Cetyltrimethylammonium bromide–silica membrane for seawater desalination through pervaporation

A simple preparation of mesostructured cetyltrimethylammonium bromide (CTAB)–silica membrane is reported. It effectively desalinates seawater to pure water through pervaporation separation process. The membrane thickness was of nanometer-length-scale obtained by deposition of CTAB–silica colloids on porous polysulfone support. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies were performed to characterize the membrane while the structure of the colloids in coating solution was probed by small-angle neutron scattering (SANS). The prepared membranes exhibited excellent salt rejection efficiency of 99.9% in desalination of synthetic seawater of 40,000 ppm NaCl by pervaporation at 25∘C. The pure water flux was in the range of 1–2.6 kg m−2 h depending upon the membrane configuration and thickness. The flux could be greatly enhanced by operating the process at higher temperatures of 40–80∘C but it was at the cost of decreased salt-rejection efficiency. The initial rejection efficiency and flux of the membrane was found to be restored upon cooling the membrane back to room temperature.