Substantially improved antifouling properties in electro-oxidative graphene laminate forward osmosis membrane

Abstract

Emerging forward osmosis (FO) technology has recently shown a great potential in water desalination and energy production. Taking advantage of electro-conductive graphene nanosheets, herein, a novel in-situ electro-oxidative approach has been proposed to alleviate organic fouling in FO membranes. A thin layer of nano-structured graphene was deposited onto the polyethersulfone support layer to fabricate graphene laminate membrane (GLM). The selectivity ratios (water flux/reverse salt flux) of GLM were experimentally assessed to be 1.48L/g and 1.44L/g in active layer facing feed solution (ALF) and active layer facing draw solution (ALD) configurations, respectively. Being employed in the FO process to treat synthetic wastewater containing 500ppm sodium alginate, the fabricated GLM demonstrated an excellent antifouling properties when 2V DC potential was imposed on its surface. To verify the improved properties of the developed membrane, fouling behavior of the GLM was compared to that of typical FO thin film composite membrane. Under electrical potential, the flux recovery ratio was significantly increased from 75.4% for thin film composite (TFC) membrane to 98.7% for the GLM, implying superior antifouling performance of the developed membrane. Direct and indirect electro-oxidation reactions at anode, oxygen bubbling effect, as well as the electrostatic repulsive interactions between GLM surface and calcium cations (bridging agent) were suggested as possible reasons for such improved GLM antifouling propensity.