Fe(III)-oxalate complexes induced photooxidation of diethylstilbestrol in water.
In this work, the photooxidation of diethylstilbestrol (DES), a synthetic estrogen, was investigated in a concentric reactor under a 125 W high-pressure mercury lamp (lambda > or = 365 nm). The photooxidation efficiencies were dependent on the pH values and Fe(III)/oxalate ratios of the system, with higher efficiency at pH 3.50+/-0.05 and Fe(III)/oxalate ratio 10.0/120.0 micromol l(-1). The photooxidation reactions obeyed the law of pseudo-first-order reaction at the concentration over the range of 2.0-10.0 mg l(-1) of DES. The photooxidation rates decreased with increasing the initial concentrations of DES. For 2.0 mg l(-1) DES, the observed photooxidation rate coefficient (k(obs)) was 0.00622 min(-1). By using GC-MS and LC-MS techniques, the predominant photooxidation products DES-o-catechol ([M](+), m/z 284) and DES-4-semiquinone ([M](-), m/z 267) were respectively identified and the mechanisms for the oxidative degradation were proposed. When DES reacted with OH radicals, C atoms in 3-position were added with OH radicals to produce hydrolyzed DES radical followed by two oxidation pathways: (1) dehydrolyzing to produce DES-4-semiquinone which was oxidized further to DES-4,4'-quinone; (2) undergoing peroxidation by O(2) and getting rid of HO(2) radical to produce DES-o-catechol. After that, the two H atoms on the hydroxy group of the catechol were extracted in two individual steps to form intermediates semiquinone radical and o-quinone. The catechol intermediates underwent further oxidation, benzene ring cleavage and decarboxylation, up to mineralization ultimately.
Zhou
Danna
D
College of Material Science and Chemical Engineering, China University of Geosciences, Wuhan, 430074, PR China. zdncug@163.com
Wu
Feng
F
Deng
Nansheng
N
D002396:Catechols / Q000737:chemistry; D004054:Diethylstilbestrol / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry; D013058:Mass Spectrometry; D010070:Oxalates / Q000737:chemistry*; D010084:Oxidation-Reduction; D010777:Photochemistry; D010782:Photolysis; D011809:Quinones / Q000737:chemistry; D013997:Time Factors; D014867:Water / Q000737:chemistry*
D002396:Catechols; D005290:Ferric Compounds; D006878:Hydroxides; D010070:Oxalates; D011809:Quinones; D014867:Water; D004054:Diethylstilbestrol; C031356:hydroxide ion; D006861:Hydrogen Peroxide