Synthesis of copper-based Fenton-like catalyst (Cu/HAP-sBC) for oxidative degradation of p-nitrophenol in aqueous solution

Abstract

p-Nitrophenol (PNP), a persistent phenolic pollutant with endocrine-disrupting and carcinogenic properties, poses substantial risks to aquatic ecosystems and human health. To address the limitations of conventional Fenton processes (e.g., sludge generation, acidic pH dependency), we developed a novel copper-impregnated hydroxyapatite-biochar composite catalyst (Cu/HAP-sBC) through ion-exchange stabilization and carbon matrix integration. Comprehensive characterization (SEM, BET, XRD, FTIR, XPS) demonstrated the hierarchical porous structure with a high specific surface area (271.5 m²/g) and homogeneous Cu dispersion, while the synergistic HAP-biochar interface effectively minimized metal leaching. Under optimized conditions (2.0 g/L catalyst, 50 mg/L PNP, 50 mM H₂O₂, pH 7.0, 25 °C), Cu/pHAP-sBC achieved 96.41 % PNP degradation within 60 min through adsorption-catalysis synergy. Mechanistic studies using EPR and LC-MS revealed hydroxyl radical (·OH)-driven stepwise degradation pathways, involving intermediates such as p-nitrocatechol and p-benzoquinone. This study pioneers a sustainable remediation strategy by synergistically utilizing renewable biochar and waste-derived hydroxyapatite, offering a sludge-free, pH-flexible alternative to traditional Fenton-like system for organic pollutant removal.