A printed circuit board wastewater treatment system and treatment process

Abstract

The application relates to the technical field of water treatment, in particular to a printed circuit board wastewater treatment system and treatment process. The printed circuit board wastewater treatment system comprises a production wastewater input pool, a pretreatment unit, an MCR tank, a concentrated water treatment unit and a recycled water pool which are connected in sequence. The pretreatment unit comprises a pH adjusting pool, a complexation adsorption section and a precipitation section which are connected in sequence, and the complexation adsorption section is provided with a composite adsorbent. The printed circuit board wastewater treatment system can be used for recycling the printed circuit board wastewater, and has the advantages of simple operation and efficient removal of complex heavy metal ions in the wastewater.

Description

Technical Field

[0001] This application relates to the field of water treatment technology, and more specifically, to a treatment system and process for wastewater from printed circuit boards. Background Technology

[0002] The printed circuit board (PCB) industry has expanded dramatically over the past decade due to rapid growth in market demand for electronic and electrical equipment. The current PCB industry involves various toxic chemicals in different manufacturing processes, such as PCB fabrication, circuit pattern transfer, etching, and electroplating. These processes pose serious potential hazards to the environment and human health. In particular, during the etching step, approximately 70% of the copper is removed from copper-clad printed circuit boards, generating waste etchant with high concentrations of copper ions. 3 The amount of waste etchant produced in printed circuit board manufacturing ranges from 1.5 to 3.5 liters, with the total global annual production of waste etchant estimated at approximately 1 billion cubic meters. 3 .

[0003] Compared to free heavy metal ions, complexed heavy metals are highly water-soluble, stable across a wide pH range, and exhibit complex forms, increasing their diffusion in environments such as groundwater. Therefore, they are readily absorbed by organisms. Complexed heavy metals typically have higher potential toxicity than both individual organic ligands and free heavy metals, and are more difficult to remove. Traditional chemical precipitation methods often fail to achieve satisfactory treatment results, and the effluent often fails to meet discharge standards. If improperly treated, they can accumulate in high concentrations in the human body once they enter the food chain, leading to serious health risks. Therefore, the treatment of wastewater containing complexed heavy metals has become one of the most pressing environmental protection issues.

[0004] Currently, wastewater treatment methods for printed circuit boards include chemical precipitation, ion exchange, and membrane separation. Regarding these related technologies, the inventors discovered that simple chemical precipitation, ion exchange, and membrane separation methods not only have complex processes and high operating costs, but also exhibit poor removal efficiency for complexed copper, nickel, and tin, making it difficult to consistently achieve high wastewater reuse rates. Furthermore, the reused water often fails to meet tap water quality standards (conductivity ≤200 μS / cm). Summary of the Invention

[0005] To improve the removal efficiency of complexed heavy metal ions in printed circuit board wastewater, this application provides a treatment system and process for printed circuit board wastewater.

[0006] In a first aspect, this application provides a wastewater treatment system for printed circuit boards, which adopts the following technical solution: A wastewater treatment system for printed circuit boards includes a production wastewater input tank, a pretreatment unit, an MCR tank, a concentrate treatment unit, and a recycled water tank connected in sequence by ports.

[0007] By adopting the above technical solution and setting up multiple units such as pretreatment unit, MCR tank, and concentrated water treatment, multi-level integrated wastewater treatment can be achieved, improving treatment efficiency. It can effectively classify and treat complex pollutants in PCB wastewater and recycle resources, which is in line with the current trend of environmental protection and sustainable development.

[0008] Optionally, the pretreatment unit includes three input terminals, and the output terminal of the production wastewater input tank is connected to the first input terminal of the pretreatment unit; The MCR tank includes two output ends. The first output end is connected to the input end of the concentrate treatment unit, and the second output end is connected to the sludge tank. The sludge tank includes two output ends. The first output end is connected to a plate and frame filter press, and the second output end is connected to the second output end of the pretreatment unit. The plate and frame filter press includes two output ends. The first output end outputs dry sludge, and the second output end is connected to the third input end of the pretreatment unit.

[0009] By adopting the above technical solution and setting up three input terminals, the flexibility and processing capacity of the pretreatment unit are enhanced. The sludge tank not only realizes centralized sludge treatment, but also forms a closed-loop treatment process through the connection of the second output terminal with the pretreatment unit. This improves the recycling rate of wastewater treatment, increases the overall treatment efficiency of the system, and the circular design also helps to reduce the use of chemicals, lower the system's operating costs, and improve the resource utilization rate of sludge.

[0010] Optionally, the MCR tank includes an MCR membrane, a self-priming pump for permeate, and instrument valves, wherein the MCR membrane flux is 12-15 L / m³. 2 •h, with a filter pore size of 0.4μm.

[0011] By adopting the above technical solutions and through precise parameter settings, the processing accuracy and stability of the MCR tank are improved, the service life of the equipment is extended, and the long-term operation and maintenance costs are reduced.

[0012] Optionally, the pretreatment unit includes a pH adjustment tank, a decomplexing adsorption section, and a precipitation section connected in sequence at the ports.

[0013] By employing the above-mentioned technical solution, through steps such as pH adjustment, decomplexing adsorption, and precipitation, complexes and suspended solids in wastewater are effectively removed. In particular, for complexed heavy metal ions, pre-treatment with decomplexing followed by precipitation significantly reduces the content of complexed heavy metal ions in the wastewater. This step-by-step treatment method improves pretreatment efficiency, reduces the load on subsequent treatment units, and provides favorable water quality conditions for subsequent MCR and reverse osmosis treatments.

[0014] Optionally, the concentrate treatment unit includes a pH adjustment tank, a primary reverse osmosis unit, and a secondary reverse osmosis unit connected in sequence at the ports. The primary reverse osmosis unit and the secondary reverse osmosis unit each include a reverse osmosis membrane, a feed pump, a high-pressure pump, and instrument valves.

[0015] By adopting the above technical solution and using two-stage reverse osmosis in series, the deep removal of metal ions from wastewater is achieved. The application of this multi-stage reverse osmosis technology significantly improves the desalination rate and metal ion removal efficiency of the system, greatly reduces the dissolved solids content in the wastewater, improves the quality of the produced water, and maximizes the utilization of wastewater resources.

[0016] Optionally, the first-stage reverse osmosis unit includes two output terminals: a first output terminal connected to the input terminal of the second-stage reverse osmosis unit, and a second output terminal connected to the input terminal of the reclaimed water tank. The secondary reverse osmosis unit includes two output terminals. The first output terminal outputs concentrated water, and the second output terminal is connected to the input terminal of the reclaimed water tank. The reverse osmosis membrane flux in the primary and secondary reverse osmosis units is 12-15 L / m³. 2 •h, desalination rate ≥97%.

[0017] Secondly, this application provides a treatment process for printed circuit board wastewater, which adopts the following technical solution: A process for treating wastewater from printed circuit boards includes the following steps: S1: Wastewater from the production wastewater input tank enters the pretreatment unit and stays for 12-16 hours. The pH is adjusted to 8-9, and a composite adsorbent is added for decomplexing adsorption and precipitation. The amount of composite adsorbent added is 40-60% of the mass of wastewater treated in a single pretreatment unit. S2: The product water after sedimentation enters the MCR tank and stays for 1-3 hours. Under the action of the MCR membrane, large particulate flocs are filtered out, and pollutants such as large particulate flocs are trapped in the MCR tank to achieve solid-liquid separation. S3: The permeate from the MCR tank enters the concentrate treatment unit, where the pH of the wastewater is adjusted to 6-7. The unadsorbed metal ions such as nickel, tin, and copper in the wastewater pumped into the concentrate treatment unit are further removed by the reverse osmosis membranes of the primary and secondary reverse osmosis units. The permeate then passes through the reverse osmosis membranes into the recycled water tank.

[0018] By adopting the above technical solution, the treatment process of this application has the advantages of simple process, low cost, good removal effect and low energy consumption, and has good prospects for promotion and application in the field of wastewater deep treatment technology.

[0019] Optionally, the raw materials of the composite adsorbent, by weight, include 10-30 parts chitosan fiber, 1-5 parts crown ether compound, 10-20 parts foam plastic, and 0.1-0.5 parts titanate coupling agent.

[0020] By adopting the above technical solution, the skeleton structure of the foam plastic has a large number of pores and a complex network structure, forming a multi-level pore system of micropores and macropores. These pores not only increase the specific surface area of ​​the foam plastic, enabling it to serve as a carrier for loading adsorbents and providing more active sites for the adsorbents, thus increasing their chances of contacting complexed heavy metals; they also provide more channels for heavy metal ions to enter the interior of the material, which is beneficial to the diffusion and adsorption of heavy metal ions.

[0021] Crown ether compounds, due to their unique cyclic structure, can more accurately identify and adsorb complexed heavy metal ions. Chitosan fibers, with their high specific surface area and porosity, provide a large number of adsorption sites. When combined with crown ether compounds, they can significantly increase the adsorption capacity for heavy metal ions, while also improving the mechanical strength and stability of the composite adsorbent and enhancing its durability.

[0022] Furthermore, chitosan possesses excellent hydrophilicity, enabling it to swell and form a gel in water. This facilitates improved contact and adsorption of heavy metal ions in aqueous solutions. The chemoselectivity of crown ether compounds, combined with the physical adsorption of chitosan microspheres, allows for more efficient heavy metal ion capture. Titanate coupling agents can chemically react with the amino or hydroxyl groups in chitosan fibers to form a chemical cross-linking network, promoting the gelation of chitosan fibers and enhancing the chemical stability and structural strength of the composite adsorbent.

[0023] Optionally, the crown ether compound is dibenzo-18-crown-6.

[0024] By adopting the above technical solution, compared with the separation of other complexed heavy metal ions, copper ions can form more stable complexes with various complexing agents, which increases the solubility and stability of copper ions in aqueous solution, making them difficult to remove by precipitation or adsorption using conventional methods. The use of dibenzo-18-crown-6 takes advantage of the single selectivity and high adsorption of crown ether polymers for metal ions, and loading it into foam plastic can effectively adsorb and separate complexed copper ions.

[0025] Optionally, the preparation method of the composite adsorbent includes the following steps: S1: Mix chitosan fiber with dibenzo-18-crown-6 evenly, mix with ethanol at a material-to-liquid ratio of 1:(5-9), continue to add titanate coupling agent, and stir evenly to form a mixture; S2: Apply the mixture evenly to the foam plastic substrate and cure it.

[0026] By adopting the above technical solution, the preparation method of the composite adsorbent of this application is simple and easy to promote in industry.

[0027] In summary, this application has the following beneficial effects: 1. The pretreatment unit of the wastewater treatment system of this application sets up a decomplexing adsorption section and a precipitation section to specifically separate and remove complexed heavy metals, which can effectively improve the removal effect of complexed heavy metal ions in printed circuit board wastewater and provide good water quality conditions for subsequent MCR treatment and reverse osmosis treatment.

[0028] 2. In this application, a composite adsorbent is prepared by loading a complex of crown ether compounds and chitosan fibers onto foam plastic as a carrier skeleton. This forms a complex porous system inside, which provides more active sites for the composite adsorbent and effectively improves the selectivity and adsorption capacity of the composite adsorbent for complexed heavy metal ions.

[0029] 3. The method of this application can realize multi-stage integrated wastewater treatment, improve treatment efficiency, and achieve effective classification, treatment and resource recovery for complex pollutant components in PCB wastewater, which is in line with the current trend of environmental protection and sustainable development. Attached Figure Description

[0030] Figure 1 This is a functional block diagram of the printed circuit board wastewater treatment system of this application.

[0031] Figure 2 This is a functional block diagram of the preprocessing unit.

[0032] Figure 3 This is a functional module diagram of the concentrated wastewater treatment unit. Detailed Implementation

[0033] The present application will be further described in detail below with reference to all the accompanying drawings.

[0034] This application provides a wastewater treatment system for printed circuit boards (PCBs) for recycling PCB wastewater.

[0035] like Figure 1 As shown, a printed circuit board wastewater treatment system of this application includes a production wastewater input tank, a pretreatment unit, an MCR tank, a concentrate treatment unit, and a recycled water tank, which are connected in sequence by ports.

[0036] The pretreatment unit includes three input terminals, with the output terminal of the production wastewater input tank connected to the first input terminal of the pretreatment unit. The pretreatment unit comprises a pH adjustment tank, a decomplexing adsorption section, and a sedimentation section, all connected sequentially. The output terminal of the sedimentation section is connected to the input terminal of the MCR tank. The production wastewater undergoes pH adjustment to alkalinity in the pH adjustment tank. Adsorbent is added to the decomplexing adsorption section, and alkali is added to the sedimentation section. Complexed heavy metal ions in the production wastewater are removed. After solid-liquid separation, the wastewater enters the MCR tank to complete the pretreatment process.

[0037] The MCR tank includes two outputs. The first output is connected to the input of the concentrate treatment unit, and the second output is connected to a sludge tank. The sludge tank also has two outputs: the first output is connected to a plate and frame filter press, and the second output is connected to the second input of the pretreatment unit. The MCR tank also includes an MCR membrane, a permeate self-priming pump, and instrument valves. The MCR membrane flux is 12-15 L / m³. 2 •h, with a filter pore size of 0.4μm.

[0038] The plate and frame filter press includes two output ends. The first output end outputs the dry sludge separated in the sludge tank for external transport, and the second output end is connected to the third input end of the pretreatment unit.

[0039] After filtration in the MCR tank, large particles and flocs are trapped and the sludge is collected in the sludge tank for preliminary sludge-water treatment and separation. The permeate then re-enters the pretreatment unit for recycling. The sludge then enters a plate and frame filter press for filtration, where solid-liquid separation occurs to form permeate and dry sludge. The permeate then enters the pretreatment unit for recycling.

[0040] The concentrate treatment unit comprises a pH adjustment tank, a primary reverse osmosis unit, and a secondary reverse osmosis unit connected sequentially at their ports. Both the primary and secondary reverse osmosis units include a reverse osmosis membrane, a feed pump, a high-pressure pump, and instrument valves. Each unit has two output terminals. The first output terminal of the primary reverse osmosis unit is connected to the input terminal of the secondary reverse osmosis unit, and the second output terminal is connected to the input terminal of the reclaimed water tank. The first output terminal of the secondary reverse osmosis unit discharges concentrate, and the second output terminal is connected to the input terminal of the reclaimed water tank.

[0041] The reverse osmosis membrane flux in the first-stage and second-stage reverse osmosis units is 12-15 L / m³. 2 •h, desalination rate ≥97%.

[0042] The permeate from the MCR tank enters the concentrate treatment unit, passes through the first-stage reverse osmosis unit, and then enters the reclaimed water tank. The concentrate enters the second-stage reverse osmosis unit for further recycling, and the recycled permeate enters the reclaimed water tank again, while the concentrate is transported off-site for further treatment.

[0043] raw material Unless otherwise specified, the raw materials used in the preparation examples, application examples, and comparative examples in this application are all commercially available products, specifically: The foam plastic is polyurethane foam plastic, selected from Huaxin Thermal Insulation Material Factory of Dongyaotou, Dacheng County, 2022, cut into cubes weighing 1-10g. Chitosan fiber, selected from Qingdao Hailan Biological Products Co., Ltd., 38DD; Dibenzo-18-crown-6, selected from Jiangsu Puleisi Biotechnology Co., Ltd., 14187-32-7; Titanate coupling agent, selected from Dongguan Shanyi Plastic Co., Ltd., Titanate coupling agent 201.

[0044] Preparation example of composite adsorbent Preparation Example 1 The composite adsorbent, the raw materials and their dosages are shown in Table 1, among which the crown ether compound is dibenzo-18-crown-6.

[0045] Table 1 Chitosan fiber / Kg 25 10 30 20 Crown ether compounds / Kg 5 2 4 1 Foam plastic / Kg 14 10 20 17 Titanate coupling agent / Kg 0.2 0.1 0.5 0.2 The preparation method of the above-mentioned composite adsorbent includes the following steps: S1: Mix chitosan fiber and crown ether compound evenly, mix with ethanol at a material-to-liquid ratio of 1:9, continue to add titanate coupling agent, and stir evenly to form a mixture; S2: Apply the mixture evenly to the foam plastic substrate and cure it.

[0046] Preparation Example 2 The composite adsorbent differs from that in Preparation Example 1 in that the raw materials and their amounts are shown in Table 1, and its preparation method includes the following steps: S1: Mix chitosan fiber with crown ether compound evenly, mix with ethanol at a material-to-liquid ratio of 1:5, continue to add titanate coupling agent, and stir evenly to form a mixture; S2: Apply the mixture evenly to the foam plastic substrate and cure it.

[0047] Preparation Example 3 The composite adsorbent differs from that in Preparation Example 1 in that the raw materials and their amounts are shown in Table 1, and its preparation method includes the following steps: S1: Mix chitosan fiber and crown ether compound evenly, mix with ethanol at a material-to-liquid ratio of 1:7, continue to add titanate coupling agent, and stir evenly to form a mixture; S2: Apply the mixture evenly to the foam plastic substrate and cure it.

[0048] Preparation Example 4 The composite adsorbent differs from Preparation Example 1 in that the raw materials and their amounts are shown in Table 1, while the other steps are the same as in Preparation Example 1.

[0049] Preparation Example 5 The composite adsorbent differs from Preparation Example 1 in that crown ether compounds are not used, and the crown ether compounds in the raw materials are replaced with an equal mass of chitosan fibers.

[0050] Preparation Example 6 The composite adsorbent differs from Preparation Example 1 in that chitosan fiber was not used; instead, the chitosan fiber in the raw material was replaced with an equal mass of crown ether compounds.

[0051] Application examples The present application discloses a wastewater treatment process for printed circuit boards, which utilizes a wastewater treatment system for printed circuit boards as described in this application. The composite adsorbent used is prepared according to Preparation Examples 1-6. Application Example 1 A process for treating wastewater from printed circuit boards, wherein the composite adsorbent is prepared by Preparation Example 1, includes the following steps: S1: Wastewater enters the pretreatment unit from the production wastewater input tank and stays for 14 hours. NaOH is added to the pH adjustment tank to adjust the pH to 8-9. Composite adsorbent is added to the decomplexing adsorption section for decomplexing adsorption. Excess NaOH is added to the precipitation section to precipitate metal ions. The amount of composite adsorbent added is 60% of the mass of wastewater treated in a single pretreatment unit. S2: After sedimentation, the permeate enters the MCR tank and stays for 2 hours. Under the action of the MCR membrane, large flocs are filtered out, and the large flocs and other sludge are trapped in the MCR tank to achieve solid-liquid separation. The sludge then enters the sludge tank for further separation treatment. The permeate enters the pretreatment unit for recycling treatment. The remaining sludge enters the plate and frame filter press for filtration and solid-liquid separation again. The liquid enters the pretreatment unit for recycling treatment, and the dry sludge is transported off-site. S3: The permeate from the MCR tank enters the concentrate treatment unit. In the pH adjustment tank, 40% H2SO4 is added to adjust the pH of the wastewater to 6-7. The unadsorbed metal ions such as nickel, tin, and copper in the wastewater pumped into the concentrate treatment unit are further removed by the reverse osmosis membranes of the primary and secondary reverse osmosis units. The permeate from the primary and secondary reverse osmosis units passes through the reverse osmosis membranes into the reclaimed water tank.

[0052] Application Example 2 A process for treating wastewater from printed circuit boards, wherein the composite adsorbent is prepared from Preparation Example 2, includes the following steps: S1: Wastewater enters the pretreatment unit from the production wastewater input tank and stays for 12 hours. NaOH is added to the pH adjustment tank to adjust the pH to 8-9. Composite adsorbent is added to the decomplexing adsorption section for decomplexing adsorption. Excess NaOH is added to the precipitation section to precipitate metal ions. The amount of composite adsorbent added is 40% of the mass of wastewater treated in a single pretreatment unit. S2: After sedimentation, the permeate enters the MCR tank and stays for 3 hours. Under the action of the MCR membrane, large flocs are filtered out, and the large flocs and other sludge are trapped in the MCR tank to achieve solid-liquid separation. The sludge then enters the sludge tank for further separation treatment. The permeate enters the pretreatment unit for recycling treatment. The remaining sludge enters the plate and frame filter press for filtration and solid-liquid separation again. The liquid enters the pretreatment unit for recycling treatment, and the dry sludge is transported off-site. S3: The permeate from the MCR tank enters the concentrate treatment unit. In the pH adjustment tank, 40% H2SO4 is added to adjust the pH of the wastewater to 6-7. The unadsorbed metal ions such as nickel, tin, and copper in the wastewater pumped into the concentrate treatment unit are further removed by the reverse osmosis membranes of the primary and secondary reverse osmosis units. The permeate from the primary and secondary reverse osmosis units passes through the reverse osmosis membranes into the reclaimed water tank.

[0053] Application Example 3 A process for treating wastewater from printed circuit boards, wherein the composite adsorbent is prepared by Preparation Example 3, includes the following steps: S1: Wastewater enters the pretreatment unit from the production wastewater input tank and stays for 16 hours. NaOH is added to the pH adjustment tank to adjust the pH to 8-9. Composite adsorbent is added to the decomplexing adsorption section for decomplexing adsorption. Excess NaOH is added to the precipitation section to precipitate metal ions. The amount of composite adsorbent added is 50% of the mass of wastewater treated in a single pretreatment unit. S2: After sedimentation, the permeate enters the MCR tank and stays for 1 hour. Under the action of the MCR membrane, large flocs are filtered out, and the large flocs and other sludge are trapped in the MCR tank to achieve solid-liquid separation. The sludge then enters the sludge tank for further separation treatment. The permeate enters the pretreatment unit for recycling treatment. The remaining sludge enters the plate and frame filter press for filtration and solid-liquid separation again. The liquid enters the pretreatment unit for recycling treatment, and the dry sludge is transported off-site. S3: The permeate from the MCR tank enters the concentrate treatment unit. In the pH adjustment tank, 40% H2SO4 is added to adjust the pH of the wastewater to 6-7. The unadsorbed metal ions such as nickel, tin, and copper in the wastewater pumped into the concentrate treatment unit are further removed by the reverse osmosis membranes of the primary and secondary reverse osmosis units. The permeate from the primary and secondary reverse osmosis units passes through the reverse osmosis membranes into the reclaimed water tank.

[0054] Application Example 4 A process for treating wastewater from printed circuit boards differs from Application Example 1 in that the composite adsorbent is prepared in Preparation Example 4, while the other steps are the same as in Application Example 1.

[0055] Application Example 5 A process for treating wastewater from printed circuit boards differs from Application Example 1 in that the composite adsorbent is prepared in Preparation Example 5, while the other steps are the same as in Application Example 1.

[0056] Application Example 6 A process for treating wastewater from printed circuit boards differs from Application Example 1 in that the composite adsorbent is prepared in Preparation Example 6, while the other steps are the same as in Application Example 1.

[0057] Comparative Example Comparative Example 1 A treatment process for printed circuit board wastewater differs from Application Example 1 in that no composite adsorbent is added to the decomposition adsorption stage, while all other steps are the same as in Application Example 1.

[0058] Performance testing The water quality indicators and metal ion content before and after recycling treatment of printed circuit board wastewater treated by the treatment process of Application Examples 1-6 and Comparative Example 1 were tested. The specific testing methods refer to GB3838-2002 "Environmental Quality Standard for Surface Water". The test water samples of each group were tested 3 times, and the average value was recorded in Table 2.

[0059] Table 2 According to the performance test data in Table 2, the wastewater treatment system for printed circuit boards of this application can effectively remove various metal ions from the wastewater. After effluent discharge, all metal ion indicators meet the Class II discharge standard of the "Surface Water Environmental Quality Standard".

[0060] According to the performance test results of Application Examples 1-4 and Comparative Example 1, the composite adsorbent used in the printed circuit board wastewater treatment process of this application can effectively promote the adsorption of various complexed metal ions in the wastewater when applied to the decomplexing adsorption stage, significantly reduce the metal ion content in the recycled water, and improve the removal efficiency of complexed metal ions.

[0061] The performance test results from Application Examples 1-4 and 5-6 show that composite adsorbents prepared using foam plastic as the framework structure have a significant effect on the removal of complexed metal ions in wastewater treatment. The combination of the physical adsorption of chitosan microspheres and the chemoselectivity of crown ether compounds enables more efficient capture of complexed heavy metal ions. Compared to simply coating foam plastic, the combined use of both forms a more complex chemical cross-linked network, increasing the adsorption capacity of the composite adsorbent for heavy metal ions and improving the efficiency of wastewater treatment.

[0062] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A wastewater treatment system for printed circuit boards, characterized in that, The system includes a production wastewater feed tank, a pretreatment unit, an MCR tank, a concentrate treatment unit, and a recycled water tank, all connected in sequence at their ports. The pretreatment unit includes a pH adjustment tank, a decomplexing adsorption section, and a sedimentation section, all connected in sequence at their ports. The concentrate treatment unit includes a pH adjustment tank, a primary reverse osmosis unit, and a secondary reverse osmosis unit, all connected in sequence at their ports. Both the primary and secondary reverse osmosis units include a reverse osmosis membrane, a feed pump, a high-pressure pump, and instrument valves. The pretreatment unit contains a composite adsorbent, which, by weight, comprises 10-30 parts chitosan fiber, 1-5 parts crown ether compound, 10-20 parts foam plastic, and 0.1-0.5 parts titanate coupling agent; the crown ether compound is dibenzo-18-crown-6. The preparation method of the composite adsorbent includes the following steps: S1: Mix chitosan fiber with dibenzo-18-crown-6 evenly, mix with ethanol at a material-to-liquid ratio of 1:(5-9), continue to add titanate coupling agent, and stir evenly to form a mixture; S2: Apply the mixture evenly to the foam plastic substrate and cure it.

2. The wastewater treatment system for printed circuit boards according to claim 1, characterized in that: The pretreatment unit includes three input terminals, and the output terminal of the production wastewater input tank is connected to the first input terminal of the pretreatment unit. The MCR tank includes two output ends. The first output end is connected to the input end of the concentrate treatment unit, and the second output end is connected to the sludge tank. The sludge tank includes two output ends. The first output end is connected to a plate and frame filter press, and the second output end is connected to the second output end of the pretreatment unit. The plate and frame filter press includes two output ends. The first output end outputs dry sludge, and the second output end is connected to the third input end of the pretreatment unit.

3. The wastewater treatment system for printed circuit boards according to claim 2, characterized in that: The MCR tank includes an MCR membrane, a self-priming pump for permeate, and instrument valves. The MCR membrane flux is 12-15 L / m³. 2 •h, with a filter pore size of 0.4μm.

4. The wastewater treatment system for printed circuit boards according to claim 1, characterized in that: The first-stage reverse osmosis unit includes two output terminals: the first output terminal is connected to the input terminal of the second-stage reverse osmosis unit, and the second output terminal is connected to the input terminal of the reclaimed water tank. The secondary reverse osmosis unit includes two output terminals. The first output terminal outputs concentrated water, and the second output terminal is connected to the input terminal of the reclaimed water tank. The reverse osmosis membrane flux in the primary and secondary reverse osmosis units is 12-15 L / m³. 2 •h, desalination rate ≥97%.

5. A process for treating wastewater from printed circuit boards, characterized in that, The treatment system for printed circuit board wastewater according to any one of claims 1-4 is used, comprising the following steps: S1: Wastewater enters the pretreatment unit from the production wastewater input tank and stays for 12-16 hours. The pH is adjusted to 8-9, and a composite adsorbent is added for decomplexing adsorption and precipitation. The amount of composite adsorbent added is 40-60% of the mass of wastewater treated in a single pretreatment unit. S2: The product water after sedimentation enters the MCR tank and stays for 1-3 hours. Under the action of the MCR membrane, large particulate flocs are filtered out, and the large particulate floc pollutants are trapped in the MCR tank to achieve solid-liquid separation. S3: The permeate from the MCR tank enters the concentrate treatment unit, where the pH of the wastewater is adjusted to 6-7. The unadsorbed metal ions of nickel, tin, and copper in the wastewater pumped into the concentrate treatment unit are further removed by the reverse osmosis membranes of the primary and secondary reverse osmosis units. The permeate then passes through the reverse osmosis membranes into the reclaimed water tank.

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