The oxidation capacity of Mn3O4 nanoparticles is significantly enhanced by anchoring them onto reduced graphene oxide to facilitate regeneration of surface-associated Mn(III)

Lin Duan; Zhongyuan Wang; Yan Hou; Zepeng Wang; Guandao Gao; Wei Chen; Pedro J J Alvarez

doi:10.1016/j.watres.2016.07.023

The oxidation capacity of Mn3O4 nanoparticles is significantly enhanced by anchoring them onto reduced graphene oxide to facilitate regeneration of surface-associated Mn(III)

Water Res. 2016 Oct 15:103:101-108. doi: 10.1016/j.watres.2016.07.023. Epub 2016 Jul 11.

Authors

Lin Duan¹, Zhongyuan Wang¹, Yan Hou¹, Zepeng Wang¹, Guandao Gao¹, Wei Chen², Pedro J J Alvarez³

Affiliations

¹ College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Wei Jin Road 94, Tianjin, 300071, China.
² College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Wei Jin Road 94, Tianjin, 300071, China. Electronic address: chenwei@nankai.edu.cn.
³ Department of Civil and Environmental Engineering, Rice University, Houston, TX, 77005, United States. Electronic address: alvarez@rice.edu.

PMID: 27448035
DOI: 10.1016/j.watres.2016.07.023

Abstract

Metal oxides are often anchored to graphene materials to achieve greater contaminant removal efficiency. To date, the enhanced performance has mainly been attributed to the role of graphene materials as a conductor for electron transfer. Herein, we report a new mechanism via which graphene materials enhance oxidation of organic contaminants by metal oxides. Specifically, Mn3O4-rGO nanocomposites (Mn3O4 nanoparticles anchored to reduced graphene oxide (rGO) nanosheets) enhanced oxidation of 1-naphthylamine (used here as a reaction probe) compared to bare Mn3O4. Spectroscopic analyses (X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy) show that the rGO component of Mn3O4-rGO was further reduced during the oxidation of 1-naphthylamine, although rGO reduction was not the result of direct interaction with 1-naphthylamine. We postulate that rGO improved the oxidation efficiency of anchored Mn3O4 by re-oxidizing Mn(II) formed from the reaction between Mn3O4 and 1-naphthylamine, thereby regenerating the surface-associated oxidant Mn(III). The proposed role of rGO was verified by separate experiments demonstrating its ability to oxidize dissolved Mn(II) to Mn(III), which subsequently can oxidize 1-naphthylamine. The role of dissolved oxygen in re-oxidizing Mn(II) was ruled out by anoxic (N2-purged) control experiments showing similar results as O2-sparged tests. Opposite pH effects on the oxidation efficiency of Mn3O4-rGO versus bare Mn3O4 were also observed, corroborating the proposed mechanism because higher pH facilitates oxidation of surface-associated Mn(II) even though it lowers the oxidation potential of Mn3O4. Overall, these findings may guide the development of novel metal oxide-graphene nanocomposites for contaminant removal.

Keywords: 1-Naphthylamine; Graphene; Mn(3)O(4)−rGO nanocomposites; Oxidation capacity.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Graphite / chemistry*
Nanoparticles / chemistry
Oxidation-Reduction
Oxides / chemistry*
Regeneration

Substances

Oxides
Graphite