Application Research Of Modified Diatomite In The Treatment Of Waste Water From The Process Of Printed Circuit Board

Printed circuit board (PCB) is high pollution industry and emphasis monitoring industry.The wastes resulted from the processing of PCB have a great influence on the environment,especially the waste water containing large amounts of ammonia nitrogen, COD, copper andother pollution factors would seriously contamination on precious water resources. The treatmenttechnology of PCB wastewater was studied in the Pearl River Delta, and the research aimed todevelop an effective treatment technology to solve the problem such as the high cost andunstable effluent. The research established a classification processing: the organic wastewaterwas treated by acid evolution and adsorption, and comprehensive wastewater was disposed byorthogonal test; diatomaceous was used to strengthenthe coagulation capabilities of polymericferric sulfate (PFS) and poly aluminum chloride (PAC) for removal of copper from PCBcomplex wastewater.(1) It was diatomaceous earth modified by thermal activation/CaCO3/NaOH that wascharacterized by TEM and IE showed the pretreating process can increase specific surface area,improve pore structure, and hydroxyl group was discovery on the surface of diatomaceous earthmodified by CaCO3; pore structure was denser and the pore volume was bigger on the surface ofdiatomaceous earth modified by NaOH.(2) The comprehensive wastewater was coagulated with PAC/PFS and diatomaceousearth by orthogonal test and the factors affecting the copper removal were optimized, such ascoagulated dosage, diatomaceous earth dosage, pH, PAM dosage, fast mixing speedetc. Theexperimental results showed: the initial pH was more significant than other factor, followed bycoagulant dosage. The result showed that it was changed a little that the optimum conditionsof comprehensive wastewater treaded with diatomite modified by thermal activation or not,but it changed the significant from related factors; pH and coagulant dosage was the mainsignificant factor when comprehensive wastewater was treated by PAC and PFS, and only thepH was the main significant factor when diatomaceous earth modified by thermal activationcoupled to PAC and PFS.(3) The pretreatment of organic wastewater mainly adopts acid evolution, thendiatomaceous modified by NaOH/thermal activation adsorbthe supernatant fluid. The experimental results showed that when the pH was adjusted below3.0, the removal rate of CODcould reach more than80%after precipitation30min; then the dosage of diatomaceousmodified by NaOH was about1.0mg/L, and the removal rate of COD was more than92%.Compared with the primary diatomaceous and modified by thermal activation, the adsorptioncapacity of diatomaceous modified byNaOH was improved greatly.(4) Diatomite was used to enhance the coagulation capabilities of PFS and PAC for removalof copper from PCB complex wastewater. The experimental results showed that diatomatemodified by CaCO3could strengthen the capacity of PAC/PFS to treat complex wastewater andthe copper mass concentration in the effluent was lower than0.4mg/L and0.5mg/L respectively;it is because diatomaceous earth was as the condensation nucleus in the coagulation processingand the adsorption capacity of diatomaceous earth was strengthened.