Triple-layer nanofiber membrane with improved energy efficiency for treatment of hypersaline solution via membrane distillation

A new triple-layer, electrospun nanofiber membrane was fabricated in sequential electrospinning steps for enhancing the thermal efficiency of the membrane for desalination of high-salinity solution in a membrane distillation process. The membrane structure is designed to form a Janus structure comprised of two hydrophobic layers made of polyvinylidene fluoride and polystyrene at the top and middle, respectively, and one hydrophilic layer made of polyacrylonitrile at the bottom layer (support). The low thermal conductivity of the polystyrene layer and the Janus structure of the membrane could considerably enhance the flux and thermal performance of the membrane for desalination of hypersaline solution. The experimental results demonstrated that the designed membrane achieved high permeate flux and high energy efficiency compared with single and double-layer membranes when used for treatment of high salinity solution. The results further showed that increasing feedwater salinity dropped the permeate flux of the single-layer membrane by over 50% and reached 10 L/m2h, while for the triple-layer membrane, it just dropped 20% for the feed salinity of 200 g/l. Moreover, the triple-layer membrane showed 20% higher energy efficiency at the same operation conditions. Furthermore, a simulation model was developed and validated via the experimental results to understand the effect of various parameters.