The influence of molecular weight (MW) and dose of Poly(N-isopropyl acrylamide) (PNIPAM) (temperature-sensitive flocculant) on sedimentation rate, sediment density, and supernatant clarity of silica suspensions was investigated. The addition of PNI-PAM resulted in rapid sedimentation (T > critical solution temperature. CST) and low sediment moisture (T < CST). Higher MW polymers resulted in more effective flocculation and sediment conslidation. At 10 ppm. PNIPAM (3.6 million Da) produced 20 m/h settling rate and 48 vol % solids sediment density, whereas 0.23 million Da polymer produced 0.1 m/h settling rate. PNIPAM produces effective flocculation and consolidation by cyclcing the interparticle interactions between repulsion and attraction as temperature is cycled around the CST. The change in temperature produces a hydrophilic/hydrophobic transition of the polymer, influencing adsorption onto the surface and the inter-particle forces. Conventional polyacrylamide flocculants (not influenced) by temperature), cannot be used to produce both rapid sedimentation and dense sediments. (C) 2009 American Institute of Chemical Engineers AIChE J. 55: 2070-2080, 2009