The Solution-Diffusion-Imperfection Transport Model for Reverse Osmosis Membranes

Membrane-based reverse osmosis (RO) has been one of the leading technologies for water desalination over the past three decades. Water and salt molecule transport through RO membranes has been rationalized widely by the solution-diffusion mechanism. However, the solution-diffusion model is often unsatisfactory in predicting transport properties of imperfect RO membranes having microscopic defects such as nanometer sized pinholes, weak membrane, non-uniformity in membrane, that are intrinsic to these membranes. In this study, the classic solution-diffusion model is modified to account for convective water and salt transport in intrinsic defects in RO membranes. The modified model also allows for quantification of the role of coatings on the performance of reverse osmosis membranes and more specifically their ability to seal defects.