Pollutant treatment method in PCB production process
PCB wastewater is divided into cleaning wastewater, ink wastewater, complex wastewater, concentrated acid waste liquid and concentrated alkali waste liquid. There are many types of wastewater contaminants, complex components and targeted treatment of wastewater, which is key to ensuring standardization of wastewater treatment. PCB wastewater treatment is mainly divided into chemical and physical methods. The chemical method is to convert the pollutants in the wastewater into an easily separable physical state (solid or gas), including chemical precipitation, redox, ion exchange and electrolysis. Etc., the physical method is to enrich the pollutants in the wastewater or separate the easily separated physical state from the wastewater, so that the wastewater reaches the discharge standard, mainly including decantation method, electrodialysis method, reverse osmosis method and the like.
The redox method is to convert harmful substances into harmless substances by using an oxidizing agent or a reducing agent, and to precipitate and precipitate them, and the cyanide-containing wastewater and the chromium-containing wastewater in the circuit board are often subjected to a redox method.
2. Chemical precipitation
Chemical precipitation is the conversion of a hazardous substance into a readily separable precipitate or precipitate using one or several chemicals. There are many kinds of chemical reagents for circuit board wastewater treatment, such as NaOH, CaO, Ca(OH)2, Na2S and the like. The precipitant converts heavy metal ions into a precipitate which is then passed through a sloping plate sedimentation tank, a sand filter and a filter press. Etc. Separate solids and liquids.
3. Ion exchange method
Chemical precipitation treatment of high concentration wastewater is difficult and is usually combined with ion exchange. First, the heavy metal ion content was reduced to about 5 mg / L by chemical precipitation, and then the heavy metal ions were reduced to the discharge standard by ion exchange.
Electrolytic treatment of high-concentration circuit board wastewater can reduce the content of heavy metal ions, but the electrolysis method is effective only for the treatment of high-concentration heavy metal ions, and consumes a large amount of electric energy, and can only process one metal.
5. Gaseous condensation - electric filtration
This novel method consists of three parts. The first part is the ionization gas generator. Air is drawn into the generator, which changes the chemical structure of the ionizing magnetic field to highly activated magnetic oxygen ions and nitrogen ions. The gas is introduced into the wastewater by means of a spraying device. Harmful substances such as metal ions and organic substances in the wastewater are oxidized and aggregated, and are easily removed by filtration. The second part is an electrolyte filter that filters out the agglomerates produced in the first part. The third part is a high-speed ultraviolet irradiation device. Ultraviolet rays are injected into water to oxidize organic matter and chemical complexing agents to reduce CODcr and BOD5.