在台灣半導體產業多數利用化學混凝沉澱法、薄膜法處理化學機械研磨廢水（Chemical Mechanical Polishing，CMP），但薄膜法因為建設及後續處理成本較高目前只被部份半導體產業採用，而化學混凝法常因加藥量不易控制導致過量產生大量污泥，造成增加後續處理成本。因此本研究利用聚矽酸鐵（Poly Silicate Iron，PSI）混凝劑進行CMP廢水的化學混凝沉降處理，以評估其顆粒沉降處理效果，不同矽鐵比PSI的混凝效果在本研究中被仔細探討。研
究結果顯示，以添加PSI之矽鐵比1(Si/Fe：1)、矽鐵比0.5(Si/Fe：0.5) 於處理SiO2廢水加藥量為20 mg/L；對於Al2O3廢水處理之加藥量為10 mg/L。SiO2廢水在添加PSI (Si/Fe：1)後最終濁度去除率可達99%、(Si/Fe：0.5)濁度去除率可達98%；Al2O3廢水添加PSI (Si/Fe：1)及(Si/Fe：0.5)後濁度去除率皆可達到約99%，而高矽鐵比因具有高分子聚合物結構，所以有較強之架橋吸附作用，可使廢水中的顆粒去穩定形成大又密實之膠羽，整體的最終處理效果以矽鐵比1為最適矽鐵比。 In the semiconductor industry in Taiwan, most of the Chemical Mechanical Polishing (CMP) Wastewater is treated by chemical coagulation sedimentation and membrane treatment. However, the membrane treatment method is currently only used by some semiconductor industries because of the high cost of construction and maintain cost. Moreover, the chemical coagulation method often produced a large amount of sludge due to the difficulty in controlling the coagulant dosage, which increases the cost of sludge treatment. In this study, Poly Silicate Iron (PSI) coagulant was used for chemical coagulation precipitation treatment of CMP wastewater to evaluate its particle sedimentation treatment. The coagulation effect of different ratios of Silicic/Iron (Si/Fe) PSI was explored in this study.
The results showed that the addition of optimal dosage for PSI (Si/Fe:1, Si/Fe:0.5) in the treatment of SiO2 wastewater is 20 mg/L. The optimal dosage for Al2O3 wastewater treatment is 10 mg/L. The turbidity removal rate of SiO2 wastewater after adding PSI (Si/Fe:1) can reach 99%, and the turbidity removal rate of (Si/Fe: 0.5) can reach 98%. After adding PSI (Si/Fe:1) and (Si/Fe:0.5) to Al2O3 wastewater, the turbidity removal rate can reach about 99%. However, higher Si/Fe ratio will produce higher aggregation iron, hence it has stronger bridging adsorption effect than high molecular weight polymer. The particles in the wastewater can be destabilized to form large and dense aggregates. Si/Fe ratio 1 showed the highest turbidity removal efficiency on CMP wastewater treatment.
