4 to 8; the inorganic acid is sulfuric acid.

[0023] Preferably, the specific operation of obtaining magnesium-rich and magnesium-poor solutions by treating the ion-exchange solution with an ion-selective membrane in step (3) includes: using an ion-selective membrane to separate monovalent and divalent metal ions in the ion-exchange solution. Specifically, the ion-selective membrane can be a CIMS series product sold by Hangzhou Lanran Technology Co., Ltd., a Chinese manufacturer.

[0024] Preferably, the sodium hydroxide solution in step (4) is mixed with a portion of the magnesium-rich solution in step (3) and then reused in the MHP precipitation process.

[0025] In the MHP settling process, this application pre-mixes sodium hydroxide with a portion of the magnesium-rich solution to generate magnesium hydroxide. Magnesium hydroxide, as a weakly alkaline substance, can avoid or mitigate the "localized over-alkaliness" effect caused by using sodium hydroxide alone, thereby ensuring a moderate nucleation rate of MHP and producing particles of suitable size and uniform distribution. This not only effectively reduces the moisture content of the filter cake but also helps reduce the transportation costs of MHP.

[0026] Preferably, when the sodium hydroxide solution in step (4) is mixed with the partially magnesium-rich solution in step (3), the Na in the sodium hydroxide solution... + With some magnesium in magnesium-rich solution 2+ The molar ratio of the substances is 1:1 to 9.

[0027] In this application, mixing magnesium-rich solution with sodium hydroxide produces magnesium hydroxide, a weakly alkaline substance. Relying solely on magnesium hydroxide as a precipitant leads to a higher magnesium content and lower nickel content in the prepared MHP, thus increasing the transportation cost of the MHP and the expense of removing magnesium using P507 extractant in subsequent refining processes. Therefore, this application controls the Na+ content in the sodium hydroxide solution... + With Mg in magnesium-rich solution 2+ The molar ratio of sodium hydroxide to magnesium hydroxide is 1:1 to 9 to achieve the coexistence of sodium hydroxide and magnesium hydroxide, and to participate in the precipitation process of MHP as a mixed precipitant.

[0028] Compared with the prior art, the beneficial effects of this application include:

[0029] This invention first involves ion exchange in the wastewater after MHP precipitation for manganese removal to recover nickel and cobalt, producing an ion-exchange liquid and a enriched nickel-cobalt solution. The enriched nickel-cobalt solution is reused in the CCD washing process. Subsequently, the ion-exchange liquid is separated into magnesium and sodium salts by extraction or ion-selective membrane technology. The sodium salts are converted into sodium hydroxide and sulfuric acid solutions via bipolar membrane electrolysis. The sulfuric acid solution is reused in the high-pressure acid leaching process; a portion of the sodium hydroxide solution is reused in the iron and aluminum removal process, while another portion is mixed with some magnesium salts and reused again in the manganese precipitation process to remove MHP. The remaining magnesium salts are recovered as magnesium sulfate through evaporation and crystallization. This invention achieves a high recovery rate for the wastewater after MHP precipitation for manganese removal. The recovered intermediate products can be further purified or extracted to obtain corresponding products, or directly reused in the preceding processes of hydrometallurgy. The entire recovery process has a minimal environmental impact. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating one embodiment of the method for recycling wastewater from laterite nickel ore hydrometallurgical processes according to this application. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0032] The main components of the laterite nickel ore solution used in the following embodiments and comparative examples of the present invention are as follows: nickel ions 3.43 g / L, cobalt ions 0.351 g / L, manganese ions 2.25 g / L, calcium ions 0.589 g / L, and magnesium ions 7.99 g / L.

[0033] Example 1

[0034] A method for recycling wastewater from hydrometallurgical treatment of laterite nickel ore comprises the following steps:

[0035] (1) Take the high-pressure acid leaching solution of laterite nickel ore and perform circulating leaching, CCD washing, iron and aluminum removal and MHP precipitation treatment, and filter to obtain the liquid after MHP precipitation; add alkali (sodium hydroxide) to the liquid to adjust the pH to 9.5~11 to remove manganese, and filter to obtain the wastewater after MHP precipitation and manganese removal; wherein, the iron and aluminum removal process controls the pH to 3.8~5.5; the MHP precipitation process controls the pH to 6.3~8.5, and reacts at 60℃ for 5 h;

[0036] (2) The wastewater after manganese removal by MHP precipitation was sent to an M4195 chelating ion exchange resin adsorption column to obtain nickel-cobalt adsorption resin and ion exchange liquid. Hydrochloric acid was used as a desorbent to desorb the nickel-cobalt adsorption resin. The H in the hydrochloric acid +The concentration of nickel-cobalt is ≥0.01mol / L, and an enriched nickel-cobalt solution is obtained; this enriched nickel-cobalt solution is reused in the CCD washing process.

[0037] The main components of the solution after ion exchange are as follows: divalent ions such as Ni, Co, and Mn are all <0.1 mg / L.

[0038] (3) First, the ion-exchange solution is extracted with BC196 extractant, kerosene is used as diluent, the saponification rate is 30%, the O / A ratio is 3, and the number of extraction stages is 8. The organic phase and raffinate are separated. Then, the organic phase is washed with sulfuric acid solution with a concentration of 0.1 mol / L for 8 stages. Finally, the organic phase is back-extracted with sulfuric acid solution with a concentration of 3.0 mol / L for 6 stages. The resulting back-extracted solution is magnesium-rich solution, and the raffinate is magnesium-poor solution. Part of the magnesium-rich solution is recycled to the MHP precipitation process, and the remaining magnesium-rich solution is evaporated and crystallized to obtain magnesium sulfate.

[0039] (4) After the magnesium-poor solution is treated by bipolar membrane electrolysis, sodium hydroxide solution and sulfuric acid solution are obtained. The sulfuric acid solution is recycled for the high-pressure acid leaching process, and part of the sodium hydroxide solution is recycled for the iron and aluminum removal process. The other part is mixed with the magnesium-rich solution described in step (3) and then recycled to the MHP precipitation process. The Na content in this part of the sodium hydroxide solution is controlled. + With some magnesium in magnesium-rich solution 2+ The molar ratio of sodium and magnesium is 1:1, and the ratio of the sum of the molar amounts of sodium and magnesium to the sum of the molar amounts of nickel and cobalt in the liquid after removing iron and aluminum from laterite nickel ore satisfies: (Na×2+Mg) / (Ni+Co)=1.

[0040] Example 2

[0041] This embodiment provides a method for recycling wastewater from hydrometallurgical treatment of laterite nickel ore, which differs from Embodiment 1 only in that:

[0042] In step (4), the Na content in this portion of the sodium hydroxide solution is controlled. + With some magnesium in magnesium-rich solution 2+ The molar ratio of the substances is 1:5, and the other steps and conditions are the same as in Example 1.

[0043] Example 3

[0044] This embodiment provides a method for recycling wastewater from hydrometallurgical treatment of laterite nickel ore, which differs from Embodiment 1 only in that:

[0045] In step (4), the Na content in this portion of the sodium hydroxide solution is controlled. + With some magnesium in magnesium-rich solution 2+ The molar ratio of the substances is 1:9, and the other steps and conditions are the same as in Example 1.

[0046] Comparative Example 1

[0047] The only difference from Example 1 is that the wastewater after MHP removal is reused in the MHP removal process, while the other steps and conditions are the same as in Example 1.

[0048] Comparative Example 2

[0049] The only difference from Example 1 is that industrial-grade sodium hydroxide and magnesium oxide are used instead of the sodium hydroxide solution obtained by bipolar membrane electrolysis and the magnesium-rich solution obtained by extraction, respectively. The other steps and conditions are the same as in Example 1.

[0050] The above embodiments and comparative examples were basically stable after 10 cycles. At this time, the composition content, particle size and moisture content of the MHP filter cake obtained by the MHP settling process after the 10th cycle were tested. The test results are shown in Table 1.

[0051] Table 1. Statistical table of MHP filter cake composition, particle size, and moisture content.

[0052]

[0053] As shown in Table 1, the MHP filter cake prepared by the method described in this invention for recycling laterite nickel ore hydrometallurgical wastewater exhibits excellent performance. Compared with the comparative method, the MHP filter cake prepared in this application demonstrates even better performance.

[0054] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Any other corresponding changes and modifications made based on the technical concept of this application should be included within the scope of protection of the claims of this application.

Claims

1. A method for recycling wastewater from hydrometallurgical processes in laterite nickel ore, characterized in that, Includes the following steps: (1) Take the high-pressure acid leaching solution of laterite nickel ore and perform circulating leaching, CCD washing, iron and aluminum removal and MHP precipitation treatment, filter to obtain MHP precipitation liquid; add alkali to the MHP precipitation liquid to remove manganese, filter to obtain MHP precipitation and manganese removal wastewater. (2) The wastewater after manganese removal by MHP is subjected to ion exchange to obtain ion exchange liquid and enriched nickel-cobalt solution. The enriched nickel-cobalt solution is reused in the CCD washing process. (3) After ion exchange, the liquid is treated by extraction or ion-selective membrane to obtain magnesium-rich liquid and magnesium-poor liquid; part of the magnesium-rich liquid is recycled for the precipitation of MHP, and the remaining part is evaporated and crystallized to obtain magnesium sulfate. (4) The magnesium-poor solution is electrolyzed by bipolar membrane, and the resulting sodium hydroxide solution is reused in the iron and aluminum removal and MHP precipitation process, while the sulfuric acid solution is reused in the high-pressure acid leaching process.

2. The method for recycling wastewater from laterite nickel ore hydrometallurgical processes according to claim 1, characterized in that, The pH value of the iron and aluminum removal process in step (1) is set to 3.8~5.5; The pH value of the MHP precipitation process in step (1) is set to 6.3~8.5; The method for removing manganese by adding alkali to the MHP precipitate in step (1) is to adjust the pH of the solution to 9.5~11 by adding alkali.

3. The method for recycling wastewater from laterite nickel ore hydrometallurgical processes according to claim 1, characterized in that, The specific operation of step (2) to obtain the ion-exchanged liquid and enriched nickel-cobalt solution by ion exchange of the wastewater after MHP manganese removal includes: sending the wastewater after MHP manganese removal to the resin adsorption column to obtain nickel-cobalt adsorption resin and ion-exchanged liquid, and using a desorbent to desorb the nickel-cobalt adsorption resin to obtain the enriched nickel-cobalt solution.

4. The method for recycling wastewater from laterite nickel ore hydrometallurgical processes according to claim 3, characterized in that, The resin adsorption column uses either cationic resin or chelating resin. The desorbent is an inorganic acid, and H in the desorbent is... + The concentration is ≥0.01mol / L.

5. The method for recycling wastewater from laterite nickel ore hydrometallurgical processes according to claim 4, characterized in that, The cation exchange resin is a strong acidic cation exchange resin, and the chelating resin is M4195 chelating ion exchange resin or IRC-748 chelating ion exchange resin. The inorganic acid is at least one of sulfuric acid, hydrochloric acid, and nitric acid.

6. The method for recycling wastewater from laterite nickel ore hydrometallurgical processes according to claim 1, characterized in that, The specific operations of obtaining magnesium-rich solution and magnesium-poor solution by extraction of the ion-exchange liquid in step (3) include: firstly, extracting the ion-exchange liquid with an extractant to separate the organic phase and raffinate; then, acid washing the organic phase; and finally, back-extraction with a back-extraction agent. The resulting back-extraction solution is the magnesium-rich solution, and the raffinate is the magnesium-poor solution. The specific operation of obtaining magnesium-rich and magnesium-poor solutions by treating the ion-exchange solution with an ion-selective membrane in step (3) includes: using an ion-selective membrane to separate monovalent and divalent metal ions in the ion-exchange solution.

7. The method for recycling wastewater from laterite nickel ore hydrometallurgical processes according to claim 6, characterized in that, The extractant is BC196; the diluent is kerosene; the saponification rate is 25-40%; the O / A ratio is 1-3; and the number of extraction stages is 3-8. The specific operation of acid washing the organic phase includes: washing with an inorganic acid with a concentration of 0.1 to 0.8 mol / L, and the number of washing stages is 6 to 10; the inorganic acid is at least one of hydrochloric acid and sulfuric acid.

8. The method for recycling wastewater from hydrometallurgical processes in laterite nickel ore according to claim 6 or 7, characterized in that, The specific operation of back-extraction using the back-extraction agent includes: back-extraction using an inorganic acid with a concentration of 3.0 to 6.5 mol / L, and the number of back-extraction stages being 4 to 8; the inorganic acid is sulfuric acid.

9. The method for recycling wastewater from laterite nickel ore hydrometallurgical processes according to claim 1, characterized in that, The sodium hydroxide solution in step (4) is mixed with a portion of the magnesium-rich solution in step (3) and then reused in the MHP precipitation process.

10. The method for recycling wastewater from laterite nickel ore hydrometallurgical processes according to claim 9, characterized in that, When the sodium hydroxide solution in step (4) is mixed with the partial magnesium-rich solution in step (3), the Na in the sodium hydroxide solution... + With some magnesium in magnesium-rich solution 2+ The molar ratio of the substances is 1:1~9.

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