Heterogeneous activation of persulfate by Ag doped BiFeO3 composites for tetracycline degradation

Persulfate (PS) activation have been extensively considered as a promising technology for removing recalcitrant pollutants, due to their production of radicals with superior oxidation reactivity. However, a catalyst with high reactive and convenient recovery for PS activation still remains to be developed. In this work, the silver-doped bismuth ferrite (Ag-x-BiFeO3, x = 0.1, 0.2, 0.3 and 0.4) catalysts with variable Ag content were synthesized via a facile sol-gel method and applied as heterogeneous catalyst in PS activation for tetracycline (TC) degradation. Ag-0.4-BiFeO3 presented the best catalytic activity compared with other Ag doped BiFeO3 composites, 91% TC could be efficiently removed within 60 min under optimized conditions and the reaction rate constant was 0.0338 min(-1). On the basis of the characterization analysis and catalytic test results, Ag could be the effective active site in PS activation and had a significant effect on PS activation. Moreover, the initial pH has negligible effect on the catalytic performance, indicating that Ag-x-BiFeO3/PS system could work in a wide pH range. The results of electron spin-resonance spectroscopy and radical quenching tests suggested that both SO4 center dot- and center dot OH radicals were involved in the Ag-0.4-BiFeO3/PS system. The possible mechanism of Ag-0.4-BiFeO3 activating PS and the major degradation pathway of TC degradation were proposed. At last, the reusability experiment results proved that Ag-0.4- BiFeO3 catalyst still has a high catalytic performance after 4 times used. (C) 2020 Published by Elsevier Inc.