Surface modification of nanostructured ceramic membranes for direct contact membrane distillation

The objective of this research was to evaluate a select number of promising surface treatments for making ceramic membranes hydrophobic and suitable for application in direct contact membrane distillation (DCMD). Alumina anodisc™ membranes were made hydrophobic through surface treatments that utilized perfluorodecyltriethoxysilane, trimethylchlorosilane, or trichloromethylsilane. The effectiveness of each surface treatment in modifying the membrane surface chemistry was assessed using contact angle measurements with water, scanning electron microscopy (SEM), infrared adsorption, and atomic force microscopy (AFM). Contact angle measurements with water showed that both perfluorodecyltriethoxysilane and trichloromethylsilane produced membrane surfaces with sufficiently high hydrophobicity and thus, suitably high pore entry pressures, for application of the membranes in DCMD. The perfluorodecyltriethoxysilane treated anodisc™ had a higher steady-state water flux than the trimethylchlorosilane treated anodisc™. Furthermore, this membrane had a 20% higher flux relative to a polymeric TF-200 membrane under similar test conditions. The superior performance of the anodisc™ is attributed to the more optimized pore structure and geometry relative to that which typifies most polymeric membranes used in DCMD.