A New Insight of Graphene oxide-Fe(III) Complex Photochemical Behaviors under Visible Light Irradiation

Renlan Liu,Xiaoying Zhu,Baoliang Chen

doi:10.1038/srep40711

Abstract

Graphene oxide (GO) contains not only aromatic carbon lattice but also carboxyl groups which enhanced the aqueous solubility of GO. To study the transformation of GO nanosheets in natural environments, GO aqueous dispersion was mixed with Fe3+ ions to form photoactive complex. Under visible light irradiation, Fe(III) of the complex would be reduced to Fe(II) which could subsequently reduce highly toxic Cr(VI) to Cr3+. The electron of the reduction was contributed by the decarboxylation of carboxyl groups on GO and iron was acting as a catalyst during the photoreduction. On the other hand, the consumption of carboxyl groups may convert GO to rGO which are tend to aggregate since the decreased electrostatic repulsion and the increased π-π attraction. The formed Cr3+ may be electrostatically adsorbed by the rGO sheets and simultaneously precipitated with the aggregated rGO sheets, resulting the effective removal of chromium and GO nanosheets from the aqueous environment. This study may shed a light on understanding the environmental transformation of GO and guide the treatment of Cr(VI).

Highlights

The coordinated hexavalent chromium denoted as Cr(VI) is a highly toxic and common pollutant in the aqueous environment[25,26]
Graphene oxide (GO) nanosheets were mixed with Fe3+ ions to form the GO-Fe(III) complex which was characterized with scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), STEM, Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS)
Fe3+ ions were fast bound by GO (Figure S1a), and the maximum saturated adsorption amounts (Qmax) derived from isotherm (Figure S1b) reached 622.4 mg/g, which suggest that GO is a strong adsorbent of Fe3+ ions

Summary

Introduction

The coordinated hexavalent chromium denoted as Cr(VI) is a highly toxic and common pollutant in the aqueous environment[25,26]. The trivalent chromium ion (Cr3+) in a lower valent state is less toxic than Cr(VI), which can be adsorbed by abundant natural negatively charged particles to form coordinated trivalent chromium Cr(III) and spontaneously precipitate to leave the aqueous environment[27]. It seems reduction is a promising approach to remove Cr(VI) from the aqueous environment. GO nanosheets were mixed with Fe3+ ions to form the GO-Fe(III) complex which was characterized with SEM, TEM, STEM, AFM, FTIR, and XPS. The characteristic differences of the GO-Fe(III) complex before and after the photoreduction were studied. The transformation of GO in the aqueous environment with the presence of Fe3+ and Cr(VI) was simulated in a lab scale

Methods

Results

Conclusion