Preparation and performance of Fe3O4@hydrophilic graphene composites with excellent Photo-Fenton activity for photocatalysis

• Fe3O4@HG composites from hydrophilic graphene and a mixed salt of Fe3+ and Fe2+.
• Fe3O4 particles with 15 nm in diameter uniformly distributing on HG nanosheets.
• The composites possessing paramagnetic characteristic and good stability in water.
• 87.68% Photo-Fenton catalytic efficiency at 53.18 wt% HG loading in Fe3O4@HG.
• HG improving the conversion of Fe3+ to Fe2+; the catalytic cycle being elucidated.

Composites (Fe3O4@HG) of hydrophilic graphene (HG) and Fe3O4 from an iron precursor of FeC13·6H2O and (NH4)2Fe(SO4)2·6H2O were prepared without any organic surfactants by a facile chemical co-precipitation method. Fe3O4 nanoparticles in Fe3O4@HG were about 15 nm in dimension and were ultra-dispersed on HG nanosheets. Fe3O4@HG exhibited paramagnetic characteristic and better stability in water. Photo-Fenton reaction results demonstrated that Fe3O4@HG composites could degrade methyl-orange (MO) dye with high efficiency in a short time. When the loading capacity of HG in Fe3O4@HG composites was 53.81 wt%, the catalytic efficiency could reach 87.68% after 30 min and the catalytic rate could be 0.055 mg min−1 in the first five minutes. A possible catalytic cycle for Fe3O4@HG catalyzed photo degradation of the dye was elucidated. The photo-generated electrons were transferred rapidly on the surface of HG and promoted the conversion efficiency of Fe3+/Fe2+ due to the good absorption and electronic conductivity of HG. The composites would be applied as photo-catalysts for treatment of wastewater.

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