USE OF POLYELECTROLYTE-ENHANCED ULTRAFILTRATION TO REMOVE CHROMATE FROM WATER

Polyelectrolyte-enhanced ultrafiltration (PEUF) is a process which can be used to remove multivalent ions from water. In PEUF a polyelectrol yte of opposite charge to the target ion is added to the water to bind the ion to be removed. The solution is then treated using ultrafiltra tion with membrane pore sizes small enough to reject the polymer and b ound ion. In this study, chromate (CrO42-) is removed from water using poly(diallyldimethyl ammonium chloride) with an average molecular wei ght of 240K as the polyelectrolyte. In the absence of other added elec trolytes, chromate rejections of up to 99.8% were observed. The presen ce of added NaCl reduces the chromate rejection substantially. A study of the flux of the system yielded a gel concentration of 0.55 M catio nic polyelectrolyte. This high gel concentration and high rejection me an that the ultrafiltration can produce a concentrated, low-volume was te stream, and a purified stream containing chromate at low concentrat ion.