The main hindrance for industrial success of membrane distillation (MD) is the availability of optimized design of MD membrane that can produce high surface hydrophobicity, high porosity, appropriate pore sizes and a higher flux. In the past few years, application of electrospun nanofiber has gained intensive attention for MD membrane and exhibit so far promising results. The aim of this study was to fabricate and optimize of polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP) electrospun nanofiber membranes. The correlation of entanglement concentration (Ce) of PVDF-HFP solution and its electrospinnability was investigated to determine the proper concentration rang for formation of bead-free and uniform PVDF-HFP fiber. Response surface methodology (RSM) based on Box-Benkhen design was employe to developed quantitative models to facilitate a more systematic understanding of the electrospinning parameters which enable the optimization of PVDF-HFP electrospun nanofiber membrane. The effective variables studied include solution concentration, the distance between needle tip and collector, feed rate and voltage. The objective was to prepare optimized electrospun nanofiber membrane with pore size in the range of 300-500nm, narrow pore size dispersion, maximum porosity and hydrophpbosity. Scanning electron microscopy (SEM), geniometer,gravimetric methodand air gap MD (AGMD) setup were used to characterize the resultant nanofiber PVDF-HFP membranes. The obtained optimal point was located in the valid region and the experimental confirmation tests were conducted showing a good compatibility between the predicted optimal points and the experimental ones. The optimum electrospinning conditions were obtained to be 23wt%concentration, 13 kV voltages, 24 cm tips to collector distance and polymer 0.4 mL/h flow rate. At the optimal operating condition the fabricated membranes were characterized with mean pore size, porosity and contact angle of 435 nm, 81% and 141 0 , respectively. The synthesized membrane was applied in desalination via air gap membrane distillation, in which a water flux of 13.6 Lh -1 m -2 with a salt rejection ratio of 99.7% was obtained. Keywords: Membrane distillation, Electrospun membrane, Response surface methodology, Box-Benkhen design, Polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP), Nanofiber membranes, Optimization
