Design of a magnetic Fenton-like catalyst by decorating diamond-shaped MIL-88A with Chenopodium-derived biochar for nitrophenol degradation: optimization and mechanistic insights

Abstract

An effective Fenton-like Fe₃O₄/MIL-88A/BC catalyst was fabricated by combining magnetite nanoparticles (Fe₃O₄) with diamond-shaped MIL-88A and Chenopodium-derived biochar for the degradation of 2-NP. The elemental composition, morphology, functional groups, surface net charge, and crystallographic phase of the Fe₃O₄/MIL-88A/BC catalyst were examined using various characterization techniques, including XPS, SEM, FTIR, ZP, and XRD. Optimization experiments were conducted to determine the optimal Fenton-like degradation conditions for 2-NP using H₂O₂/Fe₃O₄/MIL-88A/BC. Laboratory experiments showed that the 2-NP degradation efficiency by H₂O₂/Fe₃O₄/MIL-88A/BC reached 91.04% within 120 min at pH = 5, Fe₃O₄/MIL-88A/BC = 10 mg, and H₂O₂ concentration = 500 mg L⁻¹. Kinetic studies indicated that the Fenton-like degradation of 2-NP followed a second-order model, while H₂O₂ decomposition was best described by a first-order model. Quenching tests indicated that the Fenton-like reaction of 2-NP proceeded via a radical mechanism and confirmed that the ˙OH radicals are the controlling reactive O-species. The degradation mechanism of 2-NP was proposed based on the XPS spectra of the neat and used Fe₃O₄/MIL-88A/BC catalysts. The intermediates obtained from the Fenton-like degradation of 2-NP by the Fe₃O₄/MIL-88A/BC catalyst were predicted from the GC-MS spectrum.