Catalytic Properties And Preparation Of Ag/SiO₂ Nanocomposites Chelated By EDTA

Nanoparticles have unique properties,so they can be widely used in the fields of chemistry,biology,optics,medicine,etc.Thereinto,nanocomposites have broader application prospects.Especially,Silver nanocomposites are typical and emerging nanocomposites.With the further research on silver nanocomposites,the more simple and environmental and novel preparation methods of silver nanocomposites,as well as their catalytic properties gradually become the focus of the research.In this article,the preparation methods and catalytic applications of silver nanocomposites were studied,which expands the synthesis methods of silver nanocomposites and explores the catalytic performance of the prepared silver nanocomposites for the reduction of nitro aromatic compounds.The experiments were mainly conducted through the hydrothermal synthesis method,using only the surfactant disodium ethylenediaminetetraacetic acid disodium salt?Na₂EDTA?without any other reducing agent and polymer stabilizer,and adding silica sol as silver nanoparticle carrier,then adjusting the pH value of the mixed solution?alkaline?,Ag/SiO₂ nanocomposites were synthesized at high temperatures in a high-pressure reactor.The influences of hydrothermal temperature and EDTA/Ag⁺molar ratio over the growth of Ag NPs and the development of nanostructure,as well as the catalytic performance of the material for the reduction of o-nitrobenzoic acid,m-nitrobenzoic acid and p-nitrophenol were investigated concretely.The synthesized Ag/SiO₂ samples were characterized structurally and optically using UV-Vis DRs,TEM,SEM,FT-IR,XRD techniques;The catalytic properties of nanocomposites and the catalytic reaction process were detected using UV-Visible absorption spectroscopic and LC-MS.The results shown that the hydrothermal temperature had a major influence on the nanostructure of samples,such as the higher the temperature,the larger the particle size and the better the dispersion;The optimum preparation temperature is 170°C,the size of Ag NPs is 2³ nm,and the particle size distribution is uniform under this condition;The complexation ratio of EDTA and Ag⁺was 1:1,so when EDTA was excessive,Ag NPs became larger,even Ag NPs could grow to 5¹0 nm at170°C;The Ag/SiO₂ catalyst had high catalytic activity for reduction of ortho,meta and para nitro?-NO₂?aromatic compounds;It was found that the Ag/SiO₂ catalyst prepared at170°C with molar ratio of EDTA/Ag⁺=1.5 had the best catalytic effect by comparison.