Mechanism responsible for flocculation in poly (n-isopropylacrylamide) temperature responsive dewatering-attractive interaction forces induced by surface hydrophobicity

Abstract

Temperature responsive polymers such as Poly (N-isopropylacrylamide) (PNIPAM) have been shown to have potential to improve water recovery from mineral tailings by using the polymer as a flocculant at temperature above the lower critical solution temperature (LCST 32°C) and then as a consolidation aid at temperature below the LCST. The mechanism for the flocculation (at high temperature) is shown to be hydrophobic and the mechanism for the repulsion (at low temperature) is shown to be steric repulsion. The contact angle between water and air on PNIPAM covered silica glass surfaces increases with increasing temperature and increases with increasing polymer molecular weight. Atomic force micros..