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Transformation of graphene oxide by ferrous iron: Environmental implications
Author(s) -
Wang Fanfan,
Wang Fang,
Gao Guandao,
Chen Wei
Publication year - 2015
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.3055
Subject(s) - graphene , oxide , chemistry , adsorption , ferrous , raman spectroscopy , aqueous solution , humic acid , iron oxide , x ray photoelectron spectroscopy , colloid , inorganic chemistry , nuclear chemistry , chemical engineering , organic chemistry , materials science , nanotechnology , fertilizer , physics , engineering , optics
Abiotic transformation of graphene oxide (GO) in aquatic environments can markedly affect the fate, transport, and effects of GO. The authors observed that ferrous iron (Fe[II])—an environmentally abundant, mild reductant—can significantly affect the physicochemical properties of GO (examined by treating aqueous GO suspensions with Fe 2+ at room temperature, with doses of 0.032 mM Fe 2+ per mg/L, 0.08 mM Fe 2+ per mg/L, and 0.32 mM Fe 2+ per mg/L GO). Microscopy data showed stacking of GO nanosheets on Fe 2+ treatment. Spectroscopy evidence (X‐ray diffraction, Fourier transform infrared transmission, Raman and X‐ray photoelectron spectroscopy) showed significant changes in GO surface O‐functionalities, in terms of loss of epoxy and carbonyl groups but increase of carboxyl group. The reduction mechanisms were verified by treating model organic molecules (styrene oxide, p ‐benzoquinone, and benzoic acid) resembling O‐containing fragments of GO macromolecules with Fe 2+ . With sedimentation and adsorption experiments (using bisphenol A as a model contaminant), the authors demonstrated that Fe 2+ reduced GOs still maintained relatively high colloidal stability, whereas their adsorption affinities were significantly enhanced. Thus, reduction of GO by mild reductants might be of greater environmental concerns than by stronger reducing agents (e.g., N 2 H 4 and S 2– ), because the latter can result in too significant losses of surface O‐functionalities and colloidal stability of GO. This interesting aspect should be given consideration in the risk assessment of GO. Environ Toxicol Chem 2015;34:1975–1982. © 2015 SETAC