Membrane processes for the efficient recovery of anionic pollutants

The development of new “zero discharge” technologies which also permit the recovery of pollutant anions from industrial waste waters is a way of minimizing the cost of the processes and the impact on the environment. The kinetic behaviour of the removal and recovery of two different anionic pollutants is reported using membrane-based solvent extraction technologies: (1) recovery of hexavalent chromium anions contained in groundwaters by means of emulsion pertraction (EPT) and (2) recovery of zinc chlorocomplexes from spent pickling solutions by means of non dispersive solvent extraction (NDSX). Kinetic experiments were performed in order to study the influence of different variables on the separation kinetics, i.e., the NaOH concentration in the stripping phase in the case of chromium and the initial metal concentration in the aqueous feed solution in the case of zinc recovery.