Thermally activated natural chalcopyrite for Fenton-like degradation of Rhodamine B: Catalyst characterization, performance evaluation, and catalytic mechanism

In this work, catalytic activity of natural chalcopyrite (CuFeS2) was improved by thermal activation. The modified chalcopyrite was used as efficient catalyst for degradation of organic dye Rhodamine B (RhB) through advanced oxidation process (AOP). Effects of catalyst dosage, H2O2 concentration, reaction temperature, solution pH, anions, and natural organic matter on the degradation efficiency of RhB were investigated. This study revealed that thermal activation at 300°C changed the chemical valency of surface elements rather than transforming the major chemical phase of natural chalcopyrite. The Fenton-like degradation of RhB was significantly improved by thermally activated chalcopyrite. RhB degradation could be obtained under broad pH and showed high resistance to natural organic matter and anions. Under optimal conditions H2O2 43.0 mM, catalyst 0.75 g/L, initial pH 4.0, and reaction temperature 25°C, the degradation of RhB reached 96.7% at 50 min. Based on the rate constant of reaction kinetics, the activation energy for RhB degradation was calculated to be 9 kJ/mol. Radical scavenging experiments and electron paramagnetic resonance (EPR) technique demonstrated that RhB degradation was dominated by the generated hydroxyl radicals in activated chalcopyrite/H2O2 system. The formation of surface sulfates resulted from thermal activation induced the dissolved copper or iron ions, and promoted H2O2 activation and facilitated RhB degradation by reactive hydroxyl radicals. This work provides an in-depth understanding of the mechanism behind thermal activation to enhance the activity of natural chalcopyrite, offering a theoretical basis for utilizing natural minerals for Fenton-like treatment of organic wastewater towards cleaner production.