Effects of natural pyrite and g-C3N4 constructed built-in electric field activated percarbonate on NOR removal: Mechanism, pathways, and toxicity analysis

Abstract

The advanced oxidation process (AOP) using sodium percarbonate (SPC) has attracted attention for water purification, but most SPC-based catalysts suffer from metal leaching, limited pH applicability, and low degradation efficiency, limiting their environmental use. In this study, a wet ball-milling technique was used to synthesize a natural pyrite and g-C₃N₄-based Fenton-like system with SPC, enabling rapid degradation of norfloxacin (NOR) under neutral conditions. Notably, with low concentrations of catalyst (0.5 g/L) and SPC (0.03 g/L), the degradation reaction rate constant (k_obs) for NOR reached 0.34354 min⁻¹, far exceeding traditional Fenton-like reactions. DFT simulations and characterizations such as XPS and TEM indicate that the exceptional reactivity is due to the rectifying contact between pyrite@g-C₃N₄ and SPC, which generates an internal electric field that enhances electron transfer, halogen bond cleavage, and reaction site exposure. This improves charge mobility, reactivity, and overcomes kinetic limitations of reductive systems. This work demonstrates the potential of natural pyrite in resource utilization and its ability to remove antibiotics from wastewater more efficiently and at a lower cost using iron-based catalysts without chemical synthesis.