ENHANCED PHOTOCATALYTIC ACTIVITY OF ZnO NANOPARTICLES OBTAINED BY "GREEN" SYNTHESIS WITH WELL DISPERSED Pd-Au BIMETALLIC NANOPARTICLES

The aim of this work is to study the photocatalytic reduction of nitrate in drinking water using ZnO nanoparticles comparative with bimetallic Pd-Au nanoparticles loaded ZnO and formic acid as a hole scavenger. ZnO nanostructured materials are promising photocatalysts because of their non toxicity, low cost and good stability. Noble metals (Au, Ag, Pd) supported by ZnO have attracted significant interest, as it may possibly result in a superior photocatalytic activity. The ZnO nanoparticles were obtained with the extract of black tea solid waste and Zn acetate dehydrate in alkaline medium. Bimetallic nanoparticles Pd-Au of around 10 nm were obtained through a green chemistry method by adding a solution containing the gold precursor (HAuCl4) and paladium precursor Pd(NO3)(2) in a tannic acid solution. The surface and chemical state analysis of pure ZnO and Pd-Au deposited ZnO were investigated by XRD, SEM-EDX, TEM, IR-spectroscopy and UV-Vis spectroscopy. The photocatalytic activities were evaluated by nitrate reduction reactions in aqueous solutions. The Hg lamp of 120 W was used as a source for photocatalytic study. Compared with ZnO nanoparticles, Pd-Au loaded (1% weight) on ZnO catalyst shows an increased catalytic activity, which has been evaluated in terms of N-2 selectivity.