The Synthesis Of Materials Derived From Silica Nanosphere Wrapped By Titanium Dioxide And Its Research On Of Degradation Of Formaldehyde

The photocatalytic titanium dioxide materials are applied widely in the field of catalysis,air purge,water purification,antibiosis,deodorization and so on due to its excellent performance.However,the traditional photo-catalysis of titanium dioxide exhibits low catalytic efficiency,which hinders its appliance in industry.In the paper,a series of silica nanospheres（SNS）with different sizes are synthesized through modified St?ber method.The silica nanospheres with optimum size and dispersibility are selected as the template and wrapped by titanium dioxide to form titanium dioxide doped silica nanosphere composites（TSNS）with high photo-catalytic efficiency and stability by the method of liquid phase deposition.And various Characterization methods are used to evaluate the structure and performance of the TSNS,especially the degradation efficiency for methyl orange.A new type of interior wall coating that can purify indoor formaldehyde contaminants was prepared by adding this composite photocatalyst to the interior wall paint,and related experimental and theoretical studies were conducted.Following conclusions are drawn from the research work of this thesis:（1）The particle size and morphology of silica microspheres are affected by the concentration of ammonia in the catalyst and the content of tetraethoxysilane（TEOS）in the raw material.Bigger sizes and better homogeneity of SNS can be achieved with increased content of catalyst and TEOS;（2）Different dispersants exhibit different dispersing efficiency ranging from inorganic dispersants to polymeric dispersants,like that the optimum dispersing efficiency of KCl、（NaPO₃）₆、Na₅P₃O₁₀、Span-80 are obtained as the concentration of those dispersants are 7%、3%、7%and 8%respectively.Among the four dispersants,the（NaPO₃）₆ possesses the prime dispersing efficiency of 90.34%at the concentration of 3%,while the best efficiency of other dispersants is below 90%;（3）The crystalline of the silica is amorphous and the crystalline of titanium dioxide are mainly anatase with partial impurity phase in the as-synthesized TSNS;After calcination at 600℃,the crystal structure of titanium dioxide turns to be more integrated anatase and the size of the TSNS increases from 11 nm to 16 nm simultaneously.The results of FTIR and XPS indicate that the intensity of band Ti-O-Si exhibiting absorption peak at 940 cm^-11 decreases but not disappears after the calcination at 600℃,and the binding between SiO₂ and TiO₂ mainly depends on the Van der Waals force and band Ti-O-Si;（4）The degradation efficiency of the TSNS after calcination（20.0 mg/L）for methyl orange is 96%under the ultraviolet of 175 W for 300 min.And it turns to be that the TSNS after calcination can be excellent photo-catalytic degradation agents with superb application;（5）The transparency,light intensity,initial formaldehyde concentration,and number of smear layers of the photocatalytic interior wall coating will influence the formaldehyde degradation results to some extent.When other conditions are fixed,the transparency of the coating using styrene-acrylic emulsion as matrix is better than that of VAE emulsion,and the photocatalytic efficiency of formaldehyde is higher.The purification efficiency of photo-catalytic coatings for formaldehyde increases gradually with the enhancement of light intensity and the purification efficiency of the photo-catalyst is respectively 89%and 66%as the distances between the coating and the ultraviolet are 20 cm and 60 cm,and the difference in purification efficiency is 23%.In addition,the initial concentration of formaldehyde at 0.35 mg/m³ among all three concentrations at 0.2 mg/m³、0.35 mg/m³、0.56 mg/m³ proves to the optimum initial concentration,and the purification rate reached 89%.And the best purification efficiency of the photocatalytic coatings is 89%as the number of the coating is 2 lays compared to other two layers（1 and 3）.