Electrochemical behavior of NbV–EDTA and NbV–citrate systems in aqueous solutions

Abstract

AbstractThe electrochemical reduction of NbV using oxalatoniobic acid and ammonium oxooxalatoniobate salts was studied in aqueous solutions of citric acid and sodium ethylenediaminetetraacetate (EDTA), in a wide range of supporting electrolyte concentrations and pH. In EDTA two reduction processes were observed: NbV to NbIV, E = −1.000 V vs. Ag/AgCl at pH 4.50 and NbIV to NbIIIE = −1.400 V vs. Ag/AgCl (pH 4.50). In citric acid there was only one reduction process: (NbV to NbIV), E = −1.260 V vs. Ag/AgCl at pH 4.50. In both electrolytes a linear relationship was found between the diffusion current and the niobium concentration in the 1.0 × 10−5 to 5.0 × 10−3 M range. Using cyclic voltammetry, it waa observed that the charge transfer process in the NbV to NbIV process is reversible in EDTA and reversible–quasireversible in citric acid.