Study of Cr(III) desorption process from a water-soluble polymer by ultrafiltration Original Research Article

Polymer Enhanced Ultrafiltration (PEUF) has been reported as a suitable process to separate heavy metals from pollutant wastewaters. Desorption of metal ion is a required step in order to recycle the polymer. At acidic pH values, nearly quantitative desorption has been achieved for divalent ions but a limited efficiency has been reached for trivalent ions. This paper studies the Cr(III) desorption yield from ethoxylated polyethylenimine (EPEI) by means of an ultrafiltration ceramic membrane. Experimental results show that about only 20% of the chromium (III) remains adsorbed at pH 1. The feasibility of several sorption isotherms (Langmuir, Freundlich, Redlich–Peterson and Temkin) was tested to describe the binding of chromium (III) and EPEI and the Freundlich one showed the best fits with experimental data at all pH values. Further, it was observed that normalized permeate fluxes decreased as initial Cr(III) concentration and pH were higher. Membrane fouling was analyzed by long–term experiments at different pHs which indicate that the intermediate pore blocking was the main mechanism of fouling.