Liquid membrane multiple emulsion process of chromium(VI) separation from waste waters

A liquid membrane (multiple emulsion, water-in-oil-in-water (W III/O II/W I)) method of separation of chromium(VI) from simulated waste water has been described. The effect of the variation of the oil-membrane constituents and different types of chemical reactions at the II/I interface using aqueous solutions of various strippants (internal phase) have been studied for a critical appraisal of the efficiency of the process. Among others, reductions have been found to be most effective in lowering the chromium(VI) content in waste water below the toxic limit (0.05 ppm, suggested by the World Health Organisation). The ion exchange behaviour of the carriers in the membrane and coupled countertransport have been suggested to be the main cause of chromium(VI) transport. The application of the reaction site model has been found to be reasonably justified.