Synthesis of magnetic CuFe2O4 materials by a sol-gel method using dragon fruit peel extract: Comparison of synthesis methods and evaluation of catalytic activity in benzyl alcohol oxidation

Abstract

This paper presents the synthesis and evaluation of the catalytic activity of magnetic CuFe₂O₄ powders for the selective oxidation of benzyl alcohol to benzaldehyde under mild and environmentally friendly conditions, in an aqueous medium at room temperature. Three simple preparation routes, including ceramic, co-precipitation, and sol-gel methods, were employed to investigate the influence of synthesis methodology on material characteristics and catalytic behavior. More specifically, the sol-gel method was assisted by a dragon fruit peel extract, which served as a natural gelling agent to facilitate gel formation and enhance the dispersion of metal ions within CuFe₂O₄ lattice. The experimental results showed that the choice of synthetic method significantly impacts several key physicochemical properties, including phase composition, particle size, and importantly, the surface distribution of Cu²⁺ and Fe³⁺ ions. These structural and surface features played a decisive role in governing the catalytic activity during persulfate activation. While all CuFe₂O₄ samples effectively activated persulfate to drive the oxidation of benzyl alcohol following pseudo-second-order kinetics, the sol-gel-derived sample exhibited superior catalytic activity, with benzyl alcohol conversion and benzaldehyde selectivity both exceeding 85% after 24 hours of reaction. This enhanced performance was attributed to the more homogeneous dispersion and optimal surface arrangement of metal ions, which facilitated electron transfer processes and the generation of reactive species during persulfate activation. In addition to high catalytic activity, this prepared CuFe₂O₄ sample exhibited strong magnetic properties, enabling rapid and efficient separation from the solution after reactions. The catalyst also retained its activity over repeated reaction cycles, demonstrating its high stability and reusability. Overall, the CuFe₂O₄ materials could promise magnetically recoverable catalysts for green, selective oxidation processes in aqueous systems, with the bio-assisted sol–gel method emerging as the most effective synthesis route.