Uphill permeation of chromium (VI) using Cyanex 921 as ionophore across an immobilized liquid membrane

The transport of chromium (VI) through an immobilized liquid membrane (ILM) containing Cyanex 921 (phosphine oxide) as a carrier has been studied. The permeation of the metal is investigated as a function of various experimental variables: hydrodynamic conditions, concentrations of chromium (VI) and HCl in the source phase, carrier concentration and diluent in the membrane, strippant in the receiving phase and support characteristics. The mass transfer coefficient and the thickness of the aqueous boundary layer were calculated from the experimental data. Furthermore, the selectivity of Cyanex 921-based ILM towards different metal ions and the behaviour of the system against other carriers are presented. (C) 2001 Elsevier Science B.V. All rights reserved.