Electro-oxidation combined with electro-Fenton for decolorization of caramel colorant aqueous solution using BDD electrodes

Abstract

This study focused on the effects of the electro-oxidation combined with electro-Fenton process using boron-doped diamond (BDD) electrodes on the degradation of biorefractory food colorant caramel. Aqueous solutions containing Caramel Class IV, Caramel Class III and Acid Orange 7 were comparatively treated by electrochemical advanced oxidation processes, including electro-oxidation (EO), electro-Fenton (EF) and electro-oxidation combined with electro-Fenton (EO + EF). The experiments were performed in a stirred flask reactor using an inflator pump coupled with an undivided cell with BDD and Ti/Pt electrodes. In EF and EO + EF process, Fe2+ was added as catalyst. The independent parameters of air flow rate, Fe2+ concentration and current intensity in the range of 0.5–1.5 L/min, 0.05–0.2 mM and 0.4–1.5 A, respectively, were studied. The effect of electrode material on decolorization was also examined. The decolorization of pigment was enhanced with increasing air flow rate and current intensity due to the greater production of active species. The color decay was fitted to a pseudo-first-order kinetics. Complete decolorization of caramel colorant was realized with BDD electrodes under all experimental conditions and the highest kinetic constant of 2.3*10−2 min−1 was found under these conditions. This study highlighted the potential of EO + EF process with BDD electrodes for efficient degradation of caramel colorant.