Method for recycling laterite-nickel ore hydrometallurgy wastewater

Abstract

The invention discloses a laterite-nickel ore hydrometallurgy wastewater cyclic utilization method which comprises the following steps: taking a laterite-nickel ore high-pressure acid leaching solution, carrying out cyclic leaching, CCD (Charge Coupled Device) washing, removing iron and aluminum, carrying out MHP (Methyl Hydroxypropyl Phosphate) precipitation treatment, and filtering to obtain a solution after MHP precipitation; adding alkali into the post-solution to remove manganese, and filtering to obtain MHP-precipitated manganese-removed wastewater; carrying out ion exchange on the MHP-precipitated manganese-removed wastewater to recover nickel and cobalt, so as to obtain an ion-exchanged solution and an enriched nickel-cobalt solution, and reusing the enriched nickel-cobalt solution to a CCD (Charge Coupled Device) washing process; performing extraction or ion selective membrane treatment on the solution after ion exchange to obtain a magnesium-rich solution and a magnesium-poor solution; part of the magnesium-rich liquid is reused in the MHP precipitation process, and the rest part is subjected to evaporative crystallization to obtain magnesium sulfate; and the magnesium-poor solution is electrolyzed by a bipolar membrane, the obtained sodium hydroxide solution is reused for the processes of removing iron and aluminum and precipitating MHP, and the sulfuric acid solution is reused for the high-pressure acid leaching process. According to the method, the recycling rate of the laterite-nickel ore hydrometallurgy wastewater is increased, and the recycled intermediate product can be further purified or directly reused in an early-stage process.

Description

Technical Field

[0001] The present invention relates to the field of hydrometallurgy, and in particular to a method for recycling wastewater from laterite nickel ore hydrometallurgy. Background Art

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

[0003] In the hydrometallurgical production of nickel cobalt hydroxide (MHP) intermediates from laterite nickel ore, sodium hydroxide and magnesium oxide are commonly used as precipitants. However, the use of sodium hydroxide in industrial production can cause the reaction system to become locally overly alkaline, which not only increases the manganese content in MHP but also correspondingly reduces the nickel and cobalt contents. This increased manganese content increases the cost of subsequent refining steps. Furthermore, the overly alkaline environment accelerates the nucleation rate of MHP, resulting in smaller and more unevenly distributed particles. This makes effective sedimentation and filtration of MHP difficult, leading to a high moisture content in the filter cake and increased transportation costs. Furthermore, in existing processes, after the nickel and cobalt are completely precipitated and separated, the filtrate from this process primarily contains Mn and Mg. During wastewater treatment, a specific precipitant is typically used to precipitate the manganese, and the resulting manganese slag is then filtered and landfilled. The filtrate from the manganese slag filtration primarily contains Mg. Due to its alkalinity, it is typically neutralized with sulfuric acid before being discharged into the ocean.

[0004] As can be seen, existing technologies for treating laterite nickel ore hydrometallurgical wastewater still have shortcomings. New pollutants are often generated during the wastewater treatment process, resulting in adverse environmental impacts. Although a variety of technologies and methods have been applied to the treatment and recycling of this type of wastewater, challenges remain, such as high treatment costs, inter-technical compatibility issues, and the risk of secondary pollution. Therefore, how to improve wastewater recycling rates and reduce environmental impacts is a research topic worthy of in-depth exploration. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this application is to provide a method for recycling laterite nickel ore hydrometallurgical wastewater, aiming to solve the problems of low treatment efficiency and secondary pollution of laterite nickel ore hydrometallurgical wastewater in the existing technology.

[0006] This application is specifically implemented through the following technical solutions: A method for recycling laterite nickel ore hydrometallurgical wastewater comprises the following steps: (1) taking the high-pressure acid leaching liquid of laterite nickel ore and performing cyclic leaching, CCD washing, iron and aluminum removal and MHP precipitation treatment, filtering to obtain the liquid after MHP precipitation; adding alkali to the liquid after MHP precipitation to remove manganese, filtering to obtain the wastewater after MHP precipitation and manganese removal; (2) The wastewater after MHP precipitation and manganese removal is subjected to ion exchange to obtain ion exchange liquid and enriched nickel-cobalt solution, and the enriched nickel-cobalt solution is reused in the CCD washing process; (3) The ion exchange solution is subjected to extraction or ion selective membrane treatment to obtain magnesium-rich solution and magnesium-poor solution; part of the magnesium-rich solution is reused in the MHP precipitation process, and the remaining part is evaporated and crystallized to obtain magnesium sulfate; (4) The magnesium-depleted solution is electrolyzed by bipolar membrane, 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.

[0007] The present application recovers nickel and cobalt from wastewater after MHP precipitation and manganese removal through ion exchange, which not only reduces the nickel and cobalt content in the wastewater and is more in line with environmental protection requirements, but also returns the nickel and cobalt recovered after ion exchange to CCD for washing, which can also improve the utilization rate of nickel and cobalt. Magnesium salts and sodium salts are separated by extraction or ion selective membrane technology. Sodium salts are converted into sodium hydroxide solution and sulfuric acid solution by bipolar membrane electrolysis. Part of the former is reused in the iron and aluminum removal process (as a neutralizer), and part is used in the manganese precipitation process (as a precipitant) together with magnesium salts; the latter is reused in the high-pressure acid leaching process, and the remaining magnesium salts are recovered as magnesium sulfate by evaporation and crystallization. The intermediate products recovered by the recycling method of the present application can be further purified or extracted to obtain the corresponding products, or directly reused in the pre-process of hydrometallurgy to make SO4 in the wastewater 2- 、Na + Mg 2+ OH - 、Ni 2+ 、Co 2+ In addition, the present invention recycles OH in wastewater by adopting the above method. - 、Na + Mg 2+ It is also used in the MHP precipitation process. The final MHP product has the same or even better performance as the product prepared with industrial-grade sodium hydroxide and magnesium oxide, and significantly reduces the production cost.

[0008] Preferably, the pH value of the iron and aluminum removal process in step (1) is set to 3.8~5.5.

[0009] Preferably, the pH value of the MHP precipitation process in step (1) is set to 6.3-8.5.

[0010] Preferably, the method of adding alkali to the solution after precipitation of MHP in step (1) to remove manganese is: adjusting the pH value of the solution to 9.5-11 by adding alkali.

[0011] Preferably, the specific operation of subjecting the wastewater after MHP precipitation and manganese removal to ion exchange to obtain an ion-exchanged liquid and an enriched nickel-cobalt solution in step (2) includes: sending the wastewater after MHP precipitation and manganese removal to a resin adsorption column to obtain a nickel-cobalt adsorption resin and an ion-exchanged liquid, and desorbing the nickel-cobalt adsorption resin with a desorbent to obtain an enriched nickel-cobalt solution.

[0012] Preferably, the resin adsorption column adopts a cationic resin or a chelating resin; more preferably, the cationic resin is a strongly acidic cation exchange resin, and the chelating resin is M4195 chelating ion exchange resin or IRC-748 chelating ion exchange resin.

[0013] Preferably, the desorbent is an inorganic acid, and H + The concentration is ≥0.01 mol / L; more preferably, the inorganic acid is at least one of sulfuric acid, hydrochloric acid and nitric acid.

[0014] Preferably, the specific operation of extracting the ion-exchanged liquid in step (3) to obtain a magnesium-rich liquid and a magnesium-depleted liquid includes: firstly extracting the ion-exchanged liquid with an extractant to separate the organic phase and the raffinate, then acid-washing the organic phase, and finally stripping with a stripping agent, whereby the stripping liquid obtained is the magnesium-rich liquid, and the raffinate is the magnesium-depleted liquid.

[0015] 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.

[0016] Preferably, the specific operation of acid washing the organic phase includes: washing with an inorganic acid having 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.

[0017] Preferably, the specific operation of stripping with a stripping agent includes: stripping with an inorganic acid having a concentration of 3.0 to 6.5 mol / L, with the stripping stage number being 4 to 8; and the inorganic acid is sulfuric acid.

[0018] Preferably, the specific operation of treating the ion-exchanged liquid with an ion-selective membrane to obtain the magnesium-rich liquid and the magnesium-depleted liquid in step (3) includes separating the monovalent metal ions and divalent metal ions in the ion-exchanged liquid using an ion-selective membrane. Specifically, the ion-selective membrane that can be selected can be the CIMS series products sold by Hangzhou Lanran Technology Co., Ltd., a Chinese manufacturer.

[0019] Preferably, the sodium hydroxide solution in step (4) is mixed with part of the magnesium-rich solution in step (3) and then reused in the MHP precipitation process.

[0020] During the MHP precipitation process, this application premixes sodium hydroxide with a portion of the magnesium-rich solution to produce magnesium hydroxide. As a weakly alkaline substance, magnesium hydroxide can avoid or mitigate the "local over-alkalinity" effect that occurs when using sodium hydroxide alone, thereby ensuring a moderate nucleation rate for MHP and producing particles of appropriate size and uniform distribution. This not only effectively reduces the moisture content of the filter cake but also helps lower the transportation cost of MHP.

[0021] Preferably, when the sodium hydroxide solution in step (4) is mixed with the part of the magnesium-rich solution in step (3), the Na + With Mg in some magnesium-rich solution 2+ The molar ratio is 1:1~9.

[0022] In this application, magnesium-rich solution is mixed with sodium hydroxide to produce magnesium hydroxide, which is a weak alkaline substance. Relying solely on magnesium hydroxide as a precipitant will result in a high magnesium content and a low nickel content in the prepared MHP, thereby increasing the transportation cost of MHP and the cost of using P507 extractant to remove magnesium in the subsequent refining process. Therefore, this application controls the Na in the sodium hydroxide solution to + With Mg in magnesium-rich solution 2+ The molar ratio of sodium hydroxide and magnesium hydroxide is 1:1~9 to achieve the coexistence of sodium hydroxide and magnesium hydroxide, which are used as mixed precipitants to participate in the precipitation process of MHP.

[0023] Compared with the prior art, the advantages of this application include: The present invention first performs ion exchange on the wastewater after MHP precipitation and manganese removal to recover nickel and cobalt, producing an ion-exchanged liquid and an enriched nickel-cobalt solution. The enriched nickel-cobalt solution is then reused in the CCD washing process. The ion-exchanged liquid is then separated into magnesium and sodium salts through extraction or ion-selective membrane technology. The sodium salt is converted into sodium hydroxide solution and sulfuric acid solution 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 and MHP removal process. The remaining magnesium salts are recovered as magnesium sulfate through evaporation and crystallization. The present invention achieves a high recovery rate for the wastewater after MHP precipitation and manganese removal. The recovered intermediate product can be further purified or extracted to obtain the corresponding product, or directly reused in the pre-hydrometallurgical process. The entire recycling process has a minimal impact on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1This is a flow chart of an embodiment of a method for recycling laterite nickel ore hydrometallurgical wastewater according to the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0026] The main components of the laterite nickel ore after iron and aluminum removal liquid used in the following examples and comparative examples of the present invention are as follows: nickel ion is 3.43 g / L, cobalt ion is 0.351 g / L, manganese ion is 2.25 g / L, calcium ion is 0.589 g / L, and magnesium ion is 7.99 g / L.

[0027] Example 1 A method for recycling laterite nickel ore hydrometallurgical wastewater, comprising the following steps: (1) The high-pressure acid leaching liquid of laterite nickel ore was subjected to cyclic leaching, CCD washing, iron and aluminum removal, and MHP precipitation treatment, and the MHP precipitation liquid was filtered to obtain the MHP precipitation liquid; alkali (sodium hydroxide) was added to the liquid to adjust the pH to 9.5-11 to remove manganese, and the MHP precipitation and manganese removal wastewater was filtered; wherein, the iron and aluminum removal process was controlled at pH = 3.8-5.5; the MHP precipitation process was controlled at pH = 6.3-8.5, and the reaction was carried out at 60 ° C for 5 h; (2) The wastewater after MHP precipitation and manganese removal is sent to the M4195 chelate ion exchange resin adsorption column to obtain nickel-cobalt adsorption resin and ion exchange liquid. Hydrochloric acid is used as a desorbent to desorb the nickel-cobalt adsorption resin. + The concentration of nickel-cobalt is ≥0.01 mol / L to obtain an enriched nickel-cobalt solution; the enriched nickel-cobalt solution is recycled to the CCD washing process; The main components of the liquid after ion exchange are as follows: divalent ions such as Ni, Co, and Mn are all less than 0.1 mg / L.

[0028] (3) First, the ion exchange liquid was extracted with BC196 extractant, the diluent was kerosene, the saponification rate was 30%, the O / A ratio was 3, and the number of extraction stages was 8; the organic phase and the raffinate were separated, and then the organic phase was washed with a sulfuric acid solution with a concentration of 0.1 mol / L, and the number of washing stages was 8. Finally, the organic phase was stripped with a sulfuric acid solution with a concentration of 3.0 mol / L, and the number of stripping stages was 6. The stripped liquid obtained was a magnesium-rich liquid, and the raffinate was a magnesium-poor liquid; part of the magnesium-rich liquid was reused in the MHP precipitation process, and the remaining magnesium-rich liquid was evaporated and crystallized to obtain magnesium sulfate; (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 reused in the high-pressure acid leaching process, and part of the sodium hydroxide solution is reused in the iron and aluminum removal process. The other part is mixed with the magnesium-rich solution in step (3) and then reused in the MHP precipitation process. The Na in this part of the sodium hydroxide solution is controlled. + With Mg in some 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 elements to the sum of the molar amounts of nickel and cobalt elements in the laterite nickel ore after iron and aluminum removal satisfies: (Na×2+Mg) / (Ni+Co)=1.

[0029] Example 2 This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater, which differs from Example 1 only in that: In step (4), control the Na + With Mg in some magnesium-rich solution 2+ The molar ratio of the substance is 1:5, and the other steps and conditions are the same as those in Example 1.

[0030] Example 3 This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater, which differs from Example 1 only in that: In step (4), control the Na + With Mg in some magnesium-rich solution 2+ The molar ratio of the substance is 1:9, and the other steps and conditions are the same as those in Example 1.

[0031] Comparative Example 1 The only difference from Example 1 is that the wastewater after MHP precipitation and manganese removal is reused in the MHP precipitation process, and the other steps and conditions are the same as those in Example 1.

[0032] Comparative Example 2 The only difference from Example 1 is that industrial-grade sodium hydroxide and magnesium oxide are used to replace the sodium hydroxide solution obtained by bipolar membrane electrolysis and the magnesium-rich solution obtained by extraction, respectively. Other steps and conditions are the same as those in Example 1.

[0033] The above embodiments and comparative examples were basically stable after 10 cycles. At this time, the component content, particle size and moisture content of the MHP filter cake prepared in the MHP precipitation process after the 10th cycle were tested. The test results are shown in Table 1.

[0034] Table 1 Statistics of MHP filter cake composition, particle size and moisture content

[0035] The results in Table 1 show that the MHP filter cake prepared by recycling laterite nickel ore hydrometallurgical wastewater using the method described in the present invention has good performance. Compared with the method of the comparative example, the MHP filter cake prepared by the present application has better performance.

[0036] The specific implementation methods of the present application described above do not limit the scope of protection of the present application. Any other corresponding changes and modifications made based on the technical concept of the present application should be included in the scope of protection of the claims of the present application.

Claims

1. A method for recycling laterite nickel ore hydrometallurgical wastewater, characterized in that: The steps include: (1) taking the high-pressure acid leaching liquid of laterite nickel ore and performing cyclic leaching, CCD washing, iron and aluminum removal and MHP precipitation treatment, filtering to obtain the liquid after MHP precipitation; adding alkali to the liquid after MHP precipitation to remove manganese, filtering to obtain the wastewater after MHP precipitation and manganese removal; (2) The wastewater after MHP precipitation and manganese removal is subjected to ion exchange to obtain ion exchange liquid and enriched nickel-cobalt solution, and the enriched nickel-cobalt solution is reused in the CCD washing process; (3) The ion exchange solution is subjected to extraction or ion selective membrane treatment to obtain magnesium-rich solution and magnesium-poor solution; part of the magnesium-rich solution is reused in the MHP precipitation process, and the remaining part is evaporated and crystallized to obtain magnesium sulfate; (4) The magnesium-depleted solution is electrolyzed by bipolar membrane, 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.

2. The method for recycling laterite nickel ore hydrometallurgical wastewater 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 of adding alkali to the solution after precipitation of MHP in step (1) to remove manganese is: adjusting the pH value of the solution to 9.5-11 by adding alkali.

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

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

5. The method for recycling laterite nickel ore hydrometallurgical wastewater according to claim 4, characterized in that: The cationic resin is a strongly acidic cationic exchange resin, and the chelating resin is an M4195 chelating ion exchange resin or an 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 laterite nickel ore hydrometallurgical wastewater according to claim 1, characterized in that: The specific operation of extracting the ion-exchanged liquid in step (3) to obtain the magnesium-rich liquid and the magnesium-lean liquid includes: firstly extracting the ion-exchanged liquid with an extractant to separate the organic phase and the raffinate, then acid-washing the organic phase, and finally stripping the organic phase with a stripping agent, whereby the stripping liquid obtained is the magnesium-rich liquid and the raffinate is the magnesium-lean liquid; The specific operation of obtaining the magnesium-rich solution and the magnesium-depleted solution by subjecting the ion-exchanged solution to ion selective membrane treatment in step (3) includes: separating the monovalent metal ions and divalent metal ions in the ion-exchanged solution by using the ion selective membrane.

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

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

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

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