Simultaneous microwave-ultrasound irradiation of Ag/TiO2, synthesis for photoreduction of Cr(VI) using methanol as sacrificial agent

Abstract

In this work, TiO₂ and Ag/TiO₂ composites powders were synthesized via the sol-gel method assisted by a novel simultaneous microwave-ultrasound irradiation during the crystallization step. The Ag content in the samples, determined by energy-dispersive spectroscopy coupled with scanning electron microscopy (SEM-EDS), was consistent with the theoretical loadings, yielding values of 1.0 % and 4.5 % for the composites. Surface atomic percentages obtained by X-ray photoelectron spectroscopy (XPS) were 0.3 % and 0.5 %. Raman spectroscopy revealed the characteristic peaks of anatase and brookite phases, while by X-ray diffraction confirmed the crystalline phases of TiO₂ and detected signals associated with Ag. The specific surface areas of the photocatalysts ranged from 89 to 126 m²/g. The band gap energies determined from UV–Vis using the Kubelka-Munk function, were 3.0 eV for both composites. Photocatalytic performance was assessed through the photoreduction of Cr(VI) using methanol as a sacrificial agent under UV light (365 nm). Complete photoreduction of Cr(VI) to Cr(III) was achieved within 120 min using the 5 % Ag sample. In this system, Ag acted as electron traps, enhancing charge separation and thereby improving photocatalytic activity.