Radiolytic reduction of V(III) complexes in aqueous medium: effect of ligands

Lower oxidation state aqueous vanadium based formulations have several indispensible applications including decontamination of stainless steel based nuclear power plants. Gamma radiolysis can be used effectively for generating such formulations by suitably tailoring the yield of the required radicals. Formate and 2-hydroxy-2-propyl radicals were evaluated for reduction of V³⁺ ions with formate, nitrilotriacetate and citrate ligands in aqueous medium. The redox potential for these radicals are -1.9 V and -1.56 V vs. NHE respectively at pH 3 which is sufficient to reduce V³⁺ to V²⁺, the redox potential of V^3/V²⁺ being - 0.255 V vs. NHE. The V³⁺ precursor was prepared by electrolysis of NaVO₃. The solutions were irradiated in the ⁶⁰Co gamma irradiator with the dose rate of 0.65 kGy/hour with periodic UV -visible spectra measurement. The variation in the UV-visible spectra of the V(III)-formate solution in formic acid medium over the duration of irradiation is shown