Solar membrane distillation enhancement through thermal concentration

Membrane distillation (MD) has great potential as a desalination technology because of its good compatibility with other technologies. However, its low efficiency and large energy consumption impede applications due to the temperature polarization effect. Herein, we describe solar membrane distillation (SMD) using a photothermal membrane with thermal concentration that could overcome this problem. A superhydrophobic polydimethylsiloxane/multiwalled carbon nanotube/poly (vinylidene fluoride) (PDMS/MWCNT/PVDF) composite membrane with excellent light capture and photothermal conversion abilities was prepared for the SMD process. The photothermal conversion ability and solar membrane performance were experimentally evaluated, while the enhancement process was investigated by sim-ulations. It was found that this enhancement is due to the higher temperature near the membrane resulting from thermal concentration and localized heating effects. Notably, using a two-level thermal concentration method in a larger SMD module would realize additional desalination performance, and fresh water productivity could reach about 1.1 kg m(-2) h(-1). Using solar energy and benefitting from the thermal concentration effect, our designed SMD system could produce fresh water at a rate of 0.65 kg m(-2) h(-1) from 3.5 wt% salt water, with an energy consumption of pure solar energy of about 1 kW m(-2). This represents a significant improvement over the conventional SMD process. Combining the SMD technology with a renewable energy source would further reduce the cost and energy consumption, and promote its industrial application. (C) 2020 Elsevier Ltd. All rights reserved.