Relative contribution of ferryl ion species (Fe(IV)) and sulfate radical formed in nanoscale zero valent iron activated peroxydisulfate and peroxymonosulfate processes

Zhen Wang; Wei Qiu; Suyan Pang; Yuan Gao; Yang Zhou; Ying Cao; Jin Jiang

doi:10.1016/j.watres.2020.115504

Relative contribution of ferryl ion species (Fe(IV)) and sulfate radical formed in nanoscale zero valent iron activated peroxydisulfate and peroxymonosulfate processes

Water Res. 2020 Apr 1:172:115504. doi: 10.1016/j.watres.2020.115504. Epub 2020 Jan 15.

Authors

Zhen Wang¹, Wei Qiu¹, Suyan Pang², Yuan Gao³, Yang Zhou³, Ying Cao¹, Jin Jiang⁴

Affiliations

¹ State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, China.
² Key Laboratory of Songliao Aquatic Environment, Ministry of Education, School of Municipal and Environmental Engineering, Jilin Jianzhu University, Changchun, 130118, China.
³ Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou, 510006, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China.
⁴ State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, China; Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou, 510006, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China. Electronic address: jiangjinhit@126.com.

PMID: 31981901
DOI: 10.1016/j.watres.2020.115504

Abstract

Activation of persulfates (i.e., peroxydisulfate (PDS) and peroxymonosulfate (PMS)) by nanoscale zero-valent iron (nZVI) is reported to be effective in oxidative treatment of environmental contaminants. It has been widely accepted in numerous literature that sulfate radical (SO₄^•-) formed from the decomposition of persulfates activated by aqueous Fe(II) released from nZVI corrosion is responsible for the oxidative performance in nZVI/persulfates systems. In this work, by employing methyl phenyl sulfoxide (PMSO) as a probe, we demonstrated that the activation of persulfates by nZVI through electron transfer led to SO₄^•- formation, while the homogeneous activation of persulfate by the released Fe(II) resulted in ferryl ion species (Fe(IV)) generation in nZVI/persulfates systems. Similarly, nanoscale zero-valent aluminum (nZVAl) and zinc (nZVZn) were also demonstrated to be able to donate electron to persulfates leading to SO₄^•- formation. However, the insulative aluminum oxide shell hindered the electron transfer leading to the poor persulfates decomposition, while the conductive iron and zinc oxide shell enabled the electron transfer process resulting in a continuous generation of SO₄^•-. Further, it was obtained that the relative contribution of SO₄^•- and Fe(IV) in nZVI/persulfates systems was independent of the initial concentration of nZVI and PDS, but was positively correlated with PMS concentration. In addition, the increase of pH from 3 to 7 led to the decrease of the relative contribution of Fe(IV), which was rationalized by the decrease of availability of aqueous Fe(II) at higher pH. Our findings not only shed lights on the nature of the reactive intermediate formed in the nZVI/persulfates systems, but also unprecedentedly distinguished the surface activation of persulfates from the homogeneous catalysis process.

Keywords: Advanced oxidation processes; Ferryl ion; Nanoscale zero valent iron; Peroxydisulfate; Peroxymonosulfate; Sulfate radical.

MeSH terms

Iron*
Peroxides
Sulfates
Water Pollutants, Chemical*

Substances

Peroxides
Sulfates
Water Pollutants, Chemical
sulfate radical
ferryl iron
peroxymonosulfate
Iron