Carbon-mineral composite design for microwave-assisted degradation of organic contaminants

Microwave (MW)-assisted catalytic oxidation with mineral-carbon composites is a potentially promising method for treating organic pollutants, but the underlying mechanisms involving varying mineral/carbon species remain unclear. To address this, we regulated the mineral and carbon speciation in the MW-assisted synthesis of CuFe-biochar composites by varying pyrolysis conditions and evaluated their roles in the MW-assisted generation of reactive oxygen species. The presence of CuFe-biochar composites significantly promoted the generation of •O₂^- and •OH radicals with H₂O₂, with an increased removal efficiency of two organic dyes as an example for real-time image visualization in the MW reactor, Acid Orange 7 and Malachite Green (up to 97.8 % and 100 %, respectively). Increasing pyrolysis temperature and/or Fe content promoted graphitization and enhanced MW absorption (absorption broadband from 0.16 GHz to 8.56 GHz). The co-presence of Fe supported the uniform distribution of reactive Cu particles (such as Cu and Cu₂O) with smaller sizes (from 45 nm to 1.5 nm), promoting the generation of •O₂^- radicals for the organic degradation. This study reveals the key speciation of the CuFe-biochar composites that can facilitate the MW-assisted degradation of organic pollutants via radical generation, paving the way for efficient MW-assisted decontamination.