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.
College of Material Science and Chemical Engineering, China University of Geosciences, Wuhan, 430074, PR China. zdncug@163.com
Danna
D
Zhou
Feng
F
Wu
Nansheng
N
Deng
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