Nonfouling Coatings for Thin Film Composite Membranes

摘要

Polymers containing sulfonate groups were synthesized and evaluated as fouling-resistant coatings for reverse osmosis membranes. The FilmTec FT-30 membrane was used as the substrate. Best results were obtained with a coating of poly(sodium stryenesulfonate-co-chloromethyl-styrene) crosslinked with an acid catalyst. In laboratory tests with feedwaters containing tannic acid, this coating showed much lower fouling rates compared with uncoated FT-30 controls. However, initial membrane fluxes were also lowered considerably just by the act of applying this coating, so that comparative fluxes of the final fouled membranes were not particularly different. For example, using a standardized test condition (200 psi, 25C, 0.2 percent sodium chloride feed containing 500 ppm tannic acid, pH 7 adjusted with phosphoric acid, 18 hour test), uncoated FT-30 controls exhibited a typical initial flux of 15 gfd and final flux of 5.5 gfd; coated membranes showed a typical initial flux of 11 gfd and a final flux of 6.0 gfd.