Degradation of 14C-labeled few layer graphene via Fenton reaction: Reaction rates, characterization of reaction products, and potential ecological effects

• Fenton reaction of few layer graphene (FLG) occurred under environmentally relevant condition.
• 14C-labeled technique enabled the quantitative measurements of degradation kinetics of FLG.
• Structural analysis using multiple orthogonal methods revealed significant oxidation of FLG.
• Multiple intermediate products resulting from Fenton reaction of FLG were identified.
• Accumulation of the reaction products of FLG by Daphnia magna was lower than that of the pristine FLG.

Graphene has attracted considerable commercial interest due to its numerous potential applications. It is inevitable that graphene will be released into the environment during the production and usage of graphene-enabled consumer products, but the potential transformations of graphene in the environment are not well understood. In this study, 14C-labeled few layer graphene (FLG) enabled quantitative measurements of FLG degradation rates induced by the iron/hydrogen peroxide induced Fenton reaction. Quantification of 14CO2 production from 14C-labeled FLG revealed significant degradation of FLG after 3 days with high H2O2 (200 mmol L−1) and iron (100 μmol L−1) concentrations but substantially lower rates under environmentally relevant conditions (0.2–20 mmol L−1 H2O2 and 4 μmol L−1 Fe3+). Importantly, the carbon-14 labeling technique allowed for quantification of the FLG degradation rate at concentrations nearly four orders of magnitude lower than those typically used in other studies. These measurements revealed substantially faster degradation rates at lower FLG concentrations and thus studies with higher FLG concentrations may underestimate the degradation rates. Analysis of structural changes to FLG using multiple orthogonal methods revealed significant FLG oxidation and multiple reaction byproducts. Lastly, assessment of accumulation of the degraded FLG and intermediates using aquatic organism Daphnia magna revealed substantially decreased body burdens, which implied that the changes to FLG caused by the Fenton reaction may dramatically impact its potential ecological effects.

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