A method for recovering neutral electroplating solution waste water in PCB production

Abstract

The present application belongs to the field of wastewater treatment, and particularly relates to a neutral electroplating solution wastewater recovery method in PCB production. In the printed circuit board production wastewater, there are a large amount of inorganic acid and alkali (mainly H2SO4), heavy metals, organic matters, ammonia nitrogen and the like. The present application adopts an ammonia nitrogen removal step, adjusts pH and pressure, and blows off ammonia nitrogen; adopts an organic matter sedimentation step to remove organic matters in the wastewater, and then uses a plate and frame filter press to compress solid waste; adopts a heavy metal removal step to remove impurity metal ions, and obtains heavy metal precipitates for further recovery; and then adopts a membrane treatment step to use a multi-stage countercurrent bipolar membrane electrodialysis to realize recovery and utilization of the materials, to obtain separated liquid, and then to recover and reuse. The present application has high COD removal rate, low cost and high metal salt recovery rate.

Description

Technical Field

[0001] This invention relates to a method for treating neutral wastewater generated during the production of printed circuit boards (PCBs), particularly a method for treating heavy metal wastewater containing copper, lead, chromium, cadmium, nickel, etc., generated during the PCB production process. Background Technology

[0002] Waste printed circuit boards (PCBs) contain a wide variety of elements, making ordinary acid leaching processes unselective. The leaching solutions are complex and difficult to separate the elements, generally requiring an extraction-re-extraction process to purify the leaching solution and convert it into a copper sulfate solution to facilitate subsequent electrodeposition to prepare high-purity metallic copper. Therefore, the process is lengthy, making the recycling of waste PCBs difficult. Furthermore, the leaching solutions also contain certain amounts of elements such as zinc and nickel, making them unsuitable for direct electrodeposition.

[0003] After waste printed circuit boards are pretreated with nitric acid, the solder dissolves in the nitric acid solution, and elemental tin is converted into stannic acid precipitate and separated from the leaching solution. Elemental lead is converted into lead nitrate and remains in the leaching solution. After the lead nitrate is recycled and enriched to a certain concentration, sulfuric acid is added as a precipitant to generate pure lead sulfate precipitate, thus achieving the separate recovery of tin and lead. However, copper cannot be effectively processed and recovered.

[0004] The existing waste liquid treatment process has several problems: 1. The PCB board etching solution is wasted and lost in a serious manner and cannot be effectively recycled; 2. Conventional electroplating waste liquid treatment processes have high energy consumption, generate a lot of solid waste, and cannot achieve zero waste acid discharge. Summary of the Invention

[0005] To address the problems existing in the prior art, the main objective of this invention is to propose a method for recycling wastewater from electroplating solutions used in PCB manufacturing. The main steps are as follows:

[0006] The ammonia nitrogen removal process achieves ammonia nitrogen removal by controlling temperature, gas pressure, and pH.

[0007] In the organic matter sedimentation step, chemicals are used to achieve flocculation and sedimentation of wastewater. The chemicals used are activated carbon powder with a mesh size greater than 200, a 5% polyaluminum chloride solution, and a 0.3% polyacrylamide solution. Then, a plate and frame filter press is used to press the solid waste.

[0008] The heavy metal removal process enables the recovery and utilization of heavy metal ions in waste liquid;

[0009] The membrane treatment step uses a multi-stage countercurrent electrically driven ion membrane module to recycle materials and obtain the separated liquid.

[0010] The multi-effect evaporation process involves evaporating the acid and alkali chamber solutions in the membrane-treated liquid to obtain valuable components.

[0011] The beneficial effects of this invention are as follows: This invention focuses on the large amounts of inorganic acids and alkalis, heavy metals, organic matter, ammonia nitrogen, etc. contained in the wastewater from printed circuit board manufacturing. It adopts a combined process of ammonia nitrogen removal, organic matter sedimentation, heavy metal removal, membrane treatment, and multi-effect evaporation. This invention integrates various steps to achieve high COD removal rate, low cost, and high metal salt recovery rate. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a flowchart of a method for recycling electroplating wastewater from PCB manufacturing, as disclosed in this invention. Detailed Implementation

[0014] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Example 1

[0016] Specifically, for PCB wastewater generated by a certain factory, after the ammonia nitrogen removal process, the ammonia nitrogen removal rate can reach more than 80%, and the treatment cost per ton of water is less than 30 yuan.

[0017] In the organic matter sedimentation step, after treatment with activated carbon powder, PAC, and PAM, the COD removal rate of the waste liquid reaches over 85%.

[0018] In the heavy metal removal process, a three-stage series pump-type washing solution is used to treat the heavy metals and recover them to the storage tank. This can achieve a recovery rate of more than 90% for the main impurity heavy metal ions (Pb, Sn) and obtain crude tin with a tin content of more than 95%.

[0019] In the membrane treatment step, multi-stage countercurrent bipolar membrane electrodialysis was used at a flow rate of 50 L / H and an operating current of 3 A, employing 10 sets of 10*20 cm electrodialysis modules. This achieved a 92% copper recovery rate, resulting in crude copper with a copper content exceeding 95%. Furthermore, bipolar membrane electrodialysis yielded sulfuric acid with a purity exceeding 13%.

[0020] Table 1 shows the performance indicators of various indicators of Embodiment 1 disclosed in this invention and the wastewater treatment technology method of Hazardous Waste Company A.

[0021] Table 1. Indicators of Embodiment 1 of the present invention and the wastewater treatment technology of hazardous waste company A.

[0022] method Wastewater Treatment Technology and Methods of Hazardous Waste Company A A method for recycling wastewater from neutral electroplating solution in PCB manufacturing COD removal rate COD removal rate reached over 78%. COD removal rate reaches over 85%. cost Treatment cost > 270 yuan / ton of wastewater Treatment cost < 30 yuan / ton of wastewater Component recycling none The recovery rate of heavy metal ions (Pb, Sn) is over 90%, tin purity is >95%, copper recovery rate is >92%, copper purity is >95%, and sulfuric acid concentration is >13%.

[0023] Example 2

[0024] Specifically, for PCB wastewater generated by a certain factory, after the ammonia nitrogen removal process, the ammonia nitrogen removal rate can reach more than 80%, and the treatment cost per ton of water is less than 30 yuan.

[0025] In the organic matter sedimentation step, after treatment with activated carbon powder, PAC, and PAM, the COD removal rate of the waste liquid reaches over 85%.

[0026] In the heavy metal removal process, a three-stage series pump-type washing solution is used to treat the heavy metals and recover them to the storage tank. This can achieve a recovery rate of more than 95% for the main impurity heavy metal ions (Pb, Sn) and obtain crude tin with a tin content of more than 95%.

[0027] In the membrane treatment step, multi-stage countercurrent bipolar membrane electrodialysis was used at a flow rate of 60 L / H and an operating current of 5 A, employing 10 sets of 10*20 cm electrodialysis modules. This achieved a 97% copper recovery rate, resulting in crude copper with a copper content exceeding 96%. Furthermore, bipolar membrane electrodialysis yielded sulfuric acid with a purity exceeding 15%.

[0028] Table 2 shows the performance indicators of various indicators of Embodiment 2 disclosed in this invention and the wastewater treatment technology method of Hazardous Waste Company B.

[0029] Table 2. Indicators of Example 2 of this Invention and the Wastewater Treatment Technology Method of Hazardous Waste Company B

[0030] method Wastewater Treatment Technology and Methods of Hazardous Waste Company B A method for recycling wastewater from neutral electroplating solution in PCB manufacturing COD removal rate COD removal rate reached over 82%. COD removal rate reaches over 85%. cost Treatment cost > 310 yuan / ton of wastewater Treatment cost < 30 yuan / ton of wastewater Component recycling none The recovery rate of heavy metal ions (Pb, Sn) is over 95%, tin purity is >95%, copper recovery rate is >97%, copper purity is >96%, and sulfuric acid concentration is >15%.

Claims

1. A neutral electroplating wastewater recovery method for PCB production, characterized by, Includes the following steps: (1) Ammonia nitrogen removal step: Ammonia nitrogen is removed from PCB production electroplating wastewater by controlling temperature, air pressure and pH to obtain ammonia nitrogen-removed liquid; (2) Organic matter sedimentation step: After ammonia nitrogen removal, the liquid is treated with polyaluminum chloride, polyacrylamide and activated carbon to achieve flocculation and sedimentation, and then the solid waste is pressed by a plate and frame filter press to obtain the organic matter sedimentation liquid; Specifically, the organic matter sedimentation step includes treating one liter of ammonia nitrogen removal liquid with 5g of activated carbon powder with a mesh size greater than 200, 10-50mL of 5% polyaluminum chloride solution and 1-5mL of 0.3% polyacrylamide solution, adding them in the order of activated carbon powder-polyaluminum chloride-polyacrylamide and stirring to achieve flocculation and sedimentation, and then using a plate and frame filter press to separate the solid and liquid. The filtrate obtained by solid waste pressing is called the organic matter sedimentation liquid; (3) Heavy metal removal step: After the organic matter settles, the liquid undergoes sulfide precipitation to recover and utilize heavy metal ions, resulting in heavy metal removal liquid; (4) Membrane treatment step: The liquid after heavy metal removal is recycled by a multi-stage countercurrent electrically driven ion membrane module. The working elements are anion exchange membrane, cation exchange membrane and bipolar membrane. The liquid after membrane treatment includes the liquid in the acid chamber, alkali chamber and salt chamber during bipolar membrane electrodialysis. The liquid after membrane treatment is then reused and valuable components are recovered. (5) Multi-effect evaporation process: Multi-effect evaporation is used to evaporate the acid and alkali chamber liquids in the membrane treatment solution to obtain valuable components.

2. The neutral electroplating wastewater recovery method for PCB production according to claim 1, characterized in that, The ammonia nitrogen removal process in step (1) includes stripping ammonia nitrogen from PCB production electroplating wastewater at a pH greater than 11, a temperature of 30-40℃, and a gas pressure of 100-10000mbar to obtain ammonia nitrogen-removed liquid.

3. The method of claim 1, wherein the neutral electroplating wastewater is produced from a PCB manufacturing process. Step (3) involves adding Na2S to the liquid after organic matter has settled, to obtain heavy metal sulfide precipitate and heavy metal removal liquid.

4. The method of claim 1, wherein the neutral electroplating wastewater is produced from a PCB manufacturing process. Step (4) of the membrane treatment process includes adding the heavy metal removal solution to the salt chamber of the membrane treatment system by utilizing the different migration characteristics of different ions under an electric field; the membrane treatment system is a multi-stage countercurrent bipolar membrane electrodialysis system, which is suitable for treating heavy metal removal solutions with a pH range of 3-11; the ions in the feed solution move under the action of the electric field and pass through the bipolar membrane and the anion and cation exchange membrane, and the anions and cations in the neutral feed solution combine with the hydrogen ions and hydroxide ions dissociated from the bipolar membrane to form acids and bases respectively; through the multi-stage series membrane stack compartments, the concentration of acid and base solutions at each stage increases, and the concentration of salt solutions at each stage decreases, and 98% of the valuable components of the 10% salt solution are effectively recovered.

5. The method of claim 1, wherein the neutral electroplating wastewater is produced from a PCB manufacturing process. After the salt concentration is reduced, the dilute salt solution is further sent to the electroplating pretreatment as production water; while the acid and alkali chambers obtain valuable components through the multi-effect evaporation process described in step (5); the pressure of the multi-effect evaporation process is 0.5-0.8MPa, and triple or quadruple evaporation is selected for operation, with the evaporation rate controlled at 3000-15000kg / h.

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