Rough nickel salt leaching and purifying device and method

Abstract

The invention discloses a crude nickel salt leaching and purifying device and method, and belongs to the technical field of sewage treatment. The crude nickel salt leaching and purifying device comprises a leacheate pool, a multi-stage leaching column, a peristaltic pump and a leacheate regeneration pool; the leacheate pool is used for storing a saturated nickel sulfate solution as a leacheate; the multi-stage leaching column comprises a plurality of leaching columns which are connected in series, and crude nickel salt is filled in the leaching columns; the peristaltic pump is connected with the leacheate pool and the first leaching column of the multi-stage leaching columns; the leacheate regeneration pool is connected with the outlet of the last leaching column through a pipe, and the leacheate regeneration pool is provided with an anode, a cathode and an electrochemical workstation connected with the cathode and the anode. According to the method, cyclic purification of leaching purification-electrodeposition regeneration leacheate is established, in-situ purification of the crude nickel salt and recycling of the leacheate can be achieved, and the method is a green and nontoxic purification technology. The nickel salt purified by the method meets the requirements of the electroplating industry, and the problems of large geographical span, high transportation cost, high recovery cost and high drug toxicity of nickel resource recovery can be solved in a targeted manner.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a crude nickel salt eluting and purification device and method. Background Art

[0002] Electroplating wastewater contains high concentrations of heavy metals, which can harm the environment if not properly treated. Nickel is a key raw material in the electroplating industry, but it is also one of its primary pollutants. Recycling nickel from electroplating wastewater not only prevents pollution and reduces resource consumption in electroplating production, but also opens up new profit opportunities for companies.

[0003] In recent years, research on nickel resource utilization has continued to deepen at home and abroad, and a variety of methods have been developed, such as adsorption enrichment, electrochemical reduction, chemical precipitation, and resin adsorption. Although new adsorbents such as biochar, molecular sieves, and modified cellulose have shown good nickel adsorption capabilities, most methods have not converted nickel into a processable form. By precisely controlling the electrode potential, electroreduction technology can achieve graded recovery of nickel and other metals by inhibiting the reduction of some metals; Professor Liu Huijuan and others found that electric pulse reduction technology can improve the purity of metal recovery; Researcher Zhao Xu proved that in the nickel electrodeposition process, α-Ni(OH)2 is a crucial intermediate state. In order to achieve continuous and effective nickel deposition, the pH value of the electrolyte needs to be precisely controlled at around 6.58. It can be seen that although electroreduction to recover nickel is feasible, the recovery conditions are still relatively harsh and the operational feasibility is not high.

[0004] Chemical precipitation is the most commonly used process for treating nickel-containing wastewater in China. The resulting mixed sludge can be resold to sludge disposal companies at a low price, with a nickel content of approximately 5%-6% and a selling price of approximately 60,000 yuan per ton. These companies use a series of refining processes to recover the nickel and re-enter the industrial cycle. To improve recycling efficiency, some wastewater treatment plants in Fujian Province have begun using an innovative combined process of "resin adsorption enrichment followed by distillation and crystallization." This produces crude nickel salts with a nickel content of approximately 12%-15% and a selling price of approximately 105,000 yuan per ton. After refining, these can be easily converted into industrial-grade nickel salts. However, if the recovered material can be purified to a high-purity raw material such as electroplating-grade nickel sulfate, its recycling value will be significantly increased. In Fujian Province, for example, the price difference between crude nickel salts and electroplating-grade nickel sulfate is significant, with the latter costing as much as 184,000 yuan per ton. Therefore, developing nickel purification technology suitable for electroplating wastewater treatment plants will not only encourage recycling initiatives but also drive the electroplating industry towards cleaner and more efficient production models.

[0005] Organic exchange extraction has traditionally dominated nickel purification processes. This method relies on the differential ability of metal ions to transfer from an aqueous phase to an organic phase (typically using fatty acid soaps as carriers) to enrich and purify nickel. While theoretically feasible, the introduction of organic solvents into wastewater treatment plants in practice poses numerous safety risks and clearly runs counter to the concept of "clean production." Therefore, there is an urgent need to explore and develop more environmentally friendly and green purification technologies to safely purify crude nickel salts from electroplating wastewater and ultimately achieve in-situ nickel resource recovery. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems in the prior art of nickel resource recovery such as large geographical span, high transportation cost, high recovery cost and high drug toxicity, and to provide a crude nickel salt elution and purification device and method.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A crude nickel salt elution and purification device comprises an eluent pool, a multi-stage eluent column, a peristaltic pump, and an eluent regeneration pool;

[0009] The eluent pool is used to store saturated nickel sulfate solution as eluent;

[0010] The multi-stage elution column includes several elution columns connected in series, and the elution columns are filled with crude nickel salt (the impurities of the crude nickel salt are soluble metal salts);

[0011] The peristaltic pump is connected to the eluent pool and the first eluent column of the multi-stage eluent column;

[0012] The eluent regeneration pool is connected to the outlet of the last eluent column through a pipe. The eluent regeneration pool is provided with an anode, a cathode and an electrochemical workstation connected with the cathode and the anode.

[0013] The multi-stage elution column includes five elution columns connected in series.

[0014] The cathode is made of stainless steel.

[0015] The anode is made of titanium ruthenium mesh.

[0016] A crude nickel salt elution purification method comprises the following steps:

[0017] 1) A saturated nickel sulfate solution is used as the eluent and pumped into a multi-stage elution column via a peristaltic pump. The crude nickel salt is sequentially eluted in an upflow manner to dissolve the copper sulfate impurities and improve the purity of the nickel salt.

[0018] 2) Collect the eluent containing copper ions, remove the copper ions by controlled voltage electrodeposition in the eluent regeneration tank, and return the regenerated eluent to the eluent tank for recycling;

[0019] 3) Separate the purified nickel salts in the multi-stage elution column and obtain electroplating grade nickel sulfate after drying.

[0020] In step 1), the hydraulic retention time of the eluent in each eluent column is not less than 4 minutes.

[0021] In step 2), the voltage of the controlled voltage electrodeposition is 2.0-3.5 V.

[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0023] 1) The reagents used in the present invention are inexpensive and low in toxicity, the operation is simple and safe, and the process runs continuously and stably. It can be directly used in series with an electroplating wastewater plant that uses an ion resin concentration-distillation separation process to produce crude nickel salts, thereby achieving in-situ regeneration and utilization of nickel-containing electroplating wastewater;

[0024] 2) The present invention uses electrodeposition to regenerate the eluent, and the regenerated eluent can be reused;

[0025] 3) The nickel salt obtained by elution in the present invention meets the standards of electroplating-grade nickel sulfate and can be used in the electroplating industry, thereby reducing industry operating costs, improving the nickel resource recycling rate, and having great economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the elution purification device; wherein, 1-eluent tank, 2-peristaltic pump, 3-5-stage elution column, 4-eluent regeneration tank;

[0027] Figure 2 The solid nickel content in each elution column obtained from the multi-stage elution experiment; the horizontal axes 1 to 5 represent the first elution column, the second elution column, the third elution column, the fourth elution column, and the fifth elution column, respectively;

[0028] Figure 3 Cu in the effluent from each elution column 2+ The concentration changes of

[0029] Figure 4 Cu in the electrolyte of the controlled pressure electrodeposition experiment 2+ Concentration changes;

[0030] Figure 5 The morphology of copper on the cathode plate obtained by deposition at different voltages;

[0031] Figure 6 This is a picture of the plated parts in the electroplating experiment using nickel salt as the electroplating solution;

[0032] Figure 7 The SEM morphology of the electroplated surface at 1 μm scale using different electroplating solutions;

[0033] Figure 8 is the LSV curve of the plated part;

[0034] Figure 9 is the AC impedance spectrum of the plated component. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0036] The present invention uses crude nickel salt with an 8% copper sulfate content (close to the impurity content of crude nickel salt obtained by an ion resin concentration-distillation separation process in an electroplating wastewater treatment plant) as a elution column filler, uses a saturated nickel sulfate solution as an eluent, and adopts multi-stage elution to achieve efficient purification of nickel sulfate; the eluent is converted into an eluate with nickel sulfate / copper sulfate as the main solute through the multi-stage elution column, and the purity of the crude nickel salt filled in the elution column is improved; and then the Cu in the eluent is removed by pressure-controlled electrodeposition. 2+ , achieving the regeneration of nickel sulfate eluent, which can be recycled for elution and purification. The Hull cell experiment examines the electroplating performance of the purified nickel salt and verifies whether the prepared high-purity nickel sulfate meets the standards for electroplating-grade nickel sulfate.

[0037] See also Figure 1 The crude nickel salt elution and purification device of the present invention comprises an eluent pool 1, a peristaltic pump 2, a 5-stage eluent column 3, and an eluent regeneration pool 4;

[0038] The eluent pool 1 contains a saturated nickel sulfate solution as the eluent;

[0039] The peristaltic pump 2 serves as a power device and is connected to form a continuous flow system through a hose. Specifically, the peristaltic pump 2 connects the eluent pool 1 and the first eluent column (first eluent column) of the five-stage eluent column 3;

[0040] The five-stage eluent column 3 includes five eluent columns connected in series through a hose, respectively named as the first eluent column, the second eluent column, the third eluent column, the fourth eluent column and the fifth eluent column. Specifically, in this embodiment, the eluent column is composed of five cylindrical columns with a volume of 200 mL, and the eluent column is filled with about 100 g of crude nickel salt;

[0041] The eluent regeneration pool 4 is connected to the outlet of the last eluent column (the fifth eluent column) through a hose. The eluent regeneration pool is provided with an anode, a cathode and an electrochemical workstation connected to the cathode and the anode. The volume of the eluent regenerated in the eluent regeneration pool 4 is 200 mL per time. The electrode materials selected are titanium ruthenium mesh (anode) and stainless steel (cathode). The electrochemical system provides a DC power supply, and a magnetic stirrer is used for automatic stirring and real-time temperature control.

[0042] Example 1: Purity analysis of purified nickel salt

[0043] (1) Preparation of experimental materials: ① Prepare 1.5 L of eluent; ② Prepare 5 portions of crude nickel salt, each containing 100 g (92 g NiSO4·6H2O + 8 g CuSO4·5H2O); ③ Prepare ethanol solution (the volume ratio of water to ethanol is 4:1); ④ Prepare hydrochloric acid solution (the volume ratio of hydrochloric acid to water is 1:1); ⑤ Prepare ammonia solution (the volume ratio of ammonia to water is 1:1); ⑥ Prepare 200 g / L ammonium chloride solution; ⑦ Prepare 200 g / L tartaric acid solution; ⑧ Prepare 10 g / L dimethylglyoxime ethanol solution.

[0044] (2) Multi-stage elution experiment: First, measure the actual flow rate of the peristaltic pump using a stopwatch and a measuring cylinder. To keep the hydraulic retention time of the eluent in the column at about 5 minutes, the flow rate should be controlled at 40 mL / min. Figure 1 Assemble the experimental device as shown, turn on the peristaltic pump, and start timing when the eluent flows into the first eluent column. When the eluent fills the first eluent column and overflows, take out a certain amount of eluent through the outlet valve as the effluent sample of the first eluent column at time zero and start timing again. Thereafter, samples are taken at appropriate time points as the effluent samples of the first eluent column. Similarly, when the eluent gradually flows into the second eluent column and reaches full overflow, samples are taken and stored at regular intervals. Similarly, when the eluent flows out of the last eluent column as a signal, take 2 to 3 effluent samples from the fifth eluent column, stop the elution experiment, use the reverse peristaltic function of the peristaltic pump to immediately drain the eluent, separate the solids obtained in each eluent column, and dry them at low temperature for storage. After the effluent samples are appropriately diluted, use ICP-OES instrument to determine and analyze the Cu 2+ 、Ni 2+ content.

[0045] (3) Purity identification experiment: The solid obtained from each elution column in the multi-stage elution experiment was used as a sample to analyze its nickel content level. The analysis steps are as follows: weigh about 2.0 g of sample, place it in a 100 mL beaker, add 1 mL of hydrochloric acid solution and 50 mL of pure water, heat until the sample is dissolved, cool to room temperature, completely transfer to a 100 mL volumetric flask and make up the volume; accurately transfer 10 mL of sample solution to a 250 mL beaker, add 150 mL of pure water, 5 mL of ammonium chloride solution, and 5 mL of tartaric acid solution, cover with a watch glass, heat to boiling and then stop heating; when cooled to 70~80 ℃, slowly add 30 mL of dimethylglyoxime ethanol solution under constant stirring, add ammonia solution dropwise to adjust the pH to 8~9, and then add 1~2 mL in excess, and keep warm at 70~80 ℃ for 30 After the insulation is completed, large red flocculent precipitates can be observed in the beaker. The precipitates are filtered using a suction filter, washed 4 to 5 times with ethanol solution, and dried at 105°C until the mass is constant. The precipitates are weighed and the solid nickel content is calculated.

[0046] like Figure 2 、 Figure 3 As shown in the figure, after continuous elution, the nickel content of the nickel salt obtained in the first elution column can reach 21.8%, and the Cu 2+ The maximum concentration does not exceed 30 g / L. The elution device described herein operates continuously. After one round of elution in the first elution column, the solid nickel content obtained has reached the purity requirements for electroplating-grade nickel sulfate. The solids in this column can be directly removed for reuse in the next step. Simultaneously, the second elution column becomes the new first elution column in the series connection, allowing unwashed crude nickel salt to be added and added to the end of the series connection. The entire process maintains a continuous elution state, thereby producing electroplating-grade nickel sulfate that meets the standards.

[0047] Example 2: Effect of different deposition voltages on eluent recovery

[0048] (1) Preparation of experimental materials: ① Preparation of electrolyte. As shown in Example 1, in the multi-stage elution experiment, the Cu 2+ The maximum concentration does not exceed 30 g / L, so the electrolyte prepared in the controlled voltage electrodeposition experiment contains Cu 2+ 30 g / L saturated nickel sulfate solution, the electrolyte volume required for a single experiment is 200 mL; ② Prepare electrode materials. The electrode materials selected for the experiment are titanium ruthenium mesh (anode) and stainless steel (cathode). The effective contact area of the electrode is 3 cm×4 cm. Before each experiment, the electrode material needs to be pretreated, that is, soaked in 5% hydrochloric acid for more than 1 hour, then rinsed with deionized water, and dried for use.

[0049] (2) Controlled voltage electrodeposition experiment: Use an electrochemical workstation to provide constant voltage, and conduct electrodeposition experiments at voltages of 2.0 V, 2.5 V, 3.0 V, and 3.5 V, respectively. Set the current data to be recorded every 10 s. Connect the electrode plate to the positive and negative poles of the instrument through wires, turn on the power and start the experiment. During the experiment, use a magnetic stirrer to automatically stir and control the temperature in real time. The stirring speed is 300 rpm and the temperature is about 40 °C. Samples are taken every 1 h. The total experimental time is 6 h. After appropriate dilution, use an ICP-OES instrument to determine and analyze the Cu content of the solution during the power-on process. 2+ Concentration value.

[0050] like Figure 4 As shown in the figure, the greater the voltage value, the better the copper deposition efficiency. At a voltage of 3.5 V, the Cu in the electrolyte can be deposited after about 6 h of power supply. 2+ The more complete the removal of , the better the regeneration effect of the eluent. Figure 5 As shown, the greater the voltage value, the more intense the hydrogen evolution reaction, which will reduce the density of the deposited copper. The density is best at a voltage of 2.0 V and the worst at a voltage of 3.0 V.

[0051] Example 3: Electroplating performance test of purified nickel salt

[0052] (1) Preparation of experimental materials: ① Preparation of electroplating solution: The nickel salts obtained from the elution columns (including the first to fifth elution columns) after elution and purification with the original elution solution, the crude nickel salts without elution, and the nickel salts obtained after elution and purification with the regenerated elution solution were used as electrolytes (experimental groups II, III, IV, V, VI, VII, and VIII, respectively), with analytical pure nickel sulfate as a reference (experimental group I). ② Build a Hull cell, using metal nickel as the anode and metal copper as the cathode (oblique side). The length of the anode nickel plate is 63.5 mm, the length of the cathode copper plate is 103 mm, and the distance between the two ends of the cell is 47.6 mm and 127 mm, respectively. The Ni in the electrolyte is 0.1447mm. 2+ Deposited on the cathode electrode in the form of metallic nickel.

[0053] (2) Electroplating experiment: ① Use an electrochemical workstation to provide a constant voltage. Connect the electrode plate to the positive and negative electrodes of the instrument via wires. Turn on the power supply and start the experiment. Control the voltage to 2.5 V (current to 2.0 A). Use a magnetic stirrer for automatic stirring and real-time temperature control. The stirring speed is 300 rpm and the temperature is about 40°C. The electroplating time is 30 min. ② Analyze the appearance and micromorphology of the plated parts. ③ Investigate the electrochemical properties of the plated parts.

[0054] like Figure 6As shown, the plated parts of groups I (pure nickel sulfate), II (nickel salt obtained by elution from the first elution column), and VIII (nickel salt obtained by elution from the regenerated elution solution) have similar colors, while the plated parts of groups III to VI (nickel salt obtained by elution from the second to fifth elution columns) have increasingly darker colors. Figure 7 As shown, Groups II and VIII exhibit relatively smooth surfaces, essentially indistinguishable from those of Group I (analytical-grade NiSO₄·6H₂O). However, Groups III, IV, V, VI, and VI (nickel salts from the second through fifth elution columns) exhibit increased surface roughness due to shorter washing times compared to Group II (nickel salts from the first elution column). Granular grains begin to appear on the surface of the coating, and the grain size increases with shorter washing times.

[0055] like Figure 8 The linear sweep voltammetry (LSV) results shown in the figure show that under negative voltage sweep, the current change of the plated parts in group II is not obvious, and its LSV curve is almost the same as the LSV curve of the first batch of electrodes, while the current changes of other groups are obvious, indicating that the Cu content of groups I and II is negligible, while the other groups are doped with Cu to varying degrees. Figure 9 As shown, the Rct values in the impedance spectra of the plated parts in groups I, II, and VIII are the highest, while the Rct values in the impedance spectra of groups VI and VII are close and the lowest. This indicates that the Rct values of the plated parts obtained in groups II and VIII are close to those of analytically pure NiSO4 (group I), indicating that the properties of the nickel salts obtained by washing in these two groups are similar to those of the analytically pure NiSO4 in the control group, indicating that the nickel salts obtained by elution purification according to the present invention can meet the requirements of the electroplating process.

Claims

1. A crude nickel salt elution and purification device, characterized in that: Including eluent pool, multi-stage eluent column, peristaltic pump, eluent regeneration pool; The eluent pool is used to store saturated nickel sulfate solution as eluent; The multi-stage elution column comprises a plurality of elution columns connected in series, wherein the elution columns are filled with crude nickel salt; The peristaltic pump is connected to the eluent pool and the first eluent column of the multi-stage eluent column; The eluent regeneration pool is connected to the outlet of the last eluent column through a pipe. The eluent regeneration pool is provided with an anode, a cathode and an electrochemical workstation connected with the cathode and the anode.

2. A crude nickel salt elution and purification device according to claim 1, characterized in that: The multi-stage elution column includes five elution columns connected in series.

3. The crude nickel salt elution and purification device according to claim 1, wherein: The cathode is made of stainless steel.

4. The crude nickel salt elution and purification device according to claim 1, wherein: The anode is made of titanium ruthenium mesh.

5. A crude nickel salt elution purification method, characterized in that: The device according to any one of claims 1 to 4 comprises the following steps: 1) A saturated nickel sulfate solution is used as the eluent and pumped into a multi-stage elution column via a peristaltic pump. The crude nickel salt is sequentially eluted in an upflow manner to dissolve the copper sulfate impurities and improve the purity of the nickel salt. 2) Collect the eluent containing copper ions, remove the copper ions by controlled voltage electrodeposition in the eluent regeneration tank, and return the regenerated eluent to the eluent tank for recycling; 3) Separate the purified nickel salts in the multi-stage elution column and obtain electroplating grade nickel sulfate after drying.

6. A crude nickel salt elution purification method according to claim 5, characterized in that: In step 1), the hydraulic retention time of the eluent in each eluent column is not less than 4 minutes.

7. A crude nickel salt elution purification method according to claim 5, characterized in that: In step 2), the voltage of the controlled voltage electrodeposition is 2.0-3.5 V.

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