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Thiourea Dioxide Coupled with Trace Cu(II): An Effective Process for the Reductive Degradation of Diatrizoate

  • Haodan Xu
    Haodan Xu
    Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
    State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
    More by Haodan Xu
  • Lihong Wang
    Lihong Wang
    Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
    State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
    More by Lihong Wang
  • Xuchun Li
    Xuchun Li
    School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018, China
    More by Xuchun Li
  • Zhiqiang Chen
    Zhiqiang Chen
    State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
  • , and 
  • Tao Zhang*
    Tao Zhang
    Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
    *Email: [email protected]
    More by Tao Zhang
Cite this: Environ. Sci. Technol. 2021, 55, 17, 12009–12018
Publication Date (Web):August 25, 2021
https://doi.org/10.1021/acs.est.1c03823
Copyright © 2021 American Chemical Society
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Abstract

Diatrizoate, a refractory ionic iodinated X-ray contrast media (ICM) compound, cannot be efficiently degraded in a complex wastewater matrix even by advanced oxidation processes. We report in this research that a homogeneous process, thiourea dioxide (TDO) coupled with trace Cu(II) (several micromoles, ubiquitous in some wastewater), is effective for reductive deiodination and degradation of diatrizoate at neutral pH values. Specifically, the molar ratio of iodide released to TDO consumed reached 2 under ideal experimental conditions. TDO eventually decomposed into urea and sulfite/sulfate. Based on the results of diatrizoate degradation, TDO decomposition, and Cu(I) generation and consumption during the TDO–Cu(II) reaction, we confirmed that Cu(I) is responsible for diatrizoate degradation. However, free Cu(I) alone did not work. It was proposed that Cu(I) complexes are actual reactive species toward diatrizoate. Inorganic anions and effluent organic matter negatively influence diatrizoate degradation, but by increasing the TDO dosage, as well as extending the reaction time, its degradation efficiency can still be guaranteed for real hospital wastewater. This reduction reaction could be potentially useful for in situ deiodination and degradation of diatrizoate in hospital wastewater before discharge into municipal sewage networks.

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.1c03823.

  • Details on liquid chromatography-tandem mass spectrometry ((LC-)MS/MS) settings (Text S1 and Table S2); characterization of the hospital wastewater (Table S1); speciation of Cu(I) (Table S2) and degradation products of DTZ (Table S3); pseudo-first-order model fitting of DTZ degradation and TDO decomposition (Figure S1); TDO decomposition at different pH values and DTZ degradation by TDO alone (Figure S2); speciation of Cu(II) at different solution pH values (Figure S3); H2O2 generation during the TDO/Cu(II) reaction (Figure S4); influence of external iodide addition on DTZ degradation (Figure S5); DTZ degradation by TDO/Cu(II) and CuCl alone (Figure S6); Cu(I) formation and DTZ degradation during the sulfite/Cu(II) reaction (Figure S7); UV absorbance spectra of Cu(II), TDO, and TDO/Cu(II) (Figure S8); DTZ degradation by the HA/Cu(II) reaction with/without radical scavengers (Figure S9); Cu(I) formation under N2 sparging during the TDO/Cu(II) reaction (Figure S10); MS2 spectra of DTZ and its degradation products (Figure S11); evolution of DTZ and its degradation products with the TDO/DTZ molar ratio (Figure S12); and DTZ degradation in the presence of EfOM and in hospital wastewater (Figure S13) (PDF)

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