Nitrogen-doped carbon-coated Cu0 activates molecular oxygen for norfloxacin degradation over a wide pH range

Abstract

The Fenton-like activated molecular oxygen technology demonstrates significant potential in the treatment of refractory organic pollutants in wastewater, offering promising development prospects. We prepared a N-doped C-coated copper-based catalyst Cu0/NC3-600 through the pyrolysis of Mel-modified Cu-based metal–organic framework (MOF). The results indicate that the degradation of 20 mg/L norfloxacin (NOR) was achieved using 1.0 g/L Cu0/NC3-600 across a wide pH range, with a removal rate exceeding 95 % and total organic carbon (TOC) removals approaching 70 % after 60 min at pH 5–11. The nitrogen doping enhances the electronic structure of the carbon material, facilitating the adsorption of molecular oxygen. Additionally, the formed carbon layer effectively prevent copper leaching,contributing to increased stability to a certain extent. Subsequently, we propose the catalytic reaction mechanism for the Cu0/NC/air system. Under acidic conditions, Cu0/NC3-600 activates molecular oxygen to produce the •O2–, which serves as the primary active species for NOR degradation. While in alkaline conditions, the high-valent copper species Cu3+ is generated in conjunction with •O2–, both working simultaneously for NOR degradation. Furthermore, based on the LC-MS results, we deduced four possible degradation pathways. This work offers a novel perspective on expanding the pH range of copper-based catalysts with excellent ability to activate molecular oxygen for environmental water treatment.