Comprehensive assessment of the effects of operating conditions on membrane intrinsic parameters of forward osmosis (FO) based on principal component analysis (PCA)

Operating variables, such as flow direction, velocity, temperature, and osmotic pressure, affect the performance of forward osmosis (FO) systems. Water and salt permeabilities of the FO membrane have been regarded as membrane intrinsic parameters, and numerous studies have fixed the water and salt permeabilities regardless of the operating conditions except temperature. In this study, we collected approximately 700 experimental data entries on FO to analyze whether water and salt permeabilities are indeed membrane intrinsic parameters. The widely scattered water and salt permeabilities in the collected FO experimental data imply that the material of the FO membrane and the operating conditions influence the effective water and salt permeabilities significantly. To investigate the effects of operating conditions on the FO performance quantitatively, a principal component analysis (PCA) method was employed. The PCA results showed that osmotic pressure, temperature, and flow velocity are the main operating variables in the FO system, and the contribution of these variables on FO performance is similar. Unlike the common knowledge in the FO, we confirmed that the flow velocity was as important as the osmotic pressure or temperature. In this study, we revealed a new understanding of membrane intrinsic parameters and the extent of influence of operating conditions.