In the production of printed circuit boards a lot of inks are needed. According to the function and usage, the ink can be divided into 7 types: resist ink, resistant plating ink, plugging holes ink, solder resist ink (commonly known as green oil), label ink, conductive ink and peelable ink (commonly known as blue gum).
The ink water waste mainly comes from the circuit board production process: screen printing, developing, stripping and so on. The ink composition consists mainly of resin, fillers, pigments, additives and solvent. Non-used ink can be removed with the NaOH. The concentration of organics in the waste water is really high and the waste water is alkaline. Ink wastewater contains a large number of resins, easy to precipitate under acidic conditions.
At present, the main PCB ink wastewater treatment methods are: oxidation, biological treatment; filtration-adsorption, acidification-coacervation, etc. These methods are for the removal of high concentration of organics in ink wastewater.
PCB Ink Wastewater Treatment
Oxidation treatment is a strong oxidizing reaction. The costs are usually very high.
Biological treatment is commonly used contact-oxidation process. It needs high power consumption, so the processing costs are also high.
Treat PCB ink water waste by Filtering - Adsorption, after pretreatment enter the wastewater from pump into the filter, the filter can remove most of suspension, then through activated carbon adsorption, decomposition to achieve good treatment effect. But Ink has large viscosity, easy to stick on the equipment, resulting in high equipment failure rate.
Acidification - coacervation process is currently the most common used treatment of PCB ink wastewater. Generally enter the waste water from the pump into the pool of acid precipitation. Acid precipitation pool features automatic pH control instruments. Photosensitive film under acidic conditions will precipitate thick gel-like agglomerates, which are lighter than water, easy to separate. Then adjust the PH to alkaline in the neutralization reaction pool.