Method for preparing high- stable neutral mixed crystal nanometer TiO2 hydrosol

Preparation method of highly stable neutral mixed crystal nano hydrosol Technical field:

[0001] The present invention relates to a method for preparing a highly stable neutral mixed crystal nano-TiO2 hydrosol, and belongs to the technical field of preparation of photocatalytically active nano-titania materials.

Background technique:

[0002] Nano-titanium dioxide has excellent photocatalytic activity and can effectively mineralize organic pollutants into CO₂, It produces 0 and inorganic acids, and has the advantages of corrosion resistance, stable properties, and non-toxicity.

[0003] Nano Ti. The sol is a highly dispersed, crystallized hydrocolloid, which is different from the titanium dioxide powder suspension that is dispersed by a dispersant. The sol can be synthesized directly from a titanium source without being prepared into a powder. The crystallized sol can avoid the agglomeration problem in the calcining process, so the product has good dispersibility, good stability and convenient modification. Secondly, the sol is more hydrophilic than the suspension, the particles have strong adhesion, and it is easy to coat. When coating the film, the acidic sol is corrosive to the substrate, so the neutral nano-Ti0 is prepared₂Hydrosol is particularly important. In addition, the isoelectric point of TiO2 is 5-6, and the stability of pure TiO2 sol is not high under neutral conditions, and precipitation will occur after a long time of storage, and Si is added. ? After the sol, in Ti. ? Ti-0-Si bond is formed on the surface, which can change Ti0₂Zeta potential, increase Ti0₂The stability of the sol.

[0004] Ti. ? There are three crystal types: rutile, anatase and brookite. The most used are the first two. It is generally believed that for photocatalytic degradation reactions, anatase Ti0₂Catalytic activity is better than rutile Ti0₂high. However, in recent years, researchers have found that mixed crystals of anatase and rutile phases have higher photocatalytic activity. This is because the mixed crystal structure can effectively improve the separation efficiency of electron-hole pairs, thereby improving photocatalysis. effectiveness. How to prepare mixed crystal nano-Ti0₂Literature reports on powders, such as: Wang Zhenxing, etc. reported on the synthesis, structure and photocatalytic properties of highly dispersed nano-TiO2 mixed crystals (Journal of Inorganic Chemistry, 2005, 3). However, in the preparation of sol, how to control Ti. There are not many reports on the ratio of these two crystal forms in the sol. Xia Yuzheng reported on nano-Ti with mixed crystal structure. ? Low-temperature preparation of hydrosol (nano ΤΙ0 with mixed crystal structure₂Research on low-temperature preparation and photocatalytic performance of hydrosols, Coatings Industry, 2007, 37 (8): 38~42), but it did not give a method for how to control the ratio of the two crystal forms in the mixed crystal.

[0005] Ti. ? The energy band is wide, and it can only absorb the ultraviolet part of the sunlight, and the solar energy utilization rate is low. In order to meet actual needs, it is necessary to further increase Ti. The visible light activity of the sol can be doped with metal ions to change its energy band structure to prepare a titanium dioxide photocatalytic material that can be excited by visible light to enhance the catalytic performance.

[0006] At present, the chemical precipitation-degelling method is the most promising method for preparing nano-titania sol. This method mainly uses titanium alkoxides (such as tetrabutyl titanate, tetraethyl titanate, tetrapropyl titanate, etc.) and inorganic titanium salts (such as titanium tetrachloride, titanyl sulfate, etc.) as precursors, nitric acid , Hydrochloric acid, tetraalkyl hydroxide, etc. are degelling agents. The use of titanium alkoxide as the precursor requires strict control of the reaction conditions, because titanium alkoxide is easily hydrolyzed in the air, and the organic reagents used can easily introduce organic matter into the sol. In addition, the high cost of titanium alkoxide also limits the wide application of this method. Using inorganic titanium salt instead of titanium alkoxide can not only reduce the cost, but also eliminates the need to use organic reagents, which can reduce environmental pollution. D. -S. LEE (D. -S. LEE, Τ. -K. LIU. Preparation of Ti0₂ sol using TiCl₄ As a precursor. Journal of Sol-Gel Science and Technology. 25, 12Γ136, 2002) TiO? sol was prepared by using titanium tetrachloride as the precursor, but what he obtained was an acid sol, which was not conducive to coating. Tong-Xu Liu (Tong-Xu Liu, etc. Ti0₂ hydrosols with high activity for photocatalytic degradation of formaldehyde in a gaseous phase.

CN 101306838 Β

Journal of Hazardous Materials. 152 (2008), 347^355) Ti02 sol was prepared using titanyl sulfate and metatitanic acid as precursors, and the degradation effect of the sample on formaldehyde gas was studied. Similarly, what he prepared is also an acid sol. Chinese patent CN101049962A discloses a method for preparing neutral nano-titanium dioxide sol, but he introduced it in the preparation process. 2 Corrosive reagents are used as complexing agents, and the resulting sol is light yellow and the structure is pure anatase. Japanese patent JP2005-169160 discloses a method for preparing SiO by using titanium tetrachloride as a precursor.₂Coated neutral nano Ti. The method of sol, but the sol has the function of shielding ultraviolet rays and cannot be used in the field of photocatalytic degradation of organic matter.

Summary of the invention:

[0007] The purpose of the present invention is to provide a highly stable neutral crystal form ratio controllable nano TiO₂Preparation method of hydrosol. [0008] The present invention is a highly stable neutral crystal form with a controllable ratio of nano Ti. ? The preparation method of the hydrosol is characterized by the following preparation process and steps:

[0009] a. Titanium compound hydrolysis precipitation: select inorganic titanium compound as a raw material, hydrolyze and precipitate the titanium compound with an alkaline solution; the titanium compound is any one of titanium tetrachloride, metatitanic acid or titanyl sulfate; the alkaline solution is Ammonia or sodium hydroxide aqueous solution;

[0010] b Filtration and washing: Wash the precipitate obtained in the above reaction with deionized water until the conductivity of the filtrate is less than 100 μS/cm;

[0011] c Add acid hydrolysis: According to the molar ratio of the titanium compound to the acid solution (Γ2): 1, add acid to the obtained filter cake; the acid used is any of nitric acid, hydrochloric acid or sulfuric acid Species; 10^60mim debonding at a temperature of 60^100Ό;

[0012] d adding stabilizers and dopants: adding a certain amount of Si0₂Sol and metal salt, continue to react for 0.5 to 4.0 hours; SiO₂The amount of sol added is 10% of the total amount of sol; its function is to stabilize Ti0₂Sol and maintain its neutrality requirements; the amount of metal salt added is 0.01% to 0.8% of the total amount of the sol; its role is to nano-Ti0₂The doping modification is carried out to adjust the ratio between the TiO2 crystal type anatase and the rutile type; the metal salt is Fe (N0₃)3>SnCl₄,Zn(N0₃)₂Or Ce (N0₃) Any of 3

[0013] e. Add alkali to adjust the pH of the solution: adjust the pH of the above solution to 7~10 with lye;

[0014] f. Filtration and washing: After filtering the above solution, wash the resulting precipitate with deionized water until the conductivity of the filtrate is less than 100 μS/cm;

[0015] g re-dispersion: in accordance with the solid content requirements, the resulting filter cake is dissolved in a certain amount of water, re-dispersed, to obtain a neutral and stable nano ΤΙ0₂Composite hydrosol; Ti0 in the obtained hydrosol₂The content is "5%; the ratio of anatase to rutile crystals is 1:0.1 or 0.1 Γ1 is controllable.

[0016] The advantages and features of the method of the present invention are as follows:

[0017] (1) Ti prepared by the method of the present invention. The sol has good transparency, good stability, good crystallization degree, obvious photocatalytic effect, and no flocculation or precipitation.

[0018] (2) TiO prepared by the method of the present invention₂The sol, its pH = 6~8, is a neutral hydrosol and does not contain organic matter. The preparation process is conducive to environmental protection. In specific applications, it is convenient to spray without causing corrosion damage to the substrate.

[0019] (3) The present invention adopts a chemical precipitation-degelling method, and prepares anatase type and rutile type mixed crystal nano TiO under the condition of less than 100° C.₂Sol.

[0020] (4) In the process of the present invention, a metal salt is added to nano-Ti. ? Carry out doping modification, and the crystal type anatase and

CN 101306838 Β

The ratio of rutile is controllable within a certain range, which broadens the spectral response range of nano-TiO2.

[0021] (5) In the method of the present invention, Si is added. ? Sol can change Ti. ? The zeta potential of the sol stabilizes Ti. ?

The role of sol, which can produce stable neutral Ti0₂Hydrosol.

Detailed ways:

[0022] Specific embodiments of the present invention will now be described below.

[0023] Example 1:

[0024] The preparation process and steps in this embodiment are as follows:

[0025] In this embodiment, Ti. The composition and weight percentage of the hydrosol are controlled as: Ti0₂4%, Si0₂ 2.5%, metal salt SnCl₄0. 5%, 93% deionized water.

[0026] Take titanium tetrachloride as a raw material and dissolve it in water to form a solution. Add sodium hydroxide solution to the titanium tetrachloride solution under stirring, and adjust the pH value of the solution to neutral; after the reaction is complete, filter, and wash the precipitate obtained in the reaction with deionized water until the filtrate has a conductivity The rate is less than 100uS/cmo, then add acid to dissolve the gel, add nitric acid solution, add nitric acid according to the molar ratio of titanium tetrachloride to nitric acid 1.4:1, and dissolve the gel at 95°C for 40 minutes. Then add a certain amount of Si0₂Sol and metal salt SnCl₄Let it continue to react for 2 hours; then add lye to adjust the pH of the solution to 7. Then filter, wash, and wash the resulting precipitate with deionized water until the conductivity of the filtrate is less than 100 uS/cm. Then the obtained filter cake is dissolved in a certain amount of water and redispersed to finally obtain neutral and stable nano-Ti. ? Composite hydrosol. The Ti. ? The absolute value of the zeta potential of the hydrosol is greater than 50mVo

[0027] Ti0 obtained in the embodiment of the present invention₂Degradability test of hydrosol:

[0028] Take 50ml of 10mg/L methylene blue, reactive brilliant red X-3B or methyl orange solution, add 1. 7ml ±mentioned obtained Ti0₂Hydrosol, irradiate with sunlight for a period of time under stirring conditions, and observe its degradation. The test results showed that the degradation rate of the above dye solutions reached more than 95% within 2 hours.

[0029] Nano Ti produced by the present invention. The crystal form of the sol is a mixed crystal of anatase and rutile, and the ratio of the two crystal forms can be controlled by controlling the reaction conditions. The doped metal ion iron or tin or zinc or lung in the sol can make the spectral response range more than Pure Ti. ?width. Ti obtained by the method of the present invention. ? The hydrosol is neutral, has high transparency, is easy to store, does not produce flocculation, is not corrosive, and has obvious photocatalytic effects.