Unravelling the removal mechanisms of trivalent arsenic by sulfidated nanoscale zero-valent iron: The crucial role of reactive oxygen species and the multiple effects of citric acid

Yibo Yuan; Xipeng Wei; Minghan Zhu; Yuhao Cai; Yuanzheng Wang; Zhi Dang; Hua Yin

doi:10.1016/j.scitotenv.2024.170275

Unravelling the removal mechanisms of trivalent arsenic by sulfidated nanoscale zero-valent iron: The crucial role of reactive oxygen species and the multiple effects of citric acid

Sci Total Environ. 2024 Mar 15:916:170275. doi: 10.1016/j.scitotenv.2024.170275. Epub 2024 Jan 21.

Authors

Yibo Yuan¹, Xipeng Wei², Minghan Zhu¹, Yuhao Cai¹, Yuanzheng Wang¹, Zhi Dang¹, Hua Yin³

Affiliations

¹ School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, Guangzhou 510006, China.
² School of Environment, South China Normal University, Guangzhou 510006, China.
³ School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, Guangzhou 510006, China. Electronic address: huayin@scut.edu.cn.

PMID: 38262532
DOI: 10.1016/j.scitotenv.2024.170275

Abstract

The remediation of arsenic-contaminated groundwater by sulfidated nanoscale zero-valent iron (S-nZVI) has raised considerable attention. However, the role of trivalent arsenic (As(III)) oxidation by S-nZVI in oxic conditions (S-nZVI/O₂) remains controversial, and the comprehensive effect of citric acid (CA) prevalent in groundwater on As(III) removal by S-nZVI remains unclear. Herein, the mechanisms of reactive oxygen species (ROS) generation and multiple effects of CA on As(III) removal by S-nZVI/O₂ were systematically explored. Results indicated that the removal efficiency of As(III) by S-nZVI/O₂ (97.81 %) was prominently higher than that by S-nZVI (66.71 %), resulting from the significant production of ROS (mainly H₂O₂ and OH) under oxic conditions, which played a crucial role in promoting the As(III) oxidation. Additionally, CA had multiple effects on As(III) removal by S-nZVI/O₂ system: (i) CA impeded the diffusion of As(III) towards S-nZVI and increased the secondary risk of immobilized As(III) re-releasing into the environment due to the Fe dissolution from S-nZVI; (ii) CA could significantly enhance the yields of OH from 25.29 to 133.00 μM via accelerating the redox cycle of Fe(II)/Fe(III) and increasing the oriented conversion rate of H₂O₂ to OH; (iii) CA could also enrich the types of ROS (such as O₂^- and ¹O₂) in favor of further As(III) oxidation. This study contributed novel findings regarding the control of As(III) contaminated groundwater using S-nZVI technologies.

Keywords: Citric acid; Oxidation mechanism; Reactive oxygen species; Sulfidated nanoscale zero-valent iron; Trivalent arsenic.