Synthesis of Mn-Doped CrFe2O4 Nanoparticles and Their Composite with CNTs: Advanced Structural and Electronic Modifications for High-Efficiency Pollutant Degradation

Abstract

This research aims to develop and synthesize cost-effective photocatalysts for degrading organic contaminants in industrial wastewater and shows the innovative application of manganese-doped CrFe₂O₄/CNTs composite. Chromium ferrite (CF) and Mn-decorated chromium ferrite (MCF) were synthesized using coprecipitation, while MCF/CNTs composites were fabricated via ultrasonication techniques, respectively. Ferrites are considered promising photocatalysts due to their innovative properties, such as a small bandgap, stability against chemical and thermal degradation, high oxidation potential, and highly efficient photocatalytic activities for environmental remediation. The effects of manganese doping on pure CrFe₂O₄ and the strong interaction between CrFe₂O₄ and CNTs were examined using various physical and electrochemical techniques, such as XRD, FTIR, SEM, EDX, UV–Vis spectroscopy, and PL analysis. XRD analysis confirmed the cubic crystal structure, with crystallite sizes of 25.5 nm for CF, 22.1 nm for MCF, and 19.3 nm for MCF/CNTs. Bandgap energies calculated from Tauc plots were 2.15 eV for CF and 1.93 eV for MCF, demonstrating improved light absorption. Photocatalytic testing showed that MCF/CNTs composites achieved superior degradation efficiencies of 78% for crystal violet (CV) and 81% for acetylsalicylic acid (ASA), with rate constants of 0.007 min⁻¹ and 0.009 min⁻¹, respectively. These results highlight the synergistic effects of manganese doping and CNTs incorporation, which introduce crystal defects, tuned bandgap, enhanced surface area, more active site availability, reduced crystallite size, and improved charge separation efficiency and stability. This work demonstrates the significant potential of MCF/CNTs nanocomposites as highly efficient photocatalysts for removal of highly toxic compounds present in various types of waste water i.e. industrial waste water etc.