The effect of the location of an impermeable barrier, which is placed for double pass in the raffinate phase, on solvent extraction through a parallel-plate membrane module, has been investigated. Theoretical predictions are in fairly good agreement with the experimental results. Considerable improvement in performance is obtainable if the subchannel width, as well as the mass-transfer area, of concurrent flow is as large as possible than that of concurrent flow, especially for low flow rate operation. It has been also checked that the hydraulic dissipated power due to the friction loss of fluid flow is very small and generally, the operating cost in all devices may be ignored. (C) 2003 Elsevier B.V. All rights reserved.