Enhancing visible-light photocatalytic degradation of tetracycline by ZnFe2O4 loaded on UiO-66-NH2 under activated persulfate

Inspired by the wide applications of spinel oxide and metal–organic framework-modified narrow band gap materials, we herein report ZnFe2O4/UiO-66-NH2 nanocomposites synthesized by a two-step hydrothermal method in this study. Their structure, morphology and composition were characterized through XRD, FTIR, SEM, TEM and XPS. UV–Vis DRS and fluorescence spectroscopy were used to explore the photochemical properties of ZnFe2O4/UiO-66-NH2. Among all composite materials with different ratios, ZnFe2O4/10%UiO-66-NH2 exhibited the best photocatalytic degradation efficiency in the presence of persulfate. The efficiency of degradation of the environmental contaminant antibiotic tetracycline was increased about 2 times. The improved photocatalytic activity of the composite material could be attributed to its wide light absorption range and the Z-type heterojunction scheme suppressed the recombination of photogenerated electron–hole pairs. A trapping experiment indicated that sulfate ions, hydroxyl radicals and holes were the main active species in the photocatalytic reaction system. When ZnFe2O4 reacted with persulfate, numerous Fe2+ were converted into Fe3+, and the cyclic reaction could activate persulfate to a greater extent. In addition, the material also showed high recycling performance. These results demonstrate ZnFe2O4/UiO-66-NH2 nanocomposites are expected to generate a promising photocatalyst for degradation of environmental antibiotics.