A method for resourceful treatment of electroplating waste liquid

Abstract

The application is suitable for the technical field of wastewater treatment and resource recovery, and provides a resource treatment method for electroplating waste liquid, which is aimed at the waste liquid containing copper sulfate and sulfuric acid generated in the copper electroplating process, copper sulfate is generated by adding copper oxide, copper hydroxide or copper carbonate and the like into the waste liquid to react with free sulfuric acid in the waste liquid; then, the saturated copper sulfate solution after reaction is controlled in speed and cooled to crystallize, and high-purity copper sulfate crystals are separated; the crystallization mother liquor can be recycled to the reaction step to further improve the recovery rate, and finally, the tail liquid enriched with impurities is subjected to pH adjustment and ion exchange resin adsorption treatment to realize standard discharge. The application can efficiently convert sulfuric acid and copper ions in the waste liquid into electronic-grade copper sulfate products which can be directly reused in the electroplating process, realizes high-value recovery of resources, and reduces disposal cost and environmental pressure.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment and resource recycling technology, specifically a method for the resource-based treatment of electroplating waste liquid. Background Technology

[0002] Copper electroplating is a key process in the electronics manufacturing industry, widely used in core stages such as PCB (printed circuit board) production, semiconductor chip manufacturing, and advanced packaging. Its core consumable is copper sulfate electroplating solution. This solution uses ultrapure water as a base, combined with high-purity copper sulfate and high-purity sulfuric acid as core components, forming two mainstream formulation systems depending on the application scenario: High copper, low acid formula: copper sulfate concentration is 220-260g / L, sulfuric acid concentration is controlled at 30-50g / L, suitable for electroplating scenarios with high requirements for deposition rate; Low copper, high acid formulation: Copper sulfate concentration is 50-80g / L, sulfuric acid concentration is increased to 150-220g / L, mostly used in precision circuit electroplating, chip interconnect and other processes with strict requirements for deposition uniformity; The core commonality of both formulations is the extremely high purity requirement for raw materials. The purity of high-purity copper sulfate and high-purity sulfuric acid directly affects the conductivity, adhesion, and microstructure of the electroplated layer, which is crucial for ensuring the performance of electronic devices. As the electroplating process continues, two types of harmful substances gradually accumulate in the electroplating solution: first, metallic impurities (such as iron, nickel, lead, zinc, calcium, and magnesium) introduced from raw materials, equipment wear, and workpieces; and second, organic pollutants generated from the decomposition of organic additives (such as leveling agents and brighteners) during the electroplating process. When these harmful substances accumulate to a certain concentration, they will seriously affect the quality of the electroplated layer (such as pinholes, burrs, and decreased gloss). At this point, the electroplating solution must be treated, either partially replaced or completely discarded, resulting in a large amount of electroplating waste liquid.

[0003] Currently, the mainstream treatment method for electroplating waste liquid in the industry is to entrust qualified environmental protection companies to handle it. Companies need to pay high disposal fees to transfer the waste liquid to environmental protection companies. The environmental protection companies use acid-base neutralization chemical methods for treatment. The specific process is as follows: first, use 32%-50% concentration of sodium hydroxide or quicklime (CaO, Ca(OH)2) to neutralize the free sulfuric acid in the waste liquid, and then adjust the pH value of the system to ≥4 so that copper ions form copper hydroxide precipitate, thereby realizing the recovery of copper.

[0004] Existing acid-base neutralization methods have significant drawbacks: First, there is a serious waste of resources: the high-purity sulfuric acid in the waste liquid, which originally had high utilization value, is completely neutralized and cannot be recycled and reused; Secondly, the recycling value is low: the recycled copper is only used as a low-value smelting raw material, failing to fully realize its original value; Thirdly, the disposal costs are high: enterprises need to bear high outsourcing fees, and environmental protection companies also need to consume a large amount of neutralizing agents during the treatment process, resulting in poor overall economic efficiency. Therefore, in view of the above situation, there is an urgent need to provide a resource-based treatment method for electroplating wastewater to overcome the shortcomings in current practical applications. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the resource-based treatment of electroplating waste liquid, which effectively solves the problems mentioned in the background art.

[0006] This invention is implemented as follows: a method for the resource-based treatment of electroplating waste liquid, comprising the following steps: Step S1, Copper Salt Reaction and Concentration Control Stage: Add copper salt to the electroplating waste liquid to be treated, control the pH value of the reaction system to 1-4, heat to make the copper salt react with the free sulfuric acid in the waste liquid to generate copper sulfate, until the copper sulfate in the solution reaches saturation, and obtain a saturated copper sulfate solution. Step S2, Cooling Crystallization and Purification Stage: The saturated copper sulfate solution obtained in step S1 is cooled and crystallized. The cooling rate is controlled to precipitate copper sulfate crystals. Then, solid-liquid separation is performed to obtain copper sulfate crystals and crystallization mother liquor. Step S3, Recycling and End-of-Life Processing Stage: The crystallization mother liquor separated in step S2 is returned to step S1 for recycling; when impurities in the crystallization mother liquor accumulate to a set concentration, the crystallization mother liquor is subjected to precipitation treatment to remove residual copper ions, and then discharged after adsorption by ion exchange resin to meet the standards.

[0007] As a further aspect of the present invention: in step S1, the copper salt is one or more of copper oxide, copper hydroxide, or copper carbonate.

[0008] As a further aspect of the present invention: in step S1, the heating temperature range is 50-100℃.

[0009] As a further aspect of the present invention: in step S1, the pH value of the reaction system is monitored and controlled in real time by an online pH monitor.

[0010] As a further aspect of the present invention: in step S2, the specific process of cooling crystallization is as follows: the saturated copper sulfate solution is gradually cooled to below 20°C.

[0011] As a further aspect of the present invention, the cooling rate is controlled at 5-10℃ / h.

[0012] As a further aspect of the present invention: in step S2, the solid-liquid separation is performed by centrifugal separation or vacuum filtration.

[0013] As a further aspect of the present invention: in step S2, after solid-liquid separation, the obtained copper sulfate crystals are further rinsed with deionized water.

[0014] As a further aspect of the present invention: in step S3, the precipitation treatment involves adding ammonia, sodium hydroxide, or quicklime to the crystallization mother liquor to adjust the pH value of the system to above 4, so that copper ions form copper hydroxide precipitate.

[0015] As a further aspect of the present invention: in step S3, after adsorption by ion exchange resin, the concentration of copper ions in the wastewater is less than 0.5 ppm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. High resource utilization rate: The high-purity sulfuric acid that was originally wasted in the waste liquid is converted into copper sulfate through copper salt reaction, while copper ions are recovered. This achieves efficient utilization of both sulfuric acid and copper resources. The purity of copper sulfate crystals can reach electronic grade standards (purity ≥99%), and can be directly returned to the copper plating process as a copper source supplement. 2. Excellent economic efficiency: No need to entrust external environmental protection units for disposal, reducing the company's waste liquid disposal costs; recycling of crystallization mother liquor reduces raw material consumption, and the recovered electronic-grade copper sulfate can replace purchased raw materials, significantly reducing production costs; 3. Excellent environmental performance: The tail-end treatment uses pH adjustment and ion exchange resin adsorption to ensure that the copper ion concentration in the wastewater is below 0.5 ppm, which meets environmental emission standards and avoids the large amount of waste residue generated by traditional neutralization treatment, thus reducing secondary pollution; 4. Simple and controllable operation: Key parameters such as reaction temperature (50-100℃), pH value (1-4), and cooling rate are easily monitored and controlled by conventional equipment, resulting in strong process stability and suitability for industrial mass production.

[0017] This invention can be directly applied to the electroplating waste liquid treatment production lines of PCB, semiconductor chip manufacturing and advanced packaging companies, and can also be used in centralized recycling projects of electroplating waste liquid undertaken by environmental protection companies. It can not only create significant economic benefits for enterprises, but also help the electronics manufacturing industry achieve the green development goals of "cost reduction, environmental protection and resource recycling", and has broad market application space and promotion value. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the resource recovery treatment device for electroplating waste liquid provided by the present invention. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0021] The present invention will be further explained below with reference to specific embodiments.

[0022] This invention provides a method for the resource-based treatment of electroplating waste liquid, which includes the following steps: Step S1, Pretreatment Stage: Copper Salt Reaction and Concentration Control 1. Raw material addition: Add copper salts such as copper oxide, copper hydroxide or copper carbonate to the electroplating waste liquid to be treated in proportion. The amount added is calculated based on the sulfuric acid concentration in the waste liquid to ensure that the sulfuric acid reacts completely. 2. Reaction condition control: Heat the reaction system to 50-100℃, adjust the pH value of the system in real time through an online pH monitor to keep it stable at 1-4, and stir continuously to allow the copper salt and sulfuric acid to react fully until the copper sulfate concentration in the solution reaches saturation, thus obtaining a saturated copper sulfate solution; 3. Determination of reaction endpoint: After the pH value remains stable for a period of time without significant fluctuations, it is confirmed that the copper salt in the solution has been completely converted without residue, and heating and stirring are stopped.

[0023] Step S2, Core Stage: Cooling Crystallization and Purification 1. Cooling control: Transfer the saturated copper sulfate solution to the crystallization vessel and use a combination of "slow natural cooling and ice water-assisted cooling" to gradually lower the solution temperature to below 20℃. During the process, control the cooling rate (5-10℃ / h) to avoid crystallization of impurities due to excessively rapid cooling. At this time, pure copper sulfate crystals gradually form, and impurity ions remain in the solution. 2. Crystal separation: After crystallization is complete, the precipitated copper sulfate crystals are separated from the mother liquor by centrifugation or vacuum filtration, and the copper sulfate crystals and crystallization mother liquor are collected. 3. Crystal cleaning: The copper sulfate crystals are rinsed with deionized water (the rinsing water can be recycled for subsequent mother liquor replenishment) to remove trace impurities attached to the crystal surface and obtain high-purity copper sulfate crystals.

[0024] Step S3, Loop and Tail Processing Stage 1. Mother liquor recycling: The separated crystallized mother liquor is transported back to the reaction system of the pretreatment stage, and copper salt is added again to react, so as to realize the secondary recovery of residual copper ions and sulfuric acid in the mother liquor. The number of cycles is determined according to the monitoring results of the impurity concentration of the mother liquor (usually 3-5 cycles). 2. Impurity treatment: When metallic impurities (such as iron, nickel, lead, zinc, calcium, magnesium, etc.) and organic pollutants accumulate to a set threshold during the mother liquor circulation process, ammonia, sodium hydroxide or quicklime are added to the mother liquor to raise the pH value of the system to above 4, so that the residual copper ions form copper hydroxide precipitate, and the precipitate is separated by filtration (which can be recovered as copper salt raw material). 3. Compliant Discharge: The mother liquor after removing copper hydroxide precipitate is passed through an ion exchange resin column to adsorb residual trace copper ions (controlling the outlet copper ion concentration to be below 0.5 ppm). The treated wastewater enters the enterprise's wastewater treatment system for further treatment and finally meets the discharge standards.

[0025] In an embodiment of the present invention, based on the simultaneous presence of copper sulfate and sulfuric acid in the electroplating waste liquid, copper-based materials (copper oxide (CuO), copper hydroxide (Cu(OH)2), and copper carbonate (CuCO3)) are added to generate copper sulfate (CuSO4) for the recovery of sulfuric acid and the original copper ions in the waste liquid.

[0026] As a preferred technical solution, this method can adopt the following approach: Figure 1 The apparatus shown includes, but is not limited to, impurity removal equipment, reaction vessel, enamel-lined vessel, drying and dehydration device, primary mother liquor treatment device, and secondary mother liquor treatment device.

[0027] In summary, the working principle of this invention is as follows: The core of this technical solution revolves around "two key reactions + crystallization and purification": 1. Sulfuric acid conversion reaction: Copper salts such as copper oxide (CuO), copper hydroxide (Cu(OH)2), and copper carbonate (CuCO3) react with free sulfuric acid in electroplating waste liquid to produce copper sulfate (CuSO4). This process consumes excess sulfuric acid in the waste liquid and increases the concentration of copper sulfate in the solution. The reaction equation, taking copper oxide as an example, is: CuO + H2SO4 = CuSO4 + H2O. 2. Cooling crystallization purification: Based on the significant difference in solubility of copper sulfate at different temperatures (high solubility at high temperatures and a sharp drop in solubility at low temperatures), by controlling the temperature change of the solution, copper sulfate is precipitated in crystal form. The crystallization process simultaneously separates impurities, ensuring the purity of the product. 3. Mother liquor recycling and tail-end treatment: The reaction mother liquor is recycled multiple times to maximize the recovery of copper and sulfuric acid. When impurities accumulate during the recycling process to the point that they affect the purity of the product, pH adjustment and ion exchange resin adsorption are used to ensure that the tail-end wastewater meets the discharge standards.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for the resource-based treatment of electroplating waste liquid, characterized in that, Includes the following steps: Step S1, Copper Salt Reaction and Concentration Control Stage: Add copper salt to the electroplating waste liquid to be treated, control the pH value of the reaction system to 1-4, heat to make the copper salt react with the free sulfuric acid in the waste liquid to generate copper sulfate, until the copper sulfate in the solution reaches saturation, and obtain a saturated copper sulfate solution. Step S2, Cooling Crystallization and Purification Stage: The saturated copper sulfate solution obtained in step S1 is cooled and crystallized. The cooling rate is controlled to precipitate copper sulfate crystals. Then, solid-liquid separation is performed to obtain copper sulfate crystals and crystallization mother liquor. Step S3, Recycling and End-of-Life Processing Stage: The crystallization mother liquor separated in step S2 is returned to step S1 for recycling; when impurities in the crystallization mother liquor accumulate to a set concentration, the crystallization mother liquor is subjected to precipitation treatment to remove residual copper ions, and then discharged after adsorption by ion exchange resin to meet the standards.

2. The method for resource-based treatment of electroplating waste liquid according to claim 1, characterized in that, In step S1, the copper salt is one or more of copper oxide, copper hydroxide, or copper carbonate.

3. The method for resource-based treatment of electroplating waste liquid according to claim 1, characterized in that, In step S1, the heating temperature range is 50-100℃.

4. The method for resource-based treatment of electroplating waste liquid according to claim 1, characterized in that, In step S1, the pH value of the reaction system is monitored and controlled in real time using an online pH monitor.

5. The method for resource-based treatment of electroplating waste liquid according to claim 1, characterized in that, In step S2, the specific process of cooling crystallization is as follows: the saturated copper sulfate solution is gradually cooled to below 20°C.

6. The method for resource-based treatment of electroplating waste liquid according to claim 5, characterized in that, The cooling rate is controlled at 5-10℃ / h.

7. The method for resource-based treatment of electroplating waste liquid according to claim 1, characterized in that, In step S2, the solid-liquid separation is performed by centrifugation or vacuum filtration.

8. The method for resource-based treatment of electroplating waste liquid according to claim 1, characterized in that, In step S2, after solid-liquid separation, the obtained copper sulfate crystals are further rinsed with deionized water.

9. The method for resource-based treatment of electroplating waste liquid according to claim 1, characterized in that, In step S3, the precipitation treatment involves adding ammonia, sodium hydroxide, or quicklime to the crystallization mother liquor to adjust the pH of the system to above 4, so that copper ions form copper hydroxide precipitate.

10. The method for resource-based treatment of electroplating waste liquid according to claim 1, characterized in that, In step S3, after adsorption by ion exchange resin, the concentration of copper ions in the wastewater is less than 0.5 ppm.

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