Mechanism of Electrochemical Solvent Extraction of Divalent Metal Ions With Quinolin-8-ol

Abstract

The transfer of divalent metal ions (M²⁺ = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺) facilitated by quinolin-8-ol (HQ) at the nitrobenzene–water interface was studied by polarographic and voltammetric techniques. In conflict with a proposed mechanism that assumes the interfacial transfer of a divalent complex ion [M(HQ)₂²⁺], the observed current–potential curves showed characteristics similar to those of a reversible wave for monovalent-ion transfer. In this study, a new mechanism was proposed in which two monovalent ions (MQ⁺ and H₂Q⁺) are responsible for the ion-transfer current. The theoretical equation of the current–potential curve derived for the new mechanism was found to be useful for obtaining a better understanding of the ion-transfer processes.