Fe ₂ O ₃ −Clay Composite as a Robust Heterogeneous Fenton Catalyst for Photodegradation of Acid Red 114 in Aqueous Solution

Homogeneous Fenton processes are constrained by high sludge formation, narrow pH operation, and low catalyst recovery, prompting an attempt for more sustainable heterogeneous alternatives. For the purpose of synthesizing an Fe2O3−clay composite acting as an efficient heterogeneous Fenton catalyst, ferric nitrate and natural clay were coprecipitated. The synthesized composite was evaluated by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet−visible diffuse reflectance, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy/energy-dispersive X-ray spectroscopy analyses, which revealed the uniform dispersion of Fe2O3 inside the clay matrix while maintaining the structural integrity of the layered silicate framework. The strong Fe3+−O2− interactions and associated charge transfer transitions were found to decrease band gap energy and significantly enhance the absorption of visible light, thereby improving the catalyst’s photoreactivity. The photocatalytic performance was assessed by degrading acid red 114 (AR114) under visible-light irradiation. The Fe2O3−clay heterogeneous Fenton system exhibited 88% photodegradation efficiency in 90 min, which is almost three times that of homogeneous Fenton and approximately five times that of H2O2. The optimal conditions have been found to be 0.6% Fe2O3 loading, 0.5 g catalyst dosage, a calcination temperature of 500 °C, and an initial pH of 2.5. Under these conditions, the catalyst demonstrated remarkable reusability with low Fe leaching (≤0.06 mgL−1), addressing the major drawbacks associated with conventional Fenton systems. The radical scavenging experiments established •OH radicals as the principal oxidative species for photocatalytic degradation of AR114. These results show that the Fe2O3−clay composite is a highly efficient, recyclable, and environmentally friendly heterogeneous Fenton catalyst with significant potential for use in wastewater treatment applications.