Flocculation of Kaolinite Suspension with Water-soluble Cellulose-Acrylamide Graft Copolymers

Abstract

Acrylamide (AM) was graft-copolymerized onto hydroxyethyl cellulose (HEC) whose molecular chains are rigid and whose extension in an aqueous solution is large. The HEC-AM graft copolymers were isolated from the polymerization products in terms of fractional precipitation. The flocculation ability of the graft copolymers toward kaolinite suspensions and the intrinsic viscosity C which is concerned with its extension in an aqueous solution were compared with those of polyacrylamide (PAM) which are now widely used as the macromolecular flocculants. The following results were obtained: 1 The flocculation ability of the graft copolymers was scarcely affected by a small number of the grafted PAM per one HEC molecule.2 The influence of pH-values and temperature on the flocculation was less with the graft copolymers than with PAM.3 The flocculation ability of the graft copoylmers increased with increasing molecular weight of the grafted PAM and more depended on the molecular weight than on the degree of grafting.4 When the molecular weight of the grafted PAM was nearly equal to that of PAM, the flocculation ability of the copolymers was nearly equal to or superior to that of PAM.5 As 77 3-values of the graft copolymers were larger than those of PAM, the extension of the copolymers in an aqueous solution _would be larger than that of PAM, when the molecular weight (Ma) of the cdpolymers was equal to that pf PAM. This would facilitate the bridging of kaolin particles by the flocculants and would he one of the reason why the flocculation ability of the graft copolymers was superior to that of PAM.