DETERIORATION OF CELLULOSE-ACETATE BY TRANSITION-METAL SALTS IN AQUEOUS CHLORINE

In pH 7 buffered hypochlorite solutions, a rapid deterioration of cellulose acetate occurs with certain transition metal salts. The determined average molecular weight (M(W)) value of polymer derived from size exclusion chromatography analysis was used to measure deterioration. The elements chromium, cobalt, ruthenium, palladium, silver, and osmium increased the rate of attack on the polymer. Twenty-two other elements had no effect. Because cellulose acetate is the polymer for many desalting membranes, this study should be of interest to the desalting industry. Elemental analyses of sediments expected to accumulate on cellulose acetate desalting membranes were performed. This information suggests that either chromium or cobalt salts on the membranes may be pernicious to service life. Chromium and cobalt salts may accumulate on membranes by the corrosion of stainless steel feed piping during shutdown periods.