Influence of lanthanum-doping on photocatalytic properties of BiFeO 3 for phenol degradation

A series of BiFeO3 and lanthanum-doped BiFeO3 photocatalysts were synthesized by a facile sol-gel method using citric acid as complexing agent, and used to remove phenol in industrial wastewater under simulated sunlight irradiation. The samples were characterized by X-ray diffraction, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The introduction of La effectively suppressed the generation of an impurity phase. All the metals (La, Bi and Fe) are well distributed. Under simulated sunlight irradiation, the La-doped BiFeO3 photocatalysts exhibited superior photocatalytic activity to pure BiFeO3. The 15% La-doped BiFeO3 photocatalyst exhibited the best activity, with a degradation rate of 96% and COD removal rate of 81.53% after irradiation for 180 min, and it showed good recycling stability. The enhanced photocatalytic ability of 15% La-doped BiFeO3 was attributed to the increase of adsorbed surface hydroxyl groups, enhancement of visible light absorption and reduction of electron-hole recombination. We confirmed that the primary active species was •OH by adding different scavengers during the photodegradation of phenol and proposed a reaction mechanism based on these experiments.