Abstract: Silica sol was prepared by using sodium silicate as a precursor, and then the poly(silicic acid)/polyacrylamide composite flocculant was synthesized through in-situ polymerization. The chemical structure of the composite flocculant was characterized by Fourier-transform infrared spectroscopy (FTIR). The effects of pH value, reaction time and temperature on flocculation effectiveness were investigated by light transmittance and removal ratio for the oil-containing waste water. It was found that the composite flocculant exhibited the best flocculation performance when the synthetic conditions were set to the sodium silicate concentration of 0.5 mol/L, the acrylamide amount of 5.0 g, the initiator amount of 0.3 g, the poly(silicic acid) acidity of pH=5, the reaction time of 90 min, the aging time of 24 h, and the temperature of 70 ℃.

Key words: polyacrylamide, poly(silicic acid), composite flocculant, oil-containing waste water