3D imprinted superhydrophobic polyvinylidene fluoride/carbon black membrane for membrane distillation with electrochemical cleaning evaluation

Although membrane distillation (MD) operates efficiently with different types of feed, the membrane could be wetted by synthetic surfactants and natural amphiphiles. In this work, carbon black was used to improve the surface hydrophobicity of the polyvinylidene fluoride (PVDF) membrane produced through 3D imprinting. PVDF membranes blended with 2-5 wt% of carbon black showed PVDF characteristic peaks and interactions with carbon black in Fourier transform infrared spectra. The presence of carbon black in the dope solution caused the length of finger-like voids to reduce but the membrane thickness to increase. The pore size increased by adding 2 or 3 wt% of carbon black. A higher amount of carbon black resulted in reduced pore size and porosity due to pore blockage by carbon black. Nevertheless, carbon black particles increased the surface roughness to form a superhydrophobic surface without using any hydrophobic agent. Although the superhydrophobic PVDF/carbon black membrane showed similar permeate flux to the neat PVDF membrane in MD, it could be electrochemically cleaned within 4 min to restore its permeate flux after wetting by the salt solution containing surfactant. The membrane could be cleaned by hypochlorite (OCl- ) and hypochlorous acid (HOCl) or metal hydroxides pro-duced in electrochemical cleaning.