Ligand-induced drastic enhancement of catalytic activity of nano-BiFeO 3 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 2O 2 as a green oxidant. The oxidizing ability of H 2O 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 2O 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 2O 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 2O 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. © 2011 American Chemical Society.