Facile synthesis of oxygen vacancy-rich ZnxCu1-xFe2O4 nano-catalyst to activate peroxydisulfate for the efficient degradation of tetracycline

Abstract

Introduction of oxygen vacancies (OVs) into the heterogeneous catalysts is an efficient method to improve their catalytic activity for persulfate activation. The OVs-rich ZnxCu1-xFe2O4 nano-catalysts were synthesized by a facile co-precipitation method and analyzed using various characterization techniques (XRD, FE-SEM, EDS, BET surface area and XPS). OVs-rich ZnxCu1-xFe2O4 nano-catalysts exhibited a significantly higher catalytic activity for the removal of tetracycline (TC) by activating peroxydisulfate (PDS) than ZnFe2O4 and CuFe2O4 nano-catalyst. TC degradation efficiency in different ZnxCu1-xFe2O4/PDS systems demonstrated that Zn0.6Cu0.4Fe2O4 showed the best catalytic performance due to its highest OVs content, largest specific surface area and pore volume, and 90.09% of TC (20 mg/L) was degraded by Zn0.6Cu0.4Fe2O4 with PDS after 60 min. Cu in-situ introduction can increase the amount of OVs in ZnFe2O4 and affect the cross-occupancy of Zn and Fe, thus promoting the generation of the reactive oxygen species (ROS) in PDS-activated process; moreover, doped Cu can also act as an activation site for PDS and boost the formation of active Fe(Ⅱ). Mechanism study showed that all of ROS (1O2, O2•−, SO4•− and •OH) generated in ZnxCu1-xFe2O4/PDS system simultaneously engaged in TC elimination, and 1O2 played the main role. The probable TC degradation pathways in Zn0.6Cu0.4Fe2O4/PDS system were proposed. The practical application potential of magnetic Zn0.6Cu0.4Fe2O4 nano-catalyst in the treatment of TC-contaminated wastewater was assessed by investigating the reusability of Zn0.6Cu0.4Fe2O4, the removal of TC in real water matrix and the toxicity of TC degradation intermediates.