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PCB Waste Water

May 21, 2018

PCB waste water is polychlorinated biphenyl waste water, which is a kind of waste water in printing industry and circuit board factory waste water. PCB waste water is divided into: cleaning waste water, ink waste water, complex waste water, concentrated acid waste liquid, concentrated alkali waste liquid and so on. Printed circuit board (PCB) has a large amount of water for production, a large variety of waste water pollutants, and a complex composition. According to the characteristics of the waste water of different PCB manufacturers, reasonable classification and collection and quality control are the key to ensuring the standard of wastewater treatment.


For PCB board industry wastewater treatment, there are chemical methods (chemical precipitation method, ion exchange method, electrolytic method, etc.), physical methods (various decantation methods, filtration methods, electrodialysis, reverse osmosis, etc.), and chemical methods are used in wastewater. The pollutants are converted into easily separable states (solid or gaseous). The physical method is to enrich the pollutants in the wastewater or to separate the easily separable states from the wastewater, so that the wastewater meets the emission standards. The methods used at home and abroad are the following.


First, interpret method

The decantation method is actually a filtration method and is a kind of physical method in the wastewater treatment method of the PCB board industry. The deburring machine discharges copper-containing rinsing water, which is treated by a decanter to filter out copper shavings. The effluent filtered by the decanter can be reused with the rinse water of the burr machine.


Second, the chemical method

Chemical methods include redox and chemical precipitation methods. The redox method is the use of an oxidizing agent or a reducing agent to convert harmful substances into harmless substances or substances that are easily precipitated and precipitated. The cyanide-containing waste water and chromium-containing waste water in circuit boards are often subjected to redox, as detailed later.


Chemical precipitation is the use of one or more chemical agents to convert hazardous substances into easily separable precipitates or precipitates. There are many kinds of chemicals used in PCBA OEM OEM circuit board wastewater treatment, such as NaOH, CaO, Ca(OH)2, Na2S, CaS, Na2CO3, PFS, PAC, PAM, FeSO4, FeCl3, ISX, etc. Heavy metal ions can be converted into sediments, and then through the inclined plate sedimentation tank, sand filter, PE filter, filter press, etc., to solid-liquid separation.


Third, chemical precipitation - ion exchange method

Chemical precipitation treatment of high-concentration circuit board wastewater in one step to achieve emission standards is more difficult, often combined with ion exchange. The chemical precipitation method was used to treat high-concentration circuit board wastewater to reduce the heavy metal ion content to about 5 mg/L. Then, ion exchange method was used to reduce the heavy metal ions to the discharge standard.


Fourth, electrolysis - ion exchange method

PCB board industry waste water treatment method, electrolytic treatment of high-concentration circuit board wastewater can reduce the heavy metal ion content, its purpose is the same as the chemical precipitation method. However, the deficiency of the electrolytic method is that only high-concentration heavy metal ion treatment is effective, the concentration is reduced, the current is significantly reduced, the efficiency is obviously reduced, the power consumption is large, and promotion is more difficult; the electrolytic method can only handle a single metal. Electrolysis - ion exchange method is copper plating, etching waste, for other waste water, but also use other methods.


V. Chemical Method - Membrane Filtration

The waste water from the PCB board industry is subjected to chemical pretreatment, so that harmful substances can be deposited out of filterable particles (diameter>0.1μ), and then filtered by a membrane filtration device to meet the emission standards.


Six, gas condensation - electric filter

In the PCB board industry's wastewater treatment method, the gaseous coagulation-electrofiltration method is a novel wastewater treatment method developed without chemicals in the United States in the 1980s and belongs to a physical method for treating printed circuit board wastewater.


It consists of three parts. The first part is an ionized gas generator. Air is sucked into the generator. It can over-ionize the magnetic field to change its chemical structure and become highly activated magnetic oxygen and nitrogen ions. In the wastewater, the metal ions, organic substances and other harmful substances in the wastewater are oxidized and agglomerated, and are easily removed by filtration. The second part is an electrolyte filter, which removes the agglomerated substances generated in the first part; the third part is high-speed ultraviolet rays. Irradiation device, ultraviolet radiation into the water can oxidize organic compounds and chemical complexing agents, reducing CODcr and BOD5. Currently, a complete set of integrated equipment has been developed for direct application

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