Al3+ doped CuFe2O4 efficiently activates peroxymonosulfate for long-term and stable degradation of tetracycline: Synergistic and regulatory role of Al3+

The water pollution caused by the proliferation of tetracycline hydrochloride (TC) has seriously harmed human beings and the environment. Therefore, it is necessary to design a catalyst that can effectively remove TC and immobilize it for practical applications. Spinel catalysts can effectively resolve the problem of TC contamination in water. In this research, in order to solve the problems of poor dispersion, inferior performance and weak stability of copper ferrate (CuFe2O4). Al3+-doped CuFe2O4 was prepared by the one-step sol–gel-combustion method and used as a peroxymonosulfate (PMS) activator to promote the degradation of tetracycline (TC). A series of degradation experiments and characterization indicated that Al3+-doped CuFe2O4 could remove more than 95 % of TC within 20 min, its first-order kinetic degradation constant was 2.5 times higher than that of CuFe2O4. The mechanism by which Al3+ could improve the degradation of CuFe2O4 may be as follows: the presence of Al3+ increased the electron transfer rate of the metal; effectively increased the specific surface area of the catalyst, provided more active sites; the Al-O-Fe and Al-O-Cu bonds generated by Al3+ immobilized the highly reactive metal ions, reducing ion leaching and improving the stability of the catalyst. Electron paramagnetic resonance and quenching experiments identified the synergistic effect of both radicals and non-radicals in the reaction. Electrochemistry and X-ray photoelectron spectroscopy (XPS) further verified the possible catalytic mechanism. Furthermore, by further immobilization, the 1 g of catalyst could continuously degrade 9 L of TC in water without stirring, showing excellent practical applications. This work provides a reference for improving the catalytic performance of ferrite spinel materials and solving the difficult problem of catalyst recovery in the real environment.