Of Tio <sub> 2 </ Sub> Aerogels At Atmospheric Pressure Drying Method, Modification And Photocatalytic Performance Study

TiO₂ aerogels are nano-assembled colloidal particles with porous network structure and pores filled with gaseous dispersion medium of high-dispersed solid material.It has nano-structure,large majority surface area,high porosity and other characteristics.It can be widely used in catalysis,separation and adsorption areas.Many researchers have focused on the material in recent years.In this paper,TiO₂ aerogels were prepared at ambient pressure by sol-gel method using tetrabutyl titanate as row material,formamide as drying control chemical additive,tetralthyl orthosilcate(TEOS) / ethanol as pore fluids extractant.The effect of the ratio of raw materials and the processing of gelatin on the gel time and specific surface area and structure were studied in detail.By optimizing the parameters,TiO₂ aerogel has been prepared by drying at ambient pressure under the following conditions:the ratio of raw materials is n-butyl titanate:water:acetic acid:formamide(molar ratio) = 1:21:6.2:1.8:0.6,the ratio of TEOS/ethanol(with volume ratio) is 1:1 and the time of post-treatment process is 36h.Experimental results showed that as-prepared TiO₂ aerogel is in amorphous state with apparent density of 0.375 g·cm^-3 and the specific surface area of 523 m²·g^-1,the average pore size is about 9.9 nm.After calcinated at 850℃for 4h in air atmosphere,the structure of samples is transformed from amorphous to anatase-type crystal while pore volume shrinks and average pore size increases to 16.3 nm.However,the specific surface area still reaches 208 m²·g^-1.Photodegradation performance of methyl orange azo dyes using TiO2 aerogels as catalyst was investigated.The degradation dynamics was also discussed.The results show that the photocatalytic activity of aerogels are effected by both the specific surface area and crystallinity. And the kinetic equation of degradation reaction accords with apparent first order reaction.WO₃/TiO₂ composite aerogels were obtained by impregnationcalcination method using H₂WO₄ sol and TiO₂ aerogel as raw material. The structural properties of composite aerogels were characterized by means of XRD,BET,TEM,SEM,EDS,FT-IR and UV-vis-DRS etc. Photocatalytic activity of aerogels was studied and the mechanism of coordination reaction was discussed.