Removal of chromate ions from water using the polyelectrolyte-enhanced ultrafiltration process

Polysulfone (PSf) asymmetric hollow fiber membranes with the molecular weight cut-off (MWCO) of 13,000 Dalton were prepared by the dry-wet phase inversion method, with which negatively charged chromate ions, CrO42- was removed form aqueous solutions using the polyelectrolyte-enhanced ultrafiltration (PEUF) process. Parameters relating to the chromate removal such as the type of Polyelectrolyte, the loading ratio, and the pH value of the aqueous solution were studied. Poly (dially dimethylammonium chloride) (PDADMAC) was found to be the most effective polyelectrolyte. Under the optimal conditions, that is, the polyelectrolyte-metal loading ratio of 20 and the pH value 8.0 respectively, up to 100% of the chromate rejection was achieved. The used polyelectrolyte may be recovered about 70% by the acidified decomplexation combined with ultrafiltration. The concentration polarization was present but imposed limited effect on the PEUF process in the long-term operation.