Flocculation and compaction of highly concentrated suspension by using thermosensitive polymers

Flocculation and compaction of a highly concentrated suspension by using th e thermosensitive polymers which show a hydrophilic/hydrophobic transition by healing their aqueous solutions is examined. Poly (N-isopropylacrylamide ) (polyNIPAM) and the copolymers of N-isopropylacrylamide and acrylamide (p olyNIPAM-co-AAM) were synthesized as thermosensitive polymers. Kaolin suspe nsions of 125 kg/m(3 similar to)375 kg/m(3) were used, and flocculation and compaction were performed by the plunger test. A polymer solution of the d esired concentration was mixed with Kaolin suspension at a temperature belo w the transition temperature of polymer to adsorb the polymer on the surfac e of kaolin particles. Then, the mixture was transferred to a cylinder imme rsed in a water bath heated above the transition temperature of the polymer . The plunger was thrust into the mixture at a constant speed. Even if the adsorbed polymer transformed into a hydrophobic polymer by heating above th e transition temperature, the formation of flocs was observed, and the comp action was occurred by dosing the polymer exceeding 0.006 kg/kg-kaolin. Slu dge bulkiness. which describes the volumetric proportion of sludge and soli d, reaches almost 3 at a polymer dosage of 0.03 kg/kg kaolin, and it was di fficult tu thrust the plunger into the sludge any more. Such phenomena of f locculation and/or compaction are explained by the hydrophobic interaction of thermosensitive polymer.