Selective degradation of antibiotic in a novel Cu7S4/peroxydisulfate system via heterogeneous Cu(III) formation: Performance, mechanism and toxicity evaluation

Efficient degradation of antibiotic by peroxydisulfate (PDS)-based advanced oxidation processes in complex water environment is challenging due to the interference of impurities and the low activation efficiency of PDS caused by its symmetric structure. Herein, a novel Cu7S4/PDS system was developed, which can selectively remove tetracycline hydrochloride (TC) without interference of inorganic ions (e.g., Cl- and HCO3- ) and natural organic matter (e.g., humic acid). The results of quenching and probe experiments demonstrated that surface high-valent copper species (---Cu(III)), rather than radicals and 1O2, are main active species for TC degradation. ---Cu(III) can be generated via ---Cu(I)/O2 and ---Cu(II)/---Cu(I)/PDS systems and the S species on the surface of Cu7S4 promotes the cycle of ---Cu(II)/---Cu(I) and ---Cu(III)/---Cu(II), resulting in continuous generation of ---Cu (III). In addition, the degradation pathways of TC were proposed based on product analysis and DFT theory calculations. The acute toxicity, developmental toxicity and mutagenicity of treated TC were significantly reduced according to the results of toxicity estimation software tool. This study shows a promising Cu7S4/PDS system for the degradation and detoxication of antibiotic in complex water environment, while also providing a comprehensive understanding of PDS activation by Cu7S4 to generate active ---Cu(III) species.

Automated summary

A Cu7S4/PDS system was developed to selectively remove tetracycline hydrochloride in a complex water environment without interference from inorganic ions and natural organic matter. Surface high-valent copper species (---Cu(III)) were found to be the main active species for tetracycline degradation. This system shows promise for the degradation and detoxification of antibiotics in water.