Metal extraction in water/micelle systems: complex formation, stripping and recovery of Cd(II)

The extraction and recovery of cadmium from aqueous solutions has been performed by a method which avoids the use of organic solvents. The method makes use of surfactant micelles in combination with metal complexing agents. The complexed metals are concentrated on the micelle surface and then treated by a ligand-modified micellar enhanced ultrafiltration process (LM-MEUF). Subsequently the metal ions are stripped out of the micelle by addition of weakly acidic solutions of a strong electrolyte. Using the anionic surfactant sodium dodecylsulphate (SDS) and the azo-dye ligand pyridine-2-azo-p-dimethylaniline (PADA) we were able to extract Cd2+ from aqueous solution with high efficiency rates (∼99%). Once the metal has been extracted in the micellar pseudo-phase it has been recovered by means of NaCl 0.5 mol dm−3 acid solution. This procedure allows cadmium to be recovered from the aqueous solution with a yield of 80%. Moreover, the possibility of Cd(II) recovery in the presence of magnesium or zinc ions has been investigated.