Activation of oxygen with sulfite for enhanced Removal of Mn(II): The involvement of SO4•

Dandan Rao; Yuankui Sun; Binbin Shao; Junlian Qiao; Xiaohong Guan

doi:10.1016/j.watres.2019.03.095

Activation of oxygen with sulfite for enhanced Removal of Mn(II): The involvement of SO₄^•

Water Res. 2019 Jun 15:157:435-444. doi: 10.1016/j.watres.2019.03.095. Epub 2019 Apr 3.

Authors

Dandan Rao¹, Yuankui Sun¹, Binbin Shao¹, Junlian Qiao², Xiaohong Guan³

Affiliations

¹ State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
² State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China; International Joint Research Center for Sustainable Urban Water System, Tongji University, Shanghai, 200092, China.
³ State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China; International Joint Research Center for Sustainable Urban Water System, Tongji University, Shanghai, 200092, China. Electronic address: guanxh@tongji.edu.cn.

PMID: 30978665
DOI: 10.1016/j.watres.2019.03.095

Abstract

Taking advantage of the active oxidants generated in the process of Mn(II)-catalyzed sulfite oxidation by oxygen, this study sought to enhance Mn(II) removal from water by activating oxygen with sulfite. The results revealed that Mn(II) can be effectively oxidized by oxygen to MnO₂ with the addition of sulfite under environmentally relevant conditions, and the performance of this process is dependent on the dosage of sulfite and the initial pH. Mn K-edge XANES analysis indicates that Mn(II) removal is primarily due to the transformation of Mn(II) to MnO₂ and, secondarily, to the adsorption of Mn(II) on generated MnO₂. Co-existing NaCl and CaCl₂ negatively affect Mn(II) removal, while the presence of Fe(II) considerably enhances Mn(II) removal by improving both Mn(II) oxidation and Mn(II) adsorption on the generated solids. Consequently, Mn(II) removal is as high as 98% in the presence of 1.0 mg/L of Fe(II) and both the residual Mn (<0.1 mg/L Mn) and Fe (<0.3 mg/L Fe) can meet China's drinking water standard. The experiments with real water samples also demonstrate the effectiveness of the sulfite-promoted Mn(II) removal process, especially in the presence of Fe(II). The enhancing effect of sulfite on Mn(II) oxidation by oxygen is mainly associated with the generation of HSO₅^-, and the critical step for generating HSO₅^- is the rapid oxidation of SO₃^•- by oxygen. EPR and radical scavenging studies demonstrate that SO₄^•- radical is the key reactive oxygen species responsible for Mn(II) oxidation by HSO₅^-.

Keywords: Mn(II); Oxidation; Peroxymonosulfate; Sulfate radicals (SO(4)(•-)); Sulfite.

MeSH terms

China
Manganese Compounds*
Oxidation-Reduction
Oxides
Oxygen*
Sulfites

Substances

Manganese Compounds
Oxides
Sulfites
Oxygen