Photocatalytic degradation of organic dyes: Pd-γ-Al2O3 and PdO-γ-Al2O3 as potential photocatalysts

Abstract

This work describes photocatalytic application of γ-alumina (γ-Al₂O₃) surface-anchored palladium and palladium oxide nanoparticles (Pd-γ-Al₂O₃ and PdO-γ-Al₂O₃ NPs) synthesized by a novel co-precipitation technique. The palladium(0) NPs (Pd-γ-Al₂O₃) were formed by calcination of the sample in inert medium, whereas PdO NPs (PdO-γ-Al₂O₃) were obtained by calcination of the sample in atmospheric oxygen. As-synthesized Pd-γ-Al₂O₃ and PdO-γ-Al₂O₃ NPs are characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, field emission scanning electron microscopy and photoluminescence (PL) spectra. The PL spectra of Pd-γ-Al₂O₃ and PdO-γ-Al₂O₃ NPs display visible-light emissions from 450 to 500 nm at room temperature. This work aims to study the photocatalytic degradation of organic dye pollutants, including bromocresol green (BCG), bromothymol blue, methylene blue and methyl orange using Pd-γ-Al₂O₃ and PdO-γ-Al₂O₃ NPs as potential photocatalysts. Experimental parameters, including the admitting concentration of the organic dye solution, Pd-γ-Al₂O₃ and PdO-γ-Al₂O₃ photocatalyst dosage, and pH, were varied to ascertain favorable conditions for photocatalytic degradation. The results indicate that the organic dye BCG is completely (100%) degraded in aqueous solution under ultraviolet light, compared with the other organic dyes. Furthermore, Pd-γ-Al₂O₃ NPs showed better photocatalytic performance than PdO-γ-Al₂O₃ NPs. The possible photocatalytic degradation mechanism of the organic dyes by Pd-γ-Al₂O₃ and PdO-γ-Al₂O₃ photocatalysts is proposed. The studies reveal that Pd and PdO NPs anchored on the γ-Al₂O₃ surface are promising and effective catalysts for photocatalytic degradation of organic dyes.