Advanced Mn3O4/Fe3O4-carbon molecular sieve composite: a robust catalyst for heterogeneous photo-fenton oxidation of organic dyes

Abstract

The development of an efficient and sustainable heterogeneous Fenton catalyst holds significant potential for improving wastewater treatment technologies. This study introduces a novel composite material integrating Fe₃O₄ and Mn₃O₄ nanoparticles into carbon molecular sieves (CMS). By combining these components, the research aims to enhance the degradation of organic dyes and address challenges related to catalyst recovery and stability. Mn₃O₄/Fe₃O₄/CMS composite materials were synthesized and evaluated for their photo-Fenton catalytic performance. The materials were characterized using PL spectroscopy, XRD, FE-SEM, TEM, TGA, UV-Vis DRS, EDX, and VSM, which demonstrated effective interaction and synergy between the Mn₃O₄, Fe₃O₄, and CMS components. TEM analysis revealed that in the Mn₃O₄/Fe₃O₄/CMS composite, the Fe₃O₄ nanoparticles exhibited an average size of approximately 50 nm, while the Mn₃O₄ nanoparticles were relatively smaller, with an average size of around 10 nm. VSM results showed a saturation magnetization of 32.63 emu/g, facilitating easy magnetic recovery. Systematic investigations revealed that Mn₃O₄/Fe₃O₄/CMS exhibited superior photo-Fenton activity with a degradation efficiency of 99.8% for methylene blue (MB) under optimal conditions (pH 3, catalyst dosage 0.3 g/L, initial MB concentration 25 mg/L, H₂O₂ concentration 0.03 mol/L, and temperature 30 °C), surpassing its individual components and binary composites. Kinetic studies showed the highest rate constant for Mn₃O₄/Fe₃O₄/CMS at 0.047 min⁻¹. Reusability tests indicated a slight decrease in degradation efficiency from 99.8 to 84.6% after four cycles, demonstrating good stability. Mechanistic investigations confirmed that hydroxyl radicals are the primary reactive species, with metal ions and electrons also contributing significantly. These findings contribute to the advancement of advanced oxidation processes and offer valuable insights for designing next-generation catalysts for environmental applications.