摘要
The aqueous photodegradation of the widely used antibiotic chlortetracycline（CTC） was investigated under simulated sunlight.The quantum yield of photodegradation increased from 3.3 × 10-4 to 8.5 × 10-3 within the pH range of 6.0 to 9.0.The presence of Ca2＋,Fe3＋,and NO3-enhanced the photodegradation of CTC,whereas Mg2＋,Mn2＋,and Zn2＋ inhibited the degradation with the order Mn2＋ Zn2＋ Mg2＋ at pH 7.3.The monovalent cations（Na＋ and K＋） had negligible effect on the photolysis of CTC.Fulvic acid（FA） decreased the photodegradation of CTC due to light screening effect.Hydrogen peroxide（H2O2） was formed concurrently with direct photodegradation of CTC.The generation rate of H2O2 increased from 0.027 to 0.086 μmol/（L.min） when the pH ranged from 6.0 to 9.0.The CTC solution was about three-fold more toxic to the Photobacterium phosphoreum bacteria after irradiation,suggesting that the photoproducts and H2O2 formed in the CTC solution exhibited high risk on the bacteria.By LC-ESI（＋）-MS,the photoproducts of CTC were identified.The direct photodegradation of CTC was involved in hydroxylation and N-demethyl/dedismethyl processes.The main photoproducts included the iso-CTC analog containing hydroxyl groups（m/z 511.4 and 495.4）,and the N-demethyl/dedismethyl products of the photoproduct m/z 495.4（m/z 481.3 and 467.4）.In addition,the photochemical dechlorination of CTC led to tetracycline（m/z 445.5）.
The aqueous photodegradation of the widely used antibiotic chlortetracycline（CTC） was investigated under simulated sunlight.The quantum yield of photodegradation increased from 3.3 × 10-4 to 8.5 × 10-3 within the pH range of 6.0 to 9.0.The presence of Ca2＋,Fe3＋,and NO3-enhanced the photodegradation of CTC,whereas Mg2＋,Mn2＋,and Zn2＋ inhibited the degradation with the order Mn2＋ Zn2＋ Mg2＋ at pH 7.3.The monovalent cations（Na＋ and K＋） had negligible effect on the photolysis of CTC.Fulvic acid（FA） decreased the photodegradation of CTC due to light screening effect.Hydrogen peroxide（H2O2） was formed concurrently with direct photodegradation of CTC.The generation rate of H2O2 increased from 0.027 to 0.086 μmol/（L.min） when the pH ranged from 6.0 to 9.0.The CTC solution was about three-fold more toxic to the Photobacterium phosphoreum bacteria after irradiation,suggesting that the photoproducts and H2O2 formed in the CTC solution exhibited high risk on the bacteria.By LC-ESI（＋）-MS,the photoproducts of CTC were identified.The direct photodegradation of CTC was involved in hydroxylation and N-demethyl/dedismethyl processes.The main photoproducts included the iso-CTC analog containing hydroxyl groups（m/z 511.4 and 495.4）,and the N-demethyl/dedismethyl products of the photoproduct m/z 495.4（m/z 481.3 and 467.4）.In addition,the photochemical dechlorination of CTC led to tetracycline（m/z 445.5）.
基金
supported by the National Natural Science Foundation of China(No.21007018,51078161)
the Natural Science Foundation of Hubei Province (No.2010CDB01104)
the Research Fund for the Doctoral Program of Higher Education of China(No. 20100142120004)
the 11th Five-year Plan of National Water Environmental Special Program of China(No.2008ZX07211-10-02)
