Polyaluminum silicate chloride (PASiC) is a new inorganic coagulant andhas different characters from other cationic inorganic products used in watertreatment. The optimal formulas and conditions to produce and use PASiC are notthoroughly well-known. PASiC can be formed by treating AlCl3 solution withsilicate compounds and the insoluble aluminum silicates are produced thereafter. Ithas been found that partially decreasing alum acidity with silicate would form amore stable solution than polyaluminum chloride (PAC). PASiC may enhance aggregationby the silicate in it to remove turbidity especially for the water of low turbidity andalkalinity. In this research, a series of PASiC coagulants were produced from thedifferent basicities (B) and Al/Si molar ratios at the different aging temperaturesand aging times. Accordingly, PASiCs prepared by the different basicities (B) andSi/Al molar ratios were added in a synthetic water with low turbidity and alkalinityto evaluate the efficiency of PASiC for colloids removal. Finally, the raw water fromMin-Der water treatment plant (Miaoli, Taiwan) was used to evaluate the treatmentefficiency of PASiC and Aluminum Sulfate Al2(SO4)3. The results indicate that thePASiC with higher B value and lower Si/Al molar ratio has higher coagulationefficiency. We also found that under the aging temperature of 408C will increase the aging rate, and the product of PASiC formed is more stable. PASiC evidently hashigher turbidity removal efficiency than that of Al2(SO4)3 when equivalent doseswere used for Min-der reservoir water.
Separation Science and Technology, v. 41, 2006, p. 297-308