Zinc-doped and biochar support strategies to enhance the catalytic activity of CuFe 2 O 4 to persulfate for crystal violet degradation.

Sulfate radicals-based Fenton-like technology has placed more emphasis on effectively dealing with the threat of dye wastewater. In this work, the Zn-doped CuFe 2 O 4 @biochar composite (Cu 0.9 Zn 0.1 Fe 2 O 4 @BC) was prepared through the convenient sol-gel pyrolysis process and applied as heterogeneous persulfate (PS) activator for crystal violet (CV) degradation. The crystal morphology and physicochemical properties of Cu 0.9 Zn 0.1 Fe 2 O 4 @BC were investigated by scanning electron microscope (SEM), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), Brunauer-Emmett-Teller method (BET), and X-ray photoelectron spectroscopy (XPS). The morphology of the catalyst changed before and after Zn doping. The crystallite size, lattice constant, saturation magnetization, and oxygen vacancy content increased after doping Zn. Compared with CuFe 2 O 4 @BC, the CV degradation efficiency of Cu 0.9 Zn 0.1 Fe 2 O 4 @BC activating PS increased from 87.7 to 96.9%, and the corresponding reaction rate constant increased by about 3.69 times. The effect of experimental conditions was systematically studied on the degradation progress. The degradation efficiency of CV was 91% after five times cycle experiments. Multiple experiments indicated that SO 4 •- , •OH and O 2 •- predominated for CV degradation. The degradation mechanism of CV in the Cu 0.9 Zn 0.1 Fe 2 O 4 @BC/PS system involved both free radical (SO 4 •- , •OH and O 2 •- ) and non-free radical pathways (electron transfer). The possible degradation pathways were investigated according to the ultra-performance liquid chromatography mass spectrometry (UPLC-MS) analysis of degradation intermediates. The result showed that Cu 0.9 Zn 0.1 Fe 2 O 4 @BC have an excellent catalyst performance, which provides a new strategy for improving catalytic activity.