Feasibility study on the recovery of chromium (III) by polymer enhanced ultrafiltration

The viability of recovering chromium (III) was studied by polymer enhanced ultrafiltration (PEUF) and its application to tannery wastewater treatment. Four polymers with different functional group, molecular weight and acid–basic equilibrium were tested at 40 and 60 °C in order to investigate the complexation and decomplexation of chromium (III) ions on the polymer chains: polyvinyl alcohol (PVA), polyacrylic acid-co-maleic acid (PACM), polyethylenimine (PEI) and ethoxylated polyethylenimine (EPEI). The reversibility of the polymer metal binding was studied by operating in a dead-end PEUF system. The best chromium (III) rejections for both reactions were obtained by EPEI. The feasibility of recovering chromium (III) with EPEI was also studied in a cross-flow PEUF system. Chromium ions were complexed by EPEI chains at pH = 5 and decomplexed at pH = 1. Membrane fouling due to conformational variations of EPEI was observed at high ionic strengths.