Degradation of methyl orange in water by contact glow discharge electrolysis

The degradation of methyl orange in a neutral phosphate buffer solution was investigated by means of contact glow discharge electrolysis (CGDE). The methyl oranges were degraded and eventually decomposed into inorganic carbon when CGDE was conducted under the applied DC voltage of 480 V and current of ca. 80 mA. As the intermediate products, some phenolic compounds were detected as well as carboxylic acids. Experimental results showed that the oxidation process followed the first-order reaction law. Based on the analysis of the ultraviolet (UV) spectra of the solution and the intermediate products from High Pressure Liquid Chromatography-Mass Spectrum (HPLC-MS), the reaction pathway was proposed. The attack of hydroxyl radicals was considered to be a key step to start the whole oxidation process.