Polymer enhanced membrane filtration of metals: retention of single and mixed species of metal ions based on adsorption isotherms

Abstract

The binding and retention of single metal ions and mixtures of metal ions with polyethylenimine (PEI) was studied using polymer enhanced ultrafiltration (PEUF). Using a highly branched chain form of PEI (Sigma Aldrich 181979) with an average molecular weight 750,000 and approximately 60,000, ultrafiltration experiments were carried out in the stirred dead-end ultrafiltration mode. The results of the binding studies show that the Langmuir isotherm offers a good description of the binding process. At pH 5.5, the maximum polymer binding (Q max) and binding affinity constant (K L) were determined according to Langmuir isotherms. It was observed that the maximum amount of metal ions bound to the polymer for Cu2+, Zn2+, Ni2+ and Cd2+ decreased substantially in solutions containing mixtures of metal ions when compared to the values obtained for single metal ion solutions. For Cr6+ and Co2+ no significant decrease was seen. These data indicate that the binding capacity of Cr6+ and Co2+ remain constant in competit...