Mechanistic insights into singlet‑oxygen-driven Fenton-like system using 2D/2D MXene/ZnFe-LDH heterostructure for ciprofloxacin removal

Mechanistic insights into singlet‑oxygen-driven Fenton-like system using 2D/2D MXene/ZnFe-LDH heterostructure for ciprofloxacin removal

To address the widespread occurrence of ciprofloxacin (CIP) in water, which poses serious risks to both public health and environmental safety, a novel and environmentally benign MXene with ZnFe-LDH (MX@LDH) 2D/2D heterogeneous catalyst was developed for activating peroxymonosulfate (PMS). First, we developed the MXene preparation method, including nitric acid treatment, to remove the fluorine residuals caused by the conventional hydrochloric acid and lithium fluoride method and to introduce oxygen vacancies. Subsequently, ZnFe-LDH was successfully immobilized onto the MXene surface via a co-precipitation method, enabling the formation of a 2D/2D heterostructure. MX@LDH provided more active sites for PMS activation with improved electron transfer. MX@LDH-4 (34.3 % MXene) exhibited 96.7 % CIP removal and 75.8 % TOC removal within 90 min under conditions of 40 mg/L CIP, 4 mM PMS, and pH = 6. MX@LDH maintained stable catalytic performance between pH 4 and pH 10. The singlet oxygen (1O2) and superoxide radicals (·O2−) were the main reactive oxygen species, and singlet oxygen could be produced by the radical pathway, as well as mediated electron transfer. The calculated mutagenicity and bioaccumulation factor of transformation products detected by liquid chromatography-tandem mass spectrometer were lower than those of CIP, implying the effectiveness of the MX@LDH/PMS system in reducing the ecotoxicity of CIP. Owing to the high resistance to inorganic ions and humic acid, the outstanding catalytic performance toward various pharmaceuticals, even in real water, stable chemical structure, and recyclable features, the 2D/2D heterogeneous MX@LDH/PMS system could be utilized for the decomposition of organic pollutants in water.

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