Synthesis of Pd co-doped nano-TiO2–SO42– and its synergetic effect on the solar photodegradation of Reactive Red 120 dye

Abstract

Pd co-doped TiO2–SO42– photocatalyst was synthesized by sol–gel, photodeposition methods and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and BET surface area measurements. Elements present in the catalyst are shown by X-ray photoelectron spectroscopy. X-ray diffraction analysis reveals that the photocatalyst has an anatase structure. Sulfation by sulfuric acid reduces agglomeration, inhibits the phase transformation and enhances the stability of TiO2. The solar photocatalytic activity of the Pd–TiO2–SO42– is higher than that of the TiO2–P25, Pd–TiO2, bare TiO2 and TiO2–SO42– at pH 7 for the mineralization of Reactive Red 120. The modification of palladium shows higher adsorption with synergistic effect and also enhances the separation of photogenerated electron–hole pairs, leading to higher photodegradation efficiency. The effects of operational parameters such as the amount of photocatalyst, initial pH on photo mineralization have been analyzed. A dual mechanism of degradation by Pd–TiO2–SO42– is proposed to explain its higher activity in solar light. The mineralization of Reactive Red 120 has also been confirmed by CV and COD measurements. The catalyst is found to be stable and reusable. Based on the degradation intermediates identified by GC–MS analysis, a reaction pathway is proposed.