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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, P¹. 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 P1 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, P¹.

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 P¹ or the mean pressure, p.