Preparation and applications of poly vinyl alcohol (PVA) modified cellulose acetate (CA) membranes for forward osmosis (FO) processes

Polyvinyl alcohol (PVA)-coated cellulose acetate (CA)-based flat-sheet membranes have been fabricated and tested in the forward osmosis (FO) process. PVA was used as a surface modifying agent. CA membranes prepared by conventional immersion precipitation were treated in an aqueous solution of PVA and tested water flux and salt rejection. The effects of PVA concentration, treatment time on the hydrophilicity of membrane surface, water permeability, and salt retention property of the membrane were estimated. The modified membrane was characterized by X-ray photoelectron spectroscopy and contact angle measurement. A hydrophilicity of membrane surface was observed in longer modification times and the higher PVA solution concentration accounted for a attaching of the PVA chains by glutaraldehyde as cross-linking agent. The best condition of salt rejection and permeability performance was obtained by using 1 wt% PVA solution and treatment time of 2 min. In the FO process, modified CA membrane exhibited water flux 20% higher than unmodified CA membrane without salt leakage. This result indicated that PVA coating improved water flux performance for FO processes.