Ligand-Induced Drastic Enhancement of Catalytic Activity of Nano-BiFeO3 for Oxidative Degradation of Bisphenol A

Effects of chelating agents on the catalytic degradation of bisphenol A (BPA) was studied in the presence of BiFeO 3 nanoparticles as a heterogeneous catalyst and H 2 O 2 as a green oxidant. The oxidizing ability of H 2 O 2 in the presence of nano-BiFeO 3 alone was not so strong to degrade BPA at neutral pH values, due to the limited catalytic ability of nano-BiFeO 3 . Once the surface of nano-BiFeO 3 was in situ modified by adding proper organic ligands, the BPA degradation was much accelerated in the pH range of 5–9. The enhancing effect of the ligand was observed to have an order of blank < tartaric acid < formic acid < glycine < nitrilotriacetic acid < ethylenediaminetetraacetic acid (EDTA). The addition of 0.25 mmol L –1 EDTA in the H 2 O 2 –BiFeO 3 system at pH 5.0 and 30 °C increased the BPA removal from 20.4% to 91.2% with reaction time of 120 min. The enhancing effect of the ligand was found to be indifferent of the possible dissolution of iron from nano-BiFeO 3, but correlated well with the accelerated •OH formation from the H 2 O 2 decomposition at the BiFeO 3 surface, which was confirmed by ESR measurements and density functional theory studies. In general, more addition of EDTA, higher H 2 O 2 concentrations, or higher temperatures were favorable to the BPA degradation. The effect of the EDTA addition on the kinetics of BPA degradation was also clarified.