Oxygen vacancy induced peroxymonosulfate activation by NixZn1-xFe2O4 for the effective degradation of tetracycline in water

Herein, a series of NixZn1-xFe2O4 catalysts with various content of oxygen vacancy were prepared by adjusting the doping content of Ni and applied to activate peroxymonosulfate (PMS) for the degradation of tetracycline (TC). When x = 0.6, Ni0.6Zn0.4Fe2O4 with the most oxygen vacancy presented the highest TC removal efficiency and the maximum apparent rate constant (k(app)). In Ni0.6Zn0.4Fe2O4/PMS system, about 95.6% of TC was degraded within 60 min, and the k(app) was 0.113 min(-1), which was 10.18 and 3.47 times of the ZnFe2O4/PMS and NiFe2O4/PMS systems. Significantly, the role of oxygen vacancy on Ni0.6Zn0.4Fe2O4 surface was investigated. It was found that PMS ([O3S-O-O-H]-) could be adsorbed and captured by oxygen vacancy on Ni0.6Zn0.4Fe2O4 surface, and PMS could be further reduced by the free electrons in oxygen vacancy to generate SO4 center dot- and center dot OH radicals. The production of O-1(2) also be related to the surface oxygen vacancy. TC was attacked and mainly degraded by these three reactive oxygen species (ROS). In addition, TC could be also directly oxidated by donating electrons to the metastable complex that was formed by the reaction between Ni0.6Zn0.4Fe2O4 and PMS.

Automated summary

In this study, a series of NixZn1-xFe2O4 catalysts with different oxygen vacancy content were prepared by adjusting the doping content of Ni and used for activating peroxymonosulfate (PMS) to degrade tetracycline (TC). The results showed that Ni0.6Zn0.4Fe2O4 with the highest oxygen vacancy content exhibited the highest TC removal efficiency and the maximum degradation rate constant in the Ni0.6Zn0.4Fe2O4/PMS system. The role of oxygen vacancy on the Ni0.6Zn0.4Fe2O4 surface was investigated and it was found that the adsorption and capture of PMS, as well as the generation of reactive oxygen species, were promoted by the oxygen vacancy. In addition, TC could be oxidized by directly donating electrons to the metastable complex formed by the reaction between Ni0.6Zn0.4Fe2O4 and PMS.