Zeolite-supported silver and silver-iron nanoclusters and their activities as photodecomposition catalysts

摘要

Catalysts containing nanoclusters of Ag(I) and Fe_(2)O_(3) as dopants with sodalite and Y zeolite supports have been investigated in order to develop a more efficient catalyst for photodecomposition of the pesticide carbaryl and to gain insight about the reaction mechanism. Ag(I)-sodalite, Ag(I)/Fe_(2)O_(3)-sodalite, Ag(I)-Y zeolite, and Ag(I)/Fe_(2)O_(3)-Y zeolite were synthesized by ion-exchange techniques and characterized by powder X-ray diffraction (XRD), solid-state luminescence, UV-visible absorption, and atomic absorption spectroscopy measurements. The luminescence activity of the sodalite-supported and Y zeolite-supported catalysts was significantly different. Catalyst performance studies were conducted using carbaryl as the target compound and specific wavelengths of UV light as photon sources for the experiments. The studies showed that each catalyst's performance was determined primarily by the specific wavelength of the UV light with which the system was irradiated. The studies also showed that inclusion of Fe_(2)O_(3) as dopant enhanced the reactivity of the catalysts in several instances, with the Ag(I)/Fe_(2)O_(3)-sodalite catalyst and 298 nm irradiation being the most reactive of the systems studied. Additional reactions using each catalyst and 298 nm irradiation, and including either sodium bicarbonate as hydroxyl radical scavenger or D(2)O as solvent, showed that hydroxyl radicals were likely intermediates in the catalyzed photodecomposition reaction.