In-situ electrolytic regeneration process for low-concentration tin-copper wastewater

Abstract

The invention discloses an in-situ electrolytic regeneration process for low-concentration tin-copper wastewater. The regeneration process comprises the following steps: taking the low-concentration tin-copper wastewater as an electrolyte, connecting a working electrode, a counter electrode and a reference electrode, and starting to carry out rotational flow electrolysis treatment on the low-concentration tin-copper wastewater; a first additive is added into the electrolyte, a first electrochemical reaction is carried out by controlling the current and the flow velocity, and a first cathode product and the remaining tin-containing electrolyte are obtained; the adding amount of the first additive is not less than 5mg / L; the concentration of Cu < 2 + > in the residual tin-containing electrolyte is not greater than 20 mg / L; and a second additive is added into the tin-containing electrolyte, a second electrochemical reaction is carried out by controlling the current and the flow rate, and a second cathode product and other solutions are obtained. According to the in-situ electrolysis regeneration process for the low-concentration tin-copper wastewater, a hydraulic strengthening electrolysis technology is adopted, stepped recovery of low-concentration tin-copper metal is achieved, meanwhile, precipitation of toxic and harmful chlorine is avoided, and good economic and environmental benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of wastewater recycling technology, and in particular to an in-situ electrolytic regeneration process for low-concentration tin-copper wastewater. Background Technology

[0002] Flexible printed circuit board (FPCB) technology is a key supporting technology for important applications in many industries such as automotive, computers, digital cameras, and communication equipment. With the continuous progress and development of the electronics industry, the demand for FPCBs has experienced explosive growth, with an average annual growth rate (AAGR) of 13.5%. According to statistics from WSTS (World Semiconductor Trade Statistics), the market size reached US$21.94 billion in 2024, and is projected to grow at a CAGR of 6.76% by 2029. Due to the global production and application of FPCBs, a large amount of hydrochloric acid wastewater containing low concentrations of tin and copper is continuously generated and discharged during the etching process, with tin and copper concentrations of approximately 300 ppm and 50 ppm, respectively. Statistics show that an average of 1.5-3.5 liters of etching solution are consumed per square meter of FPCB produced, resulting in approximately 1 billion cubic meters of semiconductor wastewater generated globally each year. Therefore, it is essential to properly treat and recycle this low-concentration tin and copper wastewater from the semiconductor industry to achieve both heavy metal pollution control and the effective utilization of precious metal resources.

[0003] Currently, chemical precipitation using sulfides or lime as reagents is commonly used to remove tin and copper from inorganic wastewater. This process is simple to operate and highly efficient, but it generates large amounts of metal sulfide sludge and is either ineffective or too costly in treating low concentrations of tin and copper. In addition, adsorption and ion exchange technologies are widely used for tin and copper removal from water bodies and industrial wastewater. These methods offer advantages such as low cost, simple operation, and high efficiency, but also suffer from drawbacks such as time-consuming maintenance of adsorption columns (or ion exchange resins) and difficult regeneration. Biotechnology, as another mainstream treatment method, requires fewer reagents and generates less sludge. However, the removal efficiency of tin and copper ions by biological treatment is limited by the bottleneck of its slow kinetic reaction.

[0004] For example, CN 119278295 A relates to a progressive electrolytic recycling method and apparatus for acid etching waste liquid, which safely recovers copper from acid etching waste liquid and reduces the back erosion of electrolyzed copper on the cathode, but neglects the selective recovery of tin metal in acid etching waste liquid.

[0005] For example, CN 115466957 A relates to a method and apparatus for electrolytic regeneration of copper from acidic copper chloride etching waste liquid, which obtains solid copper salt precipitate and acidic filtrate as copper recovery products and regenerated etching sub-liquid, respectively, effectively solving the problem of increased etching waste liquid during the production process of existing acidic copper chloride etching solutions. However, the etching waste liquid is prone to secondary chlorine pollution during electrolytic regeneration, and at the same time reduces the reuse efficiency of the regenerated etching sub-liquid.

[0006] Therefore, a new treatment process for low-concentration tin-copper wastewater is needed. Summary of the Invention

[0007] To better address the resource loss and environmental hazards of heavy metals during the treatment of semiconductor wastewater, as well as the secondary pollution of subsequent wastewater, this invention provides an in-situ electrolytic regeneration process for low-concentration tin-copper wastewater. The process provided by this invention not only achieves in-situ electrolytic regeneration of hydrochloric acid media in low-concentration tin-copper wastewater, but also recovers tin and copper metal resources in stages, and simultaneously manufactures nano- and micro-metal powders for application in powder metallurgy, chemical catalysis, and 3D printing.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A process for in-situ electrolytic regeneration of low-concentration tin-copper wastewater includes the following steps:

[0010] (1) Using low-concentration tin-copper wastewater as electrolyte, connect the working electrode, counter electrode and reference electrode to start the cyclone electrolysis treatment of the low-concentration tin-copper wastewater;

[0011] (2) A first additive is added to the electrolyte, and a first electrochemical reaction is carried out by controlling the current and flow rate to obtain a first cathode product and a remaining tin-containing electrolyte; the amount of the first additive added is not less than 5 mg / L; the Cu in the remaining tin-containing electrolyte... 2+ The concentration should not exceed 20 mg / L;

[0012] (3) Add a second additive to the tin-containing electrolyte, and carry out a second electrochemical reaction by controlling the current and flow rate to obtain a second cathode product and other solutions;

[0013] The first cathode product is copper, the second cathode product is tin, and the other solutions are regenerated hydrochloric acid.

[0014] In step (1), the low-concentration tin-copper wastewater is a solution containing copper, tin, and chlorine; the Fe in the low-concentration tin-copper wastewater... 3+ The concentration should not exceed 30 mg / L.

[0015] Preferably, the Cu 2+Concentration of 100~1000 mg / L, Sn 4+ The concentration is 10~100 mg / L, and the Cl- concentration is 0.1~5 mol / L.

[0016] In step (1), the working electrode is a 316L stainless steel cathode with a surrounding ring, the counter electrode is a cylindrical IrO2-Ta2O5 coated titanium anode, and the reference electrode is an Ag / AgCl electrode.

[0017] In step (2), the first additive is one or more of 2,2'-bipyridine, potassium ferric cyanide, sodium propargyl sulfonate, sodium hydroxyethyl sulfonate, sodium chloride, gelatin, sodium dodecyl sulfate, and thiourea; the amount of the first additive added is not less than 10 mg / L.

[0018] In step (2), the current density of the first electrochemical reaction is not less than 30 mA / cm². 2 The swirling flow rate is not less than 50 mL / s.

[0019] In step (3), the second additive is one or more of 2,2'-bipyridine, potassium ferric cyanide, triammonium citrate, sodium chloride, gelatin, sodium dodecyl sulfate, cresol acid, and cresol sulfonic acid; the amount of the second additive added is not less than 10 mg / L.

[0020] In step (3), the current density of the second electrochemical reaction is not less than 50 mA / cm². 2 The swirling flow velocity is not less than 90 mL / s.

[0021] The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater from semiconductors further includes a step of stripping the first cathode product and the second cathode product.

[0022] Copper nano-metal powder and tin nano-metal powder can be obtained by washing and drying the first and second cathode products obtained from the stripping process.

[0023] In step (3), the impurity ion content in the other solutions is less than 50 mg / L.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater of the present invention adopts hydraulic enhanced electrolysis technology to realize the cascade recovery of low-concentration tin-copper metal, while avoiding the release of toxic and harmful chlorine gas, and has good economic and environmental benefits.

[0026] (2) When the low-concentration tin-copper wastewater in-situ electrolytic regeneration process of the present invention is applied to the treatment of low-concentration wastewater of FPCB, a hydrochloric acid solution with low impurity content is obtained after hydraulic enhanced electrolysis, realizing the in-situ regeneration of low-concentration tin-copper wastewater, which can be used as a regenerated etching solution for the etching process of flexible printed circuit boards, reducing the cost of hydrochloric acid replenishment, and eliminating the need for subsequent wastewater retreatment.

[0027] (3) The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater of the present invention utilizes inexpensive chemical additives to reduce the nucleation barrier, improve current efficiency, promote the electrodeposition of metal ion complexes, and effectively improve the recovery rate of copper and tin.

[0028] (4) In addition to improving the recovery rate of copper and tin, the low-concentration tin-copper wastewater in-situ electrolytic regeneration process of the present invention can also refine the grain size by adding inexpensive chemical additives, resulting in a dense and smooth cathode deposit surface, which greatly alleviates the shedding and redissolution of the deposit.

[0029] (5) The copper and tin nano-micro metal powders recovered by the in-situ electrolytic regeneration process of low-concentration tin-copper wastewater of the present invention have excellent spherical structure and ultra-fine particle size, exhibiting high strength, high thermal conductivity, excellent wear resistance and good welding performance, providing raw materials for powder metallurgy, catalysts and 3D printing. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the mechanism of the in-situ electrolytic regeneration process for low-concentration tin-copper wastewater of the present invention.

[0031] Figure 2 This is a process flow diagram of the in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to the present invention.

[0032] Figure 3 These are physical images and SEM images of the cathode copper product obtained in Example 3 of the present invention. Figure 3 In the diagram, 'a' represents a physical image of copper, the first cathode product. Figure 3 In the image, b is the SEM image of copper, the first cathode product.

[0033] Figure 4 This is a graph showing the experimental results of copper recovery rate obtained by the process in Example 4 of the present invention.

[0034] Figure 5 This is a graph showing the experimental results of tin recovery rate obtained from the process in Example 5 of the present invention.

[0035] Figure 6 The graph shows the experimental results of copper recovery rate and chloride ion retention rate obtained by the process in Example 6 of this invention.

[0036] Figure 7The graph shows the experimental results of copper recovery rate and chloride ion retention rate obtained by the process in Example 7 of this invention.

[0037] Figure 8 The graph shows the experimental results of tin recovery rate and chloride ion retention rate obtained by the process in Example 8 of this invention.

[0038] Figure 9 The graph shows the experimental results of tin recovery rate and chloride ion retention rate obtained by the process in Example 9 of this invention.

[0039] Figure 10 This is a graph showing the purity results of samples obtained with different process parameters in this invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0041] See Figure 1 This invention provides an in-situ electrolytic regeneration process for low-concentration tin-copper wastewater. It utilizes a synergistic strategy of hydraulic (turbulent field) enhancement and chemical additive assistance to achieve in-situ electrolytic regeneration of tin-copper metal resources and hydrochloric acid medium in semiconductor low-concentration tin-copper wastewater. Based on the differences in electrode potentials between Cu(II) / Cu, Sn(Ⅳ) / Sn(II), and Sn(II) / Sn, a tiered electrodeposition of copper and tin metals on the cathode is achieved. By leveraging the mass transfer enhancement through turbulent fields, not only is the concentration polarization of tin and copper ions on the cathode broken, but the influence of chloride ions on the purity of the cathode product is also eliminated. Notably, based on the overpotential of the titanium-based IrO2-Ta2O5 electrode for chloride ion oxidation, the chlorine evolution reaction on the anode is significantly suppressed, thereby enabling the regeneration and reuse of the hydrochloric acid medium. Furthermore, the chemical additives act as a "bridging" agent, forming complexes with the metal ions, lowering the nucleation barrier, and depolarizing the Cu(II) electrodeposition process. This strategy not only accelerates the deposition rate of metal ions, but also smooths the deposition surface and refines the grain size, resulting in nano- and micro-sized metal powders.

[0042] Electrochemical reactions on the annular 316L stainless steel cathode under hydraulically enhanced mass transfer:

[0043]

[0044] Electrochemical reaction on a cylindrical IrO2-Ta2O5 coated titanium anode:

[0045]

[0046] For details, see Figure 2 This invention provides an in-situ electrolytic regeneration process for low-concentration tin-copper wastewater, comprising the following steps:

[0047] (1) Low-concentration tin-copper chloride-hydrochloric acid wastewater is added as electrolyte to a hydraulically enhanced electrolysis device, and a 316 L stainless steel cathode (with a smooth surface after thorough polishing), a cylindrical IrO2-Ta2O5 coated titanium anode and a reference Ag / AgCl electrode are connected to start the cyclone electrolysis treatment of the low-concentration tin-copper chloride-hydrochloric acid wastewater;

[0048] (2) Add a first additive of not less than 10 mg / L to the electrolyte, and the electrolyte concentration is not less than 30 mA / cm. 2 The first electrochemical reaction was carried out at a current of 50 mL / s to obtain the first cathode product and the remaining tin-containing electrolyte.

[0049] (3) Add a second additive of not less than 20 mg / L to the tin-containing electrolyte, at a concentration of not less than 50 mA / cm 2 A second electrochemical reaction was carried out at a current of 90 mL / s to obtain the second cathode product and other solutions.

[0050] The first cathode product is copper, the second cathode product is tin, and the other solutions are hydrochloric acid.

[0051] The first and second cathode products were stripped, washed with deionized water, and dried to obtain high-purity copper and high-purity tin nano-micro metal powders, respectively.

[0052] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0053] In the following examples and comparative examples, the Cu in the low-concentration tin-copper wastewater was used 2+ The content is 500 mg / L, Sn 4+ The content is 50 mg / L, Cl - The concentration is 1 mol / L.

[0054] Example 1

[0055] An in-situ electrolytic regeneration process for low-concentration tin-copper wastewater from semiconductor manufacturing includes the following steps:

[0056] (1) The low-concentration tin-copper wastewater of semiconductors is used as the electrolyte and added to the hydraulically enhanced electrolysis equipment, and connected to the surrounding 316 L stainless steel cathode (with a smooth surface after thorough polishing), cylindrical IrO2-Ta2O5 coated titanium anode and reference Ag / AgCl electrode.

[0057] (2) Add 10 mg / L of 2,2'-bipyridine to the electrolyte and control the current density to be 35 mA / cm. 2 The flow rate of the electrolyte was controlled at 80 mL / s to carry out the first electrochemical reaction, yielding the first cathode product (copper) and the remaining tin-containing electrolyte.

[0058] (3) Add 20 mg / L of triammonium citrate to the tin-containing electrolyte and control the current density to be 60 mA / cm². 2 The flow rate of the tin-containing electrolyte was controlled at 120 mL / s to carry out a second electrochemical reaction, yielding a second cathode product (tin) and a regenerated hydrochloric acid solution.

[0059] (4) The first and second cathode products obtained in steps (2) and (3) are stripped, washed with deionized water and dried to obtain high-purity copper and tin nano-micro metal powders respectively.

[0060] The liquid phase ion concentration and cathode products after two electrochemical reactions were monitored using ICP-OES and SEM-EDS. The results showed that the recovery rates of copper and tin were 36.9% and 26.1%, respectively, and the retention rates of chloride ions after the first and second electrochemical reactions were 92.4% and 92%, respectively.

[0061] The inventors carefully analyzed the reasons for the low copper and tin recovery rates in the process and found that it was due to the presence of 200 mg / L of Fe in the low-concentration tin-copper wastewater from the semiconductor process. 3+ Further research revealed that in order to achieve a copper and tin recovery rate of over 90%, Fe in low-concentration tin-copper wastewater from semiconductor processes is crucial. 3+ The concentration must not exceed 20 mg / L. When Fe is present in low-concentration tin-copper wastewater from semiconductor processes... 3+ When the concentration is high, Fe can be removed by oxidation, hydrolysis, and precipitation. 3+ .

[0062] Example 2

[0063] This embodiment explores the impact of copper recovery rate on tin recovery rate.

[0064] The specific steps are basically the same as in Example 1, except that: by controlling the Cu content in the remaining tin-containing electrolyte... 2+The concentrations were 70 mg / L, 50 mg / L, 30 mg / L, 20 mg / L, 10 mg / L and 3 mg / L, respectively; the recoveries of tin were 27.5%, 48.7%, 66.2%, 78.6%, 86.1% and 86.3%, respectively. The specific data are shown in Table 1.

[0065] Table 1 Cu in the remaining tin-containing electrolyte 2+ Effect of concentration on tin recovery rate

[0066]

[0067] Example 3

[0068] An in-situ electrolytic regeneration process for low-concentration tin-copper wastewater from semiconductor manufacturing includes the following steps:

[0069] (1) The low-concentration tin-copper wastewater from the semiconductor process is used as the electrolyte and added to a hydraulically enhanced electrolysis device. A surrounding 316L stainless steel cathode (with a smooth surface after thorough polishing), a cylindrical IrO2-Ta2O5 coated titanium anode, and a reference Ag / AgCl electrode are connected to the device. The low-concentration tin-copper wastewater from the semiconductor process contains Fe 3+ The concentration is approximately 15 mg / L;

[0070] (2) Add 10 mg / L of 2,2'-bipyridine to the electrolyte and control the current density to be 35 mA / cm. 2 The electrolyte flow rate was controlled at 80 mL / s for the first electrochemical reaction, yielding the first cathode product (copper) and the remaining tin-containing electrolyte; the remaining tin-containing electrolyte contained Cu. 2+ The concentration is approximately 10 mg / L;

[0071] (3) Add 20 mg / L of triammonium citrate to the tin-containing electrolyte and control the current density to be 60 mA / cm². 2 The flow rate of the tin-containing electrolyte was controlled at 120 mL / s to carry out a second electrochemical reaction, yielding a second cathode product (tin) and a regenerated hydrochloric acid solution.

[0072] (4) The first and second cathode products obtained in steps (2) and (3) are stripped, washed with deionized water and dried to obtain high-purity copper and tin nano-micro metal powders respectively.

[0073] The liquid phase ion concentration and cathode products after two electrochemical reactions were monitored using ICP-OES and SEM-EDS. The results showed that the recovery rates of copper and tin were 91.9% and 86.1%, respectively, the retention rates of chloride ions after the first and second electrochemical reactions were 92.6% and 92%, respectively, and the purities of copper and tin products were 97% and 96.7%, respectively.

[0074] In addition, the physical image and microstructure diagram of the first cathode product copper are as follows: Figure 3 As shown. Among them. Figure 3 In the diagram, 'a' represents a physical image of copper, the first cathode product. Figure 3 In the image, b represents the SEM image of copper, the first cathode product. From... Figure 3 It can be seen that the first cathode product copper obtained is composed of ultrafine nano-metal particles with an average particle size of ~0.2 μm and uniform dispersion.

[0075] Example 4

[0076] This embodiment studies the effect of the first additive and its dosage on the process. The specific steps are basically the same as those in Example 3, except that the dosage of the first additive and the first additive used in step (2) are changed.

[0077] (1) Add 5 mg / L, 15 mg / L, 20 mg / L and 25 mg / L of 2,2'-bipyridine respectively;

[0078] (2) Add potassium ferric cyanide at concentrations of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L and 25 mg / L respectively;

[0079] (3) Add 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L and 25 mg / L of a mixture of 2,2'-bipyridine and potassium ferric cyanide (mass ratio of 1:1).

[0080] The test results of copper recovery rate in this embodiment and Example 3 are as follows: Figure 4 As shown, from Figure 4 As can be seen, when the dosage of the first additive is 5 mg / L, the copper recovery rate can reach 78.2%; when the dosage of the first additive is increased to 5 mg / L, the copper recovery rate increases from 78.2% to over 91%, and further increasing the dosage of the first additive slightly improves the recovery rate.

[0081] At the same time, from Figure 4 It can be seen that when the first additive is used alone, it has little effect on the copper recovery rate. However, when two additives are used together, even with the same dosage, the copper recovery effect is better than when one additive is used alone. This indicates that the "bridging" effect of the first additive is beneficial to the seeding of copper metal ions on the cathode.

[0082] Simultaneously, ICP-OES and SEM-EDS were used to monitor the liquid-phase ion concentration and cathode products after some of the two electrochemical reactions in Examples 3 and 4. The tests showed that when the first additive was 25 mg / L of 2,2'-bipyridine, the tin recovery rate was 86.9%, and the purities of the copper and tin products were 98.2% and 97.8%, respectively. When the first additive was 10 mg / L of potassium ferric cyanide, the tin recovery rate was 86.2%, and the purities of both the cathode copper and tin products were higher than 95%. When the first additive was 5 mg / L of 2,2'-bipyridine and 5 mg / L of potassium ferric cyanide, the tin recovery rate was 86.8%, and the purities of both the cathode copper and tin products were higher than 95%. Therefore, the amount and type of the first additive had a relatively low impact on the tin product recovery rate.

[0083] Example 5

[0084] This embodiment studies the effect of the second additive and its dosage on the process. The specific steps are basically the same as those in Example 3, except that the dosage of the second additive and the second additive used in step (3) are changed.

[0085] (1) Add 10 mg / L, 25 mg / L, 30 mg / L and 35 mg / L of triammonium citrate respectively;

[0086] (2) Add 10 mg / L, 20 mg / L, 25 mg / L, 30 mg / L and 35 mg / L of 2,2'-bipyridine respectively.

[0087] (3) Add 10 mg / L, 20 mg / L, 25 mg / L, 30 mg / L and 35 mg / L of a mixture of triammonium citrate and 2,2'-bipyridine (mass ratio of 1:1).

[0088] The test results of tin recovery rate in this embodiment and Example 3 are as follows: Figure 5 As shown, from Figure 5 As can be seen, when the amount of the second additive is 10 mg / L, the copper recovery rate is about 75%; when the amount of the second additive is increased to 20 mg / L, the tin recovery rate increases from 75% to about 85%, and further increasing the amount of the second additive can achieve a recovery rate of 90%.

[0089] At the same time, from Figure 5 It is evident that when only one additive (such as triammonium citrate or 2,2'-bipyridine) is used as the second additive, its impact on tin recovery is minimal. However, when two additives are used in combination, even with the same dosage, the tin recovery effect is better than when only one additive is used.

[0090] Example 6

[0091] This embodiment studies the effect of current density on the process in step (2). The specific steps are basically the same as those in embodiment 3, except that the current density in step (2) is changed.

[0092] The current density in step (2) is adjusted to 20 mA / cm². 2 30 mA / cm 2 40 mA / cm 2 45 mA / cm 2 50 mA / cm 2 .

[0093] The test results of copper recovery rate in this embodiment and Example 3 are as follows: Figure 6 As shown, from Figure 6 It can be seen from this that when the current density is 20 mA / cm 2 At that time, the copper recovery rate was only 62.6%, and the subsequent tin recovery rate was only a maximum of 21.2%. When the current density is greater than or equal to 30 mA / cm², the recovery rate is... 2 At that time, the copper recovery rate was greater than 90%, and the chloride ion retention rate reached more than 85%.

[0094] from Figure 6 It can be seen that increasing the current density of the first electrochemical reaction can promote the electromigration of copper metal ions, thereby enhancing the electrodeposition of copper metal ions. When the current density increases from 20 mA / cm², the electromigration of copper metal ions is enhanced. 2 Increased to 30 mA / cm 2 The copper recovery rate increased from 62.6% to 91.3%. The current density was further increased to 50 mA / cm². 2 The copper recovery rate can reach 94.4%, and the chloride ion retention rate is maintained at over 88%.

[0095] Example 7:

[0096] This embodiment studies the effect of the swirling flow rate in step (2) on the process. The specific steps are basically the same as those in embodiment 3, except that the swirling flow rate in step (2) is changed.

[0097] The swirl flow rates in step (2) were adjusted to 30 mL / s, 50 mL / s, 60 mL / s, 70 mL / s and 90 mL / s respectively.

[0098] The test results of copper recovery rate in this embodiment and Example 3 are as follows: Figure 7 As shown, from Figure 7As can be seen, when the swirling flow rate is 30 mL / s, the copper recovery rate is only 52.91%, the purity of the cathode copper product is only 67%, and the chloride ion retention rate is only 37%; it also seriously affects the subsequent tin recovery. However, when the swirling flow rate is greater than or equal to 50 mL / s, the copper recovery rate is greater than 90%, and the chloride ion retention rate reaches more than 85%.

[0099] from Figure 7 It can be seen that increasing the swirling flow rate of the first electrochemical reaction can break the concentration polarization between copper metal ions and chloride ions, thereby improving both copper recovery and chloride ion retention. A swirling flow rate of 50 mL / s can achieve a copper recovery rate of over 90% and a chloride ion retention rate of over 87%, and these rates increase continuously with increasing swirling flow rate.

[0100] Example 8

[0101] This embodiment studies the effect of current density on the process in step (3). The specific steps are basically the same as those in embodiment 3, except that the current density in step (3) is changed.

[0102] The current density in step (3) is adjusted to 30 mA / cm². 2 50 mA / cm 2 55 mA / cm 2 60 mA / cm 2 70 mA / cm 2 and 80 mA / cm 2 .

[0103] The test results of tin recovery rate in this embodiment and Example 3 are as follows: Figure 8 As shown, from Figure 8 It can be seen from this that when the current density is 30 mA / cm 2 At that time, the tin recovery rate was only 44.5%, indicating that tin ions are difficult to electrodeposit effectively at low current densities. When the current density is greater than or equal to 50 mA / cm², the recovery rate is significantly lower. 2 At that time, the tin recovery rate was greater than 80%, and the chloride ion retention rate reached more than 80%.

[0104] from Figure 8 It can be seen from this that when the current density of the second electrochemical reaction increases from 30 mA / cm², the reaction proceeds. 2 Increased to 50 mA / cm 2 Tin recovery increased from 44.5% to 84.5%, and the current density was further increased to 80 mA / cm². 2 Copper recovery rate can reach 87.5%. Excessive current density causes chloride ions to be released as chlorine gas on the anode, but the chloride ion retention rate is still maintained above 86%.

[0105] Example 9:

[0106] This embodiment studies the effect of the swirling flow rate in step (3) on the process. The specific steps are basically the same as those in embodiment 3, except that the swirling flow rate in step (3) is changed.

[0107] The swirl flow rates in step (3) were adjusted to 60 mL / s, 90 mL / s, 100 mL / s, 110 mL / s and 130 mL / s respectively.

[0108] The test results of copper recovery rate in this embodiment and Example 3 are as follows: Figure 9 As shown, from Figure 9 As can be seen, when the swirling flow rate is 60 mL / s, the tin recovery rate is only 27.44%, the purity of the cathode tin product is only 47%, and the chloride ion retention rate is only 32%. This is because chloride ions, under the influence of a lower turbulent field, will be converted into SnCl₂. x (1-x) In the form of cathode electrodeposition, not only is chloride ion loss caused, but the purity of the tin product is also reduced. When the swirling flow rate is greater than or equal to 90 mL / s, the tin recovery rate is greater than 80%, and the chloride ion retention rate reaches more than 85%.

[0109] from Figure 9 It can be seen that when the swirling flow rate of the second electrochemical reaction increased from 60 mL / s to 90 mL / s, the tin recovery rate increased from 27.44% to 84.1%, and the chloride ion retention rate increased from 32% to 87.1%. Further increasing the swirling flow rate to 130 mL / s resulted in tin recovery and chloride ion retention rates of 87% and 92.5%, respectively. Therefore, the swirling flow rate is a key parameter for improving chloride ion retention, thus leading to a large amount of regenerated hydrochloric acid solution.

[0110] Comparative Example 1:

[0111] This embodiment provides an in-situ electrolytic regeneration process for low-concentration tin-copper wastewater from semiconductors, which is basically the same as that in embodiment 1. The difference is that in step (1), the counter electrode of the swirl electrolysis is a graphite anode.

[0112] ICP-OES was used to monitor the liquid phase ion concentration and cathode products after the first electrochemical reaction. The results showed that the copper recovery rate was 91.8%, but the chloride ion retention rate was only 11%. It is evident that the release of chlorine gas at the anode not only causes the loss of hydrochloric acid medium, but also leads to serious secondary pollution.

[0113] Comparative Example 2:

[0114] This embodiment provides an in-situ electrolytic regeneration process for low-concentration tin-copper wastewater from semiconductors, which is basically the same as that in embodiment 1, except that the first additive is not used in step (2).

[0115] ICP-OES was used to monitor the liquid phase ion concentration and cathode products after the first electrochemical reaction. The results showed that the copper recovery rate was 78.2%, and the cathode surface deposits were not smooth or flat.

[0116] Comparative Example 3:

[0117] This embodiment provides an in-situ electrolytic regeneration process for low-concentration tin-copper wastewater from semiconductors, which is basically the same as that in embodiment 1. The difference is that in step (3), no second additive is used.

[0118] ICP-OES was used to monitor the liquid phase ion concentration and cathode products after the second electrochemical reaction. The results showed that the tin recovery rate was 66.8%, and the cathode surface deposits were not smooth or flat.

[0119] Figure 10 The purity test results are for some samples obtained in the above embodiments. Specifically, these are Sample 1 (Example 3), Sample 2 (the difference from Example 3 is that the first additive is 5 mg / L of 2,2'-bipyridine and 5 mg / L of potassium ferric cyanide), Sample 3 (the first additive is 10 mg / L of potassium ferric cyanide), and Sample 4 (the current density is controlled at 45 mA / cm² in step (2)). 2 Sample 5 (in step (2), the current density is controlled at 50 mA / cm²) 2 Sample 6 (in step (2) the swirling flow rate was controlled at 90 mL / s), and Sample 7 (in step (3) the current density was controlled at 80 mA / cm²). 2 Sample 8 (in step (3), the swirling flow rate is controlled at 130 mL / s), Sample 9 (in step (2), the swirling flow rate is controlled at 30 mL / s), and Sample 10 (in step (3), the swirling flow rate is controlled at 60 mL / s).

[0120] from Figure 10 This study demonstrates that an in-situ electrolytic regeneration process for low-concentration tin-copper wastewater from the semiconductor industry can achieve efficient separation of copper and tin metal ions, yielding high-purity (greater than 95%) copper and tin nano-micro metal powders. Furthermore, the swirling flow rate during the two electrochemical reactions is a key control parameter for achieving high-purity products, preventing the synergistic electrodeposition of chloride ions and metal ions under concentration polarization.

[0121] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0122] The parts of this invention not described in detail are well-known in the art. The above embodiments are provided merely for the purpose of describing the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A process for in-situ electrolytic regeneration of low-concentration tin-copper wastewater, characterized in that, Includes the following steps: (1) Using low-concentration tin-copper wastewater as electrolyte, connect the working electrode, counter electrode and reference electrode to start the cyclone electrolysis treatment of the low-concentration tin-copper wastewater; (2) A first additive is added to the electrolyte, and a first electrochemical reaction is carried out by controlling the current and flow rate to obtain a first cathode product and a remaining tin-containing electrolyte; the amount of the first additive added is not less than 5 mg / L; the Cu in the remaining tin-containing electrolyte... 2+ The concentration should not exceed 20 mg / L; (3) Add a second additive to the tin-containing electrolyte, and carry out a second electrochemical reaction by controlling the current and flow rate to obtain a second cathode product and other solutions; The first cathode product is copper, the second cathode product is tin, and the other solutions are regenerated hydrochloric acid.

2. The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to claim 1, characterized in that, In step (1), the low-concentration tin-copper wastewater is a solution containing copper, tin, and chlorine; the Fe in the low-concentration tin-copper wastewater 3+ The concentration should not exceed 30 mg / L.

3. The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to claim 1, characterized in that, In step (1), the working electrode is a 316L stainless steel cathode with a surrounding ring, the counter electrode is a cylindrical IrO2-Ta2O5 coated titanium anode, and the reference electrode is an Ag / AgCl electrode.

4. The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to claim 1, characterized in that, In step (2), the first additive is one or more of 2,2'-bipyridine, potassium ferric cyanide, sodium propargyl sulfonate, sodium hydroxyethyl sulfonate, sodium chloride, gelatin, sodium dodecyl sulfate, and thiourea; the amount of the first additive added is not less than 10 mg / L.

5. The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to claim 1, characterized in that, In step (2), the current density of the first electrochemical reaction is not less than 30 mA / cm². 2 The swirling flow rate is not less than 50 mL / s.

6. The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to claim 1, characterized in that, In step (3), the second additive is one or more of 2,2'-bipyridine, potassium ferric cyanide, triammonium citrate, sodium chloride, gelatin, sodium dodecyl sulfate, cresol acid, and cresol sulfonic acid; the amount of the second additive added is not less than 10 mg / L.

7. The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to claim 1, characterized in that, In step (3), the current density of the second electrochemical reaction is not less than 50 mA / cm². 2 The swirling flow velocity is not less than 90 mL / s.

8. The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to any one of claims 1 to 7, characterized in that, The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater from semiconductors also includes the step of stripping the first cathode product and the second cathode product.

9. The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to claim 8, characterized in that, The first and second cathode products obtained by stripping are washed and dried to obtain copper nano-metal powder and tin nano-metal powder.

10. The in-situ electrolytic regeneration process for low-concentration tin-copper wastewater according to claim 8, characterized in that, In step (3), the impurity ion content in the other solutions is less than 50 mg / L.

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