PCB waste water is polychlorinated biphenyls waste water, which is a kind of waste water in printing industry and PCB factory.Currently, the world produces between 300 million and 400 million tons of toxic and hazardous chemical waste every year, among which, persistent organic pollutants (POP) are very harmful to the ecology and spread most widely on the earth. In addition, PCB waste water is divided into: cleaning waste water, ink waste water, complex waste water, concentrated acid waste water, concentrated alkali waste liquid and so on.Printed circuit board (PCB) requires a lot of water to produce, and there are many kinds of pollutants in waste water.According to the characteristics of waste water of different PCB manufacturers, reasonable classification collection and quality treatment are the key to ensure that the waste water treatment is up to standard.
For PCB industry wastewater treatment with chemical method, chemical precipitation, ion exchange method, electrolytic method, etc.), physical (various decantation method, filtration method, electrodialysis, reverse osmosis, etc.), chemical method is to convert the pollutants in wastewater into a physical state (solid or gas) of the separation, the physics method is in the wastewater pollutants up or will be separated easily separated from the wastewater of state, to wastewater discharge standard.The methods adopted at home and abroad are as follows.
The decanting method is actually a filter method, which is one of the physical methods in the waste water treatment of PCB industry.The rinsing water with copper shavings discharged by the deburring machine is treated by the decanter to remove the copper shavings.The effluent filtered by the deckator can be recycled with the cleaning water of the burr machine.
Ii. Chemical method
Chemical methods include REDOX and chemical precipitation.REDOX method is to use oxidant or reducing agent to convert harmful substances into harmless substances or easy to precipitate and precipitate out of substances.The cyanogenic and chrome-containing wastewater in the circuit board is often REDOX as described below.
Chemical precipitation is the conversion of harmful substances into easily separated precipitates by one or more chemical agents.PCBA OEM PCB waste water treatment selected a variety of chemical agents, such as NaOH, CaO, Ca(OH)2, Na2S, CaS, Na2CO3, PFS, PAC, PAM, FeSO4, FeCl3, ISX, etc., precipitation agents can convert heavy metal ions into precipitates, which can then be separated by inclined plate sedimentation tank, sand filter, PE filter and pressure filter.
Chemical precipitation - ion exchange method
It is difficult to treat high-concentration PCB wastewater with chemical precipitation, which is often used in combination with ion exchange.The high concentration of PCB wastewater was treated by chemical precipitation method to reduce the content of heavy metal ions to about 5mg/L, and then the heavy metal ions were reduced to the emission standard by ion exchange method.
Electrolysis - ion exchange
High concentration PCB wastewater can be treated by electrolysis with the same purpose as chemical precipitation.However, the disadvantages of the electrolysis method are as follows: only the heavy metal ions with high concentration are treated effectively, the concentration is reduced, the current is decreased significantly and the efficiency is decreased significantly.High power consumption makes it difficult to popularize;The electrolytic method can only deal with a single metal.Electrolysis - ion exchange is copper plating, etching waste liquid, for other waste water, there are other methods.
5. Chemical method -- membrane filtration method
The waste water of PCB industry enterprises is prepared through chemical pretreatment so that the harmful substances can precipitate out the filtrable particles (>, 0.1 wives), which can be filtered through the membrane filter device to meet the discharge standard.
Gaseous condensation -- electrical filtration
Among the PCB industry wastewater treatment methods, gaseous agglomeration -- electric filtration is a novel chemical free wastewater treatment method developed in the United States in the 1980s, belonging to a physical method to treat printed circuit board wastewater.Consists of three parts, the first part is ionized gas generator, air is drawn into the generator, can ionization magnetic field changes its chemical structure, become highly activated magnetic oxygen ions and nitrogen ions, the gas is introduced into waste water with jet device, the harmful material such as metal ions, organic matter in wastewater oxidation and gathered together, easy to filter to remove;The second part is the electrolyte filter, which removes the cluster material produced in the first part.The third part is the high-speed ultraviolet irradiation device, which shoots into water to oxidize organics and chemical complexing agent, reducing CODcr and BOD5.At present, a complete set of integrated equipment has been developed for direct application.