Removal of volatile organic components (VOCs) from water by pervaporation: separation improvement by Dean vortices

Dense polydimethylsiloxane (PDMS) hollow-fibre membrane modules built in straight and coiled configurations were studied in pervaporation for volatile organic compounds (VOCs) removal. Two different aqueous organic mixtures, n-butanol-water and chloroform-water, were investigated to determine how the permeate fluxes are affected by the module geometry. Data with chloroform-water mixtures of 0.1 and 0.05 wt% chloroform revealed that, in the laminar regime, coiled modules show improved chloroform mass transfer compared to conventional modules where straight hollow-fibre membranes are aligned in parallel. The improvement factor increases with the Reynolds number to reach a value of 2.3 at N-Re = 2000. In the conventional and helical designs, with a calculated diffusion coefficient, the results are lower than those given by the Leveque equation and the mass transfer correlation previously found for water oxygenation respectively. With an apparent diffusion coefficient, these experimental values are consistent with these two equations. (C) 1998 Elsevier Science B.V.