Hydrophobic porous alumina hollow fiber for water desalination via membrane distillation process

► Hydrophobic porous alumina hollow fiber has been prepared. ► The hollow fiber can separate pure water from NaCl solution at a fast rate. ► The hollow fiber holds promise for membrane distillation desalination applications. This paper reports the development of hydrophobic porous alumina ceramic hollow fiber membranes for water desalination based on the membrane distillation process. The alumina hollow fiber with an average pore size of 0.7μm was prepared by the phase inversion and sintering method. The surface of the hollow fiber was converted from hydrophilic to hydrophobic via grafting with fluoroalkylsilane (FAS). The water desalination performance of the as-prepared hydrophobic hollow fiber was tested using the vacuum membrane distillation method. By exposing the shell side of the fiber to an aqueous solution of 4wt% NaCl at 80°C and vacuuming the lumen side of the fiber to a pressure of 0.04bar, a water flux of 42.9Lm−2h−1 was attained with a salt rejection over 99.5%, which is comparable with the best performance of polymer membrane. The water flux and salt rejection was found to decrease slowly with time, but after water washing–drying the rejection was recovered completely, and the water flux largely. The hydrophobic ceramic hollow fiber membrane developed in this work is promising for practical applications.