Investigation of the Starch Electrocatalytic Oxidation in an Acidic Environment with the Oxidant In Situ Regeneration

Abstract

The electrocatalytic oxidation of potato starch by potassium and sodium iodate in a two-chamber electrolytic cell on lead dioxide and glassy-carbon electrodes in acidic medium with the oxidant in situ regeneration is studied, in dependence on the current density, substrate concentration, oxidant nature, and reaction temperature. The optimal conditions for the production of the oxidized starch, its dialdehyde, were determined: the electrolysis time 120 min, the ultrasonic treatment time 30 min, the substrate concentration 13.3 g/L, the KIO₃ oxidant concentration 0.93 g/L, the current density 25 mA/cm², the carbonyl group content for PbO₂ 48%; for glassy carbon, 56%. The products were identified by IR and NMR spectroscopy and X-ray diffractometry. The temperature regime and ultrasound treatment of the initial starch are shown to have a significant effect on the periodate oxidation process. Analysis of the IR spectra shows that after the starch electrochemical oxidation, a new absorption band at 1730 cm^–1 appears in the oxidized sample spectrum, related to the aldehyde C=O bond stretching vibrations. The kinetics of accumulation of starch oxidation products is investigated. X-ray diffraction analysis elucidated a change in the ratio between the crystalline component (amylose) and starch amylopectin during the periodate oxidation.