Heterogeneous activation of persulfate by Ag doped BiFeO 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-BiFeO, 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-BiFeO presented the best catalytic activity compared with other Ag doped BiFeO composites, 91% TC could be efficiently removed within 60 min under optimized conditions and the reaction rate constant was 0.0338 min. 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-BiFeO/PS system could work in a wide pH range. The results of electron spin-resonance spectroscopy and radical quenching tests suggested that both SO and OH radicals were involved in the Ag-BiFeO/PS system. The possible mechanism of Ag-BiFeO activating PS and the major degradation pathway of TC degradation were proposed. At last, the reusability experiment results proved that Ag-BiFeO catalyst still has a high catalytic performance after 4 times used.