Membranes with Great Hydrophobicity: A Review on Preparation and Characterization

Membranes are commonly designed with great hydrophilicity or hydrophobicity to promote or prohibit the transportation of water, respectively. There are vast applications of hydrophobic membranes such as filtration, gas separation, membrane gas absorption, pervaporation, membrane distillation and more that cannot be attained with hydrophilic membranes. However, the development of hydrophobic membranes was relatively slow in the past, as membrane technologists and researchers were more interested in reducing membrane hydrophobicity for permeability enhancement or fouling control in the aqueous separation. Thus, literature related to hydrophobic membranes has not been reviewed elsewhere. This review reported on the characterization and preparation methods for hydrophobic membranes. Hydrophobic ceramic membranes are commonly prepared by chemical modification. Besides using different types of chemicals, the membrane surface is roughened to enhance its hydrophobicity. For polymeric membranes, great hydrophobicity can be engineered using per-fluorinated polymers or phase immersion in a dual coagulation bath. Each technique has its advantages and weaknesses.