A method for enhancing electrolytic copper extraction from PCB browning micro-etching waste liquid pretreated with bimetallic-supported activated carbon

Abstract

This invention belongs to the field of wastewater treatment technology, specifically relating to a method for pretreating PCB browning and micro-etching wastewater with bimetallic supported activated carbon to enhance electrolytic copper extraction. This invention uses widely available and inexpensive palm fiber and palm leaf as raw materials, and through steps such as cutting and washing, alkaline purification, phosphoric acid activation, and inert atmosphere carbonization, obtains Fe-Mo bimetallic supported palm activated carbon. This activated carbon can efficiently catalyze the reaction of hydrogen peroxide and persulfate in the browning and micro-etching solutions, generating ·OH and ·SO4. ‑ Active free radicals degrade organic matter in wastewater while providing a simple, safe, and economical pretreatment solution. This not only simplifies the subsequent electrolytic copper extraction process and reduces technological complexity but also lowers costs. It combines resource recycling and environmental benefits, offering an efficient and feasible solution for treating browning solutions and micro-etching solutions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a method for strengthening electrolytic copper extraction from PCB brownification micro-etching waste liquid by using bimetallic active carbon. BACKGROUND

[0002] In the PCB process, the effective implementation of the lamination process requires the implementation of brownification treatment on the inner layer board surface, the purpose of which is to form a rough surface on the copper surface and generate a brownification film, so as to enhance the bonding force of the inner layer board. This treatment usually uses a mixture of sulfuric acid and hydrogen peroxide to roughen the copper surface, and at the same time, an organic complexing agent is added to form an organic metal complex layer. At the same time, before the PCB brownification and micro-etching process, in order to remove the copper surface layer oxide, a persulfate-sulfuric acid or hydrogen peroxide-sulfuric acid micro-etching liquid system is usually used. The brownification liquid, micro-etching liquid and water washing wastewater generated in these two processes have the characteristics of high acidity, high copper content, high hydrogen peroxide and high COD. Traditional treatment methods such as neutralization method or sulfide precipitation method have problems such as large amount of reagent consumption, incomplete copper recovery, low value of recovered products and easy secondary pollution.

[0003] For high-copper and high-acidity brownification and micro-etching waste liquid, electrolytic copper extraction is an effective means to recover high-value copper, but hydrogen peroxide and organic matter in the waste liquid can significantly inhibit the efficiency of cathode copper deposition. On the one hand, the reduction potential of hydrogen peroxide is much higher than that of Cu 2 + , and it is more thermodynamically reduced, resulting in prolonged electrolysis time, increased energy consumption and risk of heating; on the other hand, the organic matter in the brownification liquid may be electrochemically reduced and polymerized during electrolysis, and deposited together with copper on the cathode, reducing the quality of electrolytic copper and affecting the revenue.

[0004] Chinese invention patent CN120229839A discloses an electrolytic copper extraction treatment process for copper-containing waste liquid such as micro-etching liquid and brownification liquid, which finally reduces the copper ion content in the waste liquid to 3-5g / L, realizes the centralized treatment of various waste liquids, and increases economic benefits. However, it needs to add various electrolytic additives and relies on chlorine gas to break the organic complex, which is unstable and has certain risk. Chinese invention patent CN112125449A discloses a brownification waste liquid treatment method, which first adds a catalyst mainly composed of sodium hypochlorite to the waste liquid for pretreatment, converts the organic matter into insoluble matter, separates it by air flotation, and then electrolyzes the copper, so that the copper ion content in the electrolytic clear liquid can be less than 2g / L. However, this method has the risk of incomplete catalysis and easy production of chlorine gas.

[0005] In recent years, the performance of activated carbon in pollutant adsorption, catalytic degradation and other aspects has attracted much attention, especially the carbon material loaded with metal ions or modified by functional groups, which has adsorption and catalytic activity, and is suitable for the treatment of brown liquid and micro-etching liquid containing hydrogen peroxide and persulfate. Therefore, it is of great significance to develop a treatment method for adsorbing and degrading hydrogen peroxide and organic matter in PCB brown micro-etching waste liquid based on modified activated carbon. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the application provides a treatment method for adsorbing and degrading hydrogen peroxide and organic matter in PCB brown micro-etching waste liquid by using modified activated carbon. - At the same time, the organic matter in the waste liquid is degraded, so that the brown liquid and micro-etching liquid are simply, safely and economically pretreated, and the operation difficulty and cost investment of subsequent electrolytic copper extraction are effectively reduced.

[0007] In order to achieve the above purpose, the technical scheme adopted by the application is:

[0008] The application provides a method for pretreating PCB brown micro-etching waste liquid by using bimetallic loaded activated carbon to strengthen electrolytic copper extraction, specifically as follows: adding bimetallic loaded activated carbon into brown and / or micro-etching waste liquid, and transferring the reaction liquid to an electrolytic device for electrolytic copper extraction after adsorption treatment.

[0009] The bimetallic loaded activated carbon is Fe-Mo bimetallic loaded activated carbon, and the preparation method comprises the following steps:

[0010] S1, soaking palm fiber and palm sheet in an alkaline solution to remove surface oil and glue organic matter, and then washing with water until the washing liquid is neutral;

[0011] S2, drying the alkali-washed biomass, and then soaking in a phosphoric acid solution to destroy the macromolecular biomass structure and activate the biomass material;

[0012] S3, drying the activated biomass, and then performing carbonization treatment in an inert gas atmosphere to obtain palm activated carbon;

[0013] S4, loading metal ions on the surface of palm activated carbon by using a coprecipitation method: dissolving iron nitrate and ammonium molybdate in water to prepare a metal ion solution, dispersing palm activated carbon in an alcohol solution to prepare a carbon solution, then mixing the metal ion solution and the carbon solution, water-bath drying, and then calcining to obtain Fe-Mo bimetallic loaded activated carbon.

[0014] Preferably, in S1, the mass ratio of the palm fiber and palm sheet is 1-2:1-2, and the alkali solution used is 1-3 mol / L NaOH solution.

[0015] Preferably, in S1, the soaking treatment is room temperature soaking for 3-6 h.

[0016] Preferably, in S2, the mass concentration of the phosphoric acid solution is 42.5%-60%, and the mass ratio of phosphoric acid to double-metal loaded activated carbon is 1-2:1.

[0017] Preferably, in S2, the soaking treatment is room temperature soaking for 18-30 h.

[0018] Preferably, in S3, the carbonization treatment is performed at a temperature of 500-700 ℃ for 20-50 min, and the heating rate is 3-6 ℃ / min.

[0019] Preferably, in S4, the mass ratio of the palm activated carbon, iron nitrate and ammonium molybdate is 0.1-0.2:0.65-0.75:0.55-0.65.

[0020] Preferably, in S4, the calcination is performed at a temperature of 300-500 ℃ for 1-3 h.

[0021] Preferably, the palm fiber and palm sheet are subjected to cutting, washing and drying pretreatment before use.

[0022] Preferably, in S3, after carbonization, the product is washed with 0.1-0.3 mol / L NaOH solution and water, respectively, and dried.

[0023] Preferably, in S4, after mixing the metal ion solution and the carbon solution, water bath evaporation and drying are performed, and then calcination is performed.

[0024] Preferably, in S4, the volume ratio of the metal ion solution and the carbon solution is 2:1.

[0025] Preferably, in S4, the alcohol solution includes ethanol, ethylene glycol, etc.

[0026] Preferably, the electrolytic device uses a titanium alloy plate as the anode to prevent corrosion and prolong the service life.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] The present application uses palm fiber and palm sheet as raw materials, which are widely available and low in cost. After cutting, washing, alkali removal, phosphoric acid activation and inert atmosphere carbonization, Fe-Mo double-metal loaded palm activated carbon is prepared. The activated carbon can efficiently catalyze hydrogen peroxide and persulfate in the browning liquid and the micro-etching liquid to generate ·OH and ·SO4- Active free radicals degrade organic matter in wastewater while simultaneously achieving simple, safe, and economical pretreatment. This not only simplifies the subsequent electrolytic copper extraction process and reduces technological complexity but also lowers costs, offering both resource recovery and environmental benefits. It provides an efficient and feasible solution for treating browning solutions and micro-etching solutions. Specifically, this invention has the following advantages:

[0029] (1) There is a synergistic effect between activated carbon support and metal active components, namely, the electronic interaction between metal-support interface, which effectively promotes the electron transfer between active components and pollutants and accelerates the catalytic effect.

[0030] (2) The adsorption effect of activated carbon accelerates the enrichment of organic matter into active components and improves the removal efficiency of pollutants in the early stage of the reaction.

[0031] (3) Bimetallic nano-ions have a good catalytic effect on active components such as hydrogen peroxide and persulfate in the browning and micro-etching system. On the one hand, they decompose hydrogen peroxide to improve the efficiency of subsequent copper electrolysis. On the other hand, they catalyze the generation of ·OH and ·SO4 by the active components. - These methods effectively degrade recalcitrant organic matter in browning wastewater, thereby improving the purity and grade of subsequent electrolytic copper.

[0032] (4) The modified catalyst can remove COD up to ≥200mg / g, has strong pollutant removal ability, and reduces the amount of catalyst added, saving the cost of use.

[0033] (5) The pretreatment process effectively reduces the energy consumption of subsequent copper electrolysis, and also reduces potential risks such as heat generation.

[0034] (6) The modified activated carbon in this invention has regenerative potential after adsorbing organic matter. It can be regenerated by simple burning and can be recycled after multiple regenerations by burning and reloading. Attached Figure Description

[0035] Figure 1 This is a microstructure diagram of the bimetallic supported activated carbon in Example 1;

[0036] Figure 2 This is a microstructure diagram of the active metal in Example 1;

[0037] Figure 3 The yield of activated carbon at different pyrolysis temperatures and the specific surface area of ​​activated carbon with different substrates;

[0038] Figure 4 Figure showing the effect of different catalyst dosages on COD removal efficiency;

[0039] Figure 5This is a diagram showing the effect of copper plating on the cathode after pilot-scale electrolysis.

[0040] Figure 6 This is a graph showing the regeneration performance of a bimetallic supported activated carbon catalyst. Detailed Implementation

[0041] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0043] Example 1: Preparation and microstructure characterization of bimetallic supported activated carbon

[0044] 1. Preparation of Palm Activated Carbon

[0045] (1) Cut and wash the palm fibers and palm flakes, and then dry them in a forced-air drying oven at 105℃ for 2 hours for pretreatment.

[0046] (2) Weigh the pretreated palm fibers and palm flakes at a mass ratio of 1:1, soak them in 1 mol / L NaOH solution for 4 hours to remove surface oils, gums and organic matter. After soaking, wash them several times with deionized water until the washing solution is neutral.

[0047] (3) Dry the alkaline washed biomass, and then soak it in a 42.5% phosphoric acid solution for 24 hours to destroy the macromolecular biomass structure and activate the biomass material. The mass ratio of phosphoric acid to activated carbon is 2:1. After soaking and activation, rinse the surface of the biomass material with deionized water and dry it in an oven.

[0048] (4) After activation, cleaning and drying, carbonization is carried out in a tube furnace under an inert gas (such as argon) atmosphere. The carbonization temperature is set at 650℃, the duration is 30 min, and the heating rate is 5℃ / min. After carbonization, the product is cooled and taken out. It is washed with 0.1 mol / L NaOH solution and deionized water respectively, and then dried to obtain palm activated carbon.

[0049] 2. Iron and molybdenum bimetallic element loading

[0050] A metal ion solution was prepared by dissolving 7.19 g of ferric nitrate nonahydrate and 5.52 g of ammonium molybdate tetrahydrate in 50 mL of water. A carbon solution was prepared by dispersing 2 g of palm activated carbon in 25 mL of anhydrous ethanol. The carbon solution was then mixed with the metal ion solution under ultrasonic conditions for 1 h. The mixture was then evaporated to dryness in a water bath at 80 °C and vacuum dried for 2 h. Finally, it was calcined in a muffle furnace at 400 °C for 2 h under air atmosphere. After cooling, the Fe-Mo bimetallic supported activated carbon was obtained.

[0051] Scanning electron microscopy (SEM) characterization analysis was performed on Fe-Mo bimetallic supported activated carbon, and the results are as follows: Figure 1 , 2 As shown in the scanning electron microscope image, the nano-metals, as the active components, are uniformly dispersed on the surface of the porous activated carbon. The activated carbon surface is relatively smooth with abundant pores. The porous structure provides the activated carbon with a good specific surface area and adsorption capacity, which is conducive to promoting the enrichment of organic matter and active substances on the surface of the activated carbon.

[0052] Example 2: Effect of different pyrolysis temperatures on the specific surface area and yield of activated carbon

[0053] The effects of different pyrolysis temperatures on the specific surface area and yield of activated carbon were compared using BET surface area analysis and activated carbon yield calculations to select a suitable experimental temperature. The calculation formulas are as follows:

[0054] Activated carbon yield = m1 / m0, where m1 is the mass of the sample after pyrolysis and m0 is the initial mass of the sample.

[0055] from Figure 3 As can be seen, with the increase of pyrolysis temperature, the specific surface area of ​​carbon materials first increases and then decreases, and the yield gradually decreases. This may be because as the temperature increases, volatiles gradually precipitate and form a porous structure, while further heating leads to the fusion and enlargement of pores, thereby reducing the specific surface area. Finally, 650℃ was chosen as the pyrolysis temperature.

[0056] Example 3: Specific surface area and adsorption properties of carbon materials with different substrates

[0057] Activated carbon was prepared using different substrates (palm, spruce, bamboo, corn cob, and peanut shell) according to the method in Example 1. BET surface area analysis was used to compare the potential loading capacity and adsorption capacity of activated carbons with different substrates. The results are as follows: Figure 3 As shown.

[0058] As can be seen from the figure, under the pyrolysis temperature and activation conditions of the present invention, the specific surface areas of palm, spruce, bamboo, corn cob, and peanut shell are significantly different, with palm activated carbon having the best specific surface area.

[0059] Example 4: Effect of different metal element loading ratios on pollutant removal efficiency

[0060] Following the method of Example 1, Fe-Mo loading at different mass ratios was used to investigate the effect of different metal element loading ratios on pollutant removal efficiency. Specifically, brown micro-etching waste liquid was taken, diluted 5 times with water, and then activated carbon with different Fe-Mo loading ratios was added at an addition rate of 10 g / L for catalytic experiments. The catalytic experiments were conducted in 1 L beakers at room temperature, with a magnetic stirrer for mixing and mass transfer. The COD removal rate was measured within 1 hour, and the results are shown in Table 1.

[0061] As shown in Table 1, the removal effect of COD gradually increases with the increase of the proportion of Mo. However, the improvement in COD removal rate is not significant after increasing the ratio to 1:4. Therefore, from an economic perspective, a Fe-Mo mass ratio of 1:3 was ultimately chosen.

[0062] Table 1. Effect of different Fe-Mo loading ratios on pollutant removal.

[0063]

[0064] Example 5: Effect of different dosages of bimetallic supported activated carbon on browning micro-etching wastewater

[0065] The browning and micro-etching waste liquids discharged from the workshop (Table 2) were mixed at a volume ratio of 1:1 to investigate the effect of different catalyst dosages on the pollutant removal efficiency.

[0066] Table 2. Wastewater Quality of Workshop Discharge

[0067]

[0068] Specifically, 100 mL of brown micro-etching waste liquid (COD = 9830 mg / L) was placed in a 250 mL Erlenmeyer flask, and different masses of carbon material were added. Adsorption catalysis experiments were conducted, and mixed samples were taken at different time points to determine the COD concentration. The COD removal rate was calculated as the evaluation index. The experimental results are as follows: Figure 4 As shown.

[0069] from Figure 4 It can be seen that the removal effect of COD in the brown micro-etching wastewater gradually increases with the increase of catalyst dosage. Catalyst dosages of 40 g / L and 50 g / L achieved approximately 90% COD removal within 6 hours, with a COD removal capacity of 226.08 mg / g. In comparison, the pollutant removal efficiency of a 40 g / L dosage is significantly higher than that of 10 g / L, 20 g / L, and 30 g / L, but the final effect is not significantly different from that of 50 g / L. Therefore, 40 g / L was ultimately selected as the optimal dosage.

[0070] Example 6: Pretreatment and Electrolysis Effects in Pilot-Scale Experiment

[0071] The browning and micro-etching waste liquid from the collection tank was discharged into the reaction tank at a 1:1 volume ratio and stirred evenly. Then, activated carbon prepared in advance according to Example 1 was added to the reaction tank at a dosage of 40-50 kg / t (the dosage should be appropriately increased in pilot or actual applications to ensure experimental results), and the reaction was carried out with mechanical stirring for 12 hours. After the reaction, COD, H2O2, and Cu were measured. 2+ And conductivity. Simultaneously, a pneumatic pump is used to pump the reaction solution into a filter press for filtration. The filtrate is then discharged into an electrolytic cell (using a titanium alloy plate as the anode and a copper plate as the cathode) for electrolysis. The concentration of copper ions in the electrolyte is measured periodically until Cu... 2+ When the concentration drops below 2 g / L, the reactor is shut down for cooling and drainage. A control group experiment was also conducted, where no catalyst pretreatment was added, and all other conditions remained unchanged. The pretreatment results of the pilot-scale experiment are shown in Table 3.

[0072] Table 3 shows that the COD value of the brown micro-etching wastewater was significantly reduced after pretreatment. During the treatment process, obvious bubbles were generated on the catalyst surface, presumably due to the catalytic decomposition of H2O2 by active metal ions. The hydrogen peroxide concentration was reduced to 0.08 g / L after pretreatment. Simultaneously, ·OH and ·SO4 may be generated during the catalytic process. - Various free radicals, such as those that can effectively promote the degradation of organic matter, are present.

[0073] Furthermore, the conductivity of the raw water could not be measured using the electrode method, possibly due to its excessively high COD value, which increased the water sample viscosity, reduced the ion migration rate, and thus interfered with the conductivity measurement. After pretreatment, the water sample achieved a conductivity of 160 mS / cm, exhibiting strong conductivity, a characteristic beneficial for the subsequent copper electrolysis process.

[0074] Table 3 Results of pilot-scale pretreatment experiments

[0075]

[0076] The results of the pilot-scale electrolysis experiment are shown in Table 4. The effect of copper plating on the cathode after electrolysis is as follows: Figure 5 As shown.

[0077] From Table 4 and Figure 5It can be seen that the electrolysis time in the experimental group was significantly shorter than that in the control group, and the electrolyte temperature in the electrolytic cell was also significantly lower than that in the control group. This indicates that the electrolysis efficiency of the experimental group was significantly higher than that of the control group. Furthermore, the pretreatment in the experimental group eliminated the consumption of current density by hydrogen peroxide during electrolysis. The copper plating effect on the cathode plate after electrolysis shows that the control group, due to the presence of a large amount of organic matter in the electrolyte, underwent reduction polymerization of organic matter at the cathode during electrolysis, thus reducing the quality of the electrolyzed copper. Additionally, the Cu content of the final electrolyzed solution... 2+ The concentration also shows that the copper recovery in the experimental group was more thorough.

[0078] Table 4. Experimental Results of Pilot-Scale Electrolysis Experiment

[0079]

[0080] Example 7: Catalyst regeneration performance

[0081] The catalyst (bimetallic supported activated carbon of Example 1) was regenerated by means of alkaline washing, alcohol washing, calcination, and reloading. Specifically, the activated carbon after catalysis was completed was first soaked and washed with 1 mol / L NaOH solution, then rinsed with anhydrous ethanol solution, and finally calcined. The calcination mainly includes two steps: desorption and regeneration. First, volatile substances were removed at 300°C, and then CO2 was introduced into the reactor for regeneration at 600°C.

[0082] like Figure 6 As shown, the catalyst's removal efficiency gradually decreases with increasing regeneration cycles, with the COD removal rate dropping from an initial 92% to 50% after the fifth regeneration within 6 hours. This phenomenon may be due to the gradual deactivation of the catalyst's active sites and the blockage of the activated carbon pores after multiple regenerations. However, the catalyst still maintains good removal efficiency for organic matter in the waste liquid after the first three regenerations. Therefore, it is recommended to reload or re-prepare the catalyst after 3-5 regenerations.

[0083] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for strengthening copper electrolysis of PCB brown micro-etching waste liquid by bimetallic loaded activated carbon pretreatment, characterized in that, The bimetallic active carbon is added into PCB brownification micro-etching waste liquid, and the reaction liquid is transferred to an electrolysis device for electrolytic copper extraction after adsorption treatment; the bimetallic active carbon can catalyze hydrogen peroxide and persulfate in the PCB brownification micro-etching waste liquid to generate ·OH and ·SO4 - , and degrade organic matters in the PCB brownification micro-etching waste liquid; The double-metal loaded activated carbon is Fe-Mo double-metal loaded activated carbon, and a preparation method thereof comprises the following steps: S1, the palm silk and palm piece are soaked with an alkali solution to remove surface oil and glue organic matters, and then washed with water until the washing liquid is neutral; the mass ratio of the palm silk and palm piece is 1-2:1-2, and the alkali solution used is a 1-3 mol / L NaOH solution; S2, the biomass after alkali washing is dried, and then soaked with a phosphoric acid solution to destroy the macromolecular biomass structure and activate the biomass material; the mass concentration of the phosphoric acid solution is 42.5%-60%; S3, the activated biomass is dried, and then carbonized under an inert gas atmosphere to prepare palm activated carbon; the carbonization temperature is 500-700 DEG C, the time is 20-50 min, and the heating rate is 3-6 DEG C / min; S4, metal ions are loaded on the surface of the palm activated carbon by a co-precipitation method: iron nitrate and ammonium molybdate are dissolved in water to prepare a metal ion solution, and the palm activated carbon is dispersed in an alcohol solution to prepare a carbon solution, then the metal ion solution and the carbon solution are mixed, and after water bath evaporation, calcination treatment is carried out to prepare Fe-Mo double-metal loaded activated carbon; the mass ratio of the palm activated carbon, iron nitrate and ammonium molybdate is 0.1-0.2:0.65-0.75:0.55-0.65; the calcination temperature is 300-500 DEG C, and the time is 1-3 h.

2. The method for pretreating PCB brown micro-etching waste liquid for copper extraction by enhanced electrolysis according to claim 1, characterized in that, In S1, the soaking treatment is room temperature soaking for 3-6 h.

3. The method for pretreating PCB brown micro-etching waste liquid by bimetallic loaded activated carbon according to claim 1, characterized in that, In S2, the soaking treatment is room temperature soaking for 18-30 h.

4. The method for pretreating PCB brown micro-etching waste liquid for copper extraction by enhanced electrolysis according to claim 1, characterized in that, The palm silk and palm piece are cut, washed and dried before use.

5. The method for pretreating PCB brown micro-etching waste liquid for copper extraction by enhanced electrolysis according to claim 1, characterized in that, In S3, after carbonization, the product is washed with a 0.1-0.3 mol / L NaOH solution and water, respectively, and dried.

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