Surface Modification of Graphite Support as an Effective Strategy to Enhance the Electro-Fenton Activity of Fe₃O₄/Graphite Composites in Situ Fabricated from Acid Mine Drainage Using an Air-Cathode Fuel Cell

Air-cathode fuel cell (AC-FC) technology provides a facile way for fabricating Fe3O4/graphite composite by in situ utilizing the FeII in acid mine drainage (AMD). Herein, surface modification of the graphite support is suggested to be an effective strategy to enhance electro-Fenton (EF) catalytic activity of the Fe3O4/graphite composite prepared from AMD. Four surface modification methods, including H2O2 treatment, electro-oxidation treatment, KOH treatment, and N2H4 treatment, are applied on commercial graphite felt (GF). Structures and properties of the modified GFs are characterized, and EF catalytic activities of corresponding Fe3O4/GF composites prepared from synthetic AMD are evaluated. The results demonstrate that surface modification of GF not only improves the electro-oxidation of FeII in AC-FC but also promotes the electro-generation of H2O2 in the heterogeneous EF process. Notably, the concentration of H2O2 generated on N2H4-treated GF (GF-N2H4) is more than three times that generated on unmodified GF (GF-Raw), and iron content in the prepared Fe3O4/GF-N2H4 composite is more than twice that in the Fe3O4/GF-Raw composite. Application of GF-N2H4 to the treatment of real AMD greatly enhances the recovery efficiency of FeII as Fe3O4. The Fe3O4/GF-N2H4 composite prepared from real AMD displays high catalytic activity and good stability in the heterogeneous EF process for mineralizing a variety of refractory organic contaminants