Study On The Preparation And Application Properties Of Micro-nano TiO₂ Composite SiO₂ And CaCo₃ Functional Materials

Micro-nano titanium dioxide(TiO₂)is an inorganic functional material with excellent optical and photocatalytic properties.It has been widely used or shown good application prospects in the fields of light industry,chemical industry,building materials,environmental purification and new energy production.However,there are still several restriction problems about resource,environment and functional efficiency improvement in the production and application of TiO₂,which need to be improved.Based on the above background,this paper proposes a strategy that constructing micro-nano TiO₂ composite functional materials to solve the existing restriction problems.The preparation of micro-nano TiO₂ composite SiO₂ and CaCO₃ functional materials and its application performance and related basic mechanism as composite white pigments,ceramic opacifiers and photocatalysts have been deeply studied.The preparation of MS-SiO₂/TiO₂ composite pigment through the co-grinding of amorphous SiO₂ microspheres(MS-SiO₂)and metatitanic acid(TiO₂·n H₂O)and the calcination of the grinding product was studied,and the performance improvement mechanism of MS-SiO₂/TiO₂was investigated.The hiding power of MS-SiO₂/TiO₂ is 24.92 g/m²,which has achieved the pigment performance equivalent to pure TiO₂.MS-SiO₂ can synergistically improve the properties of TiO₂ pigment by reducing the particle size and increasing the rutile phase conversion of TiO₂,as well as reduce the use amount of TiO₂ pigment.Compared with pure TiO₂,the rutile conversion rate of TiO₂ in MS-SiO₂/TiO₂ is increased from 11.39%to 88.57%,and the particle size is reduced from 0.3-0.6?m to 0.13-0.3?m.The white glazed sanitary ceramics without radiation using CaCO₃-TiO₂ and SiO₂-CaCO₃-TiO₂ composite opacifier were prepared and characterized.The as-prepared ceramic glazes show white appearance,with L*,a*,b*values of 89.83,-0.35,2.73(CaCO₃-TiO₂ opacifier)and 94.41,-0.67 and 3.23(SiO₂-CaCO₃-TiO₂ opacifier),respectively.The performance of the ceramic glaze with CaCO₃-TiO₂ and SiO₂-CaCO₃-TiO₂ composite opacifier is similar to that of the glaze added the same proportion of Zr SiO₄,which has inhibited the glaze yellowing caused by the direct addition of pure TiO₂.The use of CaCO₃-TiO₂ composite opacifier has eliminated the radioactive radiation of glaze from Zr SiO₄ opacifier.The opacification mechanism of CaCO₃-TiO₂ and SiO₂-CaCO₃-TiO₂ is the crystallization of titanite in the glaze layer.The mechanism of inhibiting glaze yellowing is that the pre-interface composite of TiO₂,CaCO₃ and SiO₂ has improved the degree of the high-temperature reaction of TiO₂ to form titanite and thereby hindered the formation of rutile phase.The preparation of precipitated silica(A-SiO₂)supported highly dispersed quantum dot sized-TiO₂ composite photocatalyst(A-SiO₂/TiO₂)by sol-gel method and the performance of A-SiO₂/TiO₂were studied.A-SiO₂/TiO₂ exhibits excellent photocatalytic degradation performance towars tetracycline hydrochloride,which is comparable to pure TiO₂,and its performance is basically unchanged after four times of use.The anatase TiO₂ was successfully loaded on the surface of A-SiO₂ with a loading amount of 9.88 wt%.The particle size of TiO₂ in A-SiO₂/TiO₂is significantly reduced from 20-50 nm(pure TiO₂)to 7-8 nm,TiO₂ is in the quantum dot size and highly dispersed state,which leads to an increase in its active sites and the separation efficiency of photogenerated carriers,thus enhancing the photocatalytic activity of A-SiO₂/TiO₂.The preparation and mechanism of SiO₂-TiO₂/g-C₃N₄ ternary composite photocatalyst(Si-Ti-CN)were studied.Si-Ti-CN shows excellent photocatalytic performance.The photocatalytic hydrogen production rate of Si-Ti-CN under simulated sunlight is 686.83?mol h^-1g^-1,which is12.3 times,3.1 times and 2.9 times of SiO₂-TiO₂,g-C₃N₄ and TiO₂/g-C₃N₄.Besides,Si-Ti-CN shows the good photocatalytic degradation performance on rhodamine b with a reaction rate constant of 0.0189min^-1,which is 3.9 times of TiO₂/g-C₃N₄.The particle size reduction and dispersion improvement of TiO₂ and g-C₃N₄,and the formation of efficient TiO₂/g-C₃N₄ Z-scheme heterostructure in Si-Ti-CN are the main internal mechanisms for the improvement of photocatalytic performance of Si-Ti-CN.