Rough nickel salt leaching and purifying device

Abstract

A crude nickel salt leaching and purifying device belongs to the technical field of sewage treatment and comprises a leaching solution tank, a multi-stage leaching column, a peristaltic pump and a leaching solution regeneration tank, 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 hose, 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 device disclosed by the utility model, cyclic purification of leaching purification-electrodeposition regeneration leacheate is established, so that in-situ purification of crude nickel salt and recycling of the leacheate can be realized, and the device 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] This utility model relates to the field of wastewater treatment technology, and in particular to a crude nickel salt leaching and purification device. Background Technology

[0002] Electroplating wastewater contains high concentrations of heavy metals, which can damage the environment if not treated properly. Nickel is an important raw material in the electroplating industry, but it is also one of the main pollutants generated by the industry. The recycling of nickel from electroplating wastewater can not only avoid pollution and reduce resource consumption in electroplating production, but also create new profit centers for companies.

[0003] In recent years, research on nickel resource recovery has deepened both domestically and internationally, leading to the development of various methods such as adsorption enrichment, electrochemical reduction, chemical precipitation, and resin adsorption. Although novel adsorbents such as biochar, molecular sieves, and modified cellulose have demonstrated good nickel adsorption capabilities, most methods have failed to convert nickel into a processable form. By precisely controlling the electrode potential, electroreduction technology can achieve the fractional recovery of nickel and other metals by inhibiting the reduction of some metals. Professor Liu Huijuan and others discovered that electropulse reduction technology can improve the purity of recovered metals. Researcher Zhao Xu demonstrated that α-Ni(OH)2 is a crucial intermediate state in the nickel electrodeposition process, and to achieve continuous and effective nickel deposition, the pH of the electrolyte needs to be precisely controlled at around 6.58. Therefore, although electroreduction recovery of nickel is feasible, the recovery conditions are still quite demanding, 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, containing approximately 5% to 6% nickel, can be sold at a low price to sludge disposal companies for about 60,000 yuan per ton of nickel. These companies then use a series of refining processes to recover the nickel and reintroduce it into 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-distillation crystallization," producing crude nickel salts with a nickel content of approximately 12% to 15%, priced at about 105,000 yuan per ton of nickel. After refining, this can be easily converted into industrial-grade nickel salts. However, if the recovered materials can be purified to high-purity raw materials such as electroplating-grade nickel sulfate, their recycling value will increase significantly. Taking Fujian Province as an example, the price difference between crude nickel salts and electroplating-grade nickel sulfate is significant, with the latter reaching as high as 184,000 yuan per ton of nickel. Therefore, developing nickel purification technologies suitable for electroplating wastewater treatment plants can not only incentivize companies to recycle but also promote the electroplating industry towards a cleaner and more efficient production model.

[0005] In traditional nickel purification processes, organic exchange extraction has long been dominant. This method relies on the difference in the ability of metal ions to transfer from the aqueous phase to the organic phase (usually using fatty acid soaps as a carrier) to achieve the enrichment and purification of nickel metal. Although this method is theoretically feasible, in practical applications, the introduction of organic solvents into wastewater treatment plants has raised numerous safety hazards and clearly contradicts the concept of "clean production." Therefore, there is an urgent need to explore and develop more environmentally friendly and green purification technologies to achieve the safe purification of crude nickel salts from electroplating wastewater and ultimately realize the in-situ resource recovery of nickel. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of large geographical span, high transportation costs, high recycling costs, and high drug toxicity in the existing technology of nickel resource recovery, and to provide a crude nickel salt leaching and purification device.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A crude nickel salt leaching and purification device includes a leaching solution tank, a multi-stage leaching column, and a peristaltic pump; the leaching solution tank is used to store a saturated nickel sulfate solution as the leaching solution; the multi-stage leaching column includes several leaching columns connected in series by hoses, and the leaching column is filled with crude nickel salt; the peristaltic pump is connected to the leaching solution tank and the first leaching column of the multi-stage leaching column.

[0009] This invention also includes a rinsing fluid regeneration tank, which is connected to the outlet of the last rinsing column via a hose.

[0010] The eluent regeneration tank is equipped with an anode, a cathode, and an electrochemical workstation connected to the cathode and anode.

[0011] The cathode is made of stainless steel.

[0012] The anode is made of titanium-ruthenium mesh.

[0013] The multi-stage rinsing column consists of five rinsing columns connected in series via hoses.

[0014] A method for rinsing and purifying crude nickel salts includes the following steps:

[0015] 1) A saturated nickel sulfate solution is used as the rinsing solution and pumped into a multi-stage rinsing column by a peristaltic pump. The crude nickel salt is rinsed sequentially by upflow to dissolve copper sulfate impurities and improve the purity of the nickel salt.

[0016] 2) Collect the eluent containing copper ions, remove the copper ions by voltage-controlled electrodeposition in the eluent regeneration tank, and return the regenerated eluent to the eluent tank for recycling;

[0017] 3) The purified nickel salts in the multi-stage rinsing column are separated and dried to obtain electroplating grade nickel sulfate.

[0018] In step 1), the hydraulic residence time of the rinsing solution in each rinsing column is not less than 4 minutes.

[0019] In step 2), the voltage of the controlled piezoelectric deposition is 2.0~3.5 V.

[0020] Compared with the prior art, the beneficial effects achieved by the technical solution of this utility model are:

[0021] 1) The reagents used in this utility model are inexpensive and have low toxicity. The operation is simple and safe, and the process is continuous and stable. It can be directly connected in series with electroplating wastewater treatment plants that use ion resin concentration-distillation separation process to treat crude nickel salts, so as to realize the in-situ regeneration and utilization of nickel-containing electroplating wastewater.

[0022] 2) This invention uses electrodeposition to regenerate the eluent, and the regenerated eluent can be reused;

[0023] 3) The nickel salt obtained by rinsing according to this utility model meets the standard of electroplating grade nickel sulfate, can be used in the electroplating industry, reduces industry operating costs, improves the recycling rate of nickel resources, and has great economic value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a rinsing and purification device; where 1-rinsing solution tank, 2-peristaltic pump, 3-5-stage rinsing column, 4-rinsing solution regeneration tank;

[0025] Figure 2 The table shows the solid nickel content in each elution column obtained from the multi-stage elution experiment; where the horizontal axis 1 to 5 represent the first, second, third, fourth, and fifth elution columns, respectively.

[0026] Figure 3 Cu in the effluent of each rinsing column 2+ The concentration changes;

[0027] Figure 4 Cu electrolyte in the piezoelectric electrodeposition experiment 2+ Concentration changes;

[0028] Figure 5 The morphology of copper on the cathode plate obtained by deposition at different voltages;

[0029] Figure 6 The image shows a plated part used in an electroplating experiment with nickel salt as the plating solution.

[0030] Figure 7 SEM morphology of electroplated surfaces with different electroplating solutions at the 1 μm scale;

[0031] Figure 8 The LSV curve of the plated part;

[0032] Figure 9 The AC impedance spectrum of the plated part. Detailed Implementation

[0033] To make the technical problems, technical solutions and beneficial effects of this utility model clearer and more understandable, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments.

[0034] This invention uses crude nickel salt with an 8% copper sulfate content (close to the impurity content of crude nickel salt obtained by ion exchange resin concentration-distillation separation process in electroplating wastewater treatment plants) as the packing material for the elution column, and a saturated nickel sulfate solution as the elution liquid. Multi-stage elution is employed to achieve efficient purification of nickel sulfate. Through the multi-stage elution column, the elution liquid is transformed into an eluent with nickel sulfate / copper sulfate as the main solute, while the purity of the crude nickel salt packed in the elution column is improved. Then, controlled-voltage electrodeposition is used to remove Cu from the elution liquid. 2+ This method enables the regeneration of nickel sulfate leaching solution, which can then be recycled for further leaching and purification. The electroplating performance of the purified nickel salt was examined using a Hull cell experiment to verify whether the prepared high-purity nickel sulfate met the standards for electroplating-grade nickel sulfate.

[0035] See Figure 1 The crude nickel salt rinsing and purification device of this utility model includes a rinsing liquid tank 1, a peristaltic pump 2, a 5-stage rinsing column 3, and a rinsing liquid regeneration tank 4.

[0036] The rinsing solution tank 1 contains a saturated nickel sulfate solution as the rinsing solution;

[0037] The peristaltic pump 2 serves as a power unit and is connected to a continuous flow system via a hose. Specifically, the peristaltic pump 2 is connected to the first rinsing column (first rinsing column) of the 5-stage rinsing column 3.

[0038] The 5-stage rinsing column 3 includes 5 rinsing columns connected in series by a hose, which are named the first rinsing column, the second rinsing column, the third rinsing column, the fourth rinsing column and the fifth rinsing column, respectively. Specifically, in this embodiment, it is a rinsing column composed of 5 cylindrical columns with a volume of 200 mL, and the rinsing column is filled with about 100 g of crude nickel salt.

[0039] The eluent regeneration tank 4 is connected to the outlet of the last eluent column (the fifth eluent column) via a hose. The eluent regeneration tank is equipped with an anode, a cathode, and an electrochemical workstation connected to the cathode and anode. The eluent regeneration tank 4 regenerates 200 mL of eluent in a single cycle. The selected electrode materials are titanium-ruthenium mesh (anode) and stainless steel (cathode). The electrochemical system provides DC power, and a magnetic stirrer is used for automatic stirring and real-time temperature control during the process.

[0040] Example 1: Purity Analysis of Purified Nickel Salts

[0041] (1) Preparation of experimental materials: ① Prepare 1.5 L of eluent; ② Prepare 5 portions of crude nickel salt, each 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.

[0042] (2) Multistage elution experiment: First, the actual flow rate of the peristaltic pump was measured using a stopwatch and graduated cylinder. To ensure that the hydraulic residence time of the elution fluid in the column was about 5 minutes, the flow rate was preferably controlled at 40 mL / min; then, according to... Figure 1 Assemble the experimental setup 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 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, take samples at appropriate time points as effluent samples of the first eluent column. Similarly, when the eluent gradually flows into the second eluent column and reaches full overflow, take samples at regular intervals for preservation. Continue in this manner, using the eluent flowing out of the last eluent column as a signal. After taking 2-3 effluent samples from the fifth eluent column, stop the elution experiment. Immediately drain the eluent using the reverse peristaltic function of the peristaltic pump, separate the solids obtained from each eluent column, and dry them at low temperature for preservation. Dilute each effluent sample appropriately and analyze the Cu content using an ICP-OES instrument. 2+ Ni 2+ content.

[0043] (3) Purity identification experiment: The solid obtained from each elution column in the multi-stage elution experiment was used as the sample to analyze its nickel content level. The analytical steps are as follows: Weigh about 2.0 g of the sample and place it in a 100 mL beaker. Add 1 mL of hydrochloric acid solution and 50 mL of pure water. Heat until the sample dissolves. Cool to room temperature and completely transfer to a 100 mL volumetric flask and make up to volume. Accurately transfer 10 mL of the 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 and heat to boiling. Stop heating. When cooled to 70~80 ℃, slowly add 30 mL of dimethylglyoxime ethanol solution while stirring continuously. Add ammonia solution dropwise to adjust the pH to 8~9. Add an excess of 1~2 mL and keep warm at 70~80 ℃ for 30 minutes. min; After the heat preservation is completed, large red flocculent precipitates can be observed to form in the beaker. Filter using a vacuum filter, wash 4-5 times with ethanol solution, dry at 105℃ until the mass is constant, weigh, and calculate the solid nickel content.

[0044] like Figure 2 , Figure 3 As shown, after continuous rinsing, the nickel salt obtained from the first rinsing column has a nickel content of up to 21.8%, and the Cu content in the rinsing solution is... 2+ The maximum concentration does not exceed 30 g / L. The rinsing device described in this invention operates continuously. After one round of rinsing, the solid nickel content obtained from the first rinsing column meets the purity requirements for electroplating-grade nickel sulfate. The solid in this column can be directly removed for further reuse. Simultaneously, the second rinsing column becomes the new first rinsing column in the series, and unrinsed crude nickel salt can be added and connected to the end of the series. The entire process maintains continuous rinsing, thereby obtaining electroplating-grade nickel sulfate that meets the standards.

[0045] Example 2: Effect of different deposition voltages on eluent recovery

[0046] (1) Preparation of experimental materials: ① Preparation of electrolyte. As can be seen from Example 1, in the multi-stage rinsing experiment, Cu in the rinsing solution 2+ The concentration should not exceed 30 g / L; therefore, the electrolyte prepared in the voltage-controlled electrodeposition experiment contains Cu. 2+ ① Prepare a 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 electrodes is 3 cm × 4 cm. Before each experiment, the electrode materials need to be pretreated, that is, soaked in 5% hydrochloric acid for more than 1 hour, then rinsed with deionized water and dried for later use.

[0047] (2) Voltage-controlled electrodeposition experiment: A constant voltage was provided using an electrochemical workstation, and electrodeposition experiments were conducted at voltages of 2.0 V, 2.5 V, 3.0 V, and 3.5 V. Current data was recorded every 10 s. The electrode plates were connected to the positive and negative terminals of the instrument via wires. The power was turned on to start the experiment. During the experiment, a magnetic stirrer was used for automatic stirring and real-time temperature control. The stirring speed was 300 rpm and the temperature was about 40 ℃. Samples were taken every 1 h. The total experimental time was 6 h. After appropriate dilution, the Cu content of the solution during the electrolysis process was determined and analyzed using an ICP-OES instrument. 2+ Concentration value.

[0048] like Figure 4 As shown, the higher the voltage value, the better the copper deposition efficiency. At 3.5 V, Cu deposition in the electrolyte can be achieved in about 6 hours. 2+ The more completely removed the substance, the better the regeneration effect of the eluent. For example... Figure 5 As shown, the higher the voltage, the more vigorous the hydrogen evolution reaction, which will reduce the density of the deposited copper. The density is best at 2.0 V and worst at 3.0 V.

[0049] Example 3: Performance Testing of Purified Nickel Salt Electroplating

[0050] (1) Preparation of experimental materials: ① Preparation of electroplating solution: The nickel salt obtained from the rinsing columns (including the first to fifth rinsing columns) after rinsing and purification with the original rinsing solution, the unrinsed crude nickel salt, and the nickel salt obtained after rinsing and purification with the regenerated rinsing solution were used as electrolytes (groups II, III, IV, V, VI, VII, and VIII, respectively), with analytical grade nickel sulfate as a reference (group I). ② Construct a Hull cell, using metallic nickel as the anode and metallic 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... 2+ It is deposited onto the cathode electrode in the form of metallic nickel.

[0051] (2) Electroplating experiment: ① A constant voltage was provided using an electrochemical workstation. The electrode plates were connected to the positive and negative terminals of the instrument via wires. The power was turned on to start the experiment, and the voltage was controlled at 2.5 V (current at 2.0 A). During the experiment, a magnetic stirrer was used for automatic stirring and real-time temperature control. The stirring speed was 300 rpm and the temperature was about 40 ℃. The electroplating time was 30 min. ② The appearance and microstructure of the electroplated parts were analyzed. ③ The electrochemical characteristics of the electroplated parts were investigated.

[0052] like Figure 6As shown, the plated parts obtained from groups I (pure nickel sulfate), II (nickel salt obtained from rinsing in the first rinsing column), and VIII (nickel salt obtained from rinsing in the regenerated rinsing solution) have similar colors, while the plated parts from groups III to VI (nickel salt obtained from rinsing in the second to fifth rinsing columns) have progressively darker colors. Figure 7 As shown, the plating parts in Groups II and VIII have relatively smooth surfaces, with no essential difference from the surface of Group I (analytical grade NiSO4·6H2O). However, the surface roughness of the plating parts obtained from Groups III, IV, V, VI, and VI (nickel salts obtained from the second to fifth rinsing columns) increases due to the shorter rinsing time compared to Group II (nickel salts obtained from the first rinsing column). The plating surface begins to exhibit granular grains, and the shorter the rinsing time, the larger the grain size becomes.

[0053] like Figure 8 The linear sweep voltammetry (LSV) results show that under negative voltage scanning, the current change in group II is not significant, and its LSV curve almost coincides with that of the first group of electrodes. However, the current changes in other groups are very significant, indicating that the Cu content in 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), suggesting that the properties of the nickel salts obtained from washing in these two groups are similar to those of the control group analytically pure NiSO4. This demonstrates that the nickel salts purified by rinsing using this invention can meet the requirements of the electroplating process.

Claims

1. A crude nickel salt purification device by means of a leaching, characterized by: It includes a rinsing solution tank, a multi-stage rinsing column, and a peristaltic pump; the rinsing solution tank is used to store a saturated nickel sulfate solution as the rinsing solution; the multi-stage rinsing column includes several rinsing columns connected in series by hoses, and the rinsing column is filled with crude nickel salt; the peristaltic pump connects the rinsing solution tank and the first rinsing column of the multi-stage rinsing column.

2. A crude nickel salt purification by elution apparatus as claimed in claim 1, characterized in that: It also includes a rinsing fluid regeneration tank, which is connected to the outlet of the last rinsing column via a hose.

3. A crude nickel salt purification by elution apparatus as claimed in claim 2, characterised in that: The eluent regeneration tank is equipped with an anode, a cathode, and an electrochemical workstation connected to the cathode and anode.

4. A crude nickel salt purification by elution apparatus as claimed in claim 3, characterised in that: The cathode is made of stainless steel.

5. A crude nickel salt purification by elution apparatus as claimed in claim 3, wherein: The anode is made of titanium-ruthenium mesh.

6. A crude nickel salt purification by elution apparatus as claimed in claim 1, wherein: The multi-stage rinsing column consists of five rinsing columns connected in series via hoses.

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