Catalytic Effect of Polyoxyethylene t -octylphenol (Triton X-100) Surfactant on the Oxidation of EDTA by Chromic Acid

Abstract

The effect of nonionic Triton X-100 (TX-100) micelles on the pseudo-first order rate constants ( k ƒ ) for the oxidation of EDTA by chromic acid has been studied at different perchloric acid concentrations. The micellar-mediated reaction was independent of chromic acid concentration whereas first- and complex-order dependence on [EDTA] and [HClO 4 ], respectively, were observed. Increase in the total concentration of TX-100 from 0.0 to 60.0 2 10 m 3 mol dm m 3 caused the k ƒ to increase by nearly 4-fold at constant temperature and [HClO 4 ]. The observed catalytic effect has been explained on the basis of pseudo-phase kinetic and Piszkiewicz models. The higher rate of EDTA oxidation in the micellar pseudo-phase is attributed to association of the reactants with the nonionic micellar head groups through hydrogen bonding. A mechanism is proposed in accordance with the experimental results obtained.