Synthesis Of Star Cationic Polyacrylamide, Solution Properties Of PAM Flocculants And Application

In this paper, acrylamide (AM) and methacryloyloxyethyl trimethyl ammonium chloride (DMC) copolymerization was initiated by heterogeneous redox initiator system, composed of pentaerythritol together with (NH₄)/₂Sa₂O₈. Star-copolymers (star-P(AM-DMC)) were synthesized and characterized by FTIR and ¹H-NMR. The effect of polymerization condition on synthesis was studied via intrinsic viscosity and cationic degree and it is the same with that of typical free-radical copolymerization. The optimal condition of polymerization for application of flocculants was attained.The flocculation performance of star-P(AM-DMC) in Kaolin suspensions was investigated by light transmission and the effect of molecular weight (intrinsic viscosity) and cationic degree on flocculation efficiency was obtained. It was found that the performance of star-P(AM-DMC) is the best among linear-polyacrylamide (linear-PAM), star-polyacrylamide (star-PAM) , linear-P(AM-DMC) and star-P(AM-DMC) flocculants. Because chains of star-P(AM-DMC) in solutions are extended and bridging function occurs more easily.The flocculation efficiency of parent solutions with different concentrations of linear-PAM, hydroxy aluminium polyacrylamide hybrids (Al(0H)3-PAM) and star-PAM flocculants in Kaolin suspensions were investigated. The results show that the optimal parent solution concentration C_op at which the best efficiency can be attained exist. The values of C_op are independent on the content of solid in suspensions and are inverse proportional to the intrinsic viscosity of flocculants solution. The relationship between C_op and the critical overlap concentration C^* and the dynamic contact concentration C_s was researched and the results show that C_op is a little larger than C^* and much more than C₈. But the real concentration of flocculants in kaolin suspensions is less than C but still larger than the C₈. It indicates that partial inter-chain association of polymer flocculants in parent solutions is good for flocculation and chains contact of polymer flocculants in the kaolin suspensions helps to bridging.kaolin suspensions helps to bridging.The effect of added salt and value of pH on the chain dimension of the chain coil in linear-PAlVK star-P(AM-DMC) and anion-polyacrylamide (HPAM) solutions by viscosity was studied and it shows typical polyelectrolyte domino offect. The flocculation performance of linear-PAM and star-P(AM-DMC) in Kaolin suspensions with added salt of various concentrations or at different pH. It is observed that it goes against flocculation that polymer chains coil extended in parent solutions of flocculants shrink in Kaolin suspension, and the flocculation efficiency is improved because it is good for forming close-grained floe if polymer chains coil shrunk in parent solutions extend in suspensions. The shape of polymer chains in solutions affect on flocculation performance markedly.