Selective removal of copper from an aqueous solution using ligand-modified micellar-enhanced ultrafiltration using an alkyl-beta-diketone ligand

The semiequilibrium dialysis technique has been used to investigate the concentration of Cu2+ using a water-insoluble liquid ion exchanger or ligand with cationic surfactant in a ligand-modified micellar-enhanced ultrafiltration (LM-MEUF) process. In LM-MEUF the surfactant and the ligand are added to an aqueous solution containing ions of like charge, one of which needs to be selectively removed. The ligand forms a complex with the target ion of interest and solubilizes or dissolves inside the organic interior of the micelles. Therefore, it is possible to replace typical solvent extraction solvents such as kerosene by micelles. In this study copper chloride/calcium chloride solutions were treated for the extraction of copper using a commercially available ligand, 1-phenyl-3-isoheptyl-1,3-propane dione in cetyltrimethylammonium bromide (CTAB), a cationic surfactant. The effect of pH and the concentrations of copper, calcium, surfactant, and ligand on the efficiency of copper removal from water are discussed. Copper rejections greater than 99% were obtained even in the presence of calcium. In studies of regeneration of surfactant and ligand from the retentate stream containing rejected species, stripping of copper from the retentate was achieved using sulfuric acid. Stripping efficiencies greater than 94% were attained in three to four stages, demonstrating the feasibility of this regeneration scheme.