ZnO-Saponite Nanocomposite: Input of Adsorption and Photocatalysis for Removal of Rhodamine B Dye

Abstract

The sol–gel process was applied to prepare ZnO-saponite nanocomposite for environmental remediation and investigation of photocatalysis mechanisms. The nanocomposite followed the photodegradation of Rhodamine B (RhB) as a model dye under irradiation with visible light. The materials were characterized by X-ray diffraction, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy, photoluminescence, Point of zero charges (Pcz), and Brunauer–Emmett–Teller (BET). Reuse, the effect of scavengers, and toxicity were also investigated. The results showed an effective incorporation of the semiconductor on the surface of the support, forming a hexagonal structure with the wurtzite phase of ZnO. The evaluation of texture and morphology showed the effective distribution of ZnO nanoparticles on the surface of the synthesized photocatalyst. The intensified adsorption/photocatalysis process using saponite-based nanocomposite achieved more than 85% RhB dye removal efficiency after 270 min. It followed presented pseudo-first-order kinetics with a constant equal to 6.627 × 10^–1 min⁻¹. Furthermore, the evaluation of the effect of scavengers indicated that alcohol played an important role in scavenging hydroxyl radicals. It was stable after evaluating the catalyst after successive cycles, maintaining its structure, as FTIR proved. Furthermore, the studied nanocomposites did not show evidence of toxicity, thus being promising candidates for application in the removal of polluting dye.