Kinetic studies on effects of EDTA and surfactants on reduction of vanadium(V) to vanadium(IV) in sulphuric acid medium

Reduction kinetics of vanadium(V) to vanadium(IV) by EDTA and effects of surfactant have been studied using thiourea as a reductant at 40±1 °C in acidic medium at 350 nm. UV-vis and ESR spectral techniques have been used to confirm the reduction product of vanadium(V). Electronic absorption spectra of the reaction products suggest the formation of aqua vanadium(IV) and vanadium(IV)-EDTA complex in the absence and presence of EDTA, respectively. The oxidation of thiourea by vanadium(V) has also been studied in the presence of surfactants. The anionic sodium dodecyl sulphate and non-ionic TX-100 surfactants catalyze the reaction whereas the cationic surfactant, cetyltrimethylammonium bromide, has no effect. The single electron sequence is confirmed by the formation of vanadium(IV) aqua ion. The experimentally determined intermediate complex formation constant , K es is 34 mol -1 dm 3 .