A method for separating, purifying nickel sulfate electrolysis residual liquid and concentrating sulfuric acid

Abstract

The present invention discloses a method for separating, purifying nickel sulfate electrolytic residual liquid and concentrating sulfuric acid, comprising the following steps: S1, pre-treating nickel sulfate electrolytic residual liquid; S2, mixing the reverse flow concentrated liquid of the nanofiltration system 2 and the pre-treated nickel sulfate electrolytic residual liquid in proportion to obtain the comprehensive feed liquid of the nanofiltration system 1; S3, controlling the feed liquid pressure and temperature, and using the nanofiltration system 1 for purification to obtain purified nickel sulfate concentrated liquid and the dialysis liquid of the nanofiltration system 1; S4, adjusting the feed liquid pressure and temperature, and subjecting the dialysis liquid of the nanofiltration system 1 and dilute sulfuric acid to reverse osmosis concentration system to obtain reverse osmosis concentrated liquid and reverse osmosis dialysis water; S5, adjusting the feed liquid pressure and temperature, and feeding the reverse osmosis concentrated liquid into the nanofiltration system 2 for purification to obtain nickel sulfate and sulfuric acid mixed liquid and purified sulfuric acid concentrated liquid. It solves the problems of the influence of the increase of sulfuric acid content in the nickel sulfate solution on the electrolysis efficiency during the nickel sulfate electrolysis process, the recovery of sulfuric acid in the electrolyte, the concentration of low-concentration nickel sulfate in the electrolyte, etc., and the recycling of some substances effectively saves resources.

Description

Technical Field

[0001] The present invention relates to the technical field of nickel production by electrolyzing nickel sulfate, and specifically relates to a method for separating, purifying and concentrating sulfuric acid from the electrolytic residue solution of nickel sulfate. Background Art

[0002] Membrane separation technology can separate nickel sulfate and sulfuric acid in the electrolytic residue solution of nickel sulfate and concentrate nickel sulfate, and a matching membrane concentration system can achieve the concentration of the separated sulfuric acid solution.

[0003] During the electrolysis of nickel sulfate to produce nickel hydroxide and sulfuric acid, to ensure the electrolysis efficiency during electrolysis, it is required that the nickel content in the electrolysis chamber ≥ 90 g / l. At the same time, during electrolysis, hydrogen ions are also generated in the anode chamber, which will combine with sulfate ions to form sulfuric acid. When sulfuric acid accumulates, it will enter the electrode chamber, affecting the stability of the feed liquid system and further affecting the electrolysis efficiency. Therefore, in this process, it is necessary to regularly treat the low-concentration nickel sulfate solution after electrolysis, separate sulfuric acid, and concentrate and increase the nickel concentration to ≥ 90 g / l level. Without this separation and concentration membrane process, in production, only the electrolytic dilute solution can be exported from the system and replaced with new solution for continuous electrolysis, which not only affects the continuity of the electrolysis process, but also requires adding nickel oxide again and neutralizing the sulfuric acid in the exported dilute solution and configuring it into nickel sulfate with the target concentration to return to the production line; the goal is to produce nickel hydroxide, but the treatment of dilute solution also consumes a part of electrolytic nickel and neutralizes a part of acid, resulting in process backfill, affecting the overall production efficiency and increasing the repeated energy consumption in the production process; the proposed process solves the problem that the above electrolytic production process cannot be stable and continuous, reduces the repeated energy consumption in the production process at the same time, and strongly supplements and improves the closed-loop clean production process of nickel sulfate electrolysis. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for separating, purifying and concentrating sulfuric acid from the electrolytic residue solution of nickel sulfate, which solves the problems of high sulfuric acid content and reduced nickel concentration in the electrolytic residue solution of nickel sulfate, and realizes the closed-loop clean production of nickel sulfate electrolysis at the same time. While using a nanofiltration membrane to separate and concentrate nickel sulfate, this method uses a reverse osmosis membrane to concentrate the dilute sulfuric acid dialyzed by nanofiltration, and obtains a purified nickel sulfate concentrated solution and a purified sulfuric acid concentrated solution at the same time. The filtrate of the reverse osmosis membrane during the process is recycled, forming a closed-loop clean production process for nickel sulfate electrolysis.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A method for separating, purifying and concentrating sulfuric acid from the electrolytic residue solution of nickel sulfate provided by the present invention includes the following steps:

[0007] S1. Pretreat the nickel sulfate solution after electrolysis to clarify its filtrate and obtain the electrolytic nickel residual solution that meets the conditions for entering the membrane system. The pretreatment is to use a precision filter, and the filter element intercepts the solid impurities in the feed liquid to protect the membrane system. The precision filter selects a precision filter element with a filtration accuracy of 1 μm to 5 μm.

[0008] S2. Mix the electrolytic nickel residual solution and the concentrate of nanofiltration system 2 in a volume ratio of 5:1 to obtain the comprehensive feed liquid of nanofiltration system 1 and dilute sulfuric acid. The comprehensive feed liquid of nanofiltration system 1 is a nickel sulfate concentrated solution containing a small amount of sulfuric acid.

[0009] S3. Control the feed pressure and temperature to make the comprehensive feed liquid of nanofiltration system 1 enter nanofiltration system 1 for purification, obtaining a purified nickel sulfate concentrated solution and the dialysis liquid of nanofiltration system 1. The nickel sulfate concentrated solution is returned to the production line and continues to be used as the electrolyte in circulation.

[0010] S4. According to the preset concentration in the system, adjust the feed pressure and temperature. After passing the dialysis liquid of nanofiltration system 1 and the dilute sulfuric acid in S2 through the reverse osmosis concentration system, obtain the reverse osmosis concentrate and the reverse osmosis dialysis water. Control the effluent to meet the water use standard and return it to the dialysis process of nanofiltration system 1 through the water storage tank for water replenishment.

[0011] S5. Adjust the feed pressure and temperature to make the reverse osmosis concentrate enter nanofiltration system 2 for purification, obtaining a nickel sulfate and sulfuric acid mixed solution and a purified sulfuric acid concentrated solution. The nickel sulfate and sulfuric acid mixed solution returns to the comprehensive feed liquid storage tank as the comprehensive feed liquid of nanofiltration system 1 for circulation to continue separating sulfur and recovering nickel sulfate.

[0012] Furthermore, the concentrate of nanofiltration system 2 is a mixed solution of 3%-5% sulfuric acid and 2%-5% nickel sulfate; the comprehensive feed liquid of nanofiltration system 1 is a mixed solution of nickel sulfate, sulfuric acid, and water; the dialysis liquid of nanofiltration system 1 is a mixed solution of nickel sulfate and sulfuric acid; the reverse osmosis concentrate is a solution mainly composed of trace nickel sulfate and sulfuric acid.

[0013] Further, the membrane system includes a comprehensive feed liquid storage tank, a nanofiltration system 1, a reverse osmosis concentration system, and a nanofiltration system 2; the comprehensive feed liquid storage tank is connected to the nanofiltration system 1, and the nanofiltration system 1 includes a power pump, a regulating valve a, a sensor a, a flow element a, a nanofiltration membrane of the nanofiltration system 1, a nickel sulfate concentrated liquid storage tank, and a filtrate storage tank of the nanofiltration system 1 connected by pipelines; the reverse osmosis concentration system is connected to the filtrate storage tank of the nanofiltration system 1, and the reverse osmosis concentration system includes a power pump, a regulating valve b, a sensor b, a flow element b, a reverse osmosis membrane, a reverse osmosis concentrated liquid storage tank, and a water storage tank connected by pipelines, and the water storage tank is also connected to the nanofiltration system 1; the nanofiltration system 2 is connected to the reverse osmosis concentrated liquid storage tank, and the nanofiltration system 2 includes a power pump, a regulating valve c, a sensor c, a flow element c, a nanofiltration membrane of the nanofiltration system 2, and a purified sulfuric acid concentrated liquid storage tank, and the nanofiltration system 2 is also connected to the comprehensive feed liquid storage tank by a pipeline.

[0014] Further, the sensor a includes a temperature sensor a and a pressure sensor a, the sensor b includes a temperature sensor b and a pressure sensor b, the sensor c includes a temperature sensor c and a pressure sensor c, and the sensor a, the sensor b, the sensor c, the regulating valve a, the regulating valve b, the regulating valve c, the flow element a, the flow element b, and the flow element c are electrically connected to a control system.

[0015] Further, the reverse osmosis membrane used in the membrane system is an acid-resistant high-pressure reverse osmosis membrane, and the nanofiltration membranes of the nanofiltration system 1 and the nanofiltration system 2 are acid-resistant high-pressure nanofiltration membranes.

[0016] Further, when separating and dialyzing and purifying the nickel sulfate solution with the nanofiltration system 1, the inlet pressure is 3.5 - 7 Mpa, and the temperature is 25 - 40 °C.

[0017] Further, when concentrating sulfuric acid with the reverse osmosis concentration system, the inlet pressure is 3 - 8 Mpa, and the temperature is 15 - 35 °C.

[0018] Further, when purifying sulfuric acid with the nanofiltration system 2, the inlet pressure is 3.5 - 4.5 Mpa, and the temperature is 20 - 35 °C.

[0019] Further, the nickel sulfate content in the nickel sulfate solution obtained in the step S3 reaches 250 g / l or more.

[0020] Further, the concentration of the sulfuric acid solution obtained in the step S5 reaches 180 g / l or more.

[0021] Based on the above technical solutions, the embodiments of the present invention can at least produce the following technical effects:

[0022] (1) The membrane technology can be used to concentrate and increase the nickel sulfate content in the electrolytic residue solution of nickel sulfate. During the concentration process, sulfuric acid will be separated from the water-permeable side, and the sulfuric acid concentration in the concentrated solution will increase less. By adopting the method of adding water for dialysis, nickel sulfate and sulfuric acid can be further dialyzed and separated without reducing the nickel sulfate content, achieving the purpose of concentrating nickel sulfate and separating sulfuric acid.

[0023] (2) The membrane treatment system in the process of the present invention is customized according to the production line scale and can be matched for continuous industrial production. The system process is simple, with high treatment efficiency, and the system adopts integrated intelligent control. Integrated control method: Each system is an independent skid-mounted unit. By controlling the programming logic of the CPU and relying on feedback values such as monitored pressure, flow rate, temperature, concentration, pump frequency, valve opening, etc., the system program automatically controls and adjusts the real-time operation value according to the set target value to achieve the production target. This system has a high degree of automation control, precise automatic adjustment, and realizes paperless office and unattended operation in the workshop.

[0024] (3) The water permeated in the process of the nanofiltration system 1 is concentrated by the reverse osmosis system to make the sulfuric acid content reach 180 g / l, achieving the purpose of recovering sulfuric acid. The concentrated permeated water can be directly reused in the nanofiltration dialysis process section, improving the water resource utilization rate, purifying the water resource for reuse, realizing zero discharge of the project, and comprehensively generating good economic benefits. Description of the Drawings

[0025] Figure 1 is the process flow chart of the embodiment of the present invention;

[0026] Figure 2 is the schematic diagram of the separation, purification and concentration device used in the present invention;

[0027] In the figure: 1, comprehensive inlet liquid storage tank; 2, nanofiltration membrane of nanofiltration system 1; 21, regulating valve a; 22, sensor a; 23, flow element a; 24, nickel sulfate concentrated liquid storage tank; 25, filtrate storage tank of nanofiltration system 1; 3, reverse osmosis membrane; 31, regulating valve b; 32, sensor b; 33, flow element b; 34, water storage tank; 35, reverse osmosis concentrated liquid storage tank; 4, nanofiltration membrane of nanofiltration system 2; 41, regulating valve c; 42, sensor c; 43, flow element; 44, purified sulfuric acid concentrated liquid storage tank; 5, power pump. Detailed Embodiments

[0028] Such as Figure 1 、 2As shown in the figure, the membrane system includes a comprehensive feed liquid storage tank 1, a nanofiltration system 1, a reverse osmosis concentration system, and a nanofiltration system 2. After the comprehensive feed liquid of the nanofiltration system 1 passes through the comprehensive feed liquid storage tank 1, according to the data reflected by the pressure sensor a, temperature sensor a, and flow element a23 on the sensor a22, the control system controls the regulating valve a21 to make the comprehensive feed liquid of the nanofiltration system 1 meet the conditions for entering the nanofiltration system 1, obtaining purified nickel sulfate concentrated liquid and the dialysis liquid of the nanofiltration system 1. The nickel sulfate concentrated liquid enters the nickel sulfate concentrated liquid storage tank 24. The dialysis liquid of the nanofiltration system 1 enters the filtrate storage tank 25 of the nanofiltration system 1. According to the data reflected by the pressure sensor b, temperature sensor b, and flow element b33 on the sensor b32, the control system controls the regulating valve b31 to make the dialysis liquid of the nanofiltration system 1 meet the conditions for entering the reverse osmosis concentration system, obtaining reverse osmosis concentrated liquid and reverse osmosis dialysis water. The reverse osmosis dialysis water enters the water storage tank 34 and is returned to the nanofiltration system 1 for use. The reverse osmosis concentrated liquid enters the reverse osmosis concentrated liquid storage tank 35. According to the data reflected by the pressure sensor c, temperature sensor c, and flow element c43 on the sensor c42, the control system controls the regulating valve c41 to make the reverse osmosis concentrated liquid meet the conditions for entering the nanofiltration system 2, and after purification, a nickel sulfate-sulfuric acid mixed liquid and purified sulfuric acid concentrated liquid are obtained. The nickel sulfate-sulfuric acid mixed liquid returns to the comprehensive feed liquid storage tank 1 as the comprehensive feed liquid of the nanofiltration system 1 for circulation, and the purified sulfuric acid concentrated liquid enters the purified sulfuric acid concentrated liquid storage tank 44.

[0029] The present invention provides a method for separating, purifying and concentrating sulfuric acid from nickel sulfate electrolysis waste liquid, comprising the following steps:

[0030] S1. Pretreat the mixed solution of nickel sulfate and sulfuric acid after electrolysis to make its filtrate clear, obtaining electrolytic nickel waste liquid that meets the conditions for entering the membrane system, with turbidity < 0.1 NTU;

[0031] S2. Mix the electrolytic nickel waste liquid and the concentrated liquid of the nanofiltration system 2 according to a volume ratio of 5:1 to obtain the comprehensive feed liquid of the nanofiltration system 1 and dilute sulfuric acid. The comprehensive feed liquid of the nanofiltration system 1 is a nickel sulfate concentrated solution containing a small amount of sulfuric acid;

[0032] S3. Control the feed pressure and temperature to make the comprehensive feed liquid of the nanofiltration system 1 enter the nanofiltration system 1 for purification, obtaining purified nickel sulfate concentrated liquid and the dialysis liquid of the nanofiltration system 1;

[0033] S4. According to the preset concentration in the system, adjust the feed pressure and temperature. After passing the dialysis liquid of the nanofiltration system 1 and the dilute sulfuric acid in S2 through the reverse osmosis concentration system, reverse osmosis concentrated thick liquid and reverse osmosis dialysis water are obtained. Control the effluent to meet the water use standard and return it to the dialysis process of the nanofiltration system 1 through the water storage tank for water replenishment;

[0034] S5. Adjust the inlet liquid pressure and temperature to enable the reverse osmosis concentrated liquid to enter the nanofiltration system 2 for purification, obtaining a nickel sulfate-sulfuric acid mixed liquid and a purified sulfuric acid concentrated liquid. The nickel sulfate-sulfuric acid mixed liquid can return to the comprehensive inlet liquid of the nanofiltration system 1 for circulation.

[0035] The process method used in this process for the membrane system is the invention patent (Patent No. CN111530293B) of Sichuan Greenwo Innovation Environmental Protection Engineering Co., Ltd., "A Continuous Flow-Through Membrane Filtration Device and Method".

[0036] This process involves the selection of acid-resistant high-pressure nanofiltration membranes and reverse osmosis membrane elements for the membrane concentration and membrane purification systems (all the membrane elements of this process are provided by Chengdu Connect Fluid).

[0037] Example 1

[0038] S1. Pretreat the nickel sulfate electrolysis residual liquid to obtain an electrolytic nickel residual liquid that meets the conditions for entering the membrane system, and the detected value of the clear liquid turbidity shows < 0.1 NTU.

[0039] S2. Mix the electrolytic nickel residual liquid and the concentrated liquid of the nanofiltration system 2 according to a volume ratio of 5:1 to obtain the comprehensive inlet liquid of the nanofiltration system 1 and dilute sulfuric acid. The comprehensive inlet liquid of the nanofiltration system 1 is a nickel sulfate concentrated solution containing a small amount of sulfuric acid.

[0040] S3. Control the inlet liquid temperature at 25 - 30 °C and the pressure level at 3.5 - 7 MPa to enable the comprehensive inlet liquid of the nanofiltration system 1 to enter the nanofiltration system 1 for purification, obtaining a purified nickel sulfate concentrated liquid and the dialysis liquid of the nanofiltration system 1. The nickel sulfate content in the purified nickel sulfate concentrated liquid reaches 253.22 g / l.

[0041] S4. According to the preset concentration in the system, pass the dialysis liquid of the nanofiltration system 1 through the reverse osmosis concentration system, control the inlet liquid temperature at 15 - 35 °C and the pressure level at 3 - 8 MPa, to obtain a reverse osmosis concentrated liquid mainly composed of sulfuric acid and reverse osmosis dialysis water.

[0042] S5. Enable the reverse osmosis concentrated liquid to enter the nanofiltration system 2 for purification, control the inlet liquid temperature at 25 - 30 °C and the pressure level at 3.5 - 4.5 MPa, separate to obtain a nickel sulfate-sulfuric acid mixed liquid and a purified sulfuric acid concentrated liquid. The sulfuric acid content reaches 210.49 g / l, and the nickel sulfate-sulfuric acid mixed liquid can return to the comprehensive inlet liquid of the nanofiltration system 1 for circulation.

[0043] Table 1

[0044]

[0045] Table 2

[0046]

[0047] Table 3

[0048]

[0049]

[0050] Example 2

[0051] S1. Pretreat the electrolytic nickel residual solution to obtain an electrolytic nickel residual solution that meets the conditions for entering the membrane system, and the turbidity detection value of the clear liquid shows <0.1 NTU;

[0052] S2. Mix the electrolytic nickel residual solution and the concentrate of nanofiltration system 2 in a volume ratio of 5:1 to obtain the comprehensive feed liquid of nanofiltration system 1 and dilute sulfuric acid. The comprehensive feed liquid of nanofiltration system 1 is a nickel sulfate concentrated solution containing a small amount of sulfuric acid;

[0053] S3. Control the feed liquid temperature at 25 - 30 °C and the pressure grade at 4.5 - 7 MPa, and let the comprehensive feed liquid of nanofiltration system 1 enter nanofiltration system 1 for purification to obtain a purified nickel sulfate concentrated solution and the dialysis liquid of nanofiltration system 1. The nickel sulfate content in the purified nickel sulfate concentrated solution reaches 254.25 g / l;

[0054] S4. According to the preset concentration in the system, pass the dialysis liquid of nanofiltration system 1 through the reverse osmosis concentration system, control the feed liquid temperature at 15 - 35 °C and the pressure grade at 3 - 8 MPa to obtain a reverse osmosis concentrated solution mainly composed of sulfuric acid and reverse osmosis dialysate;

[0055] S5. The reverse osmosis concentrated solution enters nanofiltration system 2 for purification. Control the feed liquid temperature at 25 - 30 °C and the pressure grade at 3.5 - 4.5 MPa to separate and obtain a nickel sulfate - sulfuric acid mixed solution and a purified sulfuric acid concentrated solution. The sulfuric acid content reaches 203.22 g / l, and the nickel sulfate - sulfuric acid mixed solution can return to the comprehensive feed liquid of nanofiltration system 1 for circulation.

[0056] Table 4

[0057]

[0058] Table 5

[0059]

[0060]

[0061] Table 6

[0062]

Claims

1. A method for separating, purifying nickel sulfate electrolysis residual liquid and concentrating sulfuric acid, characterized in that The steps include the following: S1. Pretreat the nickel sulfate solution after electrolysis to clarify its filtrate and obtain the electrolytic nickel residual solution that meets the conditions for entering the membrane system. The pretreatment is to use a precision filter with a filter element to intercept solid impurities in the feed liquid to protect the membrane system. The precision filter selects a precision filter element with a filtration accuracy of 1 μm to 5 μm. S2. Mix the electrolytic nickel residual solution and the concentrate of the nanofiltration system 2 in a volume ratio of 5:1 to obtain the comprehensive feed liquid of the nanofiltration system 1 and dilute sulfuric acid. The comprehensive feed liquid of the nanofiltration system 1 is a nickel sulfate concentrated solution containing a small amount of sulfuric acid. The concentrate of the nanofiltration system 2 is a mixed solution of 3% - 5% sulfuric acid and 2% - 5% nickel sulfate. The comprehensive feed liquid of the nanofiltration system 1 is a mixed solution of nickel sulfate, sulfuric acid, and water. The dialysate of the nanofiltration system 1 is a mixed solution of nickel sulfate and sulfuric acid. S3. Control the feed pressure and temperature to make the comprehensive feed liquid of the nanofiltration system 1 enter the nanofiltration system 1 for purification, obtaining a purified nickel sulfate concentrated solution and the dialysate of the nanofiltration system 1. The nickel sulfate concentrated solution is returned to the production line and continues to be used as the electrolyte in circulation. The nickel sulfate content in the nickel sulfate solution obtained in step S3 reaches more than 250 g / l. S4. According to the preset concentration in the system, adjust the feed pressure and temperature. After passing the dialysate of the nanofiltration system 1 and the dilute sulfuric acid in S2 through the reverse osmosis concentration system, obtain the reverse osmosis concentrate and the reverse osmosis dialysate water. Control the effluent to meet the water use standard and return it to the dialysis process of the nanofiltration system 1 through the water storage tank for water replenishment. The reverse osmosis concentrate is a solution mainly composed of trace nickel sulfate and sulfuric acid. S5. Adjust the feed pressure and temperature to make the reverse osmosis concentrate enter the nanofiltration system 2 for purification, obtaining a mixed solution of nickel sulfate and sulfuric acid and a purified sulfuric acid concentrated solution. The mixed solution of nickel sulfate and sulfuric acid returns to the comprehensive feed liquid storage tank and is used as the comprehensive feed liquid of the nanofiltration system 1 for circulation to continue separating sulfur and recovering nickel sulfate. The sulfuric acid solution obtained in step S5 has a concentration of more than 180 g / l.

2. The method for separating, purifying nickel sulfate electrolysis residual liquid and concentrating sulfuric acid according to claim 1, wherein The membrane system includes a comprehensive feed liquid storage tank (1), nanofiltration system 1, reverse osmosis concentration system, and nanofiltration system 2; the comprehensive feed liquid storage tank (1) is connected to nanofiltration system 1, and the nanofiltration system 1 includes a power pump (5), regulating valve a (21), sensor a (22), flow element a (23), nanofiltration membrane of nanofiltration system 1 (2), nickel sulfate concentrated liquid storage tank (24), and filtrate storage tank of nanofiltration system 1 (25) connected by pipelines; the reverse osmosis concentration system is connected to the filtrate storage tank of nanofiltration system 1 (25), and the reverse osmosis concentration system includes a power pump (5), regulating valve b (31), sensor b (32), flow element b (33), reverse osmosis membrane (3), reverse osmosis concentrated liquid storage tank (35), and water storage tank (34) connected by pipelines, and the water storage tank (34) is also connected to nanofiltration system 1; the nanofiltration system 2 is connected to the reverse osmosis concentrated liquid storage tank (35), and the nanofiltration system 2 includes a power pump (5), regulating valve c (41), sensor c (42), flow element c (43), nanofiltration membrane of nanofiltration system 2 (4), purified sulfuric acid concentrated liquid storage tank (44), and the nanofiltration system 2 is also connected to the comprehensive feed liquid storage tank (1) by a pipeline.

3. A method for separating, purifying nickel sulfate electrolysis residual solution and concentrating sulfuric acid according to claim 2, characterized in that, The sensor a (22) includes a temperature sensor a and a pressure sensor a, the sensor b (32) includes a temperature sensor b and a pressure sensor b, the sensor c (42) includes a temperature sensor c and a pressure sensor c, and the sensor a (22), sensor b (32), sensor c (42), regulating valve a (21), regulating valve b (31), regulating valve c (41), flow element a (23), flow element b (33), and flow element c (43) are electrically connected to the control system.

4. A method for separating, purifying nickel sulfate electrolysis residual liquid and concentrating sulfuric acid according to claim 2, characterized in that, The reverse osmosis membrane (3) used in the membrane system is an acid-resistant high-pressure reverse osmosis membrane, and the nanofiltration membrane of nanofiltration system 1 (2) and the nanofiltration membrane of nanofiltration system 2 (4) are acid-resistant high-pressure nanofiltration membranes.

5. A method for separating, purifying nickel sulfate electrolysis residual liquid and concentrating sulfuric acid according to claim 1, characterized in that, When separating and dialyzing and purifying the nickel sulfate solution with nanofiltration system 1, the inlet pressure is 3.5 - 7 Mpa, and the temperature is 25 - 40 degrees Celsius.

6. A method for separating, purifying nickel sulfate electrolysis residual liquid and concentrating sulfuric acid according to claim 1, characterized in that, When concentrating sulfuric acid with the reverse osmosis concentration system, the inlet pressure is 3 - 8 Mpa, and the temperature is 15 - 35 degrees Celsius.

7. A method for separating, purifying nickel sulfate electrolysis residual solution and concentrating sulfuric acid according to claim 1, characterized in that, When purifying sulfuric acid with nanofiltration system 2, the inlet pressure is 3.5 - 4.5 Mpa, and the temperature is 20 - 35 degrees Celsius.

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