Hydrothermal synthesis of MnO₂/Fe(0) composites from Li-ion battery cathodes for destructing sulfadiazine by photo-Fenton process

Harmless treatment of antibiotics, and recovery of precious metals from the spent Li-ion battery are two typical environmental issues with rapid development of the society. Presently, we reclaimed Mn from the spent Li-ion battery cathode materials for hydrothermally synthesizing MnO2/Fe(0) composites, which were used as the efficient heterogeneous photo-Fenton catalyst. The newcompositewaswell characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Brunauer-Emmett-Teller (BET) methods before optimizing their usage for sulfadiazine destruction. The catalytic efficiency of the MnO2 substrate was enhanced by impregnating different proportions of Fe(0) into the substrate. The MnO2: Fe(0) molar ratio at 40:1 (MnO2-40Fe) shows optimal catalytic activity. Sulfadiazine degradation by 0.2 g/L MnO2-40Fe, 6 mM H2O2 in pH 3 is almost 98.6%, and it follows first-order kinetics. The MnO2 and nano zero-valent iron synthesized using spent cathode of Li-ion batteries is equally efficient in sulfadiazine even after five times repeated use. As elucidated by mass spectroscopic data, sulfadiazine degradation by MnO2-40Fe was a multi-faceted photoFenton process which results in CO2, H2O, NH4+ and SO42- as final products. The excellent degradation performance of the as-prepared catalyst might be attributed to the introduction of nano zero-valent iron on the nanostructured MnO2, which not only providesmore active sites, but also has a synergistic effectwithMnO2 and light irradiation, leading to the generation of large amounts of activated radicals for destructing sulfadiazine. This work provides a promising method for reclamation of spent Li-ion battery cathode for environmental applications. (c) 2021 Elsevier B.V. All rights reserved.