Photothermal dual-layer hydrophilic/hydrophobic composite nanofibrous membrane for efficient solar-driven membrane distillation

Solar-driven membrane distillation (SDMD) had shown greater potential for desalination due to low energy consumption and convenient energy source compared to traditional membrane distillation. In this study, an innovative photothermal dual-layer hydrophilic/hydrophobic composite nanofibrous membrane consisting of polyacrylonitrile (PAN) nanofibrous membrane embedded with silver nanoparticles (Ag NPs) as hydrophilic layer and polyvinylidene fluoride (PVDF) nanofibrous membrane modified by polydimethylsiloxane (PDMS) as hydrophobic layer was constructed to be applied for efficient SDMD in desalination field. The photothermal particles loaded in the hydrophilic layer not only avoided clogging of the pores of the hydrophobic layer but also could be wetted completely to fully heat the feed fluid for achieving great photothermal conversion efficiency while the porous hydrophobic layer could prevent leakage of salt solute to attain high retention and vapor flux. Hence, the optimized composite nanofibrous membrane exhibited a high flux of 1.2 kg/m2/h with energy conversion efficiency of 75.2% and stable permeate conductivity (2.5 μs/cm) during 10 h SDMD test period (3.5 wt% NaCl salt feed) under 1 kw/m2 solar irradiation. Therefore, the photothermal dual-layer hydrophilic/hydrophobic composite nanofibrous membrane had promising application for desalination and provide a valuable inspiration in the development of membranes for membrane distillation.