A process for producing electroplating-grade copper oxide on-site and regenerating acidic etching sub-liquid using acidic etching copper-containing waste liquid from PCB factories

Abstract

The present invention belongs to the technical field of acid etching waste liquid treatment, and specifically relates to a process for producing electroplating-grade copper oxide and regenerating acid etching sub-liquid on-site by using acid etching copper-containing waste liquid of PCB factory. The acid etching copper-containing waste liquid is treated by using oxalic acid and oxalate, and reduced pressure distillation to obtain electroplating-grade copper oxide products, and no excess solvent or harmful gas is used in the process. The hydrogen chloride and water vapor obtained by reduced pressure distillation are condensed to obtain high-purity hydrochloric acid, which can be reused in the acid etching production line, saving a lot of cost of purchasing hydrochloric acid and caustic soda required for neutralization during wastewater treatment, achieving two-way savings, and the waste liquid (containing a large amount of sodium chloride) after extracting copper oxide can also be recycled and used as acid etching sub-liquid. The whole process is clean and environmentally friendly, and the corresponding economic value and social value are achieved and improved, which is of great significance to the production of PCBs.

Description

Technical Field

[0001] The invention belongs to the technical field of acid etching waste liquid treatment, and specifically relates to a process for producing electroplating-grade copper oxide on-site and regenerating acid etching sub-liquid by utilizing acid etching copper-containing waste liquid of a PCB factory. Background Art

[0002] At present, there are two main modes of acid etching process used by PCB manufacturers. The first mode is that PCB manufacturers purchase acid etching liquid and industrial hydrochloric acid, and the acid etching waste liquid generated after etching is handed over to qualified hazardous waste disposal companies for subsequent treatment. The transportation of acid etching waste liquid has the risks of long distance, high cost, high energy consumption, leakage, volatilization, etc., and because the acid etching solution used by circuit board companies has different components, it may be mixed with other process wastewater such as micro-etching, copper deposition, electroplating, etc., resulting in complex plating solution composition, increasing the complexity of waste liquid treatment, and may require more than two treatments, large equipment investment, and high energy consumption. The first is that the copper products produced by hazardous waste enterprises have low added value and the economic benefits are not obvious. The second is that the PCB manufacturer hands over the acid etching production line to a third party for operation, and the third party purchases the acid etching liquid. The acid etching waste liquid is electrolyzed by on-site electrolysis to remove the copper in the waste liquid, and part of the waste liquid after electrolysis is reused. In this process, on-site electrolysis requires a lot of electricity, resulting in energy waste. Secondly, there are safety risks such as by-product chlorine leakage and electrical fire in the electrolysis process. Only a small part of the secondary waste liquid after on-site electrolysis can be reused, resulting in waste of resources. In addition, the electrolyzed metallic copper is a crude copper product with low economic value.

[0003] Patent CN201410337012.3 discloses a precipitant for recycling acidic etching waste liquid and a treatment method thereof, wherein the precipitant comprises a compound with oxalate ions, a crystal growth additive and a clarifier, wherein the compound with oxalate ions is used as the main component for producing copper oxalate precipitation, and in an acidic system, oxalate ions and divalent copper ions undergo a complex precipitation reaction to generate copper oxalate precipitation, and the role of the additive and the clarifier is to make the filtrate clear and transparent. The patent technology has 1, the waste liquid is extracted The copper efficiency is very low. After copper extraction, the copper ion concentration in the tail liquid is still 60-100g / L, and the copper extraction efficiency is only 26%~53.8%, which has no actual economic value: 2. After copper extraction, the copper ion concentration in the tail liquid is still 60~100g / L, which cannot be reused in etching production. Therefore, the tail liquid reuse mentioned in the patent has no actual production possibility; 3. The separated copper oxalate does not undergo any impurity removal process in the patent, so the copper oxalate product produced can only be a semi-finished product with low economic value and market application prospects. Patent CN202010963715.2 discloses a method for recycling acidic etching waste liquid, which adjusts the pH value range of the acidic etching waste liquid, uses an extractant solution to extract the acidic etching waste liquid, and obtains an oil phase after standing and stratifying. The oil phase is stripped with a solution containing oxalate ions to obtain copper oxalate, wherein the solution containing oxalate ions is a mixed solution of oxalic acid and an alcohol solvent. The extractant solution used in the patent includes an extractant and a diluent, which increases the organic solution in the waste liquid. In actual operation, it is very difficult to extract copper oxalate by extraction. 1. In this process, the precipitation process of copper oxalate will bring in new impurities, and there is no subsequent impurity removal process. Therefore, the copper oxalate product produced can only be a semi-finished product with low economic value and poor market application prospects; 2. The efficiency of extracting copper ions is usually less than 80%, so the residual copper ions in the tail liquid will be more than 30g / L; secondly, the residual extraction oil will circulate and accumulate in the tail liquid, so this model cannot actually achieve the reuse of the tail liquid.

[0004] Therefore, in view of the current situation, it is urgent to develop research that can efficiently utilize acid etching waste liquid, save energy and avoid waste and risks. Summary of the invention

[0005] In view of the above problems, the object of the present invention is to provide a process for producing electroplating-grade copper oxide on-site and regenerating acidic etching sub-liquid by utilizing acidic etching copper-containing waste liquid from a PCB factory.

[0006] The technical contents of the present invention are as follows:

[0007] The present invention provides a process for producing electroplating-grade copper oxide on-site and regenerating acidic etching sub-liquid by using acidic etching copper-containing waste liquid of a PCB factory, comprising the following steps:

[0008] Acidic etching waste liquid (acidic copper-containing waste liquid) from a PCB factory is taken. The waste liquid mainly contains copper ions, chloride ions, hydrogen ions, and sodium ions. The solid suspended matter is initially filtered to remove it. Oxalic acid and / or oxalate are used to precipitate the copper in the acidic etching waste liquid. At the same time, vacuum distillation is performed to generate hemihydrated copper oxalate precipitate. The hemihydrated copper oxalate precipitate is then filtered and washed. The hemihydrated copper oxalate precipitate is heated and decomposed to obtain an electroplating-grade copper oxide product.

[0009] The concentration of oxalic acid and / or oxalate in the acidic etching waste liquid is 13-15%, and the amount used is Cu in the etching waste liquid. 2+ 1.05~1.1 times the amount, that is, 5~10% more than the amount used;

[0010] The oxalate includes one or more of sodium oxalate and potassium oxalate;

[0011] The conditions for the reduced pressure distillation are as follows: the negative pressure is ≥ 20 mm Hg and the temperature is ≥ 50°C;

[0012] Preferably, the negative pressure is 20-80 mm Hg and the temperature is 50-80°C;

[0013] Preferably, the negative pressure is ≥60 mm Hg and the temperature is ≥60°C;

[0014] In the process, the precipitation reaction brought about by oxalic acid and / or oxalate is: 2CuCl2 + 2H2C2O4 +H2O →2CuC2O4·1 / 2H2O↓+4HCl, and the generated hemihydrated copper oxalate precipitate does not produce by-products when used for the subsequent generation of copper oxide, thereby ensuring the quality of the copper oxide well;

[0015] During the vacuum distillation process, the reaction promoted is: 2CuCl2 + 2H2C2O4 +H2O → 2CuC2O4·1 / 2H2O↓+4HCl↑. The vacuum distillation causes hydrogen chloride to be emitted from the system (high-purity hydrochloric acid is obtained after condensation), thereby promoting the reaction in the positive direction, which can fully precipitate the copper ions in the acidic etching waste liquid and avoid the dissolution of copper oxalate in strong acid (copper oxalate is soluble in strong acid), that is, to achieve effective copper oxalate precipitation;

[0016] The hemihydrated copper oxalate precipitate formed by vacuum distillation is cleaned to reduce the sodium chloride content to below 0.1 PPM, which is helpful to obtain copper oxide products that meet the requirements of electroplating grade. The cleaned hemihydrated copper oxalate is heated to above 310°C to obtain electroplating grade copper oxide. Oxalate and crystal water form water vapor and carbon dioxide that evaporate into the air. The reaction is: 2CuC2O4·1 / 2H2O + O2 → 2CuO + H2O↑ + CO2↑. There is almost no residue in the above process.

[0017] The secondary waste liquid remaining after the vacuum distillation, which contains a large amount of sodium chloride, is recycled as an acidic etching liquid after being treated with impurities removal and neutralization.

[0018] The beneficial effects of the present invention are as follows:

[0019] The process for producing electroplating-grade copper oxide on-site and regenerating acidic etching sub-liquid by utilizing acidic etching copper-containing waste liquid of a PCB factory of the present invention realizes treatment of acidic etching copper-containing waste liquid by adopting oxalic acid and oxalate and reduced pressure distillation to obtain electroplating-grade copper oxide products, and no redundant solvent or harmful gas is used in the process, and hydrogen chloride and water vapor obtained by reduced pressure distillation are condensed to obtain high-purity hydrochloric acid, which can be reused in the acidic etching production line, thereby greatly saving the cost of purchasing hydrochloric acid and simultaneously saving the caustic soda required for neutralization during wastewater treatment, achieving two-way savings, and the waste liquid (containing a large amount of sodium chloride) after extracting copper oxide can be recycled and utilized as acidic etching sub-liquid, and the entire process is clean and environmentally friendly, and corresponding economic value and social value are realized and improved, which is of great significance to the production of PCBs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a process flow chart of the acidic etching waste liquid treatment process;

[0021] Figure 2 The figure is a result diagram of the sedimentation efficiency under different pressures in the treatment of the acidic etching waste liquid of the present invention;

[0022] Figure 3 It is a result diagram of sedimentation efficiency at different temperatures in the treatment of acidic etching waste liquid of the present invention;

[0023] Figure 4 This is a result diagram of the water washing efficiency of the hemihydrate copper oxalate precipitate of the present invention;

[0024] Figure 5 This is a graph showing the purity test results of the copper oxide product of the present invention;

[0025] Figure 6 is a particle size distribution diagram of the copper oxide product of the present invention;

[0026] Figure 7 The process flow chart of the acidic etching waste liquid treatment process of Comparative Example 1 is as follows;

[0027] Figure 8 This is a process flow chart of the acidic etching waste liquid treatment process of Comparative Example 2. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below through specific implementation cases and accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art are all within the scope of the claims attached to this application.

[0029] Unless otherwise specified, all raw materials and reagents of the present invention are raw materials and reagents from the conventional market.

[0030] Example

[0031] A process for producing electroplating grade copper oxide on-site using copper-containing acid etching waste liquid from PCB factories. The process flow is as follows: Figure 1 As shown:

[0032] Acidic etching waste liquid (acidic copper-containing waste liquid) from a PCB factory was taken. After testing, it was found that the waste liquid contained components such as copper ions, hydrogen ions, chloride ions and sodium ions. After preliminary filtration to remove suspended solids, 13-15% oxalic acid or sodium oxalate or potassium oxalate was added to the waste liquid, and the amount exceeded 5-10% of the copper salt to precipitate the copper in the acidic etching waste liquid. At the same time, vacuum distillation was performed to control the negative pressure between 20-180 mm Hg and the temperature between 50-80 °C to generate hemihydrated copper oxalate precipitate. Etching waste liquids from three different PCB factories were selected, and the contents of the main components in the waste liquid were tested, as shown in Table 1:

[0033] Table 1 Composition of acid etching copper-containing waste liquid

[0034]

[0035] The above three kinds of etching waste liquids were treated according to the process of the present invention, and the treatment parameters are shown in Table 2:

[0036] Table 2 Process parameters

[0037]

[0038] According to the process treatment in Table 2, the acid etching copper-containing waste liquid is added with a sedimentation agent and under the condition of reduced pressure distillation, the reaction is 2CuCl2 + 2H2C2O4 +H2O → 2CuC2O4·1 / 2H2O↓+4HCl↑, and the Cu in the treated filtrate is 2+ The content is lower than 5 ppm, which shows that the added sedimentation agent combined with the vacuum distillation process has an effective effect on the removal of Cu in the acid etching copper-containing wastewater. 2+ The recycling efficiency is extremely high, such as Figure 2 It can be seen that when the temperature is 60°C, the reaction speeds up as the pressure decreases; Figure 3 As shown, when the negative pressure is fixed at 60 mmHg, the reaction speeds up with increasing temperature.

[0039] The hydrogen chloride gas and water vapor obtained by vacuum distillation are condensed to obtain high-purity hydrochloric acid, which can be used for recycling;

[0040] Since there is a large amount of sodium chloride in the acidic etching waste liquid, sodium chloride remains in the semi-hydrated copper oxalate precipitate. Deionized water is used to wash and centrifuge repeatedly, and the washing efficiency is statistically analyzed. The results are as follows: Figure 4 As shown in the figure, as the number of washing times increases, the sodium ion concentration in the washing solution decreases, and after 8 washings, the sodium chloride content in the hemihydrated copper oxalate is reduced to below 0.1 PPM, and electroplating grade copper oxide is obtained;

[0041] The cleaned hemihydrated copper oxalate is heated to above 310°C, and the reaction is 2CuC2O4·1 / 2H2O + O2 →2CuO + H2O↑ + CO2↑. After the reaction, oxalate ions and crystal water form water vapor and carbon dioxide, which evaporate into the air with almost no residue. The obtained copper oxide product is tested, such as Figure 5 As shown in Table 3 and Figure 6 As shown, it can be seen that the uniformity of the obtained copper oxide particles can reach more than 99%, indicating that the copper oxide product obtained by the treatment of the present invention meets the standard of becoming electroplating grade copper oxide and can be used for recycling in PCB factories.

[0042] Table 3 Particle size distribution

[0043] Testing standards GB / T 19077-2016 Test items result Average particle size (μm) 23.974 D50 (μm) 25.503 D97 (μm) 53.019

[0044] Finally, the secondary waste liquid of hemihydrated copper oxalate (which contains a large amount of sodium chloride) is filtered and recycled to make acidic etching liquid after being treated with impurities removal and neutralization, which greatly reduces the discharge of wastewater.

[0045] The obtained acidic etching sub-liquid is used in the patent CN202111241051.X of the applicant of the present invention, a low-acidity etching production method for PCB boards and a technology of a two-liquid acidic etching liquid system, to achieve recycling, form an ammonia-nitrogen-free acidic etching liquid system, and keep the acidic etching rate above 40 μm / min.

[0046] Comparative Example 1

[0047] Traditional process routes such as Figure 7As shown, the acidic etching waste liquid (acidic copper-containing waste liquid) of the PCB factory is taken, and (alkali) NaOH with a concentration of 18~22% is added to the waste liquid for alkali neutralization, and then filtered to obtain copper hydroxide, which is processed to obtain copper sulfate, copper oxide, basic copper chloride, basic copper carbonate, etc.; a high-salt and high-ammonia nitrogen waste liquid containing about 500-1000 ppm of copper is also obtained, which is subjected to ion exchange, three-effect evaporation, etc. to obtain solid crystals (secondary treatment is required) and sewage wastewater.

[0048] The particle uniformity of the copper oxide product obtained by this process is between 75% and 80%, and the purity is low, which does not meet the standard of electroplating-grade copper oxide. In addition, the treated filtrate still contains 66 to 79 g / L of copper, and the treated solution has no reuse value.

[0049] Comparative Example 2

[0050] Traditional process routes such as Figure 8 As shown, the acidic etching waste liquid (acidic copper-containing waste liquid) of the PCB factory is electrolyzed to obtain copper-containing products, hydrogen and expansion liquid. The obtained hydrogen and expansion liquid are recovered by alkali reaction, and the obtained copper product is crude copper, which is incinerated at high temperature. The particle uniformity of the obtained copper oxide product is between 70 and 78%, and the purity is not high, which does not meet the standard of electroplating grade copper oxide, and the treated filtrate also contains 73 to 80 g / L of copper.

[0051] Comparative Example 3

[0052] Take the acidic etching waste liquid (acidic copper-containing waste liquid) from the PCB factory, add oxalic acid or sodium oxalate, potassium oxalate with a concentration of 13~15% to the waste liquid, and the amount exceeds 5~10% of the copper salt to precipitate the copper in the acidic etching waste liquid. After the reaction is completed, the cleaned hemihydrated copper oxalate is heated to above 310°C. The particle uniformity of the obtained copper oxide product is between 68~75%, and the purity is low, which does not meet the standard of electroplating grade copper oxide. It also contains 50~61 g / L of copper.

[0053] Comparative Example 4

[0054] Take the acidic etching waste liquid (acidic copper-containing waste liquid) from the PCB factory, add oxalic acid or sodium oxalate, potassium oxalate with a concentration of 13~15% to the waste liquid, and the amount is equimolar to the copper salt to precipitate the copper in the acidic etching waste liquid, and perform vacuum distillation. After the reaction is completed, the cleaned hemihydrated copper oxalate is heated to above 310°C. The particle uniformity of the obtained copper oxide product is between 85~95%. Although the purity has been improved, it still does not meet the standard of electroplating grade copper oxide, and it still contains 1~2 g / L of copper.

[0055] In summary, in the treatment of acidic etching copper-containing waste liquid, the present invention uses a slightly excessive amount of oxalic acid or oxalate, combined with a vacuum distillation process, which is beneficial to promote the reaction of 2CuCl2 + 2H2C2O4 +H2O → 2CuC2O4·1 / 2H2O↓+4HCl↑, so that the Cu in the treated filtrate is reduced to 2CuCl2 + 2H2C2O4 +H2O↓ + 4HCl↑. 2+ The content is lower than 5 ppm, and sodium chloride remains in the semi-hydrated copper oxalate precipitate obtained. It is repeatedly washed and centrifuged with deionized water, and the washed semi-hydrated copper oxalate is heated to above 310°C for decomposition: 2CuC2O4·1 / 2H2O + O2 → 2CuO + H2O↑ + CO2↑, and oxalate ions and crystal water form water vapor and carbon dioxide and evaporate into the air, with almost no residue. The obtained copper oxide product, after testing, has a uniformity of more than 99% and a purity of more than 99.3%, which meets the standard of electroplating-grade copper oxide and can be used for recycling in PCB factories. However, the traditional processes of Comparative Examples 1 and 2 cannot obtain electroplating-grade copper oxide. In Comparative Examples 3 and 4, if there is no synergistic treatment of slightly excessive oxalic acid or oxalate with reduced pressure distillation, electroplating-grade copper oxide cannot be obtained.

Claims

1. A process for producing electroplating-grade copper oxide and regenerating acidic etching sub-liquid on-site using acidic etching copper-containing waste liquid from a PCB factory, characterized in that: The steps include: The acidic etching copper-containing waste liquid from the PCB factory is taken and initially filtered to remove suspended solids. Oxalic acid and / or oxalate are used to precipitate the copper in the acidic etching waste liquid. At the same time, vacuum distillation is performed to generate hemihydrated copper oxalate precipitate. The hemihydrated copper oxalate precipitate is then filtered and washed, and the hemihydrated copper oxalate precipitate is heated and decomposed to obtain an electroplating-grade copper oxide product. In the acidic etching waste liquid, the concentration of oxalic acid and / or oxalate is 13-15%; The conditions for the reduced pressure distillation are negative pressure ≥ 20 mm Hg and temperature ≥ 50°C.

2. The process for producing electroplating-grade copper oxide and regenerating acidic etching sub-liquid on-site by utilizing copper-containing waste liquid of acid etching of PCB factory according to claim 1, characterized in that: In the acidic etching waste liquid, the amount of oxalic acid and / or oxalate exceeds the amount of Cu in the etching waste liquid. 2+ The amount is 5~10%.

3. The process for producing electroplating-grade copper oxide and regenerating acidic etching sub-liquid on-site by utilizing copper-containing waste liquid of acid etching of PCB factory according to claim 1, characterized in that: The oxalate includes one or more of sodium oxalate and potassium oxalate.

4. The process for producing electroplating-grade copper oxide and regenerating acidic etching sub-liquid on-site by utilizing copper-containing waste liquid of acid etching of PCB factory according to claim 1, characterized in that: The conditions for the reduced pressure distillation are a negative pressure of 20-80 mm Hg and a temperature of 50-80° C.

5. The process for producing electroplating-grade copper oxide and regenerating acidic etching sub-liquid on-site by utilizing copper-containing waste liquid of acid etching of PCB factory according to claim 4, characterized in that: The conditions for the reduced pressure distillation are negative pressure ≥ 60 mm Hg and temperature ≥ 60°C.

6. The process for producing electroplating-grade copper oxide and regenerating acidic etching sub-liquid on-site by utilizing PCB factory acidic etching copper-containing waste liquid according to claim 1, characterized in that: The hemihydrated copper oxalate precipitate formed by vacuum distillation is washed to reduce the sodium chloride content therein to below 0.1 ppm, and the washed hemihydrated copper oxalate is heated to above 310° C. to obtain a copper oxide product.

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