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Zhong C, Zhao H, Han Q, Cao H, Duan F, Shen J, Xie Y, Guo W, Sun S. Coupling-oxidation process promoted ring-opening degradation of 2-mecapto-5-methyl-1,3,4-thiadizaole in wastewater. WATER RESEARCH 2020; 186:116362. [PMID: 32916619 DOI: 10.1016/j.watres.2020.116362] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/28/2020] [Accepted: 08/29/2020] [Indexed: 06/11/2023]
Abstract
As an important raw material and intermediate of widely used antibiotics cefazolin and cefazedone, 2-mecapto-5-methyl-1,3,4-thiadizaole (MMTD) in antibiotic wastewater is hardly decyclized during wastewater treatment, posing great risk to the environment. This work proposed a green "coupling-oxidation" process to enhance ring-opening of MMTD during antibiotic wastewater treatment. In particular, the significant role of humic substances (HS) as pre-coupling reagent was emphasized. Real HS and different model HS, especially quinones, not only efficiently pre-coupled MMTD (>95%) but also promoted the MMTD removal by MnO2 (from 72.4% to 92.4%). Mass spectrometric analysis indicated that MMTD pre-coupled to HS would be oxidized with ring opening to environmental-friendly sulfonated HS, while direct oxidation of MMTD produced MMTD dimers or sulfonated MMTD that would not undergo ring opening. Theoretical calculations indicated that pre-coupling to HS enabled the ring-opening oxidation by increasing the nucleophilicity and decreasing ring-opening barrier of thiadiazole. Based on the density function theory (DFT), the global nucleophilicity index (Nu) followed the trend of HS-MMTD > MMTD dimer > sulfonated MMTD, while the ring-opening barrier followed the trend of HS-MMTD (274 kJ/mol) < first ring of MMTD dimers (286 kJ/mol) < MMTD (338 kJ/mol). Theoretical calculations further confirmed that the cross-coupled HS-MMTD intermediate was more likely to be decyclized than intermediates from direct oxidation. Moreover, nitrogen, acetaldehyde group, sulfate and CO2 were the products of thiadiazole ring degradation. Pre-coupling of MMTD with HS provides a new idea and strategy in developing a green and sustainable scheme for wastewater treatment.
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Affiliation(s)
- Chen Zhong
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - He Zhao
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China; Beijing Engineering Research Center of Process Pollution Control, Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China.
| | - Qingzhen Han
- Beijing Engineering Research Center of Process Pollution Control, Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China
| | - Hongbin Cao
- Beijing Engineering Research Center of Process Pollution Control, Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China
| | - Feng Duan
- Beijing Engineering Research Center of Process Pollution Control, Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China
| | - Junyi Shen
- Beijing Engineering Research Center of Process Pollution Control, Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China; Suzhou University of Science and Technology, Suzhou 215009, Jiangsu, China
| | - Yongbing Xie
- Beijing Engineering Research Center of Process Pollution Control, Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China
| | - Wanqian Guo
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Shanshan Sun
- Beijing Engineering Research Center of Process Pollution Control, Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China
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