Method for strengthening electrolytic copper extraction by pretreating PCB browning micro-etching waste liquid through bimetallic loaded activated carbon

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a method for strengthening electrolytic copper extraction by pretreating PCB brownification micro-etching waste liquid through bimetallic loaded activated carbon. The Fe-Mo bimetallic loaded palm activated carbon is prepared by taking palm fibers and palm sheets which are wide in source and low in cost as raw materials through the steps of cutting and washing, removing impurities by alkali liquor, activating by phosphoric acid, carbonizing in an inert atmosphere and the like. The activated carbon can efficiently catalyze hydrogen peroxide and persulfate in a browning solution and a micro-etching solution to generate. OH and. SO4-active free radicals, and simple, safe and economical pretreatment of the waste liquid is realized while organic matters in the waste liquid are degraded. According to the method, the operation process of subsequent electrolytic copper extraction is simplified, the process difficulty is reduced, the cost input is reduced, the method has resource recycling and environmental protection values, and an efficient and feasible solution is provided for treatment of the browning liquid and the micro-etching liquid.

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 method for treating hydrogen peroxide and organic matter in PCB brown micro-etching waste liquid by modified activated carbon adsorption and degradation. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the present application provides a method for treating hydrogen peroxide and organic matter in PCB brown micro-etching waste liquid by modified activated carbon adsorption and degradation, which utilizes the modified activated carbon to catalyze the hydrogen peroxide and persulfate in the brown liquid and micro-etching liquid to generate ·OH and ·SO4 - , and simultaneously degrades the organic matter in the waste liquid, so as to realize simple, safe and economic pretreatment of the brown liquid and micro-etching liquid, and effectively reduce the operation difficulty and cost investment of subsequent electrolytic copper extraction.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is: The present application provides a method for pretreating PCB brown micro-etching waste liquid by double-metal-loaded activated carbon to strengthen electrolytic copper extraction, which specifically comprises: adding double-metal-loaded activated carbon into the brown and / or micro-etching waste liquid, and transferring the reaction liquid to an electrolytic device after adsorption treatment for electrolytic copper extraction. The double-metal-loaded activated carbon is Fe-Mo double-metal-loaded activated carbon, and its preparation method comprises the following steps: S1, soaking palm fiber and palm sheet with an alkaline solution to remove surface oil and glue organic matter, and then washing with water until the washing liquid is neutral; S2, drying the alkali-washed biomass, and then soaking with a phosphoric acid solution to destroy the macromolecular biomass structure and activate the biomass material; S3, drying the activated biomass, and then performing carbonization treatment in an inert gas atmosphere to obtain palm activated carbon; S4, loading metal ions on the surface of the palm activated carbon by co-precipitation method: dissolving iron nitrate and ammonium molybdate in water to prepare a metal ion solution, and dispersing the palm activated carbon in an alcohol solution to prepare a carbon solution, then mixing the metal ion solution and the carbon solution, and performing calcination treatment after water bath evaporation to obtain Fe-Mo double-metal-loaded activated carbon.

[0008] Preferably, in S1, the mass ratio of palm fiber and palm sheet is 1-2:1-2, and the alkaline solution used is a 1-3 mol / L NaOH solution.

[0009] Preferably, in S1, the soaking treatment is room temperature soaking for 3-6 h.

[0010] 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.

[0011] Preferably, in S2, the soaking treatment is room temperature soaking for 18-30 h.

[0012] Preferably, in S3, the temperature of the carbonization treatment is 500-700 ℃, the time is 20-50 min, and the heating rate is 3-6 ℃ / min.

[0013] Preferably, in S4, the mass ratio of palm activated carbon, ferric nitrate and ammonium molybdate is 0.1-0.2:0.65-0.75:0.55-0.65.

[0014] Preferably, in S4, the temperature of the calcination is 300-500 ℃, and the time is 1-3 h.

[0015] Preferably, the palm fibers and palm pieces are subjected to cutting, washing and drying pretreatment before use.

[0016] Preferably, in S3, after carbonization, the product is washed with 0.1-0.3 mol / L NaOH solution and water, respectively, and dried.

[0017] Preferably, in S4, after mixing the metal ion solution and the carbon solution, water bath evaporation and drying are performed before calcination.

[0018] Preferably, in S4, the volume ratio of the metal ion solution to the carbon solution is 2:1.

[0019] Preferably, in S4, the alcohol solution includes ethanol, ethylene glycol, etc.

[0020] Preferably, the electrolytic device uses a titanium alloy plate as the anode to prevent corrosion and prolong the service life.

[0021] Compared with the prior art, the present application has the following advantages: The present application uses palm fibers and palm pieces 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 solution and micro-etching solution to generate ·OH and ·SO4 - active radicals, which can degrade organic matter in the waste liquid while achieving simple, safe and economical pretreatment of the waste liquid. Not only does it simplify the subsequent operation process of electrolytic copper extraction and reduce the process difficulty, but also reduces the cost investment, and has the values of resource recycling and environmental protection. It provides an efficient and feasible solution for the treatment of browning solution and micro-etching solution. Specifically, the present application has the following advantages: (1) Active carbon carrier and metal active component have synergistic effect, that is, electron interaction between metal-carrier interface, which effectively promotes electron transfer between active component and pollutants, and accelerates catalysis.

[0022] (2) Adsorption of active carbon accelerates enrichment of organic matter to active component, and improves removal efficiency of pollutants in early stage of reaction.

[0023] (3) Double metal nano-ions have good catalysis on active components such as hydrogen peroxide and persulfate in brownification and micro-etching system, which on one hand decomposes hydrogen peroxide to improve subsequent electrolytic copper efficiency, and on the other hand effectively degrades refractory organic matter in brownification waste liquid through ·OH, ·SO4 - and the like generated by catalysis of active components, and improves purity and grade of subsequent electrolytic copper.

[0024] (4) Modified catalyst has COD removal capacity of ≥200 mg / g, has strong pollutant removal capacity, and reduces catalyst dosage and use cost.

[0025] (5) Pretreatment process effectively reduces energy consumption of subsequent electrolytic copper, and also reduces potential risks such as heat generation.

[0026] (6) Modified active carbon in the application has renewable potential after adsorbing organic matter, and can be regenerated by simple calcination, and can be recycled through calcination and reloading after regeneration for several times. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a microstructure diagram of double metal loaded active carbon in Example 1; Figure 2 is a microstructure diagram of active metal in Example 1; Figure 3 is yield of active carbon under different pyrolysis temperatures and specific surface area of active carbon of different substrates; Figure 4 is a graph of influence of different catalyst dosages on COD removal efficiency; Figure 5 is an effect diagram of cathode copper deposition after pilot electrolysis; Figure 6 is a regeneration performance diagram of double metal loaded active carbon catalyst. DETAILED DESCRIPTION

[0028] The specific embodiments of the present application are further described below. It is to be understood that the description of these embodiments is intended to help understand the present application and is not intended to limit the present application. Furthermore, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0029] The experimental methods in the following examples are all conventional methods unless otherwise specified. The test materials used in the following examples are all commercially available unless otherwise specified.

[0030] Example 1: Preparation and micro-characterization of bimetallic supported activated carbon 1. Preparation of palm activated carbon

[0031] (1) The palm fiber and palm sheet were cut and washed, and then pre- treated by drying in a forced air drying oven at 105°C for 2h.

[0032] (2) The pre-treated palm fiber and palm sheet were weighed according to a mass ratio of 1:1, and then soaked in a 1 mol / L NaOH solution for 4h to remove surface oil and glue organic matter. After soaking, the palm fiber and palm sheet were washed several times with deionized water until the washing liquid was neutral.

[0033] (3) The alkali-washed biomass was dried, and then soaked in a 42.5% mass fraction phosphoric acid solution for 24h to destroy the structure of macromolecular biomass and activate the biomass material, wherein the mass ratio of phosphoric acid to activated carbon was 2:1. After soaking and activation, the surface of the biomass material was washed with deionized water and dried in an oven.

[0034] (4) After activation, washing and drying, the carbonization was carried out in a tube furnace under an inert gas (such as argon) atmosphere, with a carbonization temperature of 650°C, a duration of 30min, and a heating rate of 5°C / min. After carbonization, the product was cooled and taken out, washed with a 0.1 mol / L NaOH solution and deionized water, and then dried to obtain palm activated carbon.

[0035] 2. Iron and molybdenum bimetallic element loading 7.19g of iron nitrate nonahydrate and 5.52g of ammonium molybdate tetrahydrate were dissolved in 50mL of water to prepare a metal ion solution, and 2g of palm activated carbon was dispersed in 25mL of anhydrous ethanol solution to prepare a carbon solution. Then, the carbon solution and the metal ion solution were mixed together under ultrasonic conditions for 1h. The mixture was then evaporated in a water bath at 80°C, and vacuum dried for 2h. Finally, the mixture was calcined in a muffle furnace at 400°C for 2h in an air atmosphere, and then cooled to obtain Fe-Mo bimetallic supported activated carbon.

[0036] The Fe-Mo bimetallic supported activated carbon was characterized and analyzed by scanning electron microscopy, and the results are shown inFigure 1 , 2 As can be seen from the scanning electron microscope image, the nano metal as the active component is uniformly dispersed on the surface of the porous activated carbon. The surface of the activated carbon is relatively flat, and the pore is rich. The porous structure provides a good specific surface area and adsorption effect for the activated carbon, which is conducive to promoting the enrichment of organic matter and active substances on the surface layer of the activated carbon.

[0037] Example 2: Effect of different pyrolysis temperatures on specific surface area of activated carbon and yield of activated carbon The effects of different pyrolysis temperatures on the specific surface area of activated carbon and the yield of activated carbon were compared by BET specific surface area analysis and calculation of the yield of activated carbon, so as to select a suitable experimental temperature. The calculation formula is as follows: The yield of activated carbon is m1 / m0, m1: the mass of the sample after pyrolysis, m0: the initial mass of the sample.

[0038] As can be seen from the scanning electron microscope image, the nano metal as the active component is uniformly dispersed on the surface of the porous activated carbon. The surface of the activated carbon is relatively flat, and the pore is rich. The porous structure provides a good specific surface area and adsorption effect for the activated carbon, which is conducive to promoting the enrichment of organic matter and active substances on the surface layer of the activated carbon. Figure 3 As can be seen from the scanning electron microscope image, the nano metal as the active component is uniformly dispersed on the surface of the porous activated carbon. The surface of the activated carbon is relatively flat, and the pore is rich. The porous structure provides a good specific surface area and adsorption effect for the activated carbon, which is conducive to promoting the enrichment of organic matter and active substances on the surface layer of the activated carbon.

[0039] Example 3: Specific surface area and adsorption performance of different substrate carbon materials According to the method of example 1, different substrates (palm, spruce wood, bamboo, corn cob, peanut shell) were used to prepare activated carbon, and the potential loading capacity and adsorption capacity of activated carbon of different substrates were compared by BET specific surface area analysis, and the results are shown in Figure 3 .

[0040] As can be seen from the scanning electron microscope image, the nano metal as the active component is uniformly dispersed on the surface of the porous activated carbon. The surface of the activated carbon is relatively flat, and the pore is rich. The porous structure provides a good specific surface area and adsorption effect for the activated carbon, which is conducive to promoting the enrichment of organic matter and active substances on the surface layer of the activated carbon.

[0041] Example 4: Effect of different metal element loading ratios on pollutant removal effect According to the method of example 1, different mass ratios of Fe-Mo were loaded to explore the effect of different metal element loading ratios on the pollutant removal effect. Specifically, the brown micro-etching waste liquid was diluted 5 times with water, and then different Fe-Mo loading ratio activated carbon was added in an amount of 10 g / L for catalytic experiment. The catalytic experiment was carried out in a 1L beaker at room temperature, and a magnetic stirrer was used to provide mixing and mass transfer. The COD removal rate was measured within 1h, and the results are shown in Table 1.

[0042] From the results of Table 1, it can be seen that with the gradual increase of Mo element proportion, the COD removal effect is gradually enhanced, but the increase to 1:4 has no obvious effect on the COD removal rate, and the final selection of 1:3 Fe-Mo mass ratio is considered from the economic point of view.

[0043] Table 1 Removal effect of pollutants by loading different Fe-Mo ratios Example 5: Effect of different dosages of bimetallic supported activated carbon on brown micro-etching waste liquid The brown and micro-etching waste liquid discharged from the workshop (Table 2) was mixed according to the volume ratio of 1:1, and the effect of different catalyst dosages on the removal of pollutants was investigated.

[0044] Table 2 Water quality of waste liquid discharged from the workshop Specifically, 100 mL of brown micro-etching waste liquid (COD = 9830 mg / L) was placed in a 250 mL conical flask, and different amounts of carbon material were added for adsorption and catalysis experiments. The COD concentration of the mixed sample was measured at different time points, and the COD removal rate was calculated as the evaluation index. The experimental results are shown in Figure 4 .

[0045] From Figure 4 it can be seen that with the increase of catalyst dosage, the removal effect of COD in brown micro-etching waste liquid is gradually enhanced, and the catalyst dosages of 40 g / L and 50 g / L achieve about 90% COD removal effect within 6 h, and the COD removal capacity reaches 226.08 mg / g. In comparison, the pollutant removal efficiency of 40 g / L is much higher than that of 10 g / L, 20 g / L and 30 g / L, but the final effect is not much different from that of 50 g / L, so 40 g / L is finally selected as the best dosage.

[0046] Example 6: Pretreatment and electrolysis effect of pilot experiment The brown and micro-etching waste liquid in the collection barrel was discharged into the reaction barrel according to the volume ratio of 1:1 and stirred uniformly. Then the activated carbon prepared in advance according to Example 1 was added to the reaction barrel according to the dosage of 40~50 kg / t (the dosage was appropriately increased in the pilot test or actual application to ensure the experimental effect), and then the mechanical stirring reaction was carried out for 12 h. After the reaction, the COD, H2O2, Cu 2+ and conductivity were measured. At the same time, the reaction liquid was pumped into the filter press by the pneumatic pump for pressure filtration, and the filtrate was discharged into the electrolytic tank (with titanium alloy plate as anode and copper plate as cathode) for electrolysis, and the copper ion concentration in the electric clear liquid was measured at regular time. When Cu 2+<2 g / L, then stop cooling and drain. A control experiment was also performed, i.e., without adding the catalyst for pretreatment, and the rest of the conditions were unchanged. The results of the pretreatment experiment in the pilot experiment are shown in Table 3.

[0047] As shown in Table 3, after the pretreatment of the brown micro-etching waste liquid, the COD value is significantly reduced. During the treatment process, there are obvious bubbles on the surface of the catalyst, which is presumably caused by the decomposition of H2O2 catalyzed by active metal ions. After the pretreatment, the concentration of hydrogen peroxide has been reduced to 0.08 g / L. At the same time, various free radicals such as ·OH, ·SO4 - may be generated during the catalytic process, which can effectively promote the degradation of organic matter.

[0048] In addition, the conductivity of the raw water cannot be measured by the electrode method, which may be due to the fact that the COD value is too high, resulting in an increase in the viscosity of the water sample, reducing the ion migration rate, and thus interfering with the measurement of conductivity. After the pretreatment, the conductivity of the water sample reaches 160 ms / cm, which has strong conductivity, which is beneficial to the subsequent electrolytic copper process.

[0049] Table 3: Results of the pretreatment experiment in the pilot experiment

[0050] The results of the electrolysis experiment in the pilot experiment are shown in Table 4, and the effect of copper coating on the cathode after electrolysis is shown in Figure 5 .

[0051] As shown in Table 4 and Figure 5 , the electrolysis time of the experimental group is significantly shorter than that of the control group, and the temperature of the electrolyte in the electrolysis tank is also significantly lower than that of the control group, which indicates that the electrolysis efficiency of the experimental group is significantly higher than that of the control group. At the same time, the pretreatment of the experimental group eliminates the consumption of hydrogen peroxide on the current density during the electrolysis process. From the effect of copper coating on the cathode after electrolysis, it can be seen that the reduction polymerization of organic matter occurs at the cathode during the electrolysis process due to the presence of a large amount of organic matter in the electrolyte of the control group, which reduces the quality of the electrolytic copper. In addition, from the Cu 2+ concentration of the final electrolytic liquid, it can be seen that the copper recovery of the experimental group is more complete.

[0052] Table 4: Results of the electrolysis experiment in the pilot experiment Example 7: Regeneration performance of the catalyst The used catalyst (bimetallic supported activated carbon of Example 1) was regenerated by means of alkaline washing, alcohol washing, calcination, and re-loading. Specifically, the activated carbon after catalysis was first soaked and washed with 1 mol / L NaOH solution, then rinsed with anhydrous ethanol solution, and finally calcined. The calcination mainly included two steps of desorption and regeneration. First, volatile substances were removed at 300°C, and then CO2 was introduced into the reaction kettle for regeneration at 600°C.

[0053] As shown in Figure 6 Fig. 6, with the increase of regeneration times, the removal effect of the catalyst on pollutants gradually decreased, and the COD removal rate within 6 hours decreased from 92% at the beginning to 50% after the fifth regeneration. This phenomenon might be due to the gradual deactivation of the active sites of the catalyst and the blockage of the pores of the activated carbon after multiple regeneration. However, the catalyst after the first three regeneration still maintained good removal effect on the organic matter in the waste liquid, and therefore it is suggested that the catalyst be reloaded or re-prepared after 3-5 times of regeneration.

[0054] The above detailed the embodiments of the present application, but the present application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of the embodiments can be made without departing from the principles and spirits of the present application, and still fall within the protection scope of the present application.

Claims

1. A method for strengthening copper electrolysis of PCB brown micro-etching waste liquid by bimetallic loaded activated carbon pretreatment, characterized in that, Double metal loaded activated carbon is added into the brown and etching waste liquid, and the reaction liquid is transferred to an electrolysis device for electrolysis after adsorption treatment. The double metal loaded activated carbon is Fe-Mo double metal loaded activated carbon, and the preparation method comprises the following steps: S1, the palm fiber and palm sheet are soaked with an alkaline solution to remove surface oil and glue organic matter, and then washed with water until the washing liquid is neutral; S2, the biomass after alkali washing is dried, and then soaked with a phosphoric acid solution to destroy the structure of macromolecular biomass and activate the biomass material; S3, the activated biomass is dried, and then carbonized in an inert gas atmosphere to obtain palm activated carbon; S4, metal ions are loaded on the surface of the palm activated carbon by a coprecipitation 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 performed to obtain Fe-Mo double metal loaded activated carbon.

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 mass ratio of the palm fiber and palm sheet is 1-2:1-2, and the alkaline solution used is a 1-3 mol / L NaOH solution.

3. The method for pretreating PCB brown micro-etching waste liquid by bimetallic loaded activated carbon according to claim 1, characterized in that, In S1, the soaking treatment is room temperature soaking for 3-6 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, 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.

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 S2, the soaking treatment is room temperature soaking for 18-30 h.

6. 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, the carbonization treatment temperature is 500-700 ℃, the time is 20-50 min, and the heating rate is 3-6 ℃ / min.

7. The method for pretreating PCB brown micro-etching waste liquid for copper extraction by enhanced electrolysis according to claim 1, characterized in that, 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.

8. The method for pretreating PCB brown micro-etching waste liquid for copper extraction by enhanced electrolysis according to claim 1, characterized in that, In S4, the calcination temperature is 300-500 ℃, and the time is 1-3 h.

9. 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 fiber and palm sheet are cut, washed and dried before use.

10. 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 0.1-0.3 mol / L NaOH solution and water, respectively, and dried.

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