The determination of the intrinsic characteristics of reverse osmosis membranes

Abstract

General linear differential equations for the transport of water and salt through non-ideal membranes are written down. The first-order forms of these equations are derived from mathematical considerations. The equations are integrated for steady state flow across a homogeneous membrane, leading to nonlinear first-order transport equations. The constants in these equations may be transformed to the well known transport coefficients which evolve naturally without additional assumptions. A number of methods are listed by which the intrinsic coefficients of homogeneous, composite and imperfect membranes may be measured and the applicability of the first-order equations may be determined.