Enhanced degradation of tetracycline in water over Cu-doped hematite nanoplates by peroxymonosulfate activation under visible light irradiation

Herein, Cu-doped hematite nanoplates (named as CuHNPs) with abundant oxygen-vacancies were prepared through a facile one-pot solvothermal method and used for efficient peroxymonosulfate (PMS) activation to degrade tetracycline (TC) in water. The catalytic activity of optimal CuHNPs-7.5 catalyst to activate PMS for the degradation of TC in water under visible light irradiation is 7.74 and 2.93 times higher than that of pure one without and with visible light irradiation. CuHNPs-7.5 exhibited excellent degradation for TC in the broad pH range from 2.14 to 10.75, and the removal of TC was barely inhibited by co-anions. The combination of free radicals and non-radical pathway, including sulfate radicals (SO4·-), hydroxide radicals (·OH), superoxide radical (·O2-) and single oxygen (1O2), contributed to TC oxidation. The introduction of Cu2+ not only accelerated the transformation of Fe(III)/Fe(II) redox cycle but also induced rich oxygen defects in the structure of hematite, boosting more generation of reactive oxygen species (ROSs) for TC degradation. Density functional theory (DFT) calculation and electrochemical impedance spectroscopy (EIS) tests confirmed the accelerated electrons transfer of CuHNPs-7.5 in PMS activation. This study provides a strategy to construct effective catalysts of PMS activation combining radicals and non-radical pathways for environmental remediation.