Superhydrophobic electrospun membrane for heavy metals removal by air gap membrane distillation (AGMD)

This paper presents a novel approach to fabricate superhydrophobic membranes by using environmentally friendly and cost effective superhydrophobic nanoparticles to enhance nanofibrous membrane performance in term of flux and rejection of heavy metals in membrane distillation applications. Polyvinylidene fluoride (PVDF) membranes were fabricated using an electrospinning technique, in which electrospinning parameters such as polymer concentration, voltage, solvent ratio, and cationic surfactant were studied to optimize the membrane fibre diameters and produce beadless nanofibrous membranes. The nanofibrous membranes were characterized in terms of pore size, porosity, liquid entry pressure, contact angle, permeate flux and rejection percentage, and were compared to a commercial membrane. Air gap membrane distillation (AGMD) was used to demonstrate the improved ability of superhydrophobic PVDF membranes for removing heavy metals (such as lead) in comparison with pristine and commercial membranes. The results showed that pristine beadless membrane mat can be fabricated by using 15 wt% polymer concentration, 0.05 wt% cationic surfactant with 6:4 DMF to acetone ratio and 14 KV with lead rejection rate of 72.77%, liquid entry pressure (17 psi) and water contact angle of 132°. In comparison, the composite 11 wt% PVDF membranes with 20 wt% of functionalized alumina (Al₂O₃) showed 150° WCA and 27 psi as liquid entry pressure which led to 99.36% of heavy metal rejection and 5.9% increase in permeate flux.