Method for preparing mixed-phase nano-titania hydrosol photocatalyst

A kind of preparation method of mixed crystal nano titanium dioxide hydrosol photocatalystTechnical field

[0001] The present invention relates to a method for preparing a titanium dioxide hydrosol photocatalyst, in particular to a method for preparing a mixed crystal nanometer titanium dioxide hydrosol photocatalyst by adding a crystal form as a directing agent.

[0002] Background technology:

[0003] Nano-titanium dioxide is an ideal environmentally friendly photocatalyst, which has the advantages of stable chemical properties, corrosion resistance, non-toxicity, and low cost. Titanium dioxide has a multi-phase structure, and there are three crystal types of rutile, anatase, and brookite in nature. In the research reports of photocatalysis, the anatase phase titanium dioxide is generally considered to be more reactive than the rutile phase titanium dioxide (J. Phys. Chem., 1990,94:829). However, in recent years, researchers have found that mixed crystals of anatase and rutile phases have higher photocatalytic activity (Appl. Catal. B: Enviro. [J], 2000, 26: 207). Due to the different Fermi energy levels of the two crystal types of titanium dioxide, a Schottky barrier is generated between the two phase interfaces, which can promote the transfer, separation and migration of electrons and holes to the surface of the catalyst, so that the mixed crystal structure can effectively increase the electron- The separation efficiency of hole pairs improves the photocatalytic efficiency. For example, Degussa's highly active photocatalyst P25, which is recognized in the market, is a mixed crystal of anatase and rutile phase. The different crystal form ratios in mixed crystal titanium dioxide have different photocatalytic activities, and the best photocatalytic activity corresponds to an optimal mixed crystal ratio. Therefore, it is necessary to prepare mixed crystal titanium dioxide with a controllable ratio. There are many methods for preparing mixed-crystal nano-TiO2 in the current research work. In the sol-gel method, the key to the preparation of mixed-crystal nano-TiO2 lies in the choice of catalyst. Song (J. Am. Ceram. Soc., 2001, 84(1): 92~98.) and other studies have shown that acid catalysts contribute to the formation of rutile phases while base catalysts hinder the formation of rutile phases. Dan Dingο (J. Non-Cry. Sol., 1998, 232~234: 175~181.), etc., using different acid catalysts, found that the pH in the sol-gel method only affects the degree of hydrolysis, but the effect on the crystal form It is mainly determined by the nature of the catalyst itself. Zhang (Mater. Res. Bull., 2001, 36: 1957~1965) etc., using HC1 as a peptizer to obtain pure anatase type, anatase type and rutile type mixed crystal type and pure rutile type nano titanium dioxide respectively at different pH. Wang et al. (J. Chem. Mater., 1999, 11: 3113~3120.) showed that in the hydrothermal method, the reaction conditions of the hydrothermal method (reaction time, reaction temperature, stirring conditions, etc.) have a great influence on the crystal form. Big. Yang Shaofeng et al. (Chemical Journal of Colleges and Universities, 2001, 22(6): 980~983.)₂ · 2H₂0 and SnCl₄ · 5H₂0 is the source of tin, doping with Sn during the hydrolysis of Ti (SO» 2 with ammonia⁴⁺Then use ΗΝ0₃Used as a peptizer to peptize and synthesize mixed crystal titanium dioxide powders with different rutile contents. There are also reports that nano-TiO2 can be obtained by adding different additives and then calcining at a high temperature to obtain a mixed crystal phase. Pan Haibo et al. (Journal of Materials Research, 2001, 15(5): 535~539.) Using TiCl₃The solution (concentration 15%) is the titanium source, and the partial organic acid saddle (NH₄V0₃) Is a dopant, concentrated hydrochloric acid is a stabilizer, and a strong oxidant is added. 2 and the surface coating agent dodecyl benzene sulfonic acid (DBS) are continuously stirred at 60°C until a gel is formed. After drying at 80°C, it is calcined at 400°C to prepare mixed crystal titanium dioxide powder. Lin Yuanhua et al. (Journal of Inorganic Materials, 1999, 14(6): 853~860.) used ZnO coating method to obtain mixed crystal titanium dioxide powder under lower temperature calcination.

Summary of the invention

[0004] One of the objectives of the present invention is to provide a method for preparing a mixed crystal nano-titanium dioxide hydrosol photocatalyst.

[0005] In order to achieve the above objective, the present invention adopts the following technical solutions:

[0006] A method for preparing mixed crystal nano-titanium dioxide hydrosol photocatalyst, which is characterized in that the method is specific

The steps are as follows: the titanium precursor and the crystal-type directing agent zirconium salt are dissolved in an alkaline solution at a molar ratio of zirconium salt to titanium dioxide contained in the titanium precursor at a ratio of 1: (0.005~0.1) to obtain a precipitate; The precipitate is filtered and washed until the conductivity of the filtrate is less than 100 μS/cm; the washed precipitate is added to the acid solution, and the pH of the solution is controlled to be <5, and the gelation is performed at a temperature of 60~100°C for 10~ 60 minutes to obtain a solution; subject the gelled solution to a hydrothermal reaction at a temperature of 120~180°C for 12~24 hours; remove the impurity ions in the product after hydrothermal, until the conductivity of the product is less than 100 μS/cm, obtain Mixed crystal nanometer titanium dioxide hydrosol photocatalyst.

[0007] The pH of the above-mentioned mixed-crystal nano-titanium dioxide hydrosol is 6-8.

[0008] In the above-mentioned mixed crystal nano-titanium dioxide hydrosol photocatalyst, the titanium dioxide is a mixture of two crystal types of anatase and rutile, wherein the mass ratio of the anatase type and the rutile type is: (95-70): (5- 30) ο

[0009] The aforementioned titanium precursor is tetrabutyl titanate, titanium tetraisopropoxide, titanium tetrachloride, metatitanic acid or titanyl sulfate.

[0010] The above-mentioned alkaline solution is ammonia water, sodium hydroxide water or potassium hydroxide solution.

[0011] The above-mentioned alkaline solution is that the acid solution is nitric acid, hydrochloric acid or sulfuric acid.

[0012] The above-mentioned crystalline form directing agent aluminum salt is: tetra-n-butoxy aluminum, aluminum chloride.

[0013] The above-mentioned method for removing impurity ions in the product after hydrothermal is dialysis or filtration washing

[0014] The present invention provides a method for preparing mixed-crystal nano-titanium dioxide hydrosol photocatalyst by adding zirconium salt. The preparation conditions are mild, the process is simple, and the prepared mixed-crystal titanium dioxide hydrosol photocatalyst is medium without high-temperature roasting process. The ratio of anatase to rutile crystal form can be adjusted by changing the addition amount of the wrong salt.

[00 The advantages of the method of the present invention are as follows:

[0016] (1) The mixed crystal nano titanium dioxide photocatalyst prepared by the method of the present invention has good dispersibility, stability, high degree of crystallization and obvious photocatalytic effect.

[0017] (2) The preparation process of the mixed crystal nano-titanium dioxide photocatalyst prepared by the method of the present invention is relatively environmentally friendly, and the solution is neutral. In specific applications, it is convenient for spraying without causing corrosion damage to the substrate.

[0018] (3) The method of the present invention is carried out under mild conditions, and a nanometer titanium dioxide photocatalyst with a controllable ratio of anatase and rutile type is prepared by adding a crystal form directing agent zirconium metal salt. The method is simple and easy to implement, and the cost is relatively low.

Description of the drawings

[0019] FIG. 1 is a TEM diagram of the mixed crystal nano-titanium dioxide hydrosol photocatalyst obtained in Example 1

[0020] FIG. 2 is an XRD pattern of the mixed crystal nano-titanium dioxide hydrosol photocatalyst obtained in Example 1

[0021] FIG. 3 is a TEM diagram of the mixed crystal nano-titanium dioxide hydrosol photocatalyst obtained in Example 2

[0022] FIG. 4 is an XRD pattern of the mixed crystal nanometer titanium dioxide hydrosol photocatalyst obtained in Example 2

[0023] FIG. 5 is a TEM diagram of the mixed crystal nano-titanium dioxide hydrosol photocatalyst obtained in Example 3

[0024] FIG. 6 is a specific embodiment of the XRD pattern of the mixed crystal nano-titanium dioxide hydrosol photocatalyst obtained in Example 3

[0025] In order to better illustrate the content of the present invention, specific embodiments of the present invention are now set forth below.

[0026] Example 1: Taking metatitanic acid as a raw material, configured into a 50wt% aqueous solution of metatitanic acid, and adding the metal salt of aluminum chloride to the molar ratio of the theoretical content of titanium dioxide to 0.005ο under stirring, 3Μ Ammonia solution was added dropwise to the above metatitanic acid aqueous solution to adjust the pH of the solution to neutral; filtered, and the white precipitate obtained was washed with deionized water until the conductivity of the filtrate was less than 100 P S/cm. Then add hydrochloric acid according to the molar ratio of metatitanic acid to hydrochloric acid at a ratio of 2:1, and peptize at 100°C

60min; put the product obtained by reflux in a hydrothermal kettle at 180°C for 12h, cool to room temperature, put the product obtained in a dialysis bag with a cut-off flow of 14000, the dialysate is deionized water to make the dialysis The final conductivity of the solution is less than 100 μS/cm, and a neutral mixed crystal titanium dioxide hydrosol is obtained. After testing and analysis, referring to Fig. 1 and Fig. 2, the particle size of the mixed crystal titanium dioxide hydrosol catalyst obtained in this example is 8-10 nm, and the mixed crystal is composed of anatase phase and rutile phase, with high crystallinity.

[0027] Example 2: Take titanium tetrachloride as a raw material, configure a 50wt% titanium tetrachloride aqueous solution, and add the metal salt tetra-n-butoxy aluminum, so that its molar ratio to the theoretical content of titanium dioxide is 0.02 . While stirring, add 1M NaOH aqueous solution dropwise to the above titanium tetrachloride solution to adjust the pH of the solution to neutral; filter and wash the white precipitate obtained with deionized water until the conductivity of the filtrate is less than 100μS/cmo and then follow the tetrachloride The molar ratio of titanium dioxide to nitric acid is 2:1. Nitric acid is added and gelled at 80°C for 60 minutes; the refluxed product is placed in a hydrothermal kettle at 120°C for 20 hours, cooled to room temperature, The obtained product was filtered and washed with a water membrane with a pore size of 0.2μ until the conductivity of the filtrate was less than 100 μS/cm, and a neutral mixed crystal titanium dioxide hydrosol was obtained. The TEM and XRD patterns of the prepared samples are shown in Figure 3 and Figure 4.

[0028] Example 3: Take titanium tetrachloride as a raw material, configure a 50wt% titanium tetrachloride aqueous solution and add a metal salt of aluminum chloride to make the molar ratio of the theoretical content of titanium dioxide to 0.04. Under stirring, the IM KOH aqueous solution was added dropwise to the above titanium tetrachloride solution to adjust the pH of the solution to neutral; filter and wash the white precipitate obtained with deionized water until the conductivity of the filtrate is less than 100 μS/cmo and then follow The molar ratio of titanium tetrachloride to sulfuric acid is 2:1 and sulfuric acid is added. Gelled at 60°C for 100min; put the refluxed product in a hydrothermal kettle at 180°C for 16h, cool to room temperature, put the obtained product in a dialysis bag with a cut-off flow of 14000, the dialysate It is deionized water, so that the final conductivity of the dialysate is less than 100 μS/cm, and a neutral mixed crystal titanium dioxide hydrosol is obtained. The TEM and XRD patterns of the prepared samples are shown in Figure 5 and Figure 6.

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