Nonradical pathway dominated activation of peroxymonosulfate by ZnFe2O4/C composites to eliminate tetracycline hydrochloride: Insight into the cycle of Zn/Fe and electron transfer

Abstract

Magnetic ZnFe2O4 nanoparticles show promising as heterogeneous catalysts in peroxymonosulfate (PMS) activation because of their ease of separation and good reusability. However, the low catalytic activity and easy agglomeration in clusters or clumps limit the application of ZnFe2O4 nanoparticles. Herein, ZnFe2O4 nanoparticles embedding into carbon substrate are prepared. Owing to the anchoring effect of carbon substrate and the improved electron transfer for ZnFe2O4 nanoparticles, the as-prepared magnetic ZnFe2O4/C composites exhibit efficiently catalytic activity in PMS activation, in which 92.0% of tetracycline hydrochloride (TC) can be eliminated. Moreover, the composites show a wide pH adaptation range (3.04–10.99) and good stability. The catalytic oxidation of TC is mainly based on the nonradical pathways, including contributions of 1O2 and electron transport. The high performance of ZnFe2O4/C in PMS activation is mainly attributed to the accelerated redox cycles of Fe3+/Fe2+ and Zn2+/Zn+ and the improved electron transfer. Three possible TC degradation pathways were proposed, and the biotoxicity assessment results further confirm the high efficiency of the ZnFe2O4/C/PMS system. This work provides a simple strategy for the preparation of magnetic ZnFe2O4/C heterogeneous catalyst and a new insight into PMS activation, which promotes the application of spinel nanomaterials in environmental remediation.