Studies On The Synthesis Of Layered Silicate Magadiite(MD) And AgBr/MD Composite Photocatalysts

The interlayer of two-dimensional layered silicate such as magadiite(MD), kenyaite(KY) has hydrated cation that can be exchanged. They can accommodate a variety of objects. Composite materials formed by different guest molecules intercalating host layer magadiite have important values in porous materials, adsorption, catalysis and bio-composite materials.High photoactive AgBr in the reaction medium can not be well dispersed and easily aggregates in the reaction medium. So it is greatly limited in applications. In order to resolving this problem, to loading and stabilizing AgBr on layered silicate and the catalytic activities of these composite materials have been studied. In this thesis, we used silica and NaOH as raw materials, Na2CO3as catalyst, to obtain high-purity MD and KY throught hydrothermal method. The optimum conditions for preparation of MD and KY are n(SiO2):n(NaOH+Na2CO3)=5,160℃for30h and20,170℃for72h, respectively.Ag-AgBr/MD was synthesized by ion exchange route of AgBr loading on the support of MD and next photoreduction. The as-synthesized samples at different conditions including loading amount of AgBr and pH values were characterized by XRD, SEM, TEM and UV-Vis spectra and their effects on photocatalytic degradation of RhB solution under visible light illumination were also investigated. Due to stronger absorption to visible light and higher dispersion of AgBr on MD support, the best photocatalytic activity was achieved in the ratio of [Ag+] to MD of2mmol/g and at pH value of9.0. Using TBAOH to modify MD to synthesize novel Ag-AgBr/TBA-MD composite catalyst, the results show photocatalytic degradation efficiency for RhB of Ag-AgBr/TBA-MD is better than that of Ag-AgBr/MD. The best photocatalytic activity was achieved in the ratio of [Ag+]to TBA-MD of2mmol/g and at pH value of11.0.KY is also a two-dimensional layered silicates similar structure with MD, and has larger basal spacing and better thermal stability than MD. KY is a potential excellent catalyst support, we prepared a series of samples of Ag-AgBr/KY at different conditions. The results showed that when [Ag+]/KY=2mmol/g, pH=9.0, Ag-AgBr/KY had the highest photocatalytic degradation activity for RhB dye.