Abstract
In the cross-flow ultrafiltration, effects of clay on the fouling due to organic substance were evaluated by fouling model materials and clay. Fouling model materials selected were BSA (Bovin serum albumin, MW68,000), Dextran (MW70,000), and humic acid (MW8,000-200,000) for larger size than molecular weight cut-off (MWCO50,000, polysulfone) and α-lactalbumin, Dextran (MW9,300) fulvic acid (MW8,000) for smaller size than that, and kaolin was selected as a clay material. The fluxes of BSA and Dextran (MW70,000) increased with an increase in the amount of kaolin, while the flux of α-lactalbumin, Dextran (MW9,300) did not increase with kaolin. The kaolin affected the flux decreased mainly more by adsorption and deposition (gel layer) on to the membrane surface than by the flux decline due to adsorption to the pore interior, but did not affect the flux decline that occurs by organic substance through the membrane pore. In contrast, the flux of humic substances decreased with an increase in the quantity of kaolin. The wasing recovery of flux with coexistence of kaolin was greater than that of fouling model material solution without kaolin.
