Organic solvent reverse osmosis membranes for organic liquid mixture separation: A review

The separation of organic liquid mixtures by organic solvent reverse osmosis (OSRO) technology is promising owing to the high energy-efficiency. This article presents an overview of the endeavors made in the OSRO separation of organic liquid mixtures. First, the sub-nanometer separation characteristic of OSRO is introduced, and compared with pervaporation and organic solvent nanofiltration. Next, the mixtures of interest which may benefit from OSRO technology such as polar/nonpolar mixtures and their application scenarios are presented. The energy evaluation of OSRO, pervaporation, and distillation processes is also performed, highlighting the energy conservation feature of OSRO process. Subsequently, the OSRO membranes developed to date are comprehensively reviewed in term of their membrane materials, diving into organic (mainly cellulose types, polyethylene, polyamide, perfluoropolymer), inorganic (carbon molecular sieves, silica, zeolite), and composite (polymers of intrinsic microporosity-1/AlOx) materials. The OSRO separation performances of the developed membranes are summarized and compared in term of flux and separation factor. Finally, we provide perspectives regarding the challenges and state the concluding remarks, in the hope that this review will inspire future studies to address efficient OSRO separations.