DEMONSTRATION OF SOLID-LIQUID SEPARATIONS USING RECYCLED SUPERNATANT THAT CONTAINS TEMPERATURE-RESPONSIVE POLYMER

摘要

The effective use of recycled supernatant that contains temperature-responsive flocculant isrndemonstrated for solid-liquid separations. The recyclability of poly(N-isopropylacrylamide)rn(PNIPAM) of several different molecular weights and a 15 per cent negatively charged derivative arerncompared. Batch settling tests of α-alumina suspensions are first conducted at 50℃, with a subsequentrn25℃ period, after which the supernatant is harvested and used to flocculate subsequent suspensions.rnUsing this procedure consecutive separations are obtained with the repeated recycling of unchargedrnPNIPAM containing supernatant. Batch settling tests indicate that hindered settling rates increasernwith molecular weight of PNIPAM. Adsorption studies indicate that strong adsorption of PNIPAMrnonto alumina occurs with PNIPAM at 50℃ and that significant desorption occurs after cooling atrn25℃. However, the extent of desorption decreases with molecular weight resulting in low amounts ofrnPNIPAM for recycling and poor settling behaviour when high molecular weight PNIPAM is recycled.rnLittle recyclability was evident using the negatively charged PNIPAM. On the basis of these findings arnrecycling-thickener apparatus that uses low molecular weight uncharged PNIPAM is proposed.