Optimization of Graft Polymerization and Performance of Carboxymethyl Chitosan / Polyacrylamide Flocculants

Abstract

In this study, amphoteric graft copolymer-based flocculants were prepared by conventional peroxy graft copolymerization of acrylamide (AM) onto carboxymethyl chitosan (CMCH) using potassium persulphate (PPS) initiator. The optimization of grafting of AM onto CMCH was carried out by studying the influence of various process parameters including CMCH, acrylamide and PPS concentration, as well as reaction temperature and time on percent grafting. FTIR spectral and thermal analyses of polyacrylamide/carboxymethyl chitosan graft copolymer (CMCH-g-PAM) were studied to furnish evidence of grafting. By performing the grafting process via reacting carboxymethyl chitosan (2%), acrylamide (6%) in presence of PPS (0.1%), highest grafting percentage was found at reaction temperature of 55 ⁰C with reaction time of three hours. The flocculation of the kaolinite suspensions was investigated by studying the effect of CMCH-g-PAM dosage, treatment time and pH of suspensions. The graft co-polymer flocculants resultant in this study exhibited higher efficiency comparing with those obtained from homo-polymers of carboxymethyl chitosan or polyacrylamide. Furthermore, the flocculation efficiency of these grafted copolymers was significantly increased with increasing the grafting percentage, where the maximum efficiency (93%) was attained at the highest grafting percentage (146%).