Use of Ligand-Modified Micellar-Enhanced Ultrafiltration in the Selective Removal of Metal lons from Water

Abstract

Abstract Ligand-modified micellar-enhanced ultrafiltration (LM-MEUF) is a membranebased separation technique which can selectively remove specific ions from an aqueous solution containing several ions of like charge. In LM-MEUF, surfactant and amphiphilic ligand are added to the contaminated water. The surfactant forms aggregates called micelles, and the ligand is selected to complex the ion of interest and to solubilize strongly in the micelles. The result is micelles containing a high fraction of the ligand and the target ion. If the surfactant is chosen to have the same charge as the target ion, other ions in solution with this same charge will not associate with the micelles, making the retention of ions by the micelles very selective. The solution is then passed through an ultrafiltration membrane with pore sizes small enough to block the passage of micelles. In this study, divalent copper is the target ion in a solution also containing divalent calcium. A cationic surfactant is used with N-n-dodecyl-iminodiacetic acid as the copper-specific ligand. Rejections of copper of up to 99.2% are observed, with no rejection of calcium, showing that LM-MEUF has almost perfect selectively, as well as high capacity in this case.