Elucidation of the oxidation mechanisms and pathways of sulfamethoxazole degradation under Fe(II) activated percarbonate treatment

Pingping Yan; Qian Sui; Shuguang Lyu; Hongyuan Hao; Horst Friedrich Schröder; Wilhelm Gebhardt

doi:10.1016/j.scitotenv.2018.05.315

Elucidation of the oxidation mechanisms and pathways of sulfamethoxazole degradation under Fe(II) activated percarbonate treatment

Sci Total Environ. 2018 Nov 1:640-641:973-980. doi: 10.1016/j.scitotenv.2018.05.315. Epub 2018 Jun 5.

Authors

Pingping Yan¹, Qian Sui², Shuguang Lyu³, Hongyuan Hao⁴, Horst Friedrich Schröder⁵, Wilhelm Gebhardt⁵

Affiliations

¹ State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China.
² State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China. Electronic address: suiqian@ecust.edu.cn.
³ State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
⁴ Analytical Applications Center, Shimadzu (China) CO., LTD, Shanghai 200233, China.
⁵ Institute of Environmental Engineering, Environmental Analytical Laboratory, RWTH Aachen University, Templergraben 55, D-52056 Aachen, Germany.

PMID: 30021330
DOI: 10.1016/j.scitotenv.2018.05.315

Abstract

Fe(II) activated sodium percarbonate (SPC) process (SPC/Fe(II)) could efficiently remove sulfamethoxazole (SMX) in the aqueous phase, and has the potential in groundwater remediation. However, the degradation mechanisms, especially the degradation products and pathways till now have remained unclear. In the present study, intermediate products were identified using high resolution liquid chromatography coupled with ion trap and time-of-flight mass spectrometry (LCMS-IT-TOF). Nine intermediate products were identified, six of which have not yet been reported during the oxidation of SMX. The oxidation mechanisms involved hydroxyl substitution, the cleavage of sulfonamide bond, isoxazole ring opening and a rearrangement following the loss of the SO₂-group. Based on the identified intermediate products, the degradation pathways of SMX by SPC/Fe(II) process were illustrated. Fenton's reaction after the dissolution of SPC was proposed as the main reaction mechanisms, which was checked and confirmed by radical species detection tests and radical species scavenging studies. The results showed that although both O₂^- and HO were present in SPC/Fe(II) system, HO was dominant in the system while O₂^- was seldom involved in the degradation of SMX. These findings provided useful information and supported the application of this advanced oxidation process for antibiotics elimination in the groundwater.

Keywords: Intermediate products; Pharmaceuticals; Radicals; Removal performance; Sodium percarbonate; Sulfamethoxazole.