Synthesis and Physicochemical Properties of Fe3O4/γ-Fe2O3@MIL-100(Fe) and Fe3O4/γ-Fe2O3@MIL-88c(Fe) Composites for Photocatalytic Decomposition of Congo Red

Photocatalysis is an effective strategy for the treatment of industrial wastewater to eliminate toxic organic matter, which helps to improve the quality of water resources and protect public health. In this work, promising iron-containing composites Fe3O4/γ-Fe2O3@MIL-100(Fe) and Fe3O4/γ-Fe2O3@MIL-88c(Fe) for the photocatalytic decomposition of Congo Red (CR) have been synthesized. Elemental and phase composition and structure of the composites were determined using elemental and X-ray diffraction analysis, as well as IR spectroscopy. Thermal stability, ferromagnetic properties, and surface characteristics of the composites were studied using thermogravimetric analysis, vibrational magnetometry, and low-temperature nitrogen adsorption–desorption. The effective rate constants of photocatalytic degradation (k) were found to be (7.4 ± 0.8) × 10–3 and (3.2 ± 0.5) × 10–3 min–1 for Fe3O4/γ-Fe2O3@MIL-100(Fe) and Fe3O4/γ-Fe2O3@MIL-88c(Fe), respectively. The increased stability of MIL-100(Fe) in an acidic medium contributed to the increase in the photocatalytic activity of the composite.