A process for removing thallium from nickel sulfate solution

Abstract

This invention provides a process for removing thallium from nickel sulfate solution, belonging to the field of nickel-cobalt hydrometallurgical technology. It solves the problems of low efficiency, unsatisfactory results, and insufficient removal depth in existing extraction processes for thallium removal from nickel sulfate solution, which fail to meet environmental protection requirements. The invention includes the following steps: saponifying a P204 extractant with a nickel sulfate solution; then adding a thallium-containing nickel sulfate solution for extraction and impurity removal; adding a C272 extractant to the first thallium-containing nickel sulfate solution for countercurrent extraction and impurity removal; adding 6-10 times the concentration of sodium sulfide according to the remaining thallium content in the second removal solution, followed by stirring, precipitation, and filtration; heating the third thallium-containing nickel sulfate solution, and then using a C-100E cation exchange resin for thallium adsorption to obtain the final thallium-removed nickel sulfate solution. This invention achieves stable control of the thallium content in the nickel sulfate solution, and the process adopts a step-by-step approach to increase the impurity removal depth, ultimately achieving deep thallium removal from the nickel sulfate solution.

Description

Technical Field

[0001] This invention belongs to the field of nickel-cobalt hydrometallurgical technology, specifically relating to a process for removing thallium from nickel sulfate solution. Background Technology

[0002] In hydrometallurgical production, thallium is a toxic and harmful metallic element, and its environmental treatment requirements are very strict. The metallic thallium in nickel sulfate mainly comes from the production raw materials, so it is necessary to remove metallic thallium at the source of nickel sulfate production. The original method for removing thallium from nickel sulfate solution is mainly through extraction. Although the original extraction process can reduce the content of thallium in nickel sulfate solution, there are still problems such as low removal efficiency, unsatisfactory removal effect, and removal depth that does not meet environmental protection requirements. At the same time, due to the limitations of the production process, thallium accumulates in the system for a long time, which will cause fluctuations in the content of some trace impurity elements in nickel sulfate products, thereby leading to many problems in the production of downstream products or causing problems for downstream customers, thus causing production disruptions. Summary of the Invention

[0003] The purpose of this invention is to provide a process for removing thallium from nickel sulfate solution, so as to solve the problems of low efficiency, unsatisfactory effect, and failure to meet environmental protection requirements in the original extraction process for removing thallium from nickel sulfate solution.

[0004] The technical solution of this invention is: a process for removing thallium from nickel sulfate solution, comprising the following steps:

[0005] Step 1: Saponify the P204 extractant with nickel sulfate solution. After saponification, add a thallium-containing nickel sulfate solution for extraction and impurity removal. Perform the first removal of metallic thallium from the thallium-containing nickel sulfate solution. The thallium content in the thallium-containing nickel sulfate solution will be initially removed by 40%-50%.

[0006] Step 2: Add C272 extractant to the thallium-containing nickel sulfate solution after the first removal and perform countercurrent extraction to remove impurities. The organic loading and clarification time is 10-20 min. After countercurrent extraction, heat the solution to 80-85℃ to remove metallic thallium from the thallium-containing nickel sulfate solution for a second removal. This further removes 10%-20% of the thallium content from the thallium-containing nickel sulfate solution.

[0007] Step 3: Based on the concentration of thallium metal remaining in the solution after the second removal in Step 2, add 6-10 times the concentration of sodium sulfide and stir. After stirring, allow precipitation, and then filter to remove thallium metal from the nickel sulfate solution for the third time; further remove 20%-30% of the thallium content in the nickel sulfate solution.

[0008] Step 4: The thallium-containing nickel sulfate solution from the third removal process is heated to 40-55℃. The heated solution is then passed through a C-100E cation exchange resin for thallium adsorption to obtain the final thallium-free nickel sulfate solution. The thallium content in the nickel sulfate solution is further reduced by 5%-10%.

[0009] Furthermore, in step one, the saponification rate of the P204 extractant using nickel sulfate solution is 50-70%.

[0010] Furthermore, in step one, the original concentration of the thallium-containing nickel sulfate solution was 80-120 g / L.

[0011] Furthermore, in step two, the extraction ratio of C272 extractant is O / A=4:1, the number of stages of countercurrent extraction for impurity removal with C272 extractant is 6-10, and the single-stage mixing time is 1-3 min.

[0012] Furthermore, in step three, the stirring time is 30-45 minutes.

[0013] Furthermore, in step four, the flow rate of the heated solution through the C-100E cation exchange resin is 2-6 BV / h.

[0014] The beneficial effects of this invention are as follows: This invention employs a combined method of traditional extraction technology with sodium sulfate chemical precipitation filtration and resin adsorption. The overall process follows a flow that gradually increases the depth of impurity removal, effectively reducing the thallium content in nickel sulfate solution products to 0.2 ppm. The treated thallium content fully meets emission standards, eliminating the need for separate thallium removal treatment. Furthermore, the extractant, cationic resin, and other chemicals used in the thallium removal process can be reused, achieving stable control of the thallium content in nickel sulfate crystals used in electroplating and battery production. The process is simple and easy to control, possessing wide applicability in the nickel sulfate production field and ensuring stable product quality control. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the embodiments.

[0016] Example 1

[0017] Step 1: Saponify the P204 extractant with nickel sulfate solution to a saponification rate of 50%. After saponification, add a nickel sulfate solution containing thallium with a concentration of 80 g / L for extraction and impurity removal. Perform the first removal of metallic thallium in the nickel sulfate solution to initially remove 40% of the thallium content in the nickel sulfate solution.

[0018] Step 2: Add C272 extractant to the thallium-containing nickel sulfate solution after the first removal and perform countercurrent extraction to remove impurities. The extraction ratio of C272 extractant is O / A=4:1. The countercurrent extraction with C272 extractant has 6 stages, with a single-stage mixing time of 1 min and an organic loading clarification time of 10 min. After countercurrent extraction, heat the solution to 80°C to remove metallic thallium from the thallium-containing nickel sulfate solution for the second time, further removing 10% of the thallium content in the nickel sulfate solution.

[0019] Step 3: Based on the concentration of thallium metal remaining in the solution after the second removal in Step 2, add 6 times the concentration of sodium sulfide and stir for 30 minutes. After stirring, allow precipitation and then filter to remove thallium metal from the nickel sulfate solution for the third time, further removing 20% ​​of the thallium content in the nickel sulfate solution.

[0020] Step 4: The thallium-containing nickel sulfate solution removed in the third step is heated to 40°C. The heated solution is then passed through a C-100E cation exchange resin for thallium adsorption. The flow rate of the heated solution through the C-100E cation exchange resin is 2 BV / h, resulting in the final thallium-removed nickel sulfate solution. This further removes 5% of the thallium content from the nickel sulfate solution.

[0021] Example 2

[0022] Step 1: Saponify the P204 extractant with nickel sulfate solution to a saponification rate of 60%. After saponification, add a thallium-containing nickel sulfate solution with a concentration of 100 g / L for extraction and impurity removal. Perform the first removal of metallic thallium in the thallium-containing nickel sulfate solution, and initially remove 45% of the thallium content in the nickel sulfate solution.

[0023] Step 2: Add C272 extractant to the thallium-containing nickel sulfate solution after the first removal and perform countercurrent extraction to remove impurities. The extraction ratio of C272 extractant is O / A=4:1. The countercurrent extraction with C272 extractant has 8 stages, the single-stage mixing time is 2 min, and the organic loading clarification time is 15 min. After countercurrent extraction, heat the solution to 83℃ to remove metallic thallium from the thallium-containing nickel sulfate solution for the second time, further removing 15% of the thallium content in the nickel sulfate solution.

[0024] Step 3: Based on the concentration of thallium metal remaining in the solution after the second removal in Step 2, add sodium sulfide at a concentration of 8 times and stir for 45 minutes. After stirring, allow precipitation and then filter to remove thallium metal from the nickel sulfate solution for the third time, further removing 25% of the thallium content in the nickel sulfate solution.

[0025] Step 4: The thallium-containing nickel sulfate solution from the third removal process is heated to 48°C. The heated solution is then passed through a C-100E cation exchange resin for thallium adsorption. The flow rate of the heated solution through the C-100E cation exchange resin is 4 BV / h, resulting in the final thallium-removed nickel sulfate solution. This further removes 8% of the thallium from the nickel sulfate solution.

[0026] Example 3

[0027] Step 1: Saponify the P204 extractant with nickel sulfate solution to a saponification rate of 70%. After saponification, add a thallium-containing nickel sulfate solution with a concentration of 120 g / L for extraction and impurity removal. Perform the first removal of metallic thallium in the thallium-containing nickel sulfate solution to initially remove 50% of the thallium content in the nickel sulfate solution.

[0028] Step 2: Add C272 extractant to the thallium-containing nickel sulfate solution after the first removal and perform countercurrent extraction to remove impurities. The extraction ratio of C272 extractant is O / A=4:1. The countercurrent extraction with C272 extractant has 6 stages, with a single-stage mixing time of 1 min and an organic loading clarification time of 20 min. After countercurrent extraction, heat the solution to 85°C to remove metallic thallium from the thallium-containing nickel sulfate solution for the second time, further removing 20% ​​of the thallium content in the nickel sulfate solution.

[0029] Step 3: Based on the concentration of thallium metal remaining in the solution after the second removal in Step 2, add sodium sulfide at a concentration of 10 times and stir for 45 minutes. After stirring, allow precipitation and then filter to remove thallium metal from the nickel sulfate solution for the third time, further removing 30% of the thallium content in the nickel sulfate solution.

[0030] Step 4: The thallium-containing nickel sulfate solution from the third removal process is heated to 55°C. The heated solution is then passed through a C-100E cation exchange resin for thallium adsorption. The flow rate of the heated solution through the C-100E cation exchange resin is 6 BV / h, resulting in the final thallium-removed nickel sulfate solution. This further removes 10% of the thallium content from the nickel sulfate solution.

[0031] Table 1 shows the comparison of thallium concentration (g / L) in nickel sulfate solutions containing thallium after steps 1-3 in Examples 1-3.

[0032]

[0033] Table 2 shows the comparison of pH values ​​after removing thallium from nickel sulfate solutions containing thallium following steps 1-3 in Examples 1-3.

[0034]

[0035] As shown by the data comparison in Table 1, the thallium removal process of the original sulfuric acid solution using this production process effectively removes metallic thallium at each step, with the removal depth increasing progressively with each step. In particular, the concentration of metallic thallium in the original solution decreases significantly after the addition of sodium sulfide precipitation and filtration. The concentration of metallic thallium in the original solution further decreases after the addition of cation exchange resin, demonstrating a significant thallium removal effect. During the extraction process, to ensure the depth of impurity removal, the pH value in the original solution increases. As shown by the data comparison in Table 2, the pH value in the solution steadily increases after the process steps, proving that the impurity removal effect is ideal.

[0036] Meanwhile, this production process has the following advantages: This process can effectively reduce the thallium content in nickel sulfate solution products to 0.2 ppm. The thallium content after treatment can fully meet emission standards without separate thallium removal treatment. At the same time, the extractant, cationic resin and other chemicals used in the thallium removal process can be reused, improving the economic efficiency of environmentally friendly production. It achieves stable control of the thallium content in electroplating and battery nickel sulfate solution crystals, providing a guarantee for stable control of product quality. The process is simple and easy to control, and has wide applicability in the field of nickel sulfate production.

Claims

1. A process for the removal of thallium from nickel sulfate solution, characterized in that: Includes the following steps: Step 1: Saponify the P204 extractant with nickel sulfate solution. After saponification, add thallium-containing nickel sulfate solution for extraction and impurity removal, and perform the first removal of metallic thallium in the thallium-containing nickel sulfate solution. Step 2: Add C272 extractant to the thallium-containing nickel sulfate solution after the first removal and perform countercurrent extraction to remove impurities. The organic loading and clarification time is 10-20 min. After countercurrent extraction, heat the solution to 80-85℃ to remove metallic thallium from the thallium-containing nickel sulfate solution for the second time. Step 3: Based on the concentration of thallium metal remaining in the solution after the second removal in Step 2, add 6-10 times the concentration of sodium sulfide and stir. After stirring, allow precipitation, and then filter to remove thallium metal from the nickel sulfate solution containing thallium for the third time. Step 4: The thallium-containing nickel sulfate solution removed in the third step is heated to a temperature of 40-55℃. The heated solution is then passed through a C-100E cation exchange resin to undergo a thallium adsorption reaction, resulting in the final thallium-removed nickel sulfate solution.

2. The process for removing thallium from nickel sulfate solution according to claim 1, characterized in that: In step one, the saponification rate of P204 extractant by saponification with nickel sulfate solution is 50-70%.

3. The process for removing thallium from nickel sulfate solution according to claim 1, characterized in that: In step one, the concentration of nickel sulfate in the thallium-containing nickel sulfate solution is 80-120 g / L.

4. The process for removing thallium from nickel sulfate solution according to claim 1, characterized in that: In step two, the extraction ratio of C272 extractant is O / A=4:1, the number of stages of countercurrent extraction for impurity removal with C272 extractant is 6-10, and the single-stage mixing time is 1-3 min.

5. The process for removing thallium from nickel sulfate solution according to claim 1, characterized in that: In step three, the stirring time is 30-45 minutes.

6. The process for removing thallium from nickel sulfate solution according to claim 1, characterized in that: In step four, the flow rate of the heated solution through the C-100E cation exchange resin is 2-6 BV / h.

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