Abstract:
Study of chromium removal from chromium plating waste was done by using cationic polyelectrolyte, poly (diallyl dimethyl ammonium chloride) (MWCO > 10 k Daltons) binding to chromate to from polyelectrolyte-chromate complex molecules. Polyelectrolyte enhanced-ultrafitration of chromate give 99.78% rejection when the ratio of polyelectrolyte to chromate is 20:1. Effect of other ions in the waste on the rejection of chromate was studied using synthetic waste. Concentrations of ions studied were 20, 40, and 100 ppm of Cu+2 , Fe+3, Ni+2, and Zn+2 and 1000, 3000, and 600 ppm for Cl-1 No-3, and SO4-2. It is found that Cu+2 and Fe+3 precipitate with chromate while Zn+2 occurs at high concentration but Ni+2 does not precipitate at all concentrations. However, the precipitation do not affect the chromate rejections and permeation times, except the precipitation of ferric chromate. The results of all anions show that the chromate rejections decrease as the concentrations of ions increase. Single or double charges of anions give similar result, however, the double charge of sulfate ion gives longer permeation time. Ultrafiltration of chromate from plating waste was operated in a single run by mixing polyelectrolyte to chromate at a ratio of 20:1 and adding the waste for 4 times. The ultrafiltration of the actual waste does not show precipitation of any ions as occuring in the synthetic waste. Furthermore, 60-77% sulfate, but samllo amount of other ions are retained in the retentate, because the solution is more acidic than the synthetic wast.