Synergistic adsorption–Fenton degradation of 2,4-dichlorophenol using chitosan-modified attapulgite for sustainable water remediation

Abstract

2,4-Dichlorophenol (2,4-DCP), an emerging eco-contaminant with high bioaccumulation potential and persistence, was targeted for removal using chitosan-modified attapulgite (ATP@CCS) via a synergistic adsorption–Fenton process. ATP@CCS was synthesized through mild hydrothermal carbonization of chitosan, enabling dual functionality: (1) efficient adsorption/enrichment of 2,4-DCP (51% removal without H₂O₂) and (2) catalytic degradation via H₂O₂-assisted Fenton-like oxidation (97.8% removal under optimal conditions: 65 °C, pH 7, 40 mmol L⁻¹ H₂O₂, 50 mg L⁻¹ 2,4-DCP). In a scalable fixed-bed reactor employing polysulfone-ATP@CCS pellets, the system treated 15 L of 2,4-DCP solution (50 mg L⁻¹) with sustained efficiency (97.9% peak removal; 90% after 120 h), demonstrating continuous processing of 36 L contaminated water. The chitosan coating significantly suppressed iron leaching (Fe release: 1.84 ppm for raw ATP → 0.68 ppm for ATP@CCS). Kinetics adhered to pseudo-second-order models, while adsorption aligned with the Langmuir isotherm.