Influence of Bi-doping on Mn_1-xBi_xFe₂O₄ catalytic ozonation of di-n-butyl phthalate

Magnetic porous Bi-doping MnFe₂O₄ (Mn_1-xBi_xFe₂O₄, x=0, 0.005, 0.01, 0.02, 0.05) were synthesized by a sol-gel method and characterized via multiple techniques. The influence of Bi-doping on catalytic ozonation of catalysts for di-n-butyl phthalate (DBP) decomposition and ozone utilization were investigated in aqueous solutions. Varying Bi-doping amount had little effect on the crystal structure, morphology and magnetism of MnFe₂O₄. The introduction of Bi into MnFe₂O₄ enhanced the catalytic DBP degradation. Hydroxyl radicals played a critical role in the Mn_1-xBi_xFe₂O₄/O₃ heterogeneous systems. OH generation was promoted by the surface hydroxyl groups which were regarded as main active sites of catalyst. The extent of Bi-doping had an effect on crystallite size (D_XRD) and resulted in increasing surface hydroxyl site concentrations (SHSC) of catalysts. A good linear correlation between the doping amount and SHSC was observed. The initial reaction rate and DBP removal rate mainly depended on the surface hydroxyl groups in catalytic ozonation. The numbers of SHSC and average ozone utilization rate were correlated with initial reaction rates and DBP removal rates, respectively. Bi-doping not only increased the binding sites but also enhanced the tendency of ozone to decompose into OH.