Oxidation of lactic acid by Vanadium(V) in sulphuric acid medium: a kinetic and mechanistic study

Abstract

The rate of lactic acid, HL, oxidation by vanadium(V), V(V), in sulphuric acid solution has been measured by monitoring, spectrophotometrically, the absorbance change of vanadium(IV), V(IV) in 760 nm at 30°C. This oxidation is a acid-catalysed, its dependence on acidity being complex. The rate constant or not the ionic strength. This reaction exhibited first order dependence on the V(V) and HL concentrations respectively and minimal dependence on sulphuric acid at lower concentrations (0.25 - 1.00 M) and fractionary (n = 0.40) at higher range (1.25 - 1.75 M) in constant ionic strength. Without this control, the sulphuric acid dependence was greater and the order (n = 1.71) was practically doubled in the higher concentration range (1.00 - 1.75 M) when compared with the lower one (0.25 - 0.75 M) and equal to 0.87. Dielectric constant decrease of the medium increased the rate constant. Energy of activation and parameters of activation were calculated studying the reaction at different temperatures. Oxidation mechanisms are proposed.