Voltammetric Study on Transfer of UO₂²⁺ Across the Interface Between Aqueous and Nitrobenzene Solutions in the Presence of Octyl(phenyl)-N, N-diisobutylcarbamoyl-methylphosphine Oxide (CMPO)

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The characteristics of the phase transfer of UO₂²⁺ across aqueous(w)/nitrobenzene(nb) solutions interface in the presence of octyl(phenyl)-N, N-diisobutylcarbamoyl-methylphosphine oxide (CMPO) as an ionophore were investigated by cyclic voltammetry (VITIES) and polarography (PITIES) for ion transfer at the interface of two immiscible electrolyte solutions. The transfer of UO₂²⁺ from w to nb is remarkably facilitated by CMPO and the ion transfer reaction exhibits an irreversible nature. The rate-determining step of the UO₂²⁺ transfer is assigned to adsorption / desorption process of the UO₂²⁺-CMPO complex at the w/nb interface. The ion transfer potential of UO₂²⁺ shifts more positively when the two phase system is allowed to stand stationarily for a given time before the measurement of the cyclic voltammogram. The potential shift with the standing time is attributable to a decrease in the interfacial concentration of “free” CMPO due to the protonation of CMPO followed by the accumulation of the ion pair between HCMPO⁺ and TPhB^- at the w/nb interface.