title: Photodegradation of parabens by Fe(III)-citrate complexes at circumneutral pH: matrix effect and reaction mechanism.
abstract: The photodegradation of four parabens including methyl-, ethyl-, propyl-, and butyl-paraben in the presence of Fe(III)-citrate complexes under simulated sunlight was investigated. The degradation of parabens increased with decreasing pH within the range of 5.0-8.0 at the Fe(III)-to-citrate ratio of 10:150 (μM). The addition of low-molecular-weight carboxylic acids showed different effects on the photodegradation of methylparaben. The low-photoreactive carboxylic acids inhibited the photodegradation of methylparaben in the order of formic acid>succinic acid>acetic acid>malonic acid. In contrast, oxalic acid enhanced the photodegradation and exhibited appreciable synergistic effect with Fe(III)-citrate at concentration higher than 500 μM. Up to 99.0% of substrate was degraded after 30 min at pH6.0 in the Fe(III)-citrate-oxalate system. The various fractions of fulvic acid inhibited the photodegradation of methylparaben. The inhibition increased with increasing nominal molecular weight of fractionated fulvic acid. Moreover, the photodegradation of methylparaben was inhibited in natural waters in the order of Liangzi Lake<Donghu Lake<Changjiang River≈Seawater. The photoproducts of methylparaben were identified by GC-MS analyses and the degradation pathway was proposed.
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Xiaonan
authors.initials: X
authors.lastname: Feng
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. Electronic address: ychen@hust.edu.cn.
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Huazhong University of Science and Technology Wenhua College, Wuhan 430074, China.
authors.forename: Xiaoyue
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Zongping
authors.initials: Z
authors.lastname: Wang
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Tao
authors.affiliation: Department of Chemistry & Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, United States.
authors.forename: Yuegang
authors.initials: Y
authors.lastname: Zuo
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010226:Parabens / Q000032:analysis / Q000737:chemistry*; D010782:Photolysis; D013472:Sunlight; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D010226:Parabens; D014874:Water Pollutants, Chemical
keywords: Fe(III)-citrate; Matrix effect; Mechanism; Parabens; Photodegradation