Predicting power density of pressure retarded osmosis (PRO) membranes using a new characterization method based on a single PRO test

The characteristic parameters of pressure retarded osmosis (PRO) membranes (water permeability, A, solute permeability, B, and the structural parameter of the membrane support layer, S) were estimated by a single PRO test combined with a statistical approach. The single PRO test measures water and reverse solute flux (Jw and Js) as functions of the hydraulic pressure in the draw solution (DS) using sodium chloride solutions as feed and draw solutions. The PRO test data were obtained from literatures. A statistical approach developed in this work finds the most appropriate parameters (A, B, and S) to predict Js/Jw and power density of the tested PRO membrane using the internal concentration polarization (ICP) model. The model prediction results of Js/Jw and power density using the PRO membrane parameters obtained from the single PRO test matched the experimental data better than those using the membrane parameters obtained from the conventional reverse osmosis (RO) and forward osmosis (FO) tests. The A and B parameters from the single PRO test were consistently higher than those from the RO and FO tests, which could be related to the membrane deformation under the high-pressure PRO operation with the poor support by the spacer.