Removal of cadmium (II) from aqueous waste effluents by using supported liquid membrane technology

There is a growing need to develop technologies that can separate and selectively remove hazardous chemical species from waste effluents. Selective removal of cadmium ions through a supported liquid membrane (SLM) containing triethanolamine (TEA) as a mobile carrier has been studied. The effects of Cd(II) concentration, HCl in feed and carrier concentration in membrane has been studied. Cd(II) concentration increase in feed leads to an increase in flux from 2.1x10 to 8.4x10 mol-cm-sec within Cd(II) ions concentration range (2.7x10M 16.37x10M ) at 2.0M HCl in the feed and 3.0M triethanolamine in the membrane. Increase in H ion concentration from 0.5M to 3.0M results in an increase in Cd(II) ions flux but a decrease is observed beyond 2.0M HCl concentration in feed. Increase in carrier concentration in the liquid inside the membrane enhances the flux with its maxima at 3.0M carrier. Further increase in the concentration of TEA leads to a decrease in transport due to increase in viscosity of membrane liquid. The optimum conditions for Cd(II) ions transport are, 2.0M HCl in feed, 3.0M TEA in membrane and 0.1M NaOH as strip solution. Similar transport characteristics have been observed for Cd-EDTA complexed anions across TEA-cyclohexanone based SLM, thus indicating a cadmium anion transport coupled with protons and chloride or EDTA co-ions.