Chemical mechanical polishing (CMP) wastewater in semiconductor manufactory is characterized as extremely stable dispersion of nano-size silica. Generally, coagulation- flocculation and sedimentation processes are employed by most of the semiconductor manufacturers in Taiwan. This treatment needed large area for the sedimentation tank and take long time to separate the precipitate and clean water. Dissolved air flotation was recognized as a method of separating particles in the early 1900s. Small air bubbles are formed by injection of pressurized recycle water into a flotation tank using special nozzles. In this study, we use dissolved air flotation (DAF) process combined Nanometer Bubble Generator (NBG) which can produces very small bubbles. This study is divided into four parts. The first section discusses in fundamental properties of CMP wastewater and nana-bubbles. The second section is devoted to control pH value by adding acid or base and recycle ratio (R). In this section we do not add any activator or collector. It is expected that there must be some relationship between operational parameters and removal efficiency. In the third section, we add both activator (aluminum sulfate or ferric chloride) and collector (NaOl or CTAB) to measure the removal efficiency. In the final section, this study will follow the conclusion of first two sections, and confirm the best dosage (activator and collector). All experiments are design in Design of Experiment (DOE). Use central composite design for the second and final section, and 2k factorial design for third section. Experimental data were input to Minitab software for analyzing and plotting. By DOE method, this study would have minimum trials and get complete analysis. Finally this study verified that flotation technology combined NBG process show much potential for the treatment and possible reuse of CMP wastewater. But there are still some aspects didn#t investigate about chemistry interface of the bubble and particle.

CMP wastewater,Flotation,Nano-bubble