Treatment of Chemical Mechanical Polishing Wastewater by a Simultaneous Electrocoagulation/Electrofiltration Process
In this work, a novel treatment module capable of simultaneously enacting electrocoagulation and electrofiltration was designed, fabricated, and tested aiming for the reclamation of CMP (chemical mechanical polishing) wastewater. In general, CMP wastewater contains sub-micron particles and has high alkalinity, turbidity, total solids content, and silica content. Discharge of CMP wastewater without proper treatment would pose a great threat to the environment and ecology. In this investigation, oxide CMP wastewater and mixed CMP wastewater were obtained from a wafer fab in Taiwan. They were characterized by various standard methods. In this study, the efficiency of this dual-function treatment module (using aluminum as the sacrificing anode and stainless steel as the cathode) was evaluated in terms of applied electric field strength (0 ~ 112.5 V/cm), influent velocity (112 ~136 cm/s), and transmembrane pressure (1.0 ~ 3.0 kgf/cm2) on permeate qualities. Experimental results have shown that the contents of total solids of permeates could be reduced to about 180 mg/L and 426 mg/L, respectively for oxide CMP wastewater and mixed CMP wastewater. The respective values of turbidity and total organic carbon could also be reduced to below 1 NTU and 1.5 mg/L. Therefore, the treated water could be reused as the feed water for the ultrapure water production system. In this study, an empirical equation was established to relate the quantity of filtrate and applied electric field strength when CMP wastewater was subjected to electrofiltration alone. It was found that the theoretical aluminum concentration released to the reaction chamber was much greater than the actual one. This would explain why the efficiency of electrocoagulation needs to be improved in this treatment module. Experimental results also have indicated that proper backflushing would be beneficial to the flux of permeate and saving of membrane cost.
Advisor:Gordon C. C. Yang; none; Chih-pin Huang
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:electrofiltration cmp wastewater electrocoagulation
Date of Publication:02/10/2004