Ultrafine ZnCo2O4 QD-incorporated carbon nitride mediated peroxymonosulfate activation for norfloxacin oxidation: performance, mechanisms and pathways

Abstract

Recently, peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) are being actively investigated as a potential technology for water decontamination and many efforts have been made to improve the activation efficiency of PMS. Herein, a 0D metal oxide quantum dot (QD)–2D ultrathin g-C₃N₄ nanosheet (ZnCo₂O₄/g-C₃N₄) hybrid was facilely fabricated through a one-pot hydrothermal process and used as an efficient PMS activator. Benefiting from the restricted growth effect of the g-C₃N₄ support, ultrafine ZnCo₂O₄ QDs (∼3–5 nm) are uniformly and stably anchored onto the surface. The ultrafine ZnCo₂O₄ possesses high specific surface areas and shortened mass/electron transport route so that the internal static electric field (E_internal) formed in the interface between p-type ZnCo₂O₄ and the n-type g-C₃N₄ semiconductor could speed up the electron transfer during the catalytic reaction. This thereby induces the high-efficiency PMS activation for rapid organic pollutant removal. As expected, the ZnCo₂O₄/g-C₃N₄ hybrid catalysts significantly outperformed individual ZnCo₂O₄ and g-C₃N₄ in catalytic oxidative degradation of norfloxacin (NOR) in the presence of PMS (95.3% removal of 20 mg L⁻¹ of NOR in 120 min). Furthermore, the ZnCo₂O₄/g-C₃N₄-mediated PMS activation system was systematically studied in terms of the identification of reactive radicals, the impact of control factors, and the recyclability of the catalyst. The results of this study demonstrated the great potential of a built-in electric field-driven catalyst as a novel PMS activator for the remediation of contaminated water.