Synthesis and characterization of porous reduced graphene oxide based geopolymeric membrane with titanium dioxide coating for forward osmosis application

Abstract

Forward Osmosis (FO) is a promising separation technology with a wide range of applications in water and wastewater treatment. FO membrane is the core of the forward osmosis process. Recently, the organic membrane has been widely used for forward osmosis applications even though inorganic membrane has excellent mechanical properties, decent chemical resistance, high durability, high porosity, and good hydrophilicity. Nevertheless, the utilization of inorganic membrane is hindered by the heat-intensive steps involved in its fabrication and the use of expensive source material. Geopolymerization provides a cost-effective technique for the preparation of inorganic membranes because of its sintering-free steps and utilization of fly ash as source material. Herein, we present a sintering-free, environmentally friendly, and cost-effective synthesis of geopolymeric membrane for application in forward osmosis. Fly ash was mixed with alkaline activator solution and porous reduced graphene oxide (PRGO) to prepare geopolymer slurry. The hydrogen peroxide and egg albumen were used as foaming agent and surfactant, while the membrane surface was coated with titanium dioxide to enhance the hydrophilicity of the membrane surface. The PRGO content improved the mechanical properties of the geopolymeric membrane. The average maximum flux recorded was 21 L/m2 h with geopolymer substrate having a pore size of 1.8 μm and hydrophilic coated layer pore size of 0.25 μm. The varying concentrations of PRGO control the substrate's mechanical properties and pore size, as well as provide new insights for future studies. These preliminary results show that low-cost geopolymer material is a promising candidate for FO membrane fabrication.