Consolidation of suspended particles by using dual ionic thermosensitive polymers with incorporated a hydrophobic component

Abstract

The flocculation/consolidation of suspended particles using the hydrophobic transition of a thermosensitive polymer is a promising method for sludge dewatering. However, flocculation/consolidation using thermosensitive polymers requires heating of the suspension. Furthermore, although ionic thermosensitive polymers are usually effective for flocculation/consolidation of charged suspended particles, the transition temperature increases when the ionic component is incorporated into the thermosensitive polymer. To alleviate this problem, we proposed the use of dual ionic (i.e. cationic and anionic) thermosensitive polymers. The use of an anionic thermosensitive polymer in combination with a cationic thermosensitive polymer resulted in the formation of a polymer complex. As a result, the transition temperature of the polymer molecules adsorbed on the suspended particles decreased. However, heating of the sludge was still required. In this work, a hydrophobic component was incorporated into the ionic thermosensitive polymers to decrease the transition temperature, and the consolidation of suspended particles using these dual ionic thermosensitive polymers was examined. N-isopropylacrylamide, N,N-dimethylaminopropyl acrylamide, acrylic acid, and N-tert-butylacrylamide (BAAM) were used as the thermosensitive, cationic, anionic, and hydrophobic components, respectively. By incorporating BAAM into either cationic or anionic thermosensitive polymers, the transition temperature of these ionic thermosensitive polymers decreased. The consolidation of kaolin suspension was observed near room temperature by adding the anionic polymer with the incorporated BAAM in combination with the cationic polymer.