Montmorillonite clay-based membrane distillation for seawater desalination

Abstract

According to the World Health Organization (WHO), water shortage affects more than 66% of the world population. Seawater membrane distillation (MD) is one of the promising ways to solve water scarcity. Montmorillonite is the least explored low cost clay with unique properties that can act as an alternative material in membrane fabrication. This research focused on the development of hydrophobic montmorillonite clay-based hollow fibre MD for seawater desalination. The membranes with three different weight percentages of ceramic loading (36 wt. %, 38 wt. %, and 40 wt. %) were produced via phase inversion technique at a constant air gap distance and bore fluid flow rate before sintered at the temperatures of 1100, 1200, and 1300 °C. The clay hydrophilicity nature was transformed into hydrophobic property by surface modification through dip-coating with 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane solution. The physical and chemical properties of the prepared membranes were characterised using several analyses, including morphologies, mechanical stabilities, water permeability and hydrophobicity. The membrane performance was further evaluated using membrane distillation test with different concentrations of sodium chloride (NaCl) solution varied from 10,000 to 40,000 ppm and different feed temperatures varied from 50 to 80 °C under a steady condition of 20 °C permeate temperature at 1 atm. The characterization had shown that this material is equipped with the qualities to produce good clay-based hollow fibre MD for seawater desalination. The results also showed that the best performing membrane was spun at 40 wt. % ceramic loading, 5 cm air gap, 9 ml/min extrusion rate, 10 ml/min bore fluid flow rate and sintered at 1200 °C. The hydrophobic surface modification had been successfully proven by the results of the contact angle at the average of 132°. The salt rejection performance demonstrated that the montmorillonite clay-based hollow fibre membrane achieved 95% rejection. The outcome of this study is a novel and beneficial approach, especially in term of material selection, fabrication technique, and the performance in removing salt from seawater to produce fresh water.