Preparation And Photocatalytic Activity Of TiO₂ /BaSO₄ Composite Material

As a new generation of functional materials, Titania (TiO₂) photocatalyst was extensively used in purification of air and water, coatings, anti-virus and so on. However, aggregate and low recovery rate of TiO₂ nanoparticles maked it the bottleneck in the practical application, supported TiO₂ composite overcomed these drawbacks.In this thesis, the aim was to obtain TiO₂/BaSO₄ through combining the sol-gel and the layer-by-layer self-assembly technology, by way of low-cost TiCl₄ or TiOSO₄ as raw materials and BaSO₄ (paint filler) as carriers. Nanoparticles were coated on BaSO₄ uniformly that improved the photocatalytic activity of TiO₂. The research can enhance applications of nano-TiO₂ in coatings, which provided the theoretical basis in green paint.The main contents were as follows:1. TiO₂/BaSO₄ composite particles were prepared by TiOSO₄ and BaSO₄ that maded or purchased. The effects of SDS, the sol preparation and mixing were studied.The results showed that ethylene glycol was suitable for 3ml in the sol, using 8mmol/L SDS as mediums and giving stirring, which more conducive to the surface coating of TiO₂ uniformly.When purchased BaSO₄ as the carrier, sizes of four coated were about 220nm, maded BaSO₄ with a layer of about 450nm. Surface anatase TiO₂ contents increased with the coating gradually, and the content of maded carriers more than to the buy.2. We synthesised TiO₂/BaSO₄ by purchased BaSO₄ and TiCl₄. The effects of the surfactant, titanium concentration and concentration of hydrochloric acid were researched.The coated rutile TiO₂ gradually improved with layers when SDS served as mediums. When SDS was not involve in the microsphere, giving a certain stirring, the concentration of HCl was 4mol/L and the titanium sol was 0.52mol/L, combined ten times can obtained TiO₂/BaSO₄ microsphere.The microsphere was 2μm that had parts of internal cavity, and blankets were?composed of rutile TiO₂ nanorods diametered from 25 to 30nm, microsphere of ten times had the maximum BET which up to 91.215m³g^-1and pore capacity was 0.068cm² (g nm)^-1.Composite Mechanism: Carriers modified with SDS, negative charged BaSO₄ and positived TiO₂ particles coated layer by layer through electrostatic interaction; When SDS were not added , TiO₂ nanorods and BaSO₄ formed a few small aggregates, the titanium that deposited on the surface of aggregates continued to grow as the compound increase, TiO₂ rods continued growing to cluster, and so on. cluster, rods, and the BaSO₄ ball constituted crossly the TiO₂/BaSO₄ microspheres that had a internal cavity of"reinforced concrete" type.3. Experiments were tested the photocatalytic activity of TiO₂/BaSO₄.The experimental results of composite adding SDS and TiOSO₄ indicated that the best photocatalytic conditions of coated four-time's TiO₂/BaSO₄ were 95mg and the pH was 6, after six hours the organic carbon removal rate of methyl orange reached to 89.53%, the recycling rate was also better, the degradation reaction consistented with a kinetic equation.The prepareed materials of using SDS and TiCl₄ appeared that the best photocatalytic conditions were the fourth layer TiO₂/BaSO₄ of 130mg and pH was 1, after there hours TOC removal rate reached to 68.08%. Compared with pure BaSO₄ and TiO₂, composites markedly improved the absorption strength.The best photocatalytic conditions of the TiO₂/BaSO₄ by TiCl₄ and without SDS were ten times's microspheres of 60mg, the removal rate of organic carbon was up to 71.45% after half and three hours, the catalyst was recyclable. UV-visible issued that microspheres significantly improved the absorption intensity.