Direct solar desalination using nano/micro-porous polymeric membrane via thin film evaporation

Thin film evaporation from nanoporous membranes is a promising thermal desalination approach because it utilizes the passive capillary pumping of liquid to the evaporating interface and allows for high heat transfer rates due to the large evaporating area in addition to the capillary pumping driving force. In this study, solar energy was used as a heat source to evaporate seawater through in-house fabricated polyvinylidene fluoride (PVDF) nano/micro-porous membranes incorporated with nanoparticles. Compromising between the available area for evaporation via changing pore size and the available material for conductive transfer of heat to the liquid thin film is complicated and require a deep study experimentally and theoretically. The objectives of this study are to investigate the pore size effect and thermal conductivity on the vapor flux by fabricating fumed silica and carbon nanotube membranes. The fabricated membranes were characterized by scanning electron microscopy, contact angle analyzer (CA), capillary flow porometry and porosity to further under-stand the observed thin film evaporation effects. The preliminary results showed that CNT is an effective nanoparticle to obtain higher vapor flux (18.48903 g/min m^–2) in thin film evaporation that incorporated with solar simulator this is due to good ability of CNT to absorb light and converted to thermal energy. It is recommended to investigate more membranes with deep analysis to achieve the paper objective.