Abstract: The flocculation of sodium montmorillonite suspension at pH=9 was systematically studied with an polyhydroxyaluminium chloride followed by a series of polyacrylamides(M = 3×10⁶) with different hydrolyzed degrees. The results show that the bonding interactions between hydroaluminium ions arid ionic and nonionic polyacryamide have a decisive influence on the flocculation behavior of the respctive polyacrylamide towards montmorillonite suspensions. These interactions are probably specific and arise from the opposite charge interactions between the hydrolyzed metal ions and polyacrylamide, though hydrogen bonding may also play a part.It appears possibly that the positively charged hydjrolyzed metal ions can act as "anchor points" to attach the negatively charged polyacrylamides to the surfaces of negative charge. The flocculation effect of the polyacrylamide can therefore be enhanced by the increased adsorption, though an excess of "anchor points" might flatten the polyacrylamide and hinder flocculation.

Key words: Flocculation, Sodium montmorillonite, Hydrolyzed polyacrylamide, Polyhydroxyalu-minium chloride