Development of pressure retarded osmosis membrane

Pressure retarded osmosis (PRO) is a new membrane technology to produce renewable energy from osmotic pressure difference of two solutions with different concentration. Membrane used in the PRO process requires high water permeability, effective rejection of salt and ideal mechanical strength in order to achieve an excellent energy production. This paper explains the basic requirements of PRO membranes and summaries the development of the widely-used asymmetric membranes from the aspects of active layer, support layer and pre-treatment, showing the effects of membrane material, preparation and pre-treatment on the membrane performance. Meanwhile, the paper induces the research status of symmetric and quasi-symmetric membranes, which could significantly mitigate internal concentration polarization (ICP) and become a research focus in the future.