Morphological study of hydrophobic metakaolin hollow fibre membrane for membrane distillation application

Metakaolin hollow fibre membranes (MHFM) prepared by a combined phase inversion and sintering method were proposed for application in direct contact membrane distillation (DCMD). Four kinds of hydrophobic metakaolin hollow fibre membranes (h-MHFM) sintered at different temperatures (1200ºC to 1500ºC) were successfully prepared by grafting 1H,1H,2H,2H-perfluorodecyltriethoxysilane on the MHFM. Prior to the grafting process, hydrolysis with a mixture of ethanol and water with ratio 1:2 was applied for 24 hours. The effectiveness of hydrophobization on each MHFM was assessed using contact angle measurement, scanning electron microscopy (SEM) and 3-point bending. It was found that increasing sintering temperature increased the mechanical strength from 117.6 MPa to 182.3 MPa. Further increment was observed when mofification with FAS was applied. After modification, the contact angle was enhanced up to 120º. In general, membrane prepared at lower sintering temperature of 1200°C exhibited higher DCMD performance with water vapor flux of 17.5 kg/m2h due to sufficient pore size for the vapor to pass through the memrbane structure. It was suugested that this membrane is suitable for any condition of water treatment including heavy metal removal, due to its excellent properties to act in harsh condition and best DCMD performance.