The application of UV-C laser in persulfate activation for micropollutant removal: Case study with iodinated X-ray contrast medias

Zheng-Yu Dong; Bin Xu; Chen-Yan Hu; Tian-Yang Zhang; Yu-Lin Tang; Yang Pan; Mohamed Gamal El-Din; Qi-Ming Xian; Nai-Yun Gao

doi:10.1016/j.scitotenv.2021.146340

The application of UV-C laser in persulfate activation for micropollutant removal: Case study with iodinated X-ray contrast medias

Sci Total Environ. 2021 Jul 20:779:146340. doi: 10.1016/j.scitotenv.2021.146340. Epub 2021 Mar 11.

Authors

Zheng-Yu Dong¹, Bin Xu¹, Chen-Yan Hu², Tian-Yang Zhang³, Yu-Lin Tang¹, Yang Pan⁴, Mohamed Gamal El-Din⁵, Qi-Ming Xian⁴, Nai-Yun Gao⁶

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China.
² College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai 200090, PR China.
³ State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China. Electronic address: [email protected].
⁴ State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, PR China.
⁵ State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada.
⁶ State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.

PMID: 33744578
DOI: 10.1016/j.scitotenv.2021.146340

Abstract

A novel light source UV-C laser was applied in persulfate (PS) activation to effectively remove iodinated X-ray contrast medias (ICMs) including iohexol (IOX), iopamidol (IPM) and diatrizoate (DTZ) in this study. Significant ICMs degradation was observed in UV-C laser/PS systems with pseudo first-order rate constants of 0.022-0.067 s^-1. Sulfate radicals (SO₄^•-) were the main active species in the three ICMs degradation, and the steady-state concentrations ([SO₄^•-]_ss) were 3.629 × 10^-11 M (IOX), 1.702 × 10^-11 M (IPM) and 1.148 × 10^-11 M (DTZ), respectively. Under the high intensity of UV-C laser, the optimal reaction efficiency was achieved at pH = 7.0 with PS concentration of 1.0 mM, and the degradation efficiency for IOX reached 93.8% within only 40 s. Both bicarbonate and chloride ions could inhibit the three ICMs degradation and the inhibition rate increased with the increase of ions concentration. The kinetic models were established and the steady-state concentrations of radicals were calculated. Density functional theory (DFT) calculations combined with experiments were used to derive the reaction pathways for three ICMs. Cyclic voltammetry measurements detected a lower redox potential peak in IOX degradation, revealing the existence of electron shuttles under the UV-C laser irradiation to promote the redox reaction. This study is the first report of UV-C laser activation of persulfate. It is a new advanced oxidation process mediated by very effective photolysis and active species formation.

Keywords: Electron shuttle; Hydroxyl radical; Iodinated X-ray contrast media; Sulfate radical; UV-C laser.