A recycling method of laterite nickel ore hydrometallurgy wastewater

Abstract

The application provides a recycling method of laterite nickel ore hydrometallurgy wastewater, which comprises the following steps: the laterite nickel ore is sequentially subjected to high-pressure acid leaching, cyclic leaching, CCD washing, iron and aluminum removal treatment, MHP precipitation treatment and manganese precipitation treatment to obtain post-manganese precipitation wastewater; the post-manganese precipitation wastewater is subjected to ion exchange to obtain post-ion exchange liquid and nickel and cobalt enriched solution; the nickel and cobalt enriched solution is recycled to the CCD washing; the post-ion exchange liquid is subjected to magnesium separation to obtain magnesium rich liquid and magnesium poor liquid; the magnesium rich liquid is recycled to the MHP precipitation treatment, and / or the magnesium rich liquid is subjected to crystallization to obtain magnesium sulfate product; the magnesium poor liquid is subjected to bipolar membrane electrolysis to obtain sodium hydroxide solution and sulfuric acid solution; the sodium hydroxide solution is recycled to the iron and aluminum removal treatment, and the sulfuric acid solution is recycled to the cyclic leaching. The application can realize full utilization of wastewater resources, is green, environmentally friendly and economical, and has wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrometallurgy, and in particular to a method for recycling laterite nickel ore hydrometallurgical wastewater. 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 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 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, producing small and unevenly distributed particles. This makes effective sedimentation and filtration of MHP difficult, resulting in a high moisture content in the filter cake, which in turn increases MHP 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, the filtrate is typically neutralized with sulfuric acid before being discharged into the ocean.

[0004] As can be seen, existing technologies for treating laterite nickel hydrometallurgical wastewater still have shortcomings. New pollutants are often generated during the wastewater treatment process, resulting in 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, inter-technology compatibility issues, and the risk of secondary pollution.

[0005] Therefore, how to improve the recycling rate of laterite nickel ore hydrometallurgical wastewater and reduce its impact on the environment is a difficult problem that needs to be solved urgently. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for recycling laterite nickel ore hydrometallurgical wastewater, which can solve the problems of low treatment efficiency and secondary pollution of laterite nickel ore hydrometallurgical wastewater in the existing technology.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a recycling method for laterite nickel ore hydrometallurgical wastewater, which comprises the following steps:

[0009] (1) Laterite nickel ore is sequentially subjected to high-pressure acid leaching, circulating leaching, CCD washing, iron and aluminum removal treatment, MHP precipitation treatment and manganese precipitation treatment to obtain manganese precipitation wastewater;

[0010] (2) the wastewater after manganese precipitation is subjected to ion exchange to obtain an ion exchange liquid and an enriched nickel-cobalt solution; the enriched nickel-cobalt solution is circulated to the CCD washing in step (1);

[0011] (3) the ion exchanged liquid is subjected to magnesium separation to obtain a magnesium-rich liquid and a magnesium-depleted liquid; the magnesium-rich liquid is circulated to the MHP precipitation treatment in step (1), and / or the magnesium-rich liquid is crystallized to obtain a magnesium sulfate product;

[0012] (4) The magnesium-depleted solution is electrolyzed through a bipolar membrane to obtain a sodium hydroxide solution and a sulfuric acid solution; the sodium hydroxide solution is circulated to the iron and aluminum removal treatment in step (1), and the sulfuric acid solution is circulated to the high-pressure leaching in step (1).

[0013] The method for recycling laterite nickel ore hydrometallurgical wastewater provided by the present invention is mainly aimed at wastewater after manganese precipitation. By combining subsequent ion exchange, magnesium separation and bipolar membrane electrolysis processes, it is possible to achieve comprehensive recovery and recycling of magnesium, nickel, cobalt, sodium hydroxide and sulfate in the wastewater after manganese precipitation without generating additional waste liquid, and has broad application prospects.

[0014] Specifically, the present invention recovers nickel and cobalt in the wastewater after manganese precipitation 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. The sodium salt is 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 salt; the latter is reused in the acid leaching process, and the remaining magnesium salt can be recovered as magnesium sulfate by evaporation and crystallization. The intermediate product recovered by the recycling method of the present invention can be further purified or extracted to obtain the corresponding product, or directly reused in the pre-process of hydrometallurgy to make SO4 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, with broad application prospects.

[0015] In the present invention, CCD washing refers to a continuous counter-current washing process, the purpose of which is to remove dissolved substances (such as metal ions) from solid matter by continuously using solvent, thereby improving extraction efficiency. MHP treatment refers to the precipitation of metal hydroxides, which is to convert metal ions in a metal-containing solution into metal hydroxides through a chemical precipitation reaction.

[0016] Preferably, the pH value of the iron and aluminum removal treatment in step (1) is set to 3.8 to 5.5, for example, it can be 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4 or 5.5, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0017] Preferably, the pH value of the MHP precipitation treatment in step (1) is set to 6.3-8.5, for example, it can be 6.3, 6.6, 6.8, 7.1, 7.3, 7.6, 7.8, 8.1, 8.3 or 8.5, but is not limited to the listed values. Other values ​​not listed in this range are also applicable.

[0018] Preferably, the temperature of the MHP treatment in step (1) is 55 to 70°C, for example, 55°C, 57°C, 59°C, 60°C, 62°C, 64°C, 65°C, 67°C, 69°C or 70°C, but is not limited to the listed values, and other values ​​not listed in this range are also applicable. Preferably, the time of the MHP treatment in step (1) is 2 to 10 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but is not limited to the listed values, and other values ​​not listed in this range are also applicable.

[0019] Preferably, the manganese precipitation treatment in step (1) comprises adding alkali to the liquid after the MHP precipitation treatment to remove manganese.

[0020] Preferably, the pH value of the solution after adding alkali in the manganese precipitation treatment is 9.5-11, for example, it can be 9.5, 9.7, 9.9, 10, 10.2, 10.4, 10.5, 10.7, 10.9 or 11, but is not limited to the listed values. Other values ​​not listed in this range are also applicable.

[0021] The present invention has no special requirements on the specific processes and techniques of the above-mentioned cyclic leaching, CCD washing, iron and aluminum removal treatment, MHP precipitation treatment and manganese precipitation treatment. The process parameters well known to those skilled in the art can be used and will not be described in detail here.

[0022] Preferably, the solution after the MHP precipitation treatment contains nickel ions: 3-4 g / L, for example, 3 g / L, 3.2 g / L, 3.3 g / L, 3.4 g / L, 3.5 g / L, 3.6 g / L, 3.7 g / L, 3.8 g / L, 3.9 g / L or 4 g / L; cobalt ions are 0.1-0.6 g / L, for example, 0.1 g / L, 0.16 g / L, 0.22 g / L, 0.27 g / L, 0.33 g / L, 0.38 g / L, 0.44 g / L, 0.49 g / L, 0.55 g / L or 0.6 g / L; manganese ions are 2.0-3.0 g / L, for example, 2.0 g / L, 2.2 g / L, the calcium ion is 0.1-1.0 g / L, for example, it can be 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L or 1.0 g / L; the magnesium ion is 6.0-8.5 g / L, for example, it can be 6.0 g / L, 6.3 g / L, 6.6 g / L, 6.9 g / L, 7.2 g / L, 7.4 g / L, 7.7 g / L, 8 g / L, 8.3 g / L or 8.5 g / L.

[0023] Preferably, the wastewater after manganese precipitation contains magnesium: 5.8-8.6 g / L, for example, 5.8 g / L, 6.2 g / L, 6.5 g / L, 6.8 g / L, 7.1 g / L, 7.4 g / L, 7.7 g / L, 8 g / L, 8.3 g / L or 8.6 g / L, but is not limited to the listed values. Other values ​​not listed within this range are also applicable; nickel:

[0024] 2.8-4.0 g / L, for example, 2.8 g / L, 3 g / L, 3.1 g / L, 3.2 g / L, 3.4 g / L, 3.5 g / L, 3.6 g / L, 3.8 g / L, 3.9 g / L or 4.0 g / L, but not limited to the values ​​listed above, other values ​​not listed within the range are also applicable; Cobalt: 0.1-0.6 g / L, for example, 0.1 g / L, 0.16 g / L, 0.22 g / L, 0.27 g / L, 0.33 g / L, 0 0.38g / L, 0.44g / L, 0.49g / L, 0.55g / L or 0.6g / L, etc., but not limited to the listed values, other values ​​not listed within the range are equally applicable; sodium: 0.5-5g / L, for example, 0.5g / L, 1g / L, 1.5g / L, 2g / L, 2.5g / L, 3g / L, 3.5g / L, 4g / L, 4.5g / L or 5g / L, etc., but not limited to the listed values, other values ​​not listed within the range are equally applicable.

[0025] Preferably, the ion exchange in step (2) comprises: sending the wastewater after manganese precipitation to a resin adsorption column for ion exchange to obtain nickel-cobalt adsorption resin and ion-exchanged liquid, and using a desorbent to desorb the nickel-cobalt adsorption resin to obtain an enriched nickel-cobalt solution.

[0026] Preferably, the resin adsorption column comprises a cationic resin or a chelating resin.

[0027] Preferably, the cationic resin is a strongly acidic cation exchange resin.

[0028] Preferably, the chelating resin is M4195 chelating ion exchange resin and / or IRC-748 chelating ion exchange resin.

[0029] The present invention preferably uses the above resin for adsorption separation, which can separate nickel, cobalt, magnesium and sodium with high separation efficiency.

[0030] Preferably, the ion exchange temperature is 20-40°C, for example, 20°C, 23°C, 25°C, 27°C, 29°C, 32°C, 34°C, 36°C, 38°C or 40°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] Preferably, the flow rate of the wastewater after manganese precipitation in the ion exchange is 1 to 4 BV / h, for example, it can be 1 BV / h, 1.4 BV / h, 1.7 BV / h, 2 BV / h, 2.4 BV / h, 2.7 BV / h, 3 BV / h, 3.4 BV / h, 3.7 BV / h or 4 BV / h, but is not limited to the listed values. Other values ​​not listed in this range are also applicable.

[0032] The present invention preferably adopts the above flow rate for separation, which has a better separation effect.

[0033] Preferably, the desorbent comprises an inorganic acid.

[0034] Preferably, the concentration of hydrogen ions in the desorbed inorganic acid is ≥0.01 mol / L, for example, it can be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L or 0.15 mol / L, etc.

[0035] Preferably, the desorbed inorganic acid comprises any one or a combination of at least two of sulfuric acid, hydrochloric acid or nitric acid, wherein typical but non-limiting combinations are a combination of sulfuric acid and hydrochloric acid, a combination of nitric acid and hydrochloric acid, and a combination of sulfuric acid and nitric acid.

[0036] Preferably, the flow rate of the desorbent is 0.1 to 1 BV / h, for example, it can be 0.1 BV / h, 0.2 BV / h, 0.3 BV / h, 0.4 BV / h, 0.5 BV / h, 0.6 BV / h, 0.7 BV / h, 0.8 BV / h, 0.9 BV / h or 1 BV / h, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0037] Preferably, the desorption temperature is 20-40°C, for example, it can be 20°C, 23°C, 25°C, 27°C, 29°C, 32°C, 34°C, 36°C, 38°C or 40°C, but is not limited to the listed values. Other values ​​not listed within this range are also applicable.

[0038] Preferably, the ion exchange solution contains magnesium: 5.5-8.6 g / L, for example, 5.5 g / L, 5.9 g / L, 6.2 g / L, 6.6 g / L, 6.9 g / L, 7.3 g / L, 7.6 g / L, 8 g / L, 8.3 g / L or 8.6 g / L, etc., but not limited to the listed values, and other values ​​not listed within the range are also applicable; nickel: 0.01-0.05 g / L, for example, 0.01 g / L, 0.015 g / L, 0.019 g / L, 0.024 g / L, 0.028 g / L, 0.033 g / L, 0.037 g / L, 0.042 g / L, 0.046 g / L or 0.05 g / L, etc., but not limited to the listed values, and other values ​​not listed within the range are also applicable. Other unlisted values ​​are equally applicable; cobalt: 0.01-0.02 g / L, for example, 0.01 g / L, 0.012 g / L, 0.013 g / L, 0.014 g / L, 0.015 g / L, 0.016 g / L, 0.017 g / L, 0.018 g / L, 0.019 g / L or 0.02 g / L, but are not limited to the listed values, and other unlisted values ​​within this range are equally applicable; sodium: 0.5-5 g / L, for example, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L or 5 g / L, but are not limited to the listed values, and other unlisted values ​​within this range are equally applicable.

[0039] Preferably, the magnesium separation in step (3) includes extraction separation and / or membrane separation.

[0040] Preferably, the extraction and separation comprises: extracting the ion exchange liquid with an extraction system to separate an organic phase and a raffinate, then acid-washing the organic phase, and then stripping with a stripping agent, whereby the stripping liquid obtained is a magnesium-rich liquid, and the raffinate is a magnesium-poor liquid.

[0041] Preferably, the extraction system comprises an extractant and a diluent.

[0042] Preferably, the extractant comprises BC196.

[0043] The ion exchange liquid of the present invention mainly contains magnesium and sodium. BC196 is preferably used as the extractant, and kerosene is preferably used as the diluent, which can significantly improve the separation effect of magnesium and sodium.

[0044] More preferably, a co-extraction agent is also added during the extraction.

[0045] Preferably, the synergistic extractant is L-aspartic acid.

[0046] The present invention preferably adopts the above-mentioned synergistic extractant, which can better achieve the separation of magnesium and sodium and improve the separation efficiency of the two.

[0047] Preferably, the mass ratio of the co-extraction agent to the extractant is 0.1 to 0.2:1, for example, it can be 0.1:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1 or 0.2:1, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] Preferably, the mass ratio of the extractant to the diluent is 0.1 to 0.5:1, for example, it can be 0.1:1, 0.15:1, 0.19:1, 0.24:1, 0.28:1, 0.33:1, 0.37:1, 0.42:1, 0.46:1 or 0.5:1, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0049] Preferably, the diluent comprises kerosene.

[0050] Preferably, the extraction system is a saponified extraction system.

[0051] Preferably, the saponification rate of the extraction system is 25-40%, for example, it can be 25%, 27%, 29%, 30%, 32%, 34%, 35%, 37%, 39% or 40%, etc., but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0052] Preferably, the O / A ratio during the extraction process is (1-3):1, for example, 1:1, 1.3:1, 1.5:1, 1.7:1, 1.9:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3:1, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0053] Preferably, the number of extraction stages is 3 to 8, for example, it can be 3, 4, 5, 6, 7 or 8 stages.

[0054] Preferably, the acid concentration of the pickling is 0.1 to 0.8 mol / L, for example, it can be 0.1 mol / L, 0.18 mol / L, 0.26 mol / L, 0.34 mol / L, 0.42 mol / L, 0.49 mol / L, 0.57 mol / L, 0.65 mol / L, 0.73 mol / L or 0.8 mol / L, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0055] Preferably, the number of washing stages of the pickling is 6 to 10, for example, it can be 6, 7, 8, 9 or 10 stages.

[0056] Preferably, the pickling acid comprises hydrochloric acid and / or sulfuric acid.

[0057] Preferably, the stripping agent for the stripping comprises an inorganic acid.

[0058] Preferably, the inorganic acid for stripping is sulfuric acid.

[0059] Preferably, the acid concentration of the stripping is 3.0 to 6.5 mol / L, for example, 3.0 mol / L, 3.39 mol / L, 3.78 mol / L, 4.17 mol / L, 4.56 mol / L, 4.95 mol / L, 5.34 mol / L, 5.73 mol / L, 6.12 mol / L or 6.5 mol / L, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0060] Preferably, the number of stripping stages is 4 to 8, for example, 4, 5, 6, 7 or 8 stages.

[0061] Preferably, the membrane separation comprises: using an ion selective membrane to perform membrane separation on monovalent metal ions and divalent metal ions in the ion exchange liquid.

[0062] Specifically, the ion selective membrane that can be selected may be the CIMS series products sold by the Chinese manufacturer Hangzhou Lanran Technology Co., Ltd.

[0063] Preferably, the temperature of the membrane separation is 25-45°C, for example, it can be 25°C, 28°C, 30°C, 32°C, 34°C, 37°C, 39°C, 41°C, 43°C or 45°C, but is not limited to the listed values. Other values ​​not listed within this range are also applicable.

[0064] Preferably, the pressure of the membrane separation is 0.5 to 1.5 MPa, for example, it can be 0.5 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa or 1.5 MPa, but is not limited to the listed values. Other values ​​not listed within this range are also applicable.

[0065] Preferably, the current density of the bipolar membrane electrolysis is 15 to 20 A / m 2 , for example, it can be 15A / m 2 、15.6A / m 2 , 16.2A / m 2 , 16.7A / m 2 , 17.3A / m2 , 17.8A / m 2 , 18.4A / m 2 , 18.9A / m 2 、19.5A / m 2 or 20A / m 2 The above values ​​are not limited to the above values, and other values ​​not listed in the above values ​​are also applicable.

[0066] Preferably, the membrane material of the bipolar membrane electrolysis includes any one of polystyrene sulfonic acid, polytetrafluoroethylene, polyethersulfone, polyurethane or polyvinyl alcohol, or a combination of at least two thereof.

[0067] Preferably, the temperature of the bipolar membrane electrolysis is 20-45°C, for example, it can be 20°C, 23°C, 26°C, 29°C, 32°C, 34°C, 37°C, 40°C, 43°C or 45°C, but is not limited to the listed values. Other values ​​not listed within this range are also applicable.

[0068] Preferably, the sodium hydroxide solution in step (4) is mixed with the magnesium-rich solution in step (3) and then reused in the MHP precipitation process.

[0069] During the MHP precipitation process, the present invention 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 the MHP.

[0070] Preferably, 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 amount ratio of the substance is 1:(1-9), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:5, 1:6, 1:7, 1:7.5, 1:8, 1:8.5 or 1:9, etc.

[0071] In the present invention, the mixing of magnesium-rich solution and sodium hydroxide produces magnesium hydroxide, a weakly alkaline substance. Relying solely on magnesium hydroxide as a precipitant results in a high magnesium content and a low nickel content in the prepared MHP, thereby increasing the transportation cost of the MHP and the expense of using a P507 extractant to remove magnesium during the subsequent refining process. Therefore, the present invention achieves the coexistence of sodium hydroxide and magnesium hydroxide by controlling the molar ratio of Na+ in the sodium hydroxide solution to Mg2+ in the magnesium-rich solution to 1:1-9, and using them as mixed precipitants in the MHP precipitation process to improve the MHP co-precipitation effect.

[0072] Preferably, after the sodium hydroxide solution in step (4) is mixed with the magnesium-rich solution in step (3), the ratio of the sum of the molar amounts of sodium and magnesium elements in the mixed system 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.

[0073] The present invention has no special restrictions on the implicit solid-liquid separation in the above process. Any device and method for solid-liquid separation known to those skilled in the art can be used, and can also be adjusted according to the actual process. For example, it can be filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0074] The present invention has no special restrictions on the implicit drying steps in the above process. Any drying device and method known to those skilled in the art can be used, and can also be adjusted according to the actual process. For example, it can be air drying, vacuum drying, oven drying or freeze drying, or a combination of different methods.

[0075] It is worth noting that the key to the present invention is that the wastewater after the MHP treatment is sequentially subjected to manganese precipitation treatment to remove manganese, then ion exchange is performed to recover nickel and cobalt, and then magnesium separation is performed to recover magnesium, and finally bipolar membrane electrolysis is performed to recover sodium hydroxide and sulfuric acid solution. The order and the relationship between the various steps are the core inventive concept of the present invention. It is precisely by developing this set of technical routes for sequentially recovering manganese, nickel and cobalt, magnesium, sodium hydroxide and sulfuric acid that valuable substances can be efficiently recovered, which not only reduces the discharge of wastewater, but also improves the economic value of the entire process. When the order is changed or a certain step is not performed, it will cause the overall process flow to be difficult to stably circulate. These valuable substances returned to step (1) can also improve the nickel and cobalt recovery rate and the product quality of the hydroxide in the MHP treatment step.

[0076] Compared with the prior art, the present invention has at least the following beneficial effects:

[0077] (1) The recycling method of laterite nickel ore hydrometallurgical wastewater provided by the present invention can realize the comprehensive recycling and reuse of nickel, cobalt, magnesium, sodium hydroxide and sulfate in the wastewater after manganese precipitation, thereby reducing the discharge and post-processing burden of wastewater and improving economic benefits;

[0078] (2) The method for recycling laterite nickel ore hydrometallurgical wastewater provided by the present invention improves the quality of the hydroxide product obtained by precipitation by circulating the magnesium-rich liquid and the sodium hydroxide solution obtained in step (4) to the MHP precipitation treatment. Specifically, the water content of the hydroxide product is reduced to less than 50%, and the particle size D50 of the hydroxide is above 15.5 μm;

[0079] (3) The recycling method of laterite nickel ore hydrometallurgical wastewater provided by the present invention improves the recovery rate of nickel and cobalt in the overall process, with the nickel precipitation rate exceeding 99.5% and the cobalt precipitation rate exceeding 99.0%;

[0080] (4) The magnesium sulfate product prepared by the recycling method of laterite nickel ore hydrometallurgical wastewater provided by the present invention meets the external sales standards and has a purity of more than 98wt%;

[0081] (5) In the preferred embodiment of the method for recycling laterite nickel ore hydrometallurgical wastewater provided by the present invention, the recycling rate of nickel and cobalt reaches more than 99.5%, the recovery rate of magnesium ions reaches more than 98%, the recovery rate of sodium hydroxide resources reaches more than 96%, and the recovery rate of sulfate ions reaches more than 98%, and the application prospect is broad. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 The present invention provides a flow chart of a method for recycling laterite nickel ore hydrometallurgical wastewater according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0083] For the convenience of understanding the present invention, the present invention is given below with examples. It should be understood by those skilled in the art that the examples are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0084] As a specific embodiment of the present invention, a method for recycling laterite nickel ore hydrometallurgical wastewater is provided. Figure 1 , the recycling method comprises the following steps:

[0085] (1) The laterite nickel ore is sequentially subjected to high-pressure acid leaching, circulating leaching, CCD washing, iron and aluminum removal treatment, and MHP precipitation treatment to obtain MHP precipitation wastewater, and the MHP precipitation wastewater is subjected to manganese precipitation treatment to obtain manganese precipitation wastewater;

[0086] (2) the wastewater after manganese precipitation is subjected to ion exchange to obtain an ion exchange liquid and an enriched nickel-cobalt solution; the enriched nickel-cobalt solution is circulated to the CCD washing in step (1);

[0087] (3) the ion exchanged liquid is subjected to magnesium separation to obtain a magnesium-rich liquid and a magnesium-depleted liquid; the magnesium-rich liquid is circulated to the MHP precipitation treatment in step (1), and / or the magnesium-rich liquid is crystallized to obtain a magnesium sulfate product;

[0088] (4) The magnesium-depleted solution is electrolyzed through a bipolar membrane to obtain a sodium hydroxide solution and a sulfuric acid solution; the sodium hydroxide solution is circulated to the iron and aluminum removal treatment in step (1), and the sulfuric acid solution is circulated to the high-pressure leaching in step (1).

[0089] Example 1

[0090] This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater, the recycling method comprising the following steps:

[0091] (1) The laterite nickel ore is sequentially subjected to high-pressure acid leaching, circulating leaching, CCD washing, iron and aluminum removal treatment under pH = 4.0, MHP precipitation treatment under pH = 6.5 and 60° C. for 5 h, and filtered to obtain MHP precipitation wastewater; alkali is added to the MHP precipitation wastewater to adjust the pH to 10.0 to remove manganese, and filtered to obtain manganese precipitation wastewater;

[0092] (2) The wastewater after manganese precipitation was fed into the M4195 chelate ion exchange resin adsorption column at 2.5 BV / h and ion exchanged at 35°C to obtain nickel-cobalt adsorption resin and ion exchange liquid. + The nickel-cobalt adsorption resin is desorbed using 0.02 mol / L hydrochloric acid as a desorbent at a flow rate of 0.5 BV / h and a temperature of 30° C. to obtain an enriched nickel-cobalt solution, which is circulated to the CCD washing in step (1);

[0093] (3) extracting the ion exchange liquid using an extraction system (10 wt% BC196 as an extractant, 1 wt% L-aspartic acid as a co-extractant, 89 wt% kerosene as a diluent, and a saponification rate of 30%), with an O / A ratio of 3:1 and an extraction stage of 8; separating to obtain an organic phase and a raffinate, then washing the organic phase with a sulfuric acid solution having a concentration of 0.1 mol / L, with the washing stage of 8, and finally stripping with a sulfuric acid solution having a concentration of 3.0 mol / L, with the stripping stage of 6, the stripping liquid obtained is a magnesium-rich liquid, and the raffinate is a magnesium-poor liquid; part of the magnesium-rich liquid is reused in the MHP precipitation process, and the remaining magnesium-rich liquid is evaporated and crystallized to obtain magnesium sulfate;

[0094] (4) The magnesium-poor solution is electrolyzed by bipolar membrane with a current density of 18A / m 2 , the temperature is 30 ° C, to obtain sodium hydroxide solution and sulfuric acid solution; a part of the sodium hydroxide solution is circulated to the iron and aluminum removal treatment in step (1), and a part is mixed with the magnesium-rich solution in step (3) and then recycled to the MHP precipitation treatment, and the Na in this part of the sodium hydroxide solution is controlled. + With Mg in some magnesium-rich solution 2+ The molar ratio of the substance 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; the sulfuric acid solution is circulated to the high-pressure leaching in step (1).

[0095] Example 2

[0096] This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater, the recycling method comprising the following steps:

[0097] (1) The laterite nickel ore is sequentially subjected to high-pressure acid leaching, circulating leaching, CCD washing, iron and aluminum removal treatment under pH=5.5, MHP precipitation treatment under pH=6.3 and 70°C for 2 hours, and filtered to obtain MHP precipitation wastewater; alkali is added to the MHP precipitation wastewater to adjust the pH to 11 to remove manganese, and filtered to obtain manganese precipitation wastewater;

[0098] (2) The wastewater after manganese precipitation was fed into the M4195 chelate ion exchange resin adsorption column at 4.0 BV / h and ion exchanged at 20°C to obtain nickel-cobalt adsorption resin and ion exchange liquid. + The nickel-cobalt adsorption resin is desorbed using 0.03 mol / L hydrochloric acid as a desorbent at a flow rate of 0.1 BV / h and a temperature of 20° C. to obtain an enriched nickel-cobalt solution, which is circulated to the CCD washing in step (1);

[0099] (3) The ion exchange liquid is extracted using an extraction system (20 wt% of BC196 as an extractant, 4 wt% of L-aspartic acid as a co-extractant, 76 wt% of kerosene as a diluent, and a saponification rate of 40%), with an O / A ratio of 1:1 and three extraction stages; the organic phase and the raffinate are separated, and the organic phase is washed with a sulfuric acid solution having a concentration of 0.8 mol / L, with the washing stage number being 10, and finally, the organic phase is stripped with a sulfuric acid solution having a concentration of 6.5 mol / L, with the stripping stage number being 8, and the stripping liquid obtained is a magnesium-rich liquid, and the raffinate is a magnesium-poor liquid; part of the magnesium-rich liquid is reused in the MHP precipitation process, and the remaining magnesium-rich liquid is evaporated and crystallized to obtain magnesium sulfate;

[0100] (4) The magnesium-poor solution is electrolyzed by bipolar membrane with a current density of 20A / m 2 , the temperature is 45 ° C, to obtain sodium hydroxide solution and sulfuric acid solution; a part of the sodium hydroxide solution is circulated to the iron and aluminum removal treatment in step (1), and a part is mixed with the magnesium-rich solution in step (3) and then recycled to the MHP precipitation treatment, and the Na in this part of the sodium hydroxide solution is controlled. + With Mg in some magnesium-rich solution 2+ The molar ratio of the substance is 1:7, 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; the sulfuric acid solution is circulated to the high-pressure leaching in step (1).

[0101] Example 3

[0102] This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater, the recycling method comprising the following steps:

[0103] (1) The laterite nickel ore is sequentially subjected to high-pressure acid leaching, circulating leaching, CCD washing, iron and aluminum removal treatment under pH=3.8, MHP precipitation treatment under pH=8.5 and 55°C for 10 hours, and filtered to obtain MHP precipitation wastewater; alkali is added to the MHP precipitation wastewater to adjust the pH to 9.5 to remove manganese, and filtered to obtain manganese precipitation wastewater;

[0104] (2) The wastewater after manganese precipitation was fed into the M4195 chelate ion exchange resin adsorption column at 1.0 BV / h and ion exchanged at 40°C to obtain nickel-cobalt adsorption resin and ion exchange liquid. + The nickel-cobalt adsorption resin is desorbed using 0.01 mol / L hydrochloric acid as a desorbent at a flow rate of 1.0 BV / h and a temperature of 40° C. to obtain an enriched nickel-cobalt solution, which is circulated to the CCD washing in step (1);

[0105] (3) The ion exchange liquid is extracted using an extraction system (30 wt% of BC196 as an extractant, 3 wt% of L-aspartic acid as a co-extractant, 67 wt% of kerosene as a diluent, and a saponification rate of 25%), with an O / A ratio of 3:1 and a number of extraction stages of 6; the organic phase and the raffinate are separated, and the organic phase is then washed with a 0.1 mol / L sulfuric acid solution, with the number of washing stages being 6, and finally stripped with a 3.0 mol / L sulfuric acid solution, with the number of stripping stages being 4, the stripped liquid obtained being a magnesium-rich liquid, and the raffinate being a magnesium-poor liquid; part of the magnesium-rich liquid is reused in the MHP precipitation process, and the remaining magnesium-rich liquid is evaporated and crystallized to obtain magnesium sulfate;

[0106] (4) The magnesium-poor solution is electrolyzed by bipolar membrane at a current density of 15 A / m 2 , the temperature is 20 ° C, and a sodium hydroxide solution and a sulfuric acid solution are obtained; a part of the sodium hydroxide solution is circulated to the iron and aluminum removal treatment in step (1), and a part is mixed with the magnesium-rich solution in step (3) and then recycled to the MHP precipitation treatment, and the Na in this part of the sodium hydroxide solution is controlled. + With Mg in some magnesium-rich solution 2+ The molar ratio of the substance is 1:9, 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; the sulfuric acid solution is circulated to the high-pressure leaching in step (1).

[0107] Example 4

[0108] This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater, wherein the recycling method includes the sodium hydroxide solution in step (4) that is recycled to the MHP treatment. + With Mg in some magnesium-rich solution 2+ Except that the molar ratio of the substance is 1:0.5, the rest are the same as in Example 1 and will not be repeated here.

[0109] Example 5

[0110] This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater, wherein the recycling method includes the sodium hydroxide solution in step (4) that is recycled to the MHP treatment. + With Mg in some magnesium-rich solution 2+ Except that the molar ratio of the substance is 1:10, the rest are the same as in Example 1 and will not be repeated here.

[0111] Example 6

[0112] This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater. The recycling method is the same as that of Example 1, except that L-aspartic acid is not added as a co-extractant in step (3), and will not be described in detail here.

[0113] Example 7

[0114] This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater. The recycling method is the same as that in Example 1, except that the amount of L-aspartic acid added in step (3) is increased to 5wt% and the amount of kerosene is simultaneously reduced to 85wt%. The details are not repeated here.

[0115] Example 8

[0116] This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater. The recycling method is the same as that in Example 1, except that L-aspartic acid in step (3) is replaced by an equal amount of tributyl phosphate, and the details are not repeated here.

[0117] Example 9

[0118] This embodiment provides a method for recycling laterite nickel ore hydrometallurgical wastewater. The recycling method is the same as that in Example 1, except that the M4195 chelating ion exchange resin adsorption column is replaced by an IRC-748 chelating ion exchange resin adsorption column. The details are not described again.

[0119] Comparative Example 1

[0120] This comparative example provides a method for recycling laterite nickel ore hydrometallurgical wastewater. In the recycling method, the wastewater is directly reused for MHP precipitation treatment after removing MHP and manganese. The rest is the same as Example 1 and will not be repeated here.

[0121] Comparative Example 2

[0122] This comparative example provides a method for recycling laterite nickel ore hydrometallurgical wastewater. The recycling method is the same as Example 1 except that steps (3) and (4) are not performed, and 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, and added to the precipitated MHP. The rest is not repeated here.

[0123] Comparative Example 3

[0124] This comparative example provides a method for recycling laterite nickel ore hydrometallurgical wastewater. The recycling method is the same as Example 1 except that the manganese precipitation treatment is not performed and the MHP precipitation wastewater is directly subjected to the ion exchange in step (2). The details are not repeated here.

[0125] Since manganese was not removed first in this comparative example, it was difficult to carry out the subsequent ion exchange and extraction processes, and it was impossible to achieve efficient recovery of valuable resources.

[0126] The above embodiments and comparative examples were basically stable after 10 cycles. At this time, the theoretical nickel hydroxide content, cobalt hydroxide content, and manganese hydroxide content were expected to be 40%, 4%, and 7% when MHP was precipitated. The component content, particle size, and moisture content of the MHP filter cake obtained in the MHP precipitation process after the 10th cycle were tested. Examples 1 to 5 and comparative examples 1 to 2 were used as examples for the test. The test results are shown in Table 1.

[0127] Table 1

[0128]

[0129]

[0130] The results in Table 1 show the following:

[0131] (1) From Examples 1 to 3, it can be seen that the MHP filter cake prepared by recycling laterite nickel ore hydrometallurgical wastewater using the method described in the present invention has good performance, wherein the mass ratio of nickel hydroxide, cobalt hydroxide and manganese hydroxide obtained by precipitation is closer to the theoretical design, and the water content in the filter cake is as low as within 47.3%, and can even reach 45.07%. The particle size D50 is above 15.8 μm, which is easier to filter in industrial production and can effectively avoid the problem of filter cake clogging the filter device.

[0132] (2) Combining Examples 1 and 4-5, it can be seen that the Na in the sodium hydroxide solution recycled to the MHP treatment in Examples 4-5 is + With Mg in some magnesium-rich solution 2+ The amount ratio of the substances is not within the preferred range, resulting in a smaller value of the particle size D50 in the filter cake in Example 4, a high water content, and a filtration performance inferior to that of Example 1. Although the particle size D50 in Example 5 is large, the mass ratio of nickel hydroxide, cobalt hydroxide, and manganese hydroxide deviates far from the theoretical design, indicating that the Na in the sodium hydroxide solution recycled to the MHP precipitation treatment in step (4) is + With Mg in some magnesium-rich solution 2+ The amount ratio of substances is controlled within a reasonable range, which can better reduce the water content in the hydroxide product obtained by MHP precipitation treatment, and the mass ratio of nickel hydroxide, cobalt hydroxide and manganese hydroxide is closer to the theoretical design, which is more conducive to industrial production.

[0133] (3) From Example 1 and Comparative Examples 1 to 2, it can be seen that in Comparative Example 1, the wastewater after manganese removal from the MHP was directly reused in the MHP precipitation treatment, resulting in accumulation of sodium elements, high water content of the filter cake, small particle size, and relatively poor filtration performance; even if additional purchased sodium hydroxide and magnesium oxide were added in Comparative Example 2, it was difficult to achieve the effect of reducing water content and increasing particle size in Example 1. This shows that the present invention uses ion exchange resin, extraction and bipolar membrane electrolysis to recycle sodium hydroxide and magnesium-rich solution recovered to the MHP precipitation, which can not only improve resource utilization, but also improve the performance of the filter cake originally treated with the MHP precipitation, and is more conducive to industrial production.

[0134] The recovery rate of sulfate is calculated by dividing the sum of sulfate in the sulfuric acid solution produced by bipolar membrane electrolysis and sulfate in the magnesium sulfate product by the sum of sulfate in the wastewater after manganese precipitation and sulfate added in step (3); the recovery rate of sodium hydroxide is calculated by dividing the hydroxide ions produced by bipolar membrane electrolysis by the hydroxide ions in the wastewater after manganese precipitation; the amount of nickel and cobalt in the filter cake obtained by MHP precipitation is divided by the amount of nickel and cobalt in the iron and aluminum removal treatment solution, which are respectively recorded as the nickel precipitation rate and the cobalt precipitation rate; and the recovery rate of magnesium is calculated by dividing the sum of magnesium ions in the obtained magnesium sulfate and the magnesium content in the filter cake obtained by MHP precipitation by the amount of magnesium in the iron and aluminum removal treatment solution.

[0135] The data of the recovery and precipitation rate of the above embodiment and comparative example are shown in Table 2.

[0136] Table 2

[0137]

[0138]

[0139] In Table 2, “ / ” indicates that there is no relevant data.

[0140] From Table 2, we can see the following points:

[0141] (1) It can be seen from Examples 1 to 3 that the present invention can recycle laterite nickel ore hydrometallurgical wastewater to achieve a magnesium ion recovery rate of more than 98%, a sodium hydroxide resource recovery rate of more than 96%, a sulfate ion recovery rate of more than 98%, a nickel precipitation rate of more than 99.5%, and a cobalt precipitation rate of more than 99.0%. The recovery rate of each resource is excellent and the application prospect is broad.

[0142] (2) Combining Examples 1 and 4-5, it can be seen that the Na in the sodium hydroxide solution recycled to the MHP treatment in Examples 4-5 is + With Mg in some magnesium-rich solution 2+ The amount ratio of the substance is not within the preferred range, resulting in the Co precipitation rate in Example 4 dropping to 98.2%, and the Co precipitation rate and Mg recovery rate in Example 5 both dropping compared to Example 1, indicating that the present invention preferably uses the NaOH solution recycled to the MHP precipitation process. + With Mg in some magnesium-rich solution 2+ The amount of substance ratio is controlled within a reasonable range, which can better improve the Co precipitation rate and Mg recovery rate.

[0143] (3) From Example 1 and Examples 6 to 8, it can be seen that L-aspartic acid is not added as a co-extractant in Example 6, and L-aspartic acid is replaced by an equal amount of tributyl phosphate in Example 8, resulting in insufficient Mg extraction rate during the extraction process, and the Mg recovery rate is only 95.2% and 95.9%, resulting in a high magnesium content in the magnesium-lean solution, affecting the subsequent bipolar membrane electrolysis, and making it difficult to achieve the recovery of sodium hydroxide and sulfuric acid solution; in Example 7, the amount of L-aspartic acid added is relatively high, but the Mg recovery rate is reduced compared with Example 1, and there is a waste of co-extractant. This shows that the present invention preferably uses L-aspartic acid as a co-extractant and controls its content within a reasonable range, which can better improve the Mg extraction rate and is conducive to the subsequent electrolytic preparation of sodium hydroxide and sulfuric acid solution.

[0144] (4) From Example 1 and Comparative Examples 1 to 2, it can be seen that in Comparative Example 1, the wastewater after manganese removal from MHP is directly reused in the MHP precipitation treatment, and the recovery of Mg, sodium hydroxide and sulfuric acid resources cannot be achieved; in Comparative Example 2, 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, and are added to the MHP precipitation. The final precipitation rates of nickel and cobalt are lower than those in Example 1, and it is difficult to achieve the recovery of Mg, sodium hydroxide and sulfuric acid resources. This shows that the present invention can not only achieve the recovery cycle of multiple resources through a series of ion exchange, extraction and bipolar membrane electrolysis process, but also improve the precipitation rates of nickel and cobalt.

[0145] The present invention uses the above-described embodiments to illustrate the detailed features of the present invention. However, the present invention is not limited to the above-described detailed features, which does not mean that the present invention must rely on the above-described detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for the selected technical features of the present invention, additions to auxiliary technical features, and selections of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for recycling laterite nickel ore hydrometallurgical wastewater, characterized in that: The recycling method comprises the following steps: (1) Laterite nickel ore is sequentially subjected to high-pressure acid leaching, circulating leaching, CCD washing, iron and aluminum removal treatment, MHP precipitation treatment and manganese precipitation treatment to obtain manganese precipitation wastewater; (2) The wastewater after manganese precipitation is subjected to ion exchange to obtain an ion exchange liquid and a nickel-cobalt enriched solution; the nickel-cobalt enriched solution is circulated to the CCD washing in step (1); (3) The ion exchanged liquid is subjected to magnesium separation to obtain a magnesium-rich liquid and a magnesium-depleted liquid; the magnesium-rich liquid is circulated to the MHP precipitation treatment in step (1), and / or the magnesium-rich liquid is crystallized to obtain a magnesium sulfate product; (4) The magnesium-depleted solution is subjected to bipolar membrane electrolysis to obtain a sodium hydroxide solution and a sulfuric acid solution; the sodium hydroxide solution is circulated to the iron and aluminum removal treatment in step (1), and the sulfuric acid solution is circulated to the high-pressure leaching in step (1).

2. The recycling method according to claim 1, characterized in that: The ion exchange in step (2) includes: sending the wastewater after manganese precipitation to a resin adsorption column for ion exchange to obtain nickel-cobalt adsorption resin and ion-exchanged liquid, and using a desorbent to desorb the nickel-cobalt adsorption resin to obtain an enriched nickel-cobalt solution.

3. The recycling method according to claim 2, characterized in that: The resin adsorption column includes a cationic resin or a chelating resin.

4. The recycling method according to claim 3, characterized in that: The cationic resin is a strongly acidic cation exchange resin.

5. The recycling method according to claim 3, characterized in that: The chelating resin is M4195 chelating ion exchange resin and / or IRC-748 chelating ion exchange resin.

6. The recycling method according to claim 2, characterized in that: The temperature of the ion exchange is 20-40°C.

7. The recycling method according to claim 2, characterized in that: The flow rate of the wastewater after manganese precipitation in the ion exchange is 1~4BV / h.

8. The recycling method according to claim 2, characterized in that: The desorbent includes an inorganic acid; The concentration of hydrogen ions in the desorbed inorganic acid is ≥0.01 mol / L.

9. The recycling method according to claim 8, characterized in that: The desorbed inorganic acid includes any one of sulfuric acid, hydrochloric acid or nitric acid, or a combination of at least two of them.

10. The recycling method according to claim 2, characterized in that: The flow rate of the desorbent is 0.1~1BV / h.

11. The recycling method according to claim 2, characterized in that: The desorption temperature is 20-40°C.

12. The recycling method according to claim 1, characterized in that: The magnesium separation in step (3) includes extraction separation and / or membrane separation.

13. The recycling method according to claim 12, characterized in that: The extraction and separation comprises: extracting the ion exchange liquid with an extraction system to separate an organic phase and a raffinate, then acid-washing the organic phase, and then stripping with a stripping agent to obtain a stripping liquid that is a magnesium-rich liquid, and a raffinate that is a magnesium-poor liquid.

14. The recycling method according to claim 13, characterized in that: The extraction system comprises an extractant and a diluent.

15. The recycling method according to claim 14, characterized in that: The extractant includes BC196.

16. The recycling method according to claim 13, characterized in that: A co-extraction agent is also added during the extraction process.

17. The recycling method according to claim 16, characterized in that: The synergistic extractant is L-aspartic acid.

18. The recycling method according to claim 16, characterized in that: The mass ratio of the co-extraction agent to the extraction agent is 0.1-0.2:

1.

19. The recycling method according to claim 14, characterized in that: The diluent includes kerosene.

20. The recycling method according to claim 14, characterized in that: The extraction system is a saponified extraction system.

21. The recycling method according to claim 20, characterized in that: The saponification rate of the extraction system is 25-40%.

22. The recycling method according to claim 13, characterized in that: During the extraction process, the O / A ratio is (1-3):

1.

23. The recycling method according to claim 13, characterized in that: The number of stages of the extraction process is 3 to 8.

24. The recycling method according to claim 13, characterized in that: The acid concentration of the pickling is 0.1-0.8 mol / L.

25. The recycling method according to claim 13, characterized in that: The pickling washing stages are 6 to 10.

26. The recycling method according to claim 13, characterized in that: The acid used for pickling includes hydrochloric acid and / or sulfuric acid.

27. The recycling method according to claim 13, characterized in that: The stripping agent for the stripping includes an inorganic acid.

28. The recycling method according to claim 27, characterized in that: The inorganic acid for stripping is sulfuric acid.

29. The recycling method according to claim 27, characterized in that: The acid concentration of the stripping is 3.0-6.5 mol / L.

30. The recycling method according to claim 13, characterized in that: The number of stages of the stripping is 4 to 8.

31. The recycling method according to claim 12, characterized in that: The membrane separation comprises: using an ion selective membrane to perform membrane separation on the monovalent metal ions and divalent metal ions in the ion exchange liquid.

32. The recycling method according to claim 12, characterized in that: The temperature of the membrane separation is 25-45°C.

33. The recycling method according to claim 12, characterized in that: The pressure of the membrane separation is 0.5~1.5MPa.

34. The recycling method according to claim 1, characterized in that: The current density of the bipolar membrane electrolysis is 15~20A / m 2 .

35. The recycling method according to claim 1, characterized in that: The temperature of the bipolar membrane electrolysis is 20-45°C.

36. The recycling method according to claim 1, characterized in that: The sodium hydroxide solution in step (4) is mixed with the magnesium-rich solution in step (3) and then reused in the MHP precipitation process.

37. The recycling method according to claim 36, 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 amount of substance ratio is 1:(1~9).

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