Nanocarbon-Immobilized Membranes for Separation of Tetrahydrofuran from Water via Membrane Distillation

We present the application of 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 an 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 to 50 °C). All the nanocarbon-immobilized membranes exhibited significantly superior performance compared to an unmodified PTFE membrane. Among the nanocarbons, rGO–CNT performed the best in terms of 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 were due to the preferential sorption of THF on rGO–CNTs (as evident from the contact angle measurements), the nanocapillary effect through graphene sheets, along with the activated diffusion of THF via a frictionless CNT surface.