(159m) Graphene Oxide-Carbon Nanotube Hybrid Membranes for Organic Solvent Separation Using Membrane Distillation

Energy requirements and carbon foot print of current solvent recycling and recovery processes tend to be expensive, and the incineration of the solvents for waste disposal produces toxic air emissions. Tetrahydrofuran (THF) is an important volatile intermediate which is widely used in organic synthesis and its separation from water is encountered in chemical and pharmaceutical industries. We present the application of hybrid nanocarbon immobilized membranes for the separation and recovery of tetrahydrofuran (THF) from water via membrane distillation. Several nanocarbons, namely carbon nanotubes (CNTs), graphene oxide (GO), reduced graphene oxide (rGO) and rGO-CNT hybrid were immobilized on PTFE membranes. Membrane distillation was carried out in sweep gas mode (SGMD) to study the separation efficiency at relatively low temperatures (25°C to 50°C). All the nanocarbon immobilized membranes exhibited significantly superior performance compared to an unmodified PTFE membrane. Among the nanocarbons, rGO-CNT showed the highest flux and separation factor followed by the CNTs. The rGO-CNT represented an enhancement of 101% in flux, 181.78% in selectivity and 225% in mass transfer coefficient over the plain PTFE membrane for water containing 5% THF by weight and at 40°C. The improved membrane performances of the rGO-CNT membrane was attributed to the preferential sorption of THF on rGO-CNTs, nanocapillary effect through graphene sheets where rGO layers acted as selective sieves along with activated diffusion of THF via frictionless CNT surface.