CuFeS2/activated carbon heterostructure as a microwave-responsive catalyst for reductive and oxidative degradation of ibuprofen, ketoprofen, and diclofenac

Abstract

We prepared a novel microwave (MW) responsive catalyst by assembling CuFeS2 (CFS) nanoparticles to activated carbon (AC), creating a stable heterostructure named ACFS. The efficiency, structural aspects, and surface mechanisms of the ACFS catalyst were investigated through the degradation of ibuprofen (IBP), ketoprofen (KTP), and diclofenac (DCF) under optimized mild reaction conditions. Total mineralization was reached between 20 and 30 min for all compounds, following pseudo-first-order kinetics, with high catalyst recycling stability in up to 10 consecutive cyclic runs. The plausible degradation pathways proposed according to the mass spectra analysis revealed that while IBP and KTP were oxidized, DCF degradation routes split into direct oxidation or reduction followed by oxidation after 15 min of MW irradiation. We demonstrated by employing quantum chemical calculations that the preferential degradation routes for each compound were related to the generation of reactive oxygen species and its relation to the surface phenomena. The combined mechanisms revealed the occurrence of an effective electronic-charge transfer during catalytic reductions as well as •OH production enhanced by hot spots formed during oxidations. Consequently, this work proves that metal/carbon heterostructures can be robust and versatile for reductive and oxidative reactions assisted by MW.