Preparation of ultra-thin poly(vinyl alcohol) membranes supported on polysulfone hollow fiber and their application for production of pure water from seawater

• Very thin poly(vinyl alcohol) membranes supported on polysulfone hollow fiber • A controlled coating method for top membrane layer of uniform thickness • Composite hollow fiber membranes having top-layer-thickness of 0.1–1 μm • Best membrane performance so far in pervaporation desalination of saline water

The preparation and characterization of thin poly(vinyl alcohol) (PVA) membranes of nanometer-scale thickness (100–1000 nm) supported on polysulfone hollow fiber is reported here. The uniformly thin membrane coating over the cylindrical hollow fiber support was possible by using an automatic dip coating method in which sorption of the coating solution on the support and subsequently evaporation of the coating solution from the support was controlled. The composite hollow-fiber membrane, among all the reported hollow membranes so far, exhibited the best performance in pervaporation desalination of saline water. The thickest PVA membrane produced water of the lowest conductance value ~20 μS/cm while the thinnest membrane exhibited the highest water flux of 7.4 L/m2/h from the feed water of 30,000 ppm NaCl at 344 K. The apparent activation energy calculated based on the volume flux of the desalination process for the composite membranes was about 23.07–25.80 kJ/mol which corroborated with the value of other membrane systems.