Mineralization of organic acids by the photo-electrochemical process in the presence of chloride ions

This investigation demonstrates an indirect chloride photo-electrochemical method for mineralizing the organic acids (5 mM), including acetic, maleic, malonic, citric, oxalic, and succinic acids. The electrolytic reactor (12 cm × 12 cm × 30 cm) held 2.5 L solution, in which both anode and cathode were the titanium-based dimensionally stable anode (Ti-DSA) that was coated with RuO2/IrO2. Different active chlorine species with various redox potentials, including OCl−, HOCl, and Cl2, produced in NaCl medium were the major oxidants depending on the pH of the electrolysis. The results revealed that a pH in the range 2.5–7 maximized the removal rate of total organic carbon (TOC) of citric acid solution. The UV-254 nm light was then utilized in the NaCl electrolysis to support a photo-electrochemical reaction. The substantial improvement in the mineralization efficiency for all organic acids was attributed to the hydroxyl radicals ( OH) and chlorine radicals (Cl ) from HOCl upon activation by the UV irradiation.