Functionalized graphene-based ultrafiltration and thin-film composite nanofiltration membranes for arsenic, chromium, and fluoride removal from simulated groundwater: Mechanism and effect of pH

Groundwater contaminant removal using ultrafiltration (UF) and nanofiltration (NF) membranes is complex due to limitations such as low selectivity-permeability and membrane fouling tendency. In this study, we fabricated a thin film composite (TFC) membrane over a highly permeable mixed matrix support UF membrane using sulfonic acid functionalized graphene oxide (SGO) and polyethersulfone (PES) for groundwater remediation application. The pure water permeability of the PES-SGO-TFC membrane was threefold (3.09 LMH bar(-1)) compared to the pristine PES-TFC membrane. The membrane showed excellent organic fouling resistance with more than 95% flux recovery. The salts and contaminant removal were checked in a cross-flow mode to understand a more practical approach to the applicability of the developed PES-SGO-TFC membrane. The membrane rejected Cr(VI), As(V), and fluoride to the extent of similar to 89%, similar to 99%, and similar to 77%, respectively, at pH similar to 7. The membrane separation performance varied as a function of pH, with more than 90% removal for monovalent fluoride at higher pH values. In a simulated groundwater matrix, the membrane demonstrated promising results for rejecting these ions. However, the simultaneous rejection of As(V) and fluoride may be impacted by interfering co-ions. This study offers a novel approach for developing highly permeable support UF-modified TFC membranes for better separation for groundwater remediation.