Effect of the supporting layer structures on antifouling properties of forward osmosis membranes in AL-DS mode

Effect of the supporting layer structures on antifouling properties of forward osmosis (FO) membranes in active-layer-facing-draw-solution (AL-DS) mode was investigated through a series of polyketone (PK) membranes prepared by controlling the concentration of the polymer casting solution, initial casting height, and solvent system. A double-skinned FO membrane was prepared by interfacial polymerization on the bottom surface of the PK membrane. The surface pore sizes, bulk porosities, water permeability and alginic acid sodium salt rejection properties of the prepared PK membranes were determined, and the surface roughness, membrane thickness, pure water permeability, salt permeability and FO performance of the PK-based FO membranes were characterized. The alginic acid sodium salt was used to evaluate the antifouling properties of the FO membranes in AL-DS mode. The effect of surface roughness (or surface pore size), membrane thickness, and structural parameter (S value) on the membrane fouling was investigated. The results indicate that decreasing both the surface pore size of the supporting layer and the membrane thickness effectively improves the membrane performance; that is, the membrane possesses both enhanced antifouling properties and water permeability. This work provides firm guidelines for the design of proper supporting layer structures for FO membranes with high performance in AL-DS (or pressure retarded osmosis, PRO) mode.