A novel profiled core–shell nanofibrous membrane for wastewater treatment by direct contact membrane distillation†
Inspired by the profiled structure of polar bear hair that possesses excellent thermal insulation properties, a novel profiled polyacrylonitrile-polystyrene (PAN-PS) core–shell nanofibrous membrane with peculiar groove structures and excellent direct contact membrane distillation (DCMD) performance was designed and manufactured by using an eccentric-axial electrospinning technique. Fiber surface morphology analyses indicated the major contributing role of applied voltage and the shell feeding rate in determining the stability of the electrospinning fluid jet, groove length and width, and membrane structural characteristics. The superhydrophobic properties resulting from the surface hierarchical roughness, prominent void volume fraction, fabulous gas permeability, appropriate mean flow pore (MFP) size and relatively considerable liquid entry pressure of water (LEPw) of the free-standing electrospun nanofibrous membranes (ENMs) could completely satisfy the requirements of the MD process. The resultant choreographed PAN-PS core–shell ENMs with a delicate groove morphology presented an outstanding permeate flux of 60.1 kg m−2 h−1 and high quality water permeate (20 g L−1 NaCl and 1000 ppm Sunset Yellow FCF aqueous solution as feed, ΔT = 40 °C) over a DCMD test period of 36 h without detection of membrane pore wetting. This result was better than those of typical commercial PVDF membranes and exhibited considerable competitiveness as compared with the well-designed ENMs reported so far, suggesting the grooved PAN-PS core–shell ENMs as promising alternatives for MD applications.