Low-temperature synthesis of graphene/Bi2Fe4O9 composite for synergistic adsorption-photocatalytic degradation of hydrophobic pollutant under solar irradiation

A graphene-supported bismuth ferrite (BFO249/rGO4.5) that exhibits a highly effective solar photocatalysis was synthesized via a facile co-precipitation method at a low temperature of 95 °C. BFO249/rGO4.5 has a 2D composite structure and the deposited bismuth ferrite (BFO249) nanoparticles have an average size of 5 nm. Fourier transform-infrared (FT-IR) analysis shows that the resulting BFO249/rGO4.5 catalysts are chemically bonded composites possibly with Fe–O–C and/or Bi–O–C bonds. Photoluminescence evaluation indicates that rGO can effectively suppress the recombination of e−/h+ pairs in BFO249. The adsorption and photocatalytic performance was evaluated using a hydrophobic pollutant (bisphenol A). The adsorption capacity of BPA on BFO249/rGO4.5 is 4 mg g−1, which is ca. 5.5 times higher than that of pristine BFO249. Under visible-light region of full solar spectrum, BFO249/rGO4.5 shows a great synergistic adsorption-photocatalytic degradation efficiency of 62% after 3 h (∼2 times higher than that of BFO249) and the corresponding mineralization is 47%. The predominant reactive oxygen species (ROS) for BPA degradation was identified to be the O2−. When BPA solution containing BFO249/rGO4.5 was exposed to the full solar spectrum, 76% and 80% of BPA can be removed at pH 6.5 and 5, respectively, in 3 h. The presence of bicarbonate induces moderate inhibitory effect on the photocatalytic degradation (PCD) of BPA by BFO249/rGO4.5 while sulfate, chloride or nitrate exhibit only minor effect.