Preparation Of Pt And Ag@Pt Nanoparticles Supported On Sepiolite Nanofibers And Their Performance In The Catalytic Oxidation And Reduction Of Organic Pollutants

Organic pollutants such as VOCs and nitrophenol,which migrated and transformed in soil,air and water,could directly affect human health and the living of organisms,indirectly trigger various chronic and genetic diseases through the biological amplification.Compared to the traditionally biological,physical and chemical process,catalytic process,especially the noble metal catalysis,exhibits higher efficiency,better stability and lower energy consumption towards the treatment of organic pollutants.Therefore,the emphasis of the study is on the enhancement of catalytic oxidation and reduction of organic pollutants over noble metal catalysts through the adjustment of nanoparticle structure and the selection of support.The main research work is as follows:Pt/sepiolite catalysts were prepared by a reductive impregnation process,and were used for the efficient and stable removal of HCHO.TEM and HRTEM analyses indicate that Pt nanoparticles with 2-4nm in size were highly dispersed on sepiolite nanofibers with diameters of 50-150nm.FTIR and XPS spectra show the presence of abundant hydroxyls on the catalyst surface.At ambient temperature,the 1wt.%Pt/sepiolite catalyst calcined at 400°C exhibited the highest catalytic activity toward the oxidation of HCHO to CO₂ and H₂O,and still showed a good performance even after 7 cycles.The mechanism of the catalytic oxidation of HCHO was studied through the behaviors of adsorbed species on the catalyst surface using in situ DRIFTS.The efficient and stable catalytic performance of the Pt/sepiolite catalyst mainly results from the synergistic effect between the hydroxyls on sepiolite nanofibers and highly dispersed Pt nanoparticles.Ag@Pt nanoparticles were prepared by consecutive reduction at first and then supported on sepiolite nanofibers to achieve Ag@Pt/sepiolite catalyst.TEM and HRTEM analyses show that Ag@Pt nanoparticles with a diameter of 10-30nm,were composed of Ag core and Pt shell,and highly dispersed on sepiolite nanofibers.XPS analysis of Ag@Pt/sepiolite reveals that the binding energy of Ag 3d and Pt 4f is different with that of Ag/sepiolite and Pt/sepiolite,indicating that the existence of special electronic structure on Ag@Pt core-shell.The performance of Ag@Pt/sepiolite was evaluated through the catalytic reduction of nitrophenol?PNP,ONP,MNP?.2wt.%/Ag@Pt/sepiolite??Ag:Pt?n=1:1?exhibited the highest catalytic activity toward the reduction of PNP,and the reduction rate can reach 96%,higher than that of Ag/sepiolite and Pt/sepiolite with the same loading.PNP,ONP and MNP were immediately deacidized to PAP,OAP and MAP with low toxicity and recycling value,and the reduction rate of PNP rarely decreased after several cycles.The excellent performance of Ag@Pt/sepiolite for the catalytic reduction of PNP could be attributed to the synergistic effect between the adsorption of sepiolite nanofibers and the active sites of Ag@Pt nanoparticles.