Polymer-enhanced ultrafiltration for heavy metal removal: Influence of chitosan and carboxymethyl cellulose on filtration performances

Reclaiming of wastewaters contaminated by heavy metals has become a major challenge over the last decades. For this reason, nanoporous membrane processes have awaken the interest of industry and local community, and the possible ways to improve their performances has become a priority goal for researchers. Metal removal enhancement by polymer addition is a potential way that is deeply investigated herein on nickel ion rejection with chitosan and carboxymethyl cellulose addition. Due to the vanishing of electrostatic interactions induced by the large amount of salt usually contained in effluents, ion rejection consequently drastically drops. However, it is highlighted that a sufficient addition of polymer (higher than 10(-2) M of monomer unit) can offset this decrease and allow good metal removal, while permeation flux is reduced by increased viscosity. Performances are greatly affected by the pH of the filtered solution whose increase notably improves the metal rejection. Finally, ultrafiltration of an industrial discharge water with and without chitosan enhancement step shows that the rejection increase generated by the polymer addition is very low due to the competing phenomenon between the various species present in the complex mixture. (C) 2017 Elsevier Ltd. All rights reserved.