Opposite pH-dependent roles of hydroxyl radicals in ozonation and UV photolysis of genistein

Yang Huang; Lihao Su; Siyu Zhang; Qing Zhao; Xuejiao Zhang; Xuehua Li; Haibo Li; Lifen Liu; Jingwen Chen; Xiaoxuan Wei

doi:10.1016/j.scitotenv.2019.136243

Opposite pH-dependent roles of hydroxyl radicals in ozonation and UV photolysis of genistein

Sci Total Environ. 2020 Mar 20:709:136243. doi: 10.1016/j.scitotenv.2019.136243. Epub 2019 Dec 20.

Authors

Yang Huang¹, Lihao Su², Siyu Zhang³, Qing Zhao⁴, Xuejiao Zhang⁴, Xuehua Li⁵, Haibo Li⁶, Lifen Liu⁵, Jingwen Chen⁵, Xiaoxuan Wei⁷

Affiliations

¹ Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China; Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China; School of Resources and Civil Engineering, Northeastern University, Shenyang 110004, China.
² Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China; Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China; Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Food and Environment, Dalian University of Technology, Panjin, 124221, China.
³ Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China. Electronic address: syzhang@iae.ac.cn.
⁴ Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
⁵ Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China; Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Food and Environment, Dalian University of Technology, Panjin, 124221, China.
⁶ School of Resources and Civil Engineering, Northeastern University, Shenyang 110004, China.
⁷ College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China.

PMID: 31884282
DOI: 10.1016/j.scitotenv.2019.136243

Abstract

Phytoestrogens were frequently detected in municipal or industrial wastewater, and raised great attentions due to potential risks to humans or organisms. Until now, transformation mechanisms of phytoestrogens in advanced wastewater treatments were largely unknown. Here, pH influence mechanisms on transformations of phytoestrogens during two typical advanced wastewater treatments (ozonation and photolysis) were investigated, employing genistein (Gs) as a case. Removal efficiencies of Gs decreased significantly with increases of pH during ozonation, while photolytic rates increased by 44 or 200 times from pH 4.9 to 11.6 under irradiations without or with UVC. pH increases caused both dissociation of Gs and formation of hydroxyl radicals (OH) in ozonation or photolysis, however, led to opposite changes to degradation rates. This was because that OH played negatively as a competitor for O₃ in ozonation, but acted as an accelerating species inducing self-sensitized photooxidation of Gs under UV light. Ozonation and photolytic products of Gs were similar at pH 4.9 or 8.6, but were totally different at pH 11.6. Most of the transformation products maintained isoflavone structures, and might possess phytoestrogenic effects. This study provided a deep insight into the pH influencing mechanism on typical advanced wastewater treatment processes of phytoestrogens. MAIN FINDING OF THE WORK: Opposite pH-dependent degradation mechanisms caused by hydroxyl radicals (OH) were elucidated for ozonation and UV photolysis of phytoestrogens, taking genistein as a case.

Keywords: Genistein; Ozonation; Photodegradation; Phytoestrogens; pH.

MeSH terms

Genistein
Hydrogen-Ion Concentration
Hydroxyl Radical
Oxidation-Reduction
Ozone
Photolysis*
Ultraviolet Rays
Water Pollutants, Chemical
Water Purification

Substances

Water Pollutants, Chemical
Hydroxyl Radical
Ozone
Genistein