Novel thermosensitive flocculanting agent based on pullulan

New thermosensitive polysaccharide (P-g-pNIPAAm) was synthesized by graft-polymerization of p(N-isopropylacrylamide) (pNIPAAm) onto pullulan (P) using Ce(IV) ion as initiator. The grafted polysaccharide was characterized by FT-IR and H-1 NMR spectroscopy and elemental analysis. Its flocculation efficiency was studied in a clay suspension, in comparison with p(NIPAAm) homopolymer, as a function of the polymer dose, temperature and settling time. The thermosensitive polysaccharide could induce clay particle flocculation both below and above the lower critical solution temperature (LCST), but the process was more effective above the LCST. A lower value of the residual turbidity at the optimum polymer dose and a wider flocculation window were recorded at temperature above the LCST. The floc size distribution and surface morphology revealed bigger size flocs when the flocculation was performed above the LCST. The re-dispersion effect was negligible for the flocs obtained in the presence of P-g-pNIPAAm. (C) 2011 Elsevier B.V. All rights reserved.