Progress in membranes for pressure retarded osmosis application

The ever-growing global energy crisis has been pushing industries to lean towards renewable resources as an alternative for power generation. Recent research is focusing mainly towards achieving water sustainability and producing green energy without creating any liquid discharge. In this review paper, a complete analysis of the latest developments in membrane modification for pressure retarded osmosis (PRO) processes has been discussed. Moreover, the use of different nanomaterials like zeolite, graphene oxide, carbon nanotubes, halloysite nanotubes, TiO2, SiO2, silica, carbon quantum dots, covalent organic frameworks, and metal-based nanoparticles for membrane modification to maximize PRO performance have been presented. Besides, the hybrids of PRO in combination with reverse osmosis (PRO-RO), forward osmosis (PRO-FO) and PRO thermal have also been reviewed. Additionally, the recent test results on the incorporation of novel nanofibers like polyetherimide and polyacrylonitrile into different thin film composite and hollow fiber membranes have been presented here. Also, this review presents the future direction of PRO research, economic analysis on cost reduction and its commercialization potentials. Due to its immense benefits offered, the Middle East is beginning to consider PRO process to enhance the shrinking fresh water source in the region, while producing salinity gradient energy.