Fenton Catalytic Properties of FeOOH Nanoparticles Dispersed on Volcanic Ash Activated by Gliding Arc Plasma

We explore two approaches for preparing supported catalysts based on volcanic ash (VA) as support for effective Fenton heterogeneous catalysis. Firstly, the plasma deposition of FeOOH (goethite) on VA activated chemically by HCl (AM-FeOOH-30/0C) was performed. Secondly, the plasma-activation of VA and -deposition of FeOOH (VA-FeOOH-30/0) were carried out simultaneously, taking advantage of the gliding-arc-plasma acidic and oxidizing properties. Prepared materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), N₂ physisorption, and scanning electron microscopy coupled energy-dispersive X-ray spectroscopy (SEM/EDX). Performing chemical activation of VA using HCl induces a better microstructure's modification (specific surface area and porosity) and allows a better plasma-deposition of FeOOH (AM-FeOOH-30/0C) compared to performing both processes simultaneously by plasma (VA-FeOOH-30/0) which did not change its microstructure but slightly improved the texture. Otherwise, aging (plasma post-discharge treatment) of AM-FeOOH-30/0C material induces crystallite's nucleation, thus an increase of the specific surface area (AM-FeOOH-30/4C). Fenton catalytic degradation of Rhodamine-6G (25 mg/L) for 20 min revealed elimination degrees of 22%, 87%, 78%, and 82%, respectively, for VA-FeOOH-30/0, AM-2C, AM-FeOOH-30/0C, and AM-FeOOH-30/4C materials. The recyclability tests confirmed the higher catalytic stability of AM-FeOOH-30/0C compared to VA-FeOOH-30/0 material after 4 cycles, thus highlighting the necessity to perform the activation and deposition separately.