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In this paper, a facile fabrication of enhanced direct contact membrane distillation membrane via immobilization of the hydrophilic graphene oxide (GO) on the permeate side (GOIM-P) of a commercial polypropylene supported polytetrafluoroethylene (PTFE) membrane is presented. The permeate side hydrophilicity of the membrane was modified by immobilizing the GO to facilitate fast condensation and the withdrawal of the permeate water vapors. The water vapor flux was found to be as high as 64.5 kg/m2·h at 80 °C, which is 15% higher than the unmodified membrane at a feed salt concentration of 10,000 ppm. The mass transfer coefficient was observed 6.2 × 10−7 kg/m2·s·Pa at 60 °C and 200 mL/min flow rate in the GOIM-P.

Membrane distillation (MD) is emerging as an important desalination technology that can operate at relatively low temperatures and can handle high salt concentrations. In this Article, we present microwave-induced membrane distillation (MIMD) where microwave radiation is used to heat the saline water for MD. Pure water vapor flux from MIMD was compared to that generated by conventional heating, and the enhancement reached as high as 52%. Because of the higher dielectric constants, flux enhancement was more significant at high salinity, and the mass transfer coefficient at 150 000 ppm was found to be nearly 99% higher than what was observed under conventional heating. Performance enhancement in MIMD was attributed to nonthermal effects such as the generation of nanobubbles, localized superheating, and breaking down of the hydrogen-bonded salt−water clusters. These effects were investigated using FTIR, ion mobility measurements, and dynamic light scattering. In addition, microwave heating consumed nearly 20% less energy to heat water to the same temperature. The combination of energy savings and higher flux represents a significant advancement over the state of the art for MD.

Methyl tert-butyl ether (MTBE) is a widely used gasoline additive that has high water solubility, and is difficult to separate from contaminated ground and surface waters. We present the development in functionalized carbon nanotube-immobilized membranes (CNIM-f) and graphene oxide-immobilized membranes (GOIM) for enhanced separation of MTBE via sweep gas membrane distillation (SGMD). Both types of modified membranes demonstrated high performance in MTBE removal from its aqueous mixture. Among the membranes studied, CNIM-f provided the best performance in terms of flux, removal efficiency, mass transfer coefficients and overall selectivity. The immobilization f-CNTs and GO altered the surface characteristics of the membrane and enhanced partition coefficients, and thus assisted MTBE transport across the membrane. The MTBE flux reached as high as 1.4 kg/m2 h with f-CNTs, which was 22% higher than that of the unmodified PTFE membrane. The maximum MTBE removal using CNIM-f reached 56% at 0.5 wt % of the MTBE in water, and at a temperature of 30 °C. With selectivity as high as 60, MTBE recovery from contaminated water is very viable using these nanocarbon-immobilized membranes.

Membrane distillation (MD) is an emerging technology that has much potential in desalination and treatment of saline waste.