Plasma in fabrication and modification of polymeric membranes

Polymer materials are mostly used in the fabrication of permeable and selective interfaces, known as membranes, for distinct membrane processes. According to their application in membrane processes, there is a need to improve specific properties such as functionality, charge, stability, hydrophilicity and chemical/physical resistance. Mostly, the surface post-modification of the membranes is suitable. In this regard, plasma, as an active area for the functionalization of materials, has been extensively applied for the fabrication and modification of membranes to tailor membrane surfaces and structures and thus produce outperforming membranes. This review timely reviews the different plasma treatments in polymer membranes, including oxidative plasma, CO₂, water vapor, reductive, inert plasma, corona discharge, radio-frequency discharge, dielectric barrier discharge, microwave discharge, direct current, and laser-based sources. Here, the principles, advantages, and disadvantages of the various plasma processes used in membrane fabrication and modification were addressed. Particular emphasis has been paid to the effect of the plasma treatment on the separation performance of membranes when implemented in different membrane processes for selective separations, such as membrane gas separation, liquid filtration, pervaporation and membrane distillation. After reviewing the literature, the perspectives and research gaps in the field are given as well.