Adsorption of divalent transition metal ions with a chelating agent on octadecyl silica gel.

This investigation looked at the extraction ability of divalent transition metal ions onto an octadecyl silica gel (C18g) with a 4,4-trifluoro-1-(2-thienyl)-1,3-butadione (TTA) chelating agent. A method of retaining TTA onto C18g (TTA-C18g) was developed in order to adsorb the metal ions. The difference in the half-adsorption and half-extraction pH values between transition metals Ni2+-Co2+ was found to be 0.7 in this system. This is better than previously published results of 0.3 for the conventional extraction method using TTA in nitrobenzene. More than 96% of the metal ions in aqueous solution could be adsorbed onto TTA-C18g. Our system, which has no organic phase, can achieve a better removal or separation of transition metal ions than the conventional solvent-extraction methods using TTA in toluene or nitrobenzene.