Review on methodology for determining forward osmosis (FO) membrane characteristics: Water permeability (A), solute permeability (B), and structural parameter (S)

Forward osmosis (FO) has attracted growing interest in both academic research and industrial development due to its fundamental and technical advantages. One of the key challenges that needs to be addressed to further advance this technology is the identification of an ideal membrane. However, the reliable methodology for characterizing FO membrane performance parameters has not yet been standardized, and thus various methods have been utilized to evaluate FO membrane performance. The RO-FO based method is the most widely used protocol, but it has fundamental problems in the measurement of intrinsic parameters. Non-pressurized methods have newly been suggested as another approach to evaluate FO membranes but they also have shown certain limitations, such as inaccurate performance prediction of pressure-applied FO processes. The development of a standard and reliable characterization method for FO membranes is an important step to enable the standardization of the results from different research works and to facilitate data exchange and interpretation. Process-optimized standardization method, which can accurately measure the intrinsic characteristics of the different osmosis processes, thus should be investigated in more detail through further research.