Efficient removal of acid orange 7 using a porous adsorbent-supported zero-valent iron as a synergistic catalyst in...

This study focuses on the synthesis of granular red mud reinforced by zero-valent iron (Fe@GRM) and its application for the removal acid orange 7 (AO7) from aqueous solution. Then ZVI is employed as a catalyst for the activation of persulfate (PS) to produce sulfate radicals (SO₄^•-) that are produced at 900 °C in an anoxic atmosphere using the direct reduction of iron oxide in the red mud with maize straw as the reductant. Furthermore, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are used to illustrate the morphology and porous structure of the Fe@GRM. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed that Fe@GRM was loaded with zero-valent iron. This characterization confirmed that the Fe@GRM was a porous structure material that contained zero-valent iron. The influence of conditions for AO7 elimination, including initial pH, Fe@GRM dosage, initial AO7 concentrations, and temperature, is also investigated. The removal efficiency of AO7 was 90.78% using Fe@GRM/PS, while only 18.15% was removed when Fe@GRM was used alone. The degradation kinetics were well fitted to a pseudo-first-order kinetic model, and the rate of removal increased with temperature, demonstrating an endothermic elimination process. The Arrhenius activation energy of the process was 20.77 kJ/mol, which indicated that the reduction of AO7 was a diffusion-mediated reaction. Fe@GRM is a low-cost material that demonstrated outstanding performance with great potential for wastewater treatment.