Ion-Transfer Current-Scan Polarographic Studies of Metal Extractants with Ascending Water Electrode: Transfer of Divalent Metal Ion Complexes of Phenanthrolines across a Liquid-Liquid Interface

Abstract

The transfer mechanism of Ni²⁺, Co²⁺, Zn²⁺ and Cd²⁺ ions from an aqueous to a dichloroethane (DCE) solution of phenanthroline derivatives (Phen) was studied. Included were 1, 10-phenanthroline (phen), 4, 7-dimethyl-1, 10-phenanthroline (4, 7-DMP), 4, 7-diphenyl-1, 10-phenanthroline (4, 7-DPP) and 2, 9-dimethyl-1, 10-phenanthroline (2, 9-DMP). The investigation was carried out by current-scan polarography at the ascending water electrode (AWE). Some polarographic waves were observed that can be attributed to the slow formation of 1:1 M²⁺-Phen complexes. In some cases, as with the Ni²⁺-Phen systems and the Co²⁺-4, 7-DPP system, no wave was observed, because the complexation rates are too slow. All of the Cd²⁺-Phen and all of the Zn²⁺-Phen systems, except for the Zn²⁺-4, 7-DPP system which exhibits a kinetic wave, yielded diffusion-controlled waves. Furthermore, a number of these systems appear to be affected by significant interfacial adsorption of the M²⁺-Phen complexes.