Experimental Evaluation of Graphene Oxide-Modified Membranes for Enhanced Water Purification and Heavy Metal Separation

Abstract

Contamination of surface and groundwater with heavy metals still stands out as one of the major environmental problems caused by effluent discharge from industries, mining operations and inadequate wastewater treatment. The use of polymeric membranes can help in the purification of water but their efficiency has been hindered by poor hydrophilicity, fouling and poor selectivity towards metal ions dissolved in the water. In this research work, the effect of polyethersulfone (PES) membranes coated with varying amounts of graphene oxide (GO) (0, 0.1, 0.25, 0.5 and 1.0 wt%) on water purification and separation of heavy metals has been experimentally assessed. The graphene oxide has been prepared using a modified Hummers process and then embedded in the polymeric matrix by non-solvent induced phase inversion technique. The most promising results were obtained using the 0.5 wt% GO modified membrane; the water contact angle was decreased from 78° to 58° and the pure water flux was increased from 42 to 95 L m⁻² h⁻¹ bar⁻¹. The removal of Pb²⁺ ions reached 94.5%, whereas the control PES membrane showed only 48.0% rejection of this ion. The membrane exhibited the enhanced fouling resistance and maintained the rejection level of 83.7% after five successive filtration cycles. These results suggest that GO modification could be used for the enhancement of embrane permeability and efficiency at the same time.