Retention of cadmium ions from aqueous solutions by poly(ammonium acrylate) enhanced ultrafiltration

Cadmium removal from aqueous solution by polyelectrolyte enhanced ultrafiltration (PEUF) with relatively low transmembrane pressure was investigated at varying conditions of polyelectrolyte and cadmium concentrations, transmembrane pressure, ionic strength and pH. The poly(ammonium acrylate), with two average molecular weights (8000 and 15 000 Da) were used as polyelectrolyte. Flux declines during ultrafiltration of polyelectrolyte solutions. An effort has been made to evaluate these resistances independently at different operating conditions. The hydraulic membrane resistance is higher for processing solutions of PAmA8 than solutions of PAmA15. The study of ionic strength effect demonstrates that it decreases the retention of cadmium ions and increases the permeate flux. More than 99% of cadmium was retained for a NaNO3 feed concentration less than 5 × 10−2 mol L−1. The pH effect study on the cadmium recovery revealed a maximum retention around 98% for pH 4.