In-situ fabrication of supported iron oxides from synthetic acid mine drainage: High catalytic activities and good stabilities towards electro-Fenton reaction

• In-situ fabricate heterogeneous electro-Fenton catalyst from acid mine drainage.
• Nano-scaled iron oxide/GF composites are obtained using an air-cathode fuel cell.
• Fe3O4/GF exhibits higher electro-Fenton activity than Fe2O3/GF and FeOOH/GF.
• Decomposition of H2O2 on iron oxides is completely surface-catalysis controlled.
• Iron oxides maintain structures and show stabilities in recycling utilization.

Acid mine drainage (AMD) contains a large amount of ferrous iron and the recovery of iron oxides from the AMD has been of extensive research interest. Here we report a novel air-cathode fuel cell strategy to in-situ utilize ferrous iron in the AMD for the fabrication of heterogeneous electro-Fenton catalysts. Three types of nano-structured iron oxide/graphite felt (GF) composites, including FeOOH/GF, Fe2O3/GF and Fe3O4/GF, were fabricated from a synthetic AMD and their catalytic activities towards the electro-Fenton reaction were evaluated at neutral pH with Rhodamine B (RhB) as a probe pollutant. The electro-Fenton system with GF cathode only removed 30 ± 1.4% of RhB after 120 min of reaction. In comparison, RhB removal efficiencies were significantly improved to 62.5 ± 2.0%, 95.4 ± 0.9% and 95.6 ± 0.7% when the FeOOH/GF, Fe2O3/GF and Fe3O4/GF composites were used as the cathodes, respectively. Among the three types of composites, the Fe3O4/GF exhibited the highest electro-Fenton catalytic activity whereas the lowest activity was observed for the FeOOH/GF. The decomposition of H2O2 on the iron oxides followed a completely surface-catalyzed mechanism in which the iron oxides maintained their structures without leaching of iron species. The air-cathode fuel cell technology has a potential for iron recovery from the AMD, and provides an effective way for fabricating heterogeneous electro-Fenton catalyst with high catalytic activity and good stability.

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