Influence of pressure and/or pressure differential on membrane permeability

Abstract

Using different annealed asymmetric cellulose acetate membranes, a Cuprophane membrane 325 PM, and two strong anion exchange membranes (BAYER membrane and ASAHI's CA-I membrane), the volume fluxes, q, were measured in hyperfiltration experiments as a function of the brine pressure, P 1. In addition, the hydrodynamic permeability, l p, of some asymmetric cellulose acetate membranes and the Cuprophane membrane were determined as functions of pressure and/or pressure differential employing a high pressure dialysis cell. The experimental results show that the hydrodynamic permeability of the asymmetric cellulose acetate membranes and the strong anion exchange membranes depends only on the pressure P 1 but not on the pressure differential, ΔP, across the membrane. On the other hand, the Cuprophane membrane behaves opposite possessing a hydrodynamic permeability which depends only on the pressure differential, ΔP, but not on the pressure, P 1. A theoretical description of the experimental findings is possible formally by applying suitable Taylor series expansions of the volume flux in terms of ΔP as well as of the hydrodynamic permeability, l p, in terms of P 1 or the mean pressure, p .