Treatment of phenol-containing aqueous solutions by membrane-based solvent extraction in coupled ultrafiltration modules

Extractive treatment of phenol-containing aqueous streams by two coupled hollow fiber modules (for simultaneous extraction and stripping) is experimentally and theoretically studied. The effects of hydrodynamic conditions (linear velocities of all three liquids) and concentrations (initial phenol concentrations) are explored and an optimal combination of these process parameters is found for maximisation of the phenol fluxes in both modules. The extraction/stripping performance of the coupled HF modules was compared when using different organic solvent (alcohols and alkanes). Analysis of the mass-transfer resistances of the different liquid layers in both modules is presented based on mathematical model and experimental data from equilibrium measurements and kinetic experiments. It is found that an important part of the overall resistance is located in the aqueous phase's boundary layers. A substantial improvement of the stripping yield is reached by using a series of stripping modules. (C) 2004 Elsevier B.V. All rights reserved.