title: Mineralization of citric acid wastewater by photo-electrochemical chlorine oxidation.
abstract: This work demonstrates a novel chloride photo-electrochemical method for mineralizing citric acid. The electrolytic reactor with a length of 12 cm, a width of 12 cm and a height of 30 cm held 2.5 L of solution, which was involved in the batch reaction. Both anode and cathode were made of titanium coated with RuO2/IrO2. The results revealed that the solution pH dominated the production of hypochlorous acid (HOCl) oxidant in the presence of NaCl as direct current electricity was used. The chloride electrochemical process at pH 5.5 removed 59% of total organic carbon (TOC) in 4 h (NaCl = 200 mM, current = 5 A). UV irradiation (254 nm) in the reactor induced the photo-electrochemical reaction, increasing the TOC removal from 59% to 99.4%. Finally, the reaction pathway for citric acid mineralization was discussed with reference to the detection of intermediates using a liquid chromatography-mass spectrometry (LC-MS).
authors.affiliation: Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Kuan-Hsiang
authors.initials: KH
authors.lastname: Chen
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Shih
authors.forename: Yao-Hui
authors.initials: YH
authors.lastname: Huang
mesh_terms: D002713:Chlorine / Q000737:chemistry; D002853:Chromatography, Liquid; D019343:Citric Acid / Q000737:chemistry*; D055664:Electrochemical Techniques; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D012965:Sodium Chloride / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry*
chemical_list: D002713:Chlorine; D019343:Citric Acid; D012965:Sodium Chloride; D062065:Wastewater