title: Distinct effects of oxalate versus malonate on the iron redox chemistry: Implications for the photo-Fenton reaction.
abstract: The dicarboxylic acids oxalate (Oxal) and malonate (Mal) are frequently detected as the final low-molecular-weight organic acids during oxidative degradation of aromatic compounds. Here a distinct effect of Oxal versus Mal on iron-based photocatalytic technologies was reported by testing the degradation efficiency of the dye rhodamine B. The rates of dye degradation in irradiated Fe(III) solutions depended on Fe(III/II) speciation, photoreactivities of Fe complexes and reactivities of Fe(II) complexes with H2O2. Photolysis of the Fe(III)-oxalato complex was favorable due to the formation of O2-, HO2 and OH for oxidizing the dye; however, an excess of H2O2 could quench the excited state of ferrioxalate, decreasing the degradation efficiency. In contrast, activities of UV/Fe(III) in the presence of Mal were significantly diminished because Fe(III)-Mal complexes, with much lower quantum yield of Fe(II) from photoreduction, dominated Fe(III) speciation. The results provide data for an understanding of the mechanism of iron redox (photo)chemistry mediated by diacids, which will aid in selecting appropriate Fe ligands, screening photo-Fenton conditions and designing UV/Fe(III) treatability.
authors.affiliation: State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China.
authors.forename: Dongxue
authors.initials: D
authors.lastname: Xiao
authors.affiliation: State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China.
authors.forename: Yaoguang
authors.initials: Y
authors.lastname: Guo
authors.affiliation: State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China.
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Lou
authors.affiliation: State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China.
authors.forename: Changling
authors.initials: C
authors.lastname: Fang
authors.affiliation: State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China. Electronic address: zhaohuiwang@dhu.edu.cn.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China. Electronic address: liujianshe@dhu.edu.cn.
authors.forename: Jianshe
authors.initials: J
authors.lastname: Liu
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D008314:Malonates / Q000737:chemistry*; D010070:Oxalates / Q000737:chemistry*; D019815:Oxalic Acid / Q000737:chemistry*; D010084:Oxidation-Reduction; D010782:Photolysis; D012235:Rhodamines / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D005456:Fluorescent Dyes; D008314:Malonates; D010070:Oxalates; D012235:Rhodamines; C034942:ferrioxalate; D019815:Oxalic Acid; C030290:malonic acid; D006861:Hydrogen Peroxide; C029773:rhodamine B
keywords: Dicarboxylic acid; Fenton chemistry; Photochemistry; Reactive oxygen species