Method of recovering copper sulfate by joint treatment from low copper containing wastewater of printed circuit board

Abstract

This invention discloses a method for the combined treatment and recovery of copper sulfate from PCB low-copper wastewater, specifically including the following steps: (1) adjusting the pH of the cleaning wastewater system to 2.8~3.2; (2) adsorbing copper ions through a three-column cation exchange resin; (3) when the resin column is saturated, eluting with sulfuric acid solution; (4) mixing the eluent with SPS micro-etching wastewater; (5) adding copper oxide, stirring, and controlling the final pH value to 4~5; (6) filtering, evaporating and crystallizing, drying to obtain copper sulfate pentahydrate. This invention's method can rationally treat and recover resources from low-concentration copper-containing wastewater.

Description

[Technical Field]

[0001] This invention relates to the field of wastewater recycling technology, and more specifically to a method for the combined treatment and recovery of copper sulfate from PCB low-copper wastewater. [Previous Technology]

[0002] Currently, China has become the world's largest producer of printed circuit boards (PCBs). According to statistics, China's PCB production reached US$57 billion in 2021.

[0003] During the production of printed circuit boards, various types of aged high-concentration waste bath solutions and low-concentration copper-containing wastewater are discharged. These wastewaters have complex compositions and large concentration differences. Among them, the low-concentration copper-containing wastewater mainly contains pollutants such as copper ions, acids, sodium persulfate (SPS), and ethylenediaminetetraacetic acid (EDTA) complex ions. Depending on the production volume, thousands or even tens of thousands of tons are generated every day. If not effectively treated, it will cause serious environmental pollution.

[0004] Depending on the different technologies and reagents used in each production line, low-concentration copper-containing wastewater can be classified into cleaning wastewater, complexing wastewater, sulfuric acid-hydrogen peroxide micro-etching wastewater, and SPS micro-etching wastewater. Existing treatment methods primarily rely on coagulation and sedimentation. For example, complexing wastewater requires initial acidification to break down the complex under acidic conditions (Fenton oxidation), followed by coagulation in a coagulation tank where sodium hydroxide is added to adjust the pH to 7-8, and coagulants such as iron and aluminum salts are added for coagulation and sedimentation to produce copper hydroxide sludge for removal. SPS micro-etching wastewater contains approximately 15 g / L of copper. A further improvement involves adding a cyclone electrolysis unit to recover electrolytic copper. When the copper content decreases to 7-8 g / L, the value of the electrolytic copper produced is offset by electricity costs; further electrolysis would generate negative benefits, and reduced recovery efficiency is its drawback.

[0005] Therefore, how to reasonably treat and recycle low-concentration copper-containing wastewater is a problem that urgently needs to be solved by those skilled in the art. [Summary of the Invention]

[0006] In view of the above, the purpose of the present invention is to provide a method for the combined treatment and recovery of copper sulfate from PCB low copper content wastewater, so as to solve the shortcomings of the prior art.

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

[0008] A method for the combined treatment and recovery of copper sulfate from PCB low-copper wastewater, wherein the PCB low-copper cleaning wastewater includes cleaning wastewater and SPS micro-etching waste liquid;

[0009] The above method specifically includes the following steps:

[0010] (1)Adjust the pH value of the cleaning wastewater system to 2.8~3.2 to obtain mixed solution A;

[0011] (2) The mixture A is passed through a three-column cation exchange resin to adsorb copper ions;

[0012] (3)When the resin column is saturated, it is eluted with sulfuric acid solution to obtain an eluent containing copper sulfate and sulfuric acid;

[0013] (4) Mix the eluent and the SPS micro-etching waste liquid to obtain mixture B;

[0014] (5) Add copper oxide to mixture B and react with sulfuric acid. Stir until the copper oxide is completely dissolved and control the final pH value to 4~5 to obtain a reaction solution containing copper sulfate.

[0015] (6)Filter the reaction solution, evaporate to crystallize, and dry to obtain copper sulfate pentahydrate.

[0016] Further, the above-mentioned cleaning wastewater includes copper plating water washing water, complexing wastewater, SPS micro-etching water washing water and acid etching water washing water, and the main pollutants are copper ions, complexing agents and acids.

[0017] Furthermore, the copper content of the copper plating wash water is <30ppm; the complexing wastewater is copper plating wash water containing complexing agent, with a copper content of <30ppm.

[0018] The beneficial effect of adopting the above-mentioned further technical solution is that the copper washing water contains the complexing agent EDTA-2Na, which has no complexing power when the pH value is 2.8~3.2. Copper ions can be adsorbed and the complexing agent can be stripped by a strong acid cation exchange resin.

[0019] Furthermore, the copper content of the above-mentioned SPS micro-etching waste liquid is 14.8-15.7 g / L.

[0020] Furthermore, in step (2) above, the copper content of the mixture A after removing copper ions is ≤0.1ppm, and it is discharged into the neutralization tank.

[0021] Furthermore, in step (3) above, the weight percentage of sulfuric acid solution is 8%~10%.

[0022] Furthermore, in step (5) above, copper oxide is obtained by using acidic etching waste liquid.

[0023] The beneficial effect of adopting the above-mentioned further technical solution is that copper oxide reacts with sulfuric acid in mixed solution B to produce copper sulfate, and the reaction formula is as follows: CuO + H2SO4 = CuSO4 + H2O.

[0024] Furthermore, the above-mentioned method for preparing copper oxide specifically includes the following steps:

[0025] 1) Neutralization: After filtering out insoluble solid impurities, the acidic copper chloride etching waste liquid is injected into a sodium hydroxide solution with a weight percentage of 30-35% and a temperature of 40-60℃, and the pH is continuously maintained at 8.0. The acidic copper chloride etching waste liquid reacts with sodium hydroxide to form copper hydroxide. By controlling the reaction temperature, the copper hydroxide immediately dehydrates and forms mud-like copper oxide in the lower layer, while a neutralized liquid is formed in the upper layer.

[0026] 2) Washing and desalting: Solid-liquid separation is performed to remove the mud-like copper oxide, and then washing is performed to remove the salt contained in the copper oxide. The washing is completed when the conductivity of the washing solution is ≤100μS / cm.

[0027] 3) Drying and sintering: Dry and sinter copper oxide at 100-300℃ to obtain needle-like copper oxide with a purity greater than 99.0%;

[0028] 4) Evaporation and crystallization: Mix the neutralized liquid produced in step 1) and the washing liquid produced in step 2), heat them, and evaporate and crystallize them to obtain industrial salt (industrial grade copper sulfate pentahydrate) and distilled water.

[0029] The beneficial effect of adopting the above-mentioned further technical solution is that the method can effectively recover the copper in the acidic copper chloride etching waste liquid and generate high-precision copper oxide. The neutralization reaction liquid is heated, evaporated and crystallized to form industrial salt and distilled water. Therefore, by adopting this method, the original low copper rinsing water and the sulfuric acid contained in SPS are also utilized as resources. There is no need to add sodium hydroxide for neutralization, so no neutralization wastewater is generated. The waste acid is also comprehensively utilized, which has a very good environmental protection effect.

[0030] As can be seen from the above-described technology, the present invention has significant advantages over the prior art:

[0031] The method of the present invention can reasonably treat and recycle low-concentration copper-containing wastewater.

Implementation Method

[0032] 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, and 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.

[0033] In the following embodiments, the method for preparing copper oxide refers to the applicant's earlier application (Chinese Patent Application No. 201010269573.6, entitled "Method for Preparing High-Purity Copper Oxide Using Acidic Etching Waste Liquid", patentee: Kunshan Lianding Environmental Protection Technology Co., Ltd., inventors: Jiang Dexin, Zhuang Canghong, and Ji Mingyu, application date: September 2, 2010, authorization announcement number: CN101935062B, authorization announcement date: May 30, 2012). Taking acidic copper chloride etching waste liquid (its composition: copper 145g / L, hydrochloric acid 12%) as an example, the specific steps include:

[0034] 1) Neutralization: The acidic copper chloride etching waste liquid from the printing board manufacturer is filtered to remove insoluble solid impurities and then injected into a 30-35% (by weight) sodium hydroxide solution at an initial temperature of 40-60℃. The sodium hydroxide solution is continuously stirred until the final pH is ≥ 8.0. When the acid solution is injected, copper hydroxide is produced, which is immediately dehydrated into mud-like copper oxide at a temperature of 40-60℃. The reaction process is maintained at pH ≥ 8.0. The mud-like copper oxide is located in the lower layer, and the upper layer is the neutralized liquid after the reaction.

[0035] The chemical reaction formula for the above reaction is: HCl + NaOH → NaCl + H2O

[0036] CuCl2+2NaOH→Cu(OH)2+2NaCl.

[0037] Such a neutralization reaction will produce a eutectic of copper chloride and copper hydroxide when pH < 6. If the method of adding acid to alkali is used, the temperature needs to be controlled at a low temperature of 10-30℃, and the temperature needs to be raised to convert it into copper oxide after all the reaction has been completed. However, in this method, acid is added to alkali, and the reaction process is maintained at pH ≥ 8.0. This avoids the formation of eutectic of copper chloride and copper hydroxide, and copper oxide can be obtained immediately.

[0038] 2) Washing and desalting: Solid-liquid separation is performed to remove the mud-like copper oxide. The neutralization solution contains 25-30% salt, therefore the mud-like copper oxide contains a lot of salt and needs to be washed with deionized water multiple times to achieve high-purity copper oxide. The copper oxide produced in step 1) has a needle-like crystal structure, which is easy to wash and filter to remove salt (chloride ions). The washing status can be understood by measuring the conductivity of the washing water. When the conductivity of the washing water is ≤100μS / cm, the washing is complete.

[0039] 3) Drying and sintering: The washed copper oxide is dried by microwave or infrared oven to remove the moisture and sinter at 300℃ to obtain high-purity needle-shaped copper oxide with a purity greater than 99.0%.

[0040] 4) Mix the neutralized liquid produced in step 1) and the washing liquid produced in step 2), heat them, evaporate and crystallize them to obtain industrial salt and distilled water.

[0041] The following description takes PCB waste acid etching solution (composition: copper 145g / L, hydrochloric acid 12%) as an example.

[0042] First, 500g of a 30wt% sodium hydroxide solution was placed in a 1000cc glass beaker and stirred on a magnetic stirrer at 50°C. Then, acidic etching waste liquid was slowly injected into the sodium hydroxide solution. The initial color was pale blue, which immediately turned black, indicating that the generated copper hydroxide immediately converted to black copper oxide. At pH 10.7, the amount of acidic etching solution added was 560ml, and the final temperature was 65°C. The copper oxide precipitate was washed, desalted, filtered, and then dried in an oven at 100°C for 2 hours. Subsequently, it was sintered at 300°C for 2 hours and subjected to chemical analysis. The analysis showed that the purity of the copper oxide was 99.58%. SEM scanning revealed that the copper oxide consisted of needle-like crystals. The washing solution and the neutralized solution after the neutralization reaction were heated to evaporate and crystallize, yielding industrial salt and distilled water.

[0043] Example 1

[0044] A method for the combined treatment and recovery of copper sulfate from PCB low-copper wastewater, wherein the PCB low-copper wastewater includes cleaning wastewater and SPS micro-etching waste liquid;

[0045] The cleaning wastewater includes copper plating wash water with a copper content of <30ppm, copper immersion wash water with a copper content of <30ppm and containing a complexing agent, SPS micro-etching wash water and acid etching wash water.

[0046] The copper content of the SPS micro-etching waste liquid is 15.2 g / L;

[0047] The above method specifically includes the following steps:

[0048] (1)Adjust the pH value of the cleaning wastewater system to 2.8 to obtain mixed solution A;

[0049] (2)The copper ions in the mixture A are adsorbed by a three-column cation exchange resin. After removing the copper ions, the copper content in the mixture A is ≤0.1ppm and is discharged into the neutralization tank.

[0050] (3)When the resin column is saturated, it is eluted with a sulfuric acid solution of 8% by weight to obtain an eluent containing copper sulfate and sulfuric acid;

[0051] (4) Mix the eluent and the SPS micro-etching waste liquid to obtain mixture B;

[0052] (5)Add the copper oxide obtained by acid etching waste liquid into the mixture B and react with sulfuric acid. Stir until the copper oxide is completely dissolved and control the final pH value to 4 to obtain a reaction solution containing copper sulfate.

[0053] (6)Filter the reaction solution, evaporate to crystallize, and dry to obtain copper sulfate pentahydrate.

[0054] Example 2

[0055] A method for the combined treatment and recovery of copper sulfate from PCB low-copper wastewater, wherein the PCB low-copper wastewater includes cleaning wastewater, complexing wastewater and SPS micro-etching waste liquid;

[0056] The cleaning wastewater includes copper plating wash water with a copper content of <30ppm, copper immersion wash water with a copper content of <30ppm and containing a complexing agent, SPS micro-etching wash water and acid etching wash water.

[0057] The copper content of the SPS micro-etching waste liquid is 14.8 g / L;

[0058] The above method specifically includes the following steps:

[0059] (1)Adjust the pH value of the cleaning wastewater system to 3.0 to obtain mixed solution A;

[0060] (2)The copper ions in the mixture A are adsorbed by a three-column cation exchange resin. After removing the copper ions, the copper content of the mixture A is ≤0.1ppm and is discharged into the neutralization tank.

[0061] (3)When the resin column is saturated, it is eluted with a sulfuric acid solution of 9% by weight to obtain an eluent containing copper sulfate and sulfuric acid;

[0062] (4)Mix the eluent and the SPS micro-etching waste liquid to obtain mixture B;

[0063] (5)Add the copper oxide obtained by acid etching waste liquid into the mixture B and react with sulfuric acid. Stir until the copper oxide is completely dissolved and control the final pH value to 4.5 to obtain a reaction solution containing copper sulfate.

[0064] (6) Filter the reaction solution, evaporate to crystallize, and dry to obtain copper sulfate pentahydrate.

[0065] Example 3

[0066] A method for the combined treatment and recovery of copper sulfate from PCB low-copper wastewater, wherein the PCB low-copper wastewater includes cleaning wastewater and SPS micro-etching waste liquid;

[0067] The cleaning wastewater includes copper plating wash water with a copper content of <30ppm, copper immersion wash water with a copper content of <30ppm and containing a complexing agent, SPS micro-etching wash water and acid etching wash water;

[0068] The copper content of the SPS micro-etching waste liquid is 15.7 g / L;

[0069] The above method specifically includes the following steps:

[0070] (1) Mix the cleaning wastewater and complexed wastewater, and adjust the pH of the system to 3.2 to obtain mixture A;

[0071] (2)The copper ions in the mixture A are adsorbed by a three-column cation exchange resin. After removing the copper ions, the copper content in the mixture A is ≤0.1ppm and is discharged into the neutralization tank.

[0072] (3)When the resin column is saturated, it is eluted with a sulfuric acid solution of 10% by weight to obtain an eluent containing copper sulfate and sulfuric acid;

[0073] (4)Mix the eluent and the SPS micro-etching waste liquid to obtain mixture B;

[0074] (5)Add the copper oxide obtained by acid etching waste liquid into the mixture B and react with sulfuric acid. Stir until the copper oxide is completely dissolved and control the final pH value to 5 to obtain a reaction solution containing copper sulfate.

[0075] (6)Filter the reaction solution, evaporate to crystallize, and dry to obtain anhydrous copper sulfate.

[0076] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. [Simplified Explanation of the Diagram]

[0077] None

Claims

1. A method for the combined treatment and recovery of copper sulfate from PCB low-copper wastewater, wherein the PCB low-copper wastewater includes cleaning wastewater and SPS micro-etching waste liquid; the method specifically includes the following steps: (1) adjusting the pH of the cleaning wastewater system to 2.8~3.2 to obtain a mixed solution A; (2) adsorbing copper ions onto the mixed solution A through a three-column cation exchange resin; (3) when the resin column is saturated, eluting with sulfuric acid solution to obtain an eluent containing copper sulfate and sulfuric acid; (4) mixing the eluent with the SPS micro-etching waste liquid to obtain a mixed solution B; (5) adding copper oxide to the mixed solution B to react with sulfuric acid, stirring until the copper oxide is completely dissolved, and controlling the final pH value to 4~5 to obtain a reaction solution containing copper sulfate; (6) filtering the reaction solution, evaporating and crystallizing, drying to obtain copper sulfate pentahydrate.

2. The method for co-treatment and recovery of copper sulfate from PCB low-copper wastewater as described in claim 1, wherein, The cleaning wastewater includes copper plating wash water, complexing wastewater, SPS micro-etching wash water, and acid etching wash water, with the main pollutants being copper ions, complexing agents, and acids.

3. The method for combined treatment and recovery of copper sulfate from PCB low-copper wastewater as described in claim 2, wherein, The copper content of the copper plating rinse water is <30ppm; the complexing wastewater is copper plating rinse water containing a complexing agent, with a copper content <30ppm.

4. The method for combined treatment and recovery of copper sulfate from PCB low-copper wastewater as described in claim 1, wherein, The copper content of the SPS micro-etching waste liquid is 14.8-15.7 g / L.

5. The method for combined treatment and recovery of copper sulfate from PCB low-copper wastewater as described in claim 1, wherein, In step (2), the copper content of the mixture A after removing copper ions is ≤0.1ppm, and it is discharged into the neutralization tank.

6. The method for combined treatment and recovery of copper sulfate from PCB low-copper wastewater as described in claim 1, wherein, In step (3), the sulfuric acid solution has a weight percentage of 8% to 10%.

7. The method for combined treatment and recovery of copper sulfate from PCB low-copper wastewater as described in claim 1, wherein, In step (5), the copper oxide is obtained using acidic etching waste liquid.

8. A method for the combined treatment and recovery of copper sulfate from PCB low-copper wastewater as described in any one of claims 1 or 7, wherein, The preparation method of the copper oxide specifically includes the following steps: 1) Neutralization: After filtering out insoluble solid impurities, the acidic copper chloride etching waste liquid is injected into a sodium hydroxide solution with a weight percentage of 30-35% and a temperature of 40-60℃, and continuously stirred to maintain the pH at 8.

0. The acidic copper chloride etching waste liquid reacts with sodium hydroxide to form copper hydroxide, which immediately dehydrates to form mud-like copper oxide in the lower layer and a neutralized liquid in the upper layer; 2) Washing and desalting: The mud-like copper oxide is separated by solid-liquid separation and washed to remove the salt contained in the copper oxide. The washing is completed when the conductivity of the washing liquid is ≤100μS / cm; 3) Drying and sintering: The copper oxide is dried and sintered at 100-300℃ to obtain needle-like copper oxide with a purity greater than 99.0%; 4) Evaporation and crystallization: The neutralized liquid generated in step 1) and the washing liquid generated in step 2) are mixed, heated, and evaporated to crystallize, yielding industrial salt and distilled water.