Tuning of electronic activation and mechanisms in chalcopyrite/MWCNT ordered catalyst for microwave-assisted H2O2/driven degradation of paracetamol and naproxen

Abstract

A key challenge in microwave-assisted catalysis lies in the short catalyst lifespan and poor control of electronic activity. In this work, we demonstrate that multi-walled carbon nanotubes (MWCNTs), used as ordered carbonaceous supports for chalcopyrite (CuFeS₂) nanoparticles, enable precise control over irradiation-induced effects. Under mild conditions (500 W, 0.5 g L⁻¹ catalyst, H₂O₂ dosage of 1.28 mM L⁻¹), complete mineralization of acetaminophen (ACT) and naproxen (NPX) was achieved within 12 and 16 mins, respectively. Kinetic analysis revealed faster molecular degradation ($k_{\mathrm{ACT}}$ = 0.4592±0.021 min⁻¹; $k_{\mathrm{NPX}}$ = 0.4439±0.019 min⁻¹) than mineralization ($k_{\mathrm{ACT}}$ = 0.2257±0.009 min⁻¹; $k_{\mathrm{NPX}}$ = 0.2163±0.007 min⁻¹), indicating the formation of intermediate organic compounds. The system maintained over 80% global efficiency across 20 cycles, despite a 50% reduction in degradation rate. This high performance is attributed to synergistic effects from the enhanced electronic mobility of the CuFeS₂/MWCNT heterostructure. Experimental and theoretical analyses revealed two main degradation pathways: (i) hydroxyl radicals (•OH) governing the initial breakdown, and (ii) charge-transfer mechanisms driving mineralization. Quantum chemical calculations based on fragmentation patterns from mass spectrometry clarified the reactivity of key intermediates and their alignment with each pathway. Finally, ecotoxicological assays confirmed that the degradation byproducts were significantly less harmful to model organisms than the parent compounds. This study advances the mechanistic understanding of microwave-responsive catalysts and offers a recyclable, efficient, and environmentally benign approach for pharmaceutical pollutant removal.