A Brief Introduction to Basics Concepts and Fields of Applications

ores can be regarded as channels and sub-nanometer free pathways, in which transport can take place through. Porous membranes can be classified by pore size and subsequent capability to discriminate among molecular species according to various mechanisms. Transport mechanisms through porous media can be described according to mathematical equations, while structural elements can be regarded as critical issue for membrane productivity and efficiency. A classification is herein proposed for membranes used in pressure-driven membrane processes, including microfiltration, ultrafiltration, nanofiltration, and reverse osmosis, with a brief outline of dialysis and electrodialysis. Structure-property relationships are critically discussed for other advanced membrane operations, including membrane distillation, membrane crystallization, membrane condensation, and membrane emulsification. Finally, a consideration on free volume compared to free paths on an Å length scale is also provided for membranes worked in gas separation and pervaporation.