Chapter 20 - Reverse Osmosis

Abstract

Solute and water transport has been widely investigated and described in the literature, because the reverse osmosis process has been industrially applied for several decades. This chapter gives a brief survey of solute transport across a dense reverse osmosis membrane, emphasizing the irreversible thermodynamic model. The diffusive mass transfer rate using the solution/diffusion model is defined for the active membrane layer and this transfer rate is combined with the transfer rate of the polarization layer, with which the overall mass transfer rate, the interface concentrations on the two sides of the membrane, is expressed. Accordingly, the enrichment and intrinsic enrichment factors are expressed as a function of the mass transport parameters as a mass transfer coefficient of the transport layers and water flux. These expressions are missing in the conventional literature equations, which consider the membrane as a “black box.” Finally, the overall mass transfer rate and the outlet concentration are given in the presence of the cake layer.