Influence of aspartic acid functionalized graphene oxide presence in polyvinylchloride mixed matrix membranes on chromium removal from aqueous feed containing humic acid

Abstract

Incorporation of adsorbent nanomaterials into the membrane matrix has the dual function of membrane filtration and adsorption. In this study, aspartic acid (Asp) functionalized graphene oxide (GO) nanolayers with the ability of adsorption and also regeneration possibility was synthesized and used to fabricate polyvinylchloride (PVC) nanocomposite membranes. The physicochemical properties of resultant membranes were evaluated with a series of analyses. An aqueous feed containing both chromium (Cr) and humic acid (HA) was used for operational testing. Also, the effects of their electrostatic interaction on membrane fouling and cleaning were investigated. The bridging effect of Cr cation between HA molecules as an electrostatic interaction led to formation of large size HA-Cr complexes and consequently increasing the Cr removal using membrane filtration. According to the results of zeta potential, Asp functionalized GO (GO-Asp) had a significant effect on the membranes negative charge and could change the -8.72 mV zeta potential of neat PVC to -33.17 mV. Among the samples, GO-Asp embedded membrane showed the best performance of membrane flux, Cr removal and also, fouling resistance during five filtration and regeneration cycles due to its desirable properties in terms of both filtration and adsorption. In addition, the tensile strength and elongation of the membranes increased from 4.66 MPa and 25.27 % to 5.75 MPa and 38.86 %, in the presence of GO-Asp nanolayers.