Photocatalytic degradation of organic dyes: Pd-γ-Al 2 O 3 and PdO-γ-Al 2 O 3 as potential photocatalysts.

This work describes photocatalytic application of γ-alumina (γ-Al 2 O 3 ) surface-anchored palladium and palladium oxide nanoparticles (Pd-γ-Al 2 O 3 and PdO-γ-Al 2 O 3 NPs) synthesized by a novel co-precipitation technique. The palladium(0) NPs (Pd-γ-Al 2 O 3 ) were formed by calcination of the sample in inert medium, whereas PdO NPs (PdO-γ-Al 2 O 3 ) were obtained by calcination of the sample in atmospheric oxygen. As-synthesized Pd-γ-Al 2 O 3 and PdO-γ-Al 2 O 3 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-Al 2 O 3 and PdO-γ-Al 2 O 3 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-Al 2 O 3 and PdO-γ-Al 2 O 3 NPs as potential photocatalysts. Experimental parameters, including the admitting concentration of the organic dye solution, Pd-γ-Al 2 O 3 and PdO-γ-Al 2 O 3 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-Al 2 O 3 NPs showed better photocatalytic performance than PdO-γ-Al 2 O 3 NPs. The possible photocatalytic degradation mechanism of the organic dyes by Pd-γ-Al 2 O 3 and PdO-γ-Al 2 O 3 photocatalysts is proposed. The studies reveal that Pd and PdO NPs anchored on the γ-Al 2 O 3 surface are promising and effective catalysts for photocatalytic degradation of organic dyes.