Synthesis of a novel amphoteric chelating polymer flocculant and its performance in Cu2+ removal

A novel amphoteric chelating polymer flocculant (ACPF) was synthesized. The synthesis involved the copolymerization of dimethyldiallylammonium chloride and acrylamide to prepare poly(dimethyldiallylammonium chloride-co-acrylamide) [P(DMDAAC-co-AM)], Mannich reaction of P(DMDAAC-co-AM) with triethylenetetramine and formaldehyde to prepare P(DMDAAC-co-AM)-graft-TETA, and xanthogenation of P(DMDAAC-co-AM)-graft-TETA with CS2 and NaOH. The removal performance of ACPF toward Cu2+ was investigated, and the ACPF structure was characterized. ACPF performance considerably improved at 121187 mL/g intrinsic viscosity, 20.7828.32 mol % cationic degree of P(DMDAAC-co-AM), and 22.1128.44% sulphur content of ACPF. The Cu2+ removal rate was above 99% at a 1.98 : 1 molar ratio of -CSS- to Cu2+. This rate was 5.86% higher than that using polyacrylamide-graft-triethylenetetramine-dithiocarbamate (PAM-graft-TETA-DTC). The zeta potential and sedimentation rate of flocs obtained from ACPF were higher and their volume was smaller than those from sodium triethylenetetramine-multidithiocarbamate and PAM-graft-TETA-DTC at the same sulphur dosage. This result indicates that the positive charges of ACPF polymeric chains effectively neutralize excess negative charges in flocs, which benefits the bridging of flocs with negative charges to promote their formation and growth. These positive charges can also cause the flocs to become larger and tighter, thereby improving flocculation and settling performance. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013