A purification treatment process for copper foil with chromium passivation solution

Abstract

This invention discloses a purification process for chromium-containing passivation solution of copper foil, belonging to the field of metal passivation technology. The purification process for chromium-containing passivation solution of copper foil includes the following steps: (1) In the electrolytic copper foil passivation process, at least two adsorption devices are set up. The chromium-containing passivation solution after passivation is passed through the first adsorption device, and after adsorption, it is returned to the passivation solution supply system. During operation, after the first adsorption device is saturated, it is switched to other adsorption devices. The adsorption devices are filled with ion exchange resin. (2) After the adsorption device is saturated, a regeneration solution is added, and the resin is regenerated by water washing-acid washing-water washing. This invention can directionally capture impurity elements in the chromium-containing passivation solution and efficiently retain the core components of the passivation solution and Cr. 6+ This method eliminates the need for frequent replacement of the solution, making it both environmentally friendly and cost-effective. It is suitable for acidic chromium passivation systems.

Description

Technical Field

[0001] This invention relates to the field of metal passivation technology, and more specifically, to a process for purifying copper foil using a chromium passivation solution. Background Technology

[0002] Copper foil and copper alloys, due to their excellent electrical and thermal conductivity and machinability, are widely used in printed circuit boards (PCBs), lithium-ion battery negative electrode current collectors, power transmission, and electronic components. However, copper, as a chemically reactive metal, readily undergoes oxidation reactions with oxygen and moisture in the air at room temperature and pressure, forming a loose and porous oxide layer. This oxide layer not only affects the surface appearance and electrical conductivity of the material but also reduces its adhesion to other materials, severely shortening the product's lifespan. Therefore, surface anti-oxidation treatment is a crucial step in the processing of copper foil and copper alloys.

[0003] Currently, anti-oxidation treatment technologies for copper foil and copper alloy surfaces have formed a diversified system, which can be divided into three main categories based on their treatment principles: First, passivation treatment technology, which forms a dense and stable passivation film on the material surface through chemical or electrochemical methods, isolating the substrate from the corrosive environment. This is currently the most widely used technical approach. Second, coating protection technology, which covers the surface with organic coatings or metal plating through physical or chemical deposition methods, such as zinc plating, tin plating, and coating with anti-rust oil. Third, modification treatment technology, which changes the chemical composition of the material surface through surface alloying, ion implantation, etc., to enhance its oxidation resistance. Among these, passivation treatment technology occupies a dominant market position due to its advantages such as simple operation, controllable cost, and significant protective effect. Chromium passivation treatment technology has long been regarded as the benchmark process in this field.

[0004] Currently, chromium passivation solutions used in industry are mainly divided into two categories: acidic chromate systems and alkaline chromate systems. Among them, acidic systems are more widely used due to their high passivation efficiency and good film density. Although environmental policies have become increasingly stringent in recent years and chromium-free passivation technology has developed rapidly, chromium passivation treatment has not completely disappeared from the market in some special scenarios with extremely high protection requirements. Its technological evolution and application status still have a significant impact on the industry's development. Moreover, the core constraint of chromium passivation treatment is not only the passivation process itself, but also the chromium-containing waste liquid generated after passivation. This type of waste liquid contains highly toxic, recalcitrant hexavalent chromium and complex auxiliary components, making its treatment difficulty and environmental risks significantly higher than ordinary industrial wastewater. Its treatment effect directly determines whether chromium passivation technology can continue to operate legally and whether its application boundaries can be reasonably expanded.

[0005] During the passivation process, chromium passivation solutions adsorb onto the substrate surface through chemical and physical adsorption, simultaneously displacing impurities. These impurities affect both the purity of the passivation solution and the passivation effect, ultimately necessitating the periodic preparation of fresh solution and the discharge of waste liquid. Currently, the industry mainstream technologies for treating chromium passivation solution waste liquid include the following four:

[0006] One method is the chemical reduction-precipitation method. Its core principle is to convert highly toxic hexavalent chromium into less toxic trivalent chromium through a redox reaction, followed by precipitation separation to remove the chromium. However, this technology suffers from high reagent consumption and high treatment costs. Furthermore, chromium-containing passivation wastewater typically contains complexing agents such as sodium citrate and phytic acid, which form stable complexes with chromium ions, hindering the reduction reaction and precipitation formation, leading to decreased treatment efficiency. This necessitates the addition of complex-breaking agents, further increasing process complexity and cost. Moreover, the resulting chromium-containing sludge is hazardous waste, containing large amounts of chromium ions and other heavy metals. Improper storage, transportation, or disposal can easily lead to leakage and secondary pollution of soil and groundwater.

[0007] Secondly, there are physicochemical treatment technologies. These technologies mainly achieve the separation and enrichment of chromium ions through physical adsorption, membrane separation, or ion exchange, and some processes can realize the recycling of chromium resources. However, physical adsorption is not effective in treating high-concentration chromium-containing wastewater; membrane separation technology uses expensive membrane modules; and ion exchange resin technology can only achieve the separation and enrichment of chromium ions, and the recovered chromium salts have low purity and require a recrystallization process, which increases the cost of resource recovery.

[0008] Thirdly, there is biological treatment technology, an environmentally friendly treatment approach that has emerged in recent years. This technology utilizes the metabolic activity of microorganisms to reduce and remove chromium ions, offering advantages such as low energy consumption and minimal secondary pollution. However, this technology has stringent requirements for the treatment environment. The microorganisms are sensitive to parameters such as pH, temperature, and dissolved oxygen in the wastewater, and the treatment cycle is long. Furthermore, the screening and cultivation of highly efficient functional strains is time-consuming, and they are prone to degradation in industrial applications, requiring regular replenishment of the strains and optimization of reaction conditions, which increases the technical maintenance costs and operational complexity.

[0009] Fourthly, there is resource recovery technology, mainly targeting high-concentration chromium-containing passivation waste liquid (hexavalent chromium concentration > 500 mg / L). Some enterprises adopt resource recovery processes to achieve the recycling of chromium, reducing environmental pressure and raw material consumption. However, this technology is difficult to adapt to complex waste liquid compositions. Currently, most chromium passivation liquids are composite systems containing various complexing agents, buffers, surfactants, etc. These substances can form stable complexes with chromium ions or interfere with chemical reactions and adsorption during the treatment process, making it difficult for a single treatment technology to achieve the desired effect. Multiple processes need to be combined, increasing the complexity of the system. At the same time, this technology aims at "achieving emission standards" but fails to achieve effective recovery of chromium resources, resulting in resource waste. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a purification process for copper foil using a chromium passivation solution. This method can selectively capture impurity elements in the passivation solution while efficiently retaining the core components and Cr of the passivation solution. 6+ This method eliminates the need for frequent replacement of the solution, making it both environmentally friendly and cost-effective. It is suitable for acidic chromium passivation systems.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] This invention provides a purification process for copper foil using a chromium passivation solution, comprising the following steps:

[0013] (1) In the passivation process of electrolytic copper foil, at least two adsorption devices are set up. The passivated chromium passivation solution is flowed through the first adsorption device and then returned to the passivation solution supply system after adsorption. During operation, after the first adsorption device is saturated, it is switched to other adsorption devices. The adsorption devices are filled with ion exchange resin, which is selected from one of D001, T-52H, MC245 and IR-120.

[0014] (2) After the adsorption device is saturated, add regeneration solution and regenerate the resin by water washing-acid washing-water washing.

[0015] In some embodiments, in step (1), the initial impurity adsorption capacity of the ion exchange resin is m, in mg, and m satisfies the following relationship:

[0016] ,

[0017] Where k is the saturation constant of the ion exchange resin; t represents the volume of the ion exchange resin in L; t represents the adsorption time in H; and β represents the influent flow rate of the chromium passivation solution in m³. 3 / H.

[0018] In some implementations, k satisfies: 0.75 ≤ k ≤ 0.78.

[0019] In some implementations, β satisfies: 0.10 m 3 / H≤β≤0.40 m 3 / H.

[0020] In some implementations, step (1) includes one or more of the following technical features:

[0021] (a) The average particle size of the ion exchange resin is 0.3-1.2 mm;

[0022] (b) The permissible temperature range for the ion exchange resin is -20 to 120°C;

[0023] (c) The Cr in the chromium passivation solution 6+ The concentration is 0.5~0.6 g / L, the pH is 2.0~4.0, and the COD is 4000~8000 mg / L;

[0024] (d) Cr in the purified passivation solution 3+ Concentration ≤0.5g / L, Cu 2+ Concentration ≤ 0.28 g / L.

[0025] In some embodiments, the chromium passivation solution comprises the following raw material components in parts by weight:

[0026] 1-15 parts hexavalent chromium compound; 1-55 parts industrial glucose; 1-15 parts pure water.

[0027] In some embodiments, the hexavalent chromium compound is chromium anhydride.

[0028] In some embodiments, the industrial glucose has a purity of ≥98% and a DE value of ≥95.

[0029] In some embodiments, in step (2), the regenerated liquid is a hydrate containing a regenerated medium.

[0030] In some embodiments, the regeneration medium includes at least one of concentrated sulfuric acid, hydrochloric acid, and oxalic acid.

[0031] In some embodiments, the mass concentration of the regeneration medium in the regeneration solution is 5-15%.

[0032] In some embodiments, the ratio of the influent volume of the regenerated liquid to the volume of the ion exchange resin is λ, where λ satisfies: 1.0 ≤ λ ≤ 5.0.

[0033] In some embodiments, the ratio of the amount of impurities adsorbed after the first adsorption and regeneration of the ion exchange resin to the amount of impurities adsorbed during the first adsorption is Φ, where Φ satisfies: Φ≥80%.

[0034] In some embodiments, the specific process of resin regeneration treatment in step (2) is as follows:

[0035] First, pure water is introduced from the top of the adsorption device to clean the residual passivation solution on the surface of the ion exchange resin; wait until the cleaning solution is clear and the Cr in the cleaning solution is removed. 6+ If the content is ≤0.05ppm, the cleaning is qualified;

[0036] Then, regeneration solution is introduced from the bottom of the adsorption device, and the Cu in the outflowing regeneration solution is... 2+ When the content is ≤80ppm, the regeneration is considered complete;

[0037] Finally, rinse the remaining regeneration solution with pure water from bottom to top. When the effluent pure water is neutral, the resin regeneration is considered complete.

[0038] The beneficial effects of this invention are as follows:

[0039] 1. Significant environmental benefits: This invention can achieve closed-loop circulation and zero discharge of chromium passivation liquid, avoiding soil and groundwater pollution caused by direct discharge of chromium-containing waste liquid and reducing the generation of hazardous waste.

[0040] 2. Significant cost reduction effect: This invention eliminates the need for periodic preparation of new passivation solution, reducing raw material consumption; the adsorption material can be recycled, reducing consumable costs; and it eliminates the costs of waste liquid treatment agents and equipment operation.

[0041] 3. Stable passivation performance: This invention can accurately remove impurities, such as Cu. 2+ Cr 3+ By retaining the core components of the passivation solution and maintaining its stable performance, a dense passivation film is formed on the copper foil surface, ensuring key properties such as anti-oxidation, conductivity, and adhesion.

[0042] 4. Improved resource utilization: This invention can avoid the waste of chromium resources caused by waste liquid discharge or sludge disposal, and achieve efficient utilization of chromium resources through recycling, thereby reducing costs and increasing efficiency. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0045] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0046] This invention provides a purification process for copper foil using a chromium passivation solution, comprising the following steps:

[0047] (1) In the passivation process of electrolytic copper foil, at least two adsorption devices are set up. The passivated chromium passivation solution is flowed through the first adsorption device and then returned to the passivation solution supply system after adsorption. During operation, after the first adsorption device is saturated, it is switched to other adsorption devices. The adsorption devices are filled with ion exchange resin, which is selected from one of D001, T-52H, MC245 and IR-120.

[0048] (2) After the adsorption device is saturated, add regeneration solution and regenerate the resin by water washing-acid washing-water washing.

[0049] Currently, the core processes in copper foil production mainly include the preparation of passivation solution, electrolytic foil production, and the passivation process. This invention incorporates an adsorption device filled with ion exchange resin into the passivation process. The ion exchange resin is used to purify the chromium passivation solution after passivation treatment. Specific ion exchange resins are used to precisely capture impurities (such as copper ions, suspended solids, and complexed byproducts) accumulated during the recycling of the chromium passivation solution. This achieves efficient retention of the core components of the chromium passivation solution and targeted removal of impurities. There is no need to discharge waste passivation solution; the stability of the passivation solution is maintained solely through adsorption-regeneration cycles. Ultimately, this achieves the goal of closed-loop recycling and zero emissions of the chromium passivation solution.

[0050] The ion exchange resin selected in this invention is a hydrogen-form strong acidic cation with a sulfonic acid group as its functional group. Its core principle is a cation exchange reaction, that is, when a chromium passivation solution passes through the cation exchange resin, divalent copper will undergo an equal charge exchange with the hydrogen ions in the resin and be fixed on the resin, while the hydrogen ions are released into the solution. At the same time, the resin will not adsorb hexavalent chromium in anionic form, thus achieving selective adsorption.

[0051] In some embodiments, in step (1), the initial impurity adsorption capacity of the ion exchange resin is m, in mg, and m satisfies the following relationship:

[0052] ,

[0053] Where k is the saturation constant of the ion exchange resin; t represents the volume of the ion exchange resin in L; t represents the adsorption time in H; and β represents the influent flow rate of the chromium passivation solution in m³. 3 / H.

[0054] This invention, through continuous research, has revealed the above-mentioned relationship between the initial impurity adsorption amount m of ion exchange resin. This allows for precise control of the purification process of chromium passivation solution, ensuring stable performance of the passivation solution and improving process reliability. This solves the problems of existing purification processes lacking quantitative standards, having unstable treatment effects, and being prone to incomplete impurity removal or loss of core components.

[0055] In some implementations, k satisfies: 0.75 ≤ k ≤ 0.78, for example, it can be a range of 0.75, 0.76, 0.77, 0.78 or any two of them.

[0056] In some implementations, β satisfies: 0.10 m 3 / H≤β≤0.40 m 3 / H, for example, could be 0.10 m 3 / H, 0.15m 3 / H, 0.20m 3 / H, 0.25m 3 / H, 0.30m 3 / H, 0.35m 3 / H, 0.40m 3 / H or a range consisting of any two of them.

[0057] In this invention, if the influent flow rate of the chromium passivation solution is too low, the amount of passivation solution passing through the resin adsorption column per unit time will decrease. Although the contact time between impurities and the resin is prolonged, the overall adsorption efficiency decreases. Furthermore, a low flow rate allows impurities (such as Cu) in the passivation solution to pass through the resin. 2+ Cr 3+ The inability to remove H⁺ in time leads to an increase in its concentration. Simultaneously, the resin releases less H⁺, enhancing the system's buffering effect and raising the pH of the passivation solution, which is detrimental to the stable formation of the passivation film. Excessive flow rate can accelerate resin adsorption saturation, but the active sites of the resin do not recover sufficiently during regeneration. Furthermore, an excessively high flow rate allows for more thorough contact between the resin and the passivation solution, hindering the adsorption of Cu by the resin. 2+ While releasing a large amount of H+, it is also a cation. +This can lead to a decrease in the pH value of the passivation solution, potentially causing excessive corrosion of the copper foil substrate and affecting the adhesion of the passivation film. Therefore, this invention, by controlling the flow rate of the chromium-containing passivation solution, helps to improve the amount of impurities adsorbed, the stability of the passivation solution performance, and the resin regeneration efficiency.

[0058] In some embodiments, in step (1), the average particle size of the ion exchange resin is 0.3-1.2 mm, for example, it can be a range of 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm or any combination thereof.

[0059] In some embodiments, in step (1), the permissible temperature of the ion exchange resin is -20 to 120°C. In this invention, "permissible temperature" refers to the temperature range within which the ion exchange resin can maintain its physical structure stability and its chemical properties (such as ion exchange capacity and selective adsorption) are not significantly affected during use. Within this range, the functional groups of the resin are normally active, the resin particles are not prone to swelling, shrinkage, or breakage, and the adsorption and regeneration cycle of impurity ions can be stably achieved.

[0060] In some embodiments, in step (1), the Cr in the chromium passivation solution... 6+ The concentration is 0.5~0.6 g / L, the pH is 2.0~4.0, and the COD is 4000~8000 mg / L.

[0061] In some embodiments, in step (1), the Cr in the purified passivation solution 3+ Concentration ≤0.5g / L, Cu 2+ Concentration ≤ 0.28 g / L. This invention limits the impurity concentration (Cr) of the passivation solution after purification. 3+ Cu 2+ This technology can achieve zero discharge of passivation liquid, reduce the pressure of waste liquid treatment, and reduce environmental risks, thereby solving the problems of existing technologies that make it difficult to achieve passivation liquid recycling, large waste liquid discharge, high treatment costs, and environmental pollution.

[0062] In some embodiments, the chromium passivation solution comprises the following raw material components in parts by weight:

[0063] 1-15 parts hexavalent chromium compound; 1-55 parts reducing agent; 1-15 parts pure water.

[0064] In some embodiments, the hexavalent chromium compound is present in 1 to 15 parts by weight in the chromium passivation solution, for example, it can be 1 part, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 15 parts or any combination thereof.

[0065] In some embodiments, the reducing agent is in the chromium passivation solution in the range of 1 to 55 parts by weight, for example, it can be 1 part, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts or any combination thereof.

[0066] In some embodiments, the hexavalent chromium compound is chromium anhydride (chromium trioxide).

[0067] In some embodiments, the reducing agent comprises industrial glucose with a purity ≥98% and a DE value (glucose equivalent) ≥95.

[0068] In some embodiments, the industrial glucose is hydrated or anhydrous D-glucose obtained from starch-based biomass raw materials through liquefaction, saccharification, purification, and crystallization drying.

[0069] In some embodiments, the starch-based biomass raw materials include, but are not limited to, corn starch, cassava starch, and wheat starch.

[0070] In some embodiments, at least one of a film-forming promoter, a complexing agent, and a surfactant may be added to the chromium passivation solution.

[0071] In some embodiments, the film-forming promoter includes one of cerium nitrate and potassium fluorozirconate; the complexing agent includes at least one of citric acid, oxalic acid, and gluconic acid; and the surfactant includes at least one of sodium dodecyl sulfate and Tween-80.

[0072] In some embodiments, the film-forming promoter is present in 0 to 2 parts by weight in the chromium passivation solution, for example, it can be 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts or any combination thereof.

[0073] In some embodiments, the complexing agent is present in 0 to 5 parts by weight in the chromium passivation solution, for example, it can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts or any combination thereof.

[0074] In some embodiments, the surfactant is present in 0-3 parts by weight in the chromium passivation solution, for example, it can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts or any combination thereof.

[0075] In some embodiments, the chromium passivation solution is prepared as follows: pure water is added to a preparation tank, a hexavalent chromium compound is added and stirred until completely dissolved; then industrial glucose is added and stirring is continued for 30-60 minutes to obtain the chromium passivation solution.

[0076] In some embodiments, in step (2), the regenerated liquid is a hydrate containing a regenerated medium.

[0077] In some embodiments, the regeneration medium includes at least one of concentrated sulfuric acid, hydrochloric acid, and oxalic acid.

[0078] In some embodiments, the regeneration medium is industrial concentrated sulfuric acid. The present invention chooses industrial concentrated sulfuric acid as the regeneration medium for two reasons: first, the electrolytic copper foil system itself uses concentrated sulfuric acid, and using sulfuric acid for regeneration will not introduce other elements; second, sulfuric acid has high regeneration efficiency.

[0079] In some embodiments, the mass concentration of the regeneration medium in the regeneration solution is 5-15%, for example, it can be a range of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any combination thereof.

[0080] The ion exchange resin of this invention is regenerated through a regeneration medium to form an adsorption-regeneration closed loop, which helps to reduce the consumption cost of adsorption materials, reduce the generation of solid waste, meet environmental protection requirements, and thus solve the problem that adsorption materials in existing treatment technologies are mostly single-use or difficult to regenerate, which increases the treatment cost.

[0081] In some embodiments, the ratio of the influent volume of the regenerated liquid to the volume of the ion exchange resin is λ, where λ satisfies: 1.0 ≤ λ ≤ 5.0, for example, it can be a range of 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 or any combination thereof.

[0082] In some embodiments, the ratio of the amount of impurities adsorbed after the first adsorption and regeneration of the ion exchange resin to the amount of impurities adsorbed during the first adsorption is Φ, where Φ satisfies: Φ≥80%.

[0083] In some embodiments, the specific process of resin regeneration treatment in step (2) is as follows:

[0084] First, pure water is introduced from the top of the adsorption device to clean the residual passivation solution on the surface of the ion exchange resin; wait until the cleaning solution is clear and the Cr in the cleaning solution is removed. 6+ If the content is ≤0.05ppm, the cleaning is qualified;

[0085] Then, regeneration solution is introduced from the bottom of the adsorption device, and the Cu in the outflowing regeneration solution is... 2+ When the content is ≤80ppm, the regeneration is considered complete;

[0086] Finally, rinse the remaining regeneration solution with pure water from bottom to top. When the effluent pure water is neutral, the resin regeneration is considered complete.

[0087] In some implementations, the passivation process consumes Cr from the chromium passivation solution. 6+The presence of COD causes a decrease in its content. To maintain the Cr content in the chromium passivation solution, 4-6 parts chromium anhydride, 2-4 parts industrial glucose, and 1-2 parts pure water can be added daily. 6+ Concentrations of 0.5-0.6 g / L and COD of 4000-8000 mg / L.

[0088] In the following embodiments, unless otherwise specified, all the raw materials of the present invention are commercially available or prepared according to conventional methods in the art.

[0089] Example 1

[0090] This embodiment discloses a purification process for copper foil using a chromium passivation solution, including the following steps:

[0091] (1) Preparation of chromium passivation solution: The chromium passivation solution comprises the following raw material components in parts by weight: 13 parts chromium anhydride; 47 parts industrial glucose; and 10 parts pure water. In this chromium passivation solution: Cr 6+ Concentration: 0.57 g / L; pH: 3.2; COD: 6500 mg / L.

[0092] The preparation method of the chromium passivation solution is as follows: add pure water to the preparation tank according to the ratio, add chromium anhydride and stir until completely dissolved; then add industrial glucose and continue stirring for 50 min to obtain the chromium passivation solution.

[0093] (2) In the electrolytic copper foil passivation process, two adsorption devices are set in the passivation system, each filled with 250L of ion exchange resin. The used chromium passivation solution is then diverted at a flow rate of 0.10m... 3 The flow rate is / H. The first adsorption device is used, and after adsorption, it is returned to the passivation solution supply system through the return pipe. During operation, one device is used as a backup, that is, the second adsorption device is switched after the first adsorption device is saturated.

[0094] (3) After the first adsorption device is saturated, a regeneration solution is added and the resin is regenerated by water washing-acid washing-water washing to replace the impurities adsorbed in the resin and restore it to its original state. The regeneration solution is a 5wt% sulfuric acid aqueous solution, and the ratio of the regeneration solution inlet volume to the resin volume λ is 1.0.

[0095] The specific process of resin regeneration is as follows:

[0096] First, pure water is introduced from the top of the adsorption device to clean the residual passivation solution on the surface of the ion exchange resin; wait until the cleaning solution is clear and the Cr in the cleaning solution is removed. 6+ If the content is ≤0.05ppm, the cleaning is qualified;

[0097] Then, regeneration solution is introduced from the bottom of the adsorption device, and the Cu in the outflowing regeneration solution is...2+ When the content is ≤80ppm, the regeneration is considered complete;

[0098] Finally, rinse the remaining regeneration solution with pure water from bottom to top. When the effluent pure water is neutral, the resin regeneration is considered complete.

[0099] Circulating adsorption process parameters: Resin type: T-52H; Inlet flow rate β: 0.10 m / s² 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 1020 mg.

[0100] During operation, this invention uses a passivation solution in the passivation solution supply system to treat the copper foil surface against oxidation. The treated passivation solution then flows back into the purification system via a return pipe, is purified, and re-enters the passivation solution supply system, allowing for cyclical use without the discharge of hexavalent chromium waste liquid. Because the passivation solution treats the copper foil surface against oxidation, it consumes Cr in the passivation solution. 6+ The presence of COD causes a decrease in its content, therefore only a certain amount of chromium anhydride, industrial glucose, and pure water need to be added daily to maintain the Cr content in the passivation solution. 6+ The concentration of the active ingredient is 0.5~0.6 g / L and the COD is 4000~8000 mg / L. The ingredients are: 5 parts chromic anhydride, 3 parts AN powder, and 2 parts pure water by weight.

[0101] Example 2

[0102] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.15 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 1450 mg. In step (3), the regenerated solution is a 5wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 3.0.

[0103] Example 3

[0104] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.20 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 1820 mg. In step (3), the regenerated solution is a 5wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 5.0.

[0105] Example 4

[0106] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.25 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 2220 mg. In step (3), the regenerated solution is a 10wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 2.0.

[0107] Example 5

[0108] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.30 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 2520 mg. In step (3), the regenerated solution is a 10wt% sulfuric acid aqueous solution, and the ratio of regenerated solution influent volume to resin volume λ: 3.0.

[0109] Example 6

[0110] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.35 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 2900 mg. In step (3), the regenerated solution is a 10wt% sulfuric acid aqueous solution, and the ratio of regenerated solution influent to resin volume λ: 4.0.

[0111] Example 7

[0112] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.40 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 3250 mg. In step (3), the regenerated solution is a 15wt% sulfuric acid aqueous solution, and the ratio of regenerated solution influent to resin volume λ: 2.0.

[0113] Example 8

[0114] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.20 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 1880 mg. In step (3), the regenerated solution is a 15wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 3.0.

[0115] Example 9

[0116] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.20 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 1850 mg. In step (3), the regenerated solution is a 15wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 4.0.

[0117] Example 10

[0118] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type D001, inlet flow rate β: 0.20 m. 3 / H, adsorption saturation constant k: 0.78, adsorption time 24h, initial impurity adsorption amount m: 1698 mg. In step (3), the regenerated solution is a 5wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 3.0.

[0119] Example 11

[0120] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type D001, inlet flow rate β: 0.30 m. 3 / H, adsorption saturation constant k: 0.78, adsorption time 24h, initial impurity adsorption amount m: 2358 mg. In step (3), the regenerated solution is a 10wt% sulfuric acid aqueous solution, and the ratio of regenerated solution influent to resin volume λ: 3.0.

[0121] Example 12

[0122] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type MC245, inlet flow rate β: 0.20 m. 3 / H, adsorption saturation constant k: 0.73, adsorption time 24h, initial impurity adsorption amount m: 1744 mg. In step (3), the regenerated solution is a 5wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 3.0.

[0123] Example 13

[0124] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type MC245, inlet flow rate β: 0.30 m. 3 / H, adsorption saturation constant k: 0.73, adsorption time 24h, initial impurity adsorption amount m: 2486 mg. In step (3), the regenerated solution is a 10wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 3.0.

[0125] Example 14

[0126] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.05 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 398 mg. In step (3), the regenerated solution is a 10wt% sulfuric acid aqueous solution, and the ratio of regenerated solution influent to resin volume λ: 3.0.

[0127] Example 15

[0128] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.50 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 3680 mg. In step (3), the regenerated solution is a 10wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 3.0.

[0129] Example 16

[0130] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.20 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 1830 mg. In step (3), the regenerated solution is a 2wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 5.0.

[0131] Example 17

[0132] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.20 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 1825 mg. In step (3), the regenerated solution is a 2wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 10.0.

[0133] Example 18

[0134] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.20 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 1820 mg. In step (3), the regenerated solution is a 20wt% sulfuric acid aqueous solution, and the ratio of regenerated solution inlet volume to resin volume λ: 1.0.

[0135] Example 19

[0136] The difference from Example 1 is that the cyclic adsorption process parameters are: resin type T-52H, inlet flow rate β: 0.20 m. 3 / H, adsorption saturation constant k: 0.75, adsorption time 24h, initial impurity adsorption amount m: 1820 mg. In step (3), the regenerated solution is a 20wt% sulfuric acid aqueous solution, and the ratio of regenerated solution influent to resin volume λ: 6.0.

[0137] Comparative Example 1

[0138] The difference from Example 1 is that CH-90 Na of equal mass is used instead of T-52H.

[0139] The parameters involved in the above embodiments and comparative examples are shown in Table 1.

[0140] Table 1

[0141]

[0142] Performance testing

[0143] 1. The corrosion resistance of the passivated samples was evaluated by neutral salt spray test (NSS). The test method strictly followed the national standard GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test".

[0144] (1) Test conditions

[0145] 1) Preparation of salt spray solution: It is prepared by dissolving 5% analytical grade sodium chloride aqueous solution in deionized water with a conductivity of 20 μS / cm (25℃); the pH value of the solution is adjusted to 7.0 at 25℃.

[0146] 2) Test chamber environmental parameters: The uniform temperature inside the test chamber is controlled at 35℃; the salt spray deposition rate is controlled at 2.0 mL / (80 cm²). 2 •h); Salt spray settles freely on the sample surface, and the samples do not block or contact each other during the test.

[0147] 3) Test cycle: The test is conducted by continuous spraying until visible oxidation points or discoloration appear on the surface of the sample. The time when the first corrosion occurs is recorded, which is the tolerance time of the sample.

[0148] (2) Sample preparation and evaluation criteria

[0149] 1) Sample preparation: The copper foil sample treated with the purified passivation solution of this invention and dried is cut into standard test pieces with a size of 210mm×297mm. The passivated surface is used as the test surface. The sample is suspended in the test chamber using plastic clips and the test chamber is turned on for salt spray.

[0150] 2) Evaluation criteria: The time when the test surface of the test piece first shows point-like rust and regional discoloration is used as the basis for judging corrosion resistance; the longer the tolerance time (passing time of neutral salt spray test), the better the corrosion resistance of the passivation film.

[0151] 2. High-temperature anti-oxidation performance test: After purification and passivation treatment with anti-oxidation solution, the copper foil is baked at 150℃ for 10min. Visually inspect the surface of the copper foil for oxidation points. If there are no oxidation points, it is qualified.

[0152] 3. Resin regeneration efficiency: The ratio Φ of the amount of impurities adsorbed after the first adsorption and regeneration of the ion exchange resin to the amount of impurities adsorbed during the first adsorption.

[0153] The test results are shown in Table 2.

[0154] Table 2

[0155]

[0156] Examples 1-7 show that, under the same adsorption time and resin conditions, the higher the inlet flow rate β of the chromium passivation solution, the higher the impurity adsorption amount m per unit time. The inlet flow rate of the chromium passivation solution increases from 0.10 m / s² to... 3 / H increased to 0.40 m 3 At a flow rate of / H, the impurity adsorption capacity increased from 1020 g to 3250 g, satisfying the formula m=(v×t×β) / k±300. Furthermore, when the influent flow rate of the chromium passivation solution was between 0.10 and 0.40 m / s... 3 Within the / H range, Cr can be controlled 3+ ≤0.5 g / L, resin's effect on byproduct Cr 3+ It possesses stable removal capabilities. However, if the flow rate is too low (Example 14), Cr... 3+ Accumulated to 0.51 g / L, causing Cr 3+ A concentration >0.5 g / L leads to a decrease in the high-temperature oxidation resistance of copper foil. Simultaneously, increased flow rate significantly enhances the Cu... 2+ Capture efficiency, Cu 2+ Gradually reducing the concentration from 0.28 g / L to 0.10 g / L is beneficial for improving the corrosion resistance of copper foil.

[0157] As can be seen from Examples 10-13 and Examples 8-9, there are certain differences in the selectivity of different types of resins: T-52H for Cr 3+ The optimal removal efficiency was achieved with D001 (0.38~0.39 g / L), followed by D001 (0.44 g / L), and MC245 was slightly weaker (0.46 g / L). However, different types of resins showed varying efficiencies in removing Cu. 2+ All of them have high selectivity and can stably control it below 0.28 g / L, giving the copper foil excellent corrosion resistance and high-temperature oxidation resistance.

[0158] A comparison of Examples 14-15 with Example 1 shows that if the influent flow rate of the chromium passivation solution is too low, it will lead to insufficient processing throughput, impurity accumulation, a significant decrease in adsorption capacity, and a high pH value, which is detrimental to the stable formation of the passivation film. If the influent flow rate of the chromium passivation solution is too high, the pH value of the passivation solution will be too low, which may cause excessive corrosion of the copper foil substrate, thereby reducing the resin regeneration efficiency. Therefore, this invention controls the influent flow rate of the chromium passivation solution to be between 0.1 and 0.40 m. 3 Within the range of / H, it is beneficial to improve the amount of impurity adsorption, corrosion resistance and resin regeneration efficiency.

[0159] As shown in Examples 1-9, the resin regeneration efficiency Φ is determined by the synergistic coupling of the regenerated solution concentration and the regenerated solution inlet / resin volume ratio λ, exhibiting a clear optimal matching range and quantification rule: when the sulfuric acid concentration is 5wt%~15wt% and λ=1.0~5.0, the two form an optimal synergy, H + With sufficient supply and adequate regeneration contact, the resin active site recovery rate is high, and the regeneration efficiency Φ remains stable at 83.6%~89.1%, all ≥80%, meeting the requirements for long-term cycling. As shown in Examples 16-19, when the sulfuric acid concentration is below 5wt% or above 15wt%, and λ exceeds the range of 1.0~5.0, the synergistic effect is disrupted, and H... + Insufficient supply or resin erosion can significantly reduce regeneration efficiency to 64.5%~79.3%, below the 80% threshold, making it impossible to guarantee stable impurity removal and long-term recycling.

[0160] Comparing Comparative Example 1 with Example 1, it can be seen that although CH-90 resin can adsorb copper ions from the chromium passivation solution during the initial adsorption, and even with better results, sodium ions are released during the adsorption process. Furthermore, CH-90 resin regeneration requires an alkaline regeneration solution, such as sodium hydroxide; acid regeneration is very ineffective. Simultaneously, sodium ions are released during both the regeneration and adsorption processes. These sodium ions can enter the copper sulfate electrolyte system along with the copper foil, potentially causing poor copper foil crystallization, increased brittleness, easy oxidation, and pinhole breakage.

[0161] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A purification process for copper foil using a chromium passivation solution, characterized in that, Includes the following steps: (1) In the passivation process of electrolytic copper foil, at least two adsorption devices are set up. The chromium passivation solution after passivation is flowed through the first adsorption device and then returned to the passivation solution supply system after adsorption. During operation, the first adsorption device is switched to other adsorption devices after it is saturated. The adsorption device is filled with ion exchange resin, which is selected from one of D001, T-52H, MC245, and IR-120. (2) After the adsorption device is saturated, add regeneration solution and regenerate the resin by water washing-acid washing-water washing.

2. The copper foil purification process using a chromium passivation solution according to claim 1, characterized in that, In step (1), the initial impurity adsorption capacity of the ion exchange resin is m, in mg, and m satisfies the following relationship: ， Where k is the saturation constant of the ion exchange resin; t represents the volume of the ion exchange resin in L; t represents the adsorption time in H; and β represents the influent flow rate of the chromium passivation solution in m³. 3 / H.

3. The copper foil purification process using a chromium passivation solution according to claim 2, characterized in that, The condition k satisfies: 0.7 ≤ k ≤ 0.8; And / or, the β satisfies: 0.10 m 3 / H≤β≤0.40 m 3 / H.

4. The copper foil purification process using a chromium passivation solution according to claim 1, characterized in that, Step (1) includes one or more of the following technical features: (a) The average particle size of the ion exchange resin is 0.3-1.2 mm; (b) The permissible temperature range for the ion exchange resin is -20 to 120°C; (c) The Cr in the chromium passivation solution 6+ The concentration is 0.5~0.6 g / L, the pH is 2.0~4.0, and the COD is 4000~8000 mg / L; (d) Cr in the purified passivation solution 3+ Concentration ≤0.5g / L, Cu 2+ Concentration ≤ 0.28 g / L.

5. The copper foil purification process using a chromium passivation solution according to claim 1, characterized in that, The chromium passivation solution comprises the following raw material components in parts by weight: 1-15 parts hexavalent chromium compound; 1-55 parts industrial glucose; 1-15 parts pure water.

6. The copper foil purification process using a chromium passivation solution according to claim 5, characterized in that, The hexavalent chromium compound is chromium anhydride; And / or, the purity of the industrial glucose is ≥98%, and the DE value is ≥95.

7. The copper foil purification process using a chromium passivation solution according to claim 1, characterized in that, In step (2), the regenerated liquid is a hydrate containing a regenerated medium.

8. The copper foil purification process using a chromium passivation solution according to claim 7, characterized in that, The regeneration medium includes at least one of concentrated sulfuric acid, hydrochloric acid, and oxalic acid; And / or, the mass concentration of the regeneration medium in the regeneration solution is 5-15%.

9. The copper foil purification process using a chromium passivation solution according to claim 1, characterized in that, The ratio of the influent volume of the regenerated liquid to the volume of the ion exchange resin is λ, where λ satisfies: 1.0≤λ≤5.0; And / or, the ratio of the amount of impurities adsorbed after the first adsorption and regeneration of the ion exchange resin to the amount of impurities adsorbed during the first adsorption is Φ, where Φ satisfies: Φ≥80%.

10. The copper foil purification process using a chromium passivation solution according to claim 1, characterized in that, The specific process of resin regeneration in step (2) is as follows: First, pure water is introduced from the top of the adsorption device to clean the surface of the ion exchange resin of any residual chromium passivation solution; wait until the cleaning solution is clear and the chromium content in the cleaning solution is reduced. 6+ If the content is ≤0.05ppm, the cleaning is qualified; Then, regeneration solution is introduced from the bottom of the adsorption device, and the Cu in the outflowing regeneration solution is... 2+ When the content is ≤80ppm, the regeneration is considered complete; Finally, rinse the remaining regeneration solution with pure water from bottom to top. When the effluent pure water is neutral, the resin regeneration is considered complete.

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