Use of Poly electrolyte-Enhanced Ultra filtration to Remove Chromate from Water

Abstract

Poly electrolyte-enhanced ultra filtration (PEUF) is a process which can be used to remove multivalent ions from water. In PEUF a poly electrolyte 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 ultra filtration with membrane pore sizes small enough to reject the polymer and bound ion. In this study, chromate (CrO² ₄ ⁻) is removed from water using poly(diallyldimethyl ammonium chloride) with an average molecular weight of 240K as the poly electrolyte. In the absence of other added electrolytes, chromate rejections of up to 99.8% were observed. The presence of added NaCl reduces the chromate rejection substantially. A study of the flux of the system yielded a gel concentration of 0.55 M cationic poly electrolyte. This high gel concentration and high rejection mean that the ultra filtration can produce a concentrated, low-volume waste stream, and a purified stream containing chromate at low concentration.