CN109678379B

CN109678379B - Modified titanium dioxide and preparation method thereof

Info

Publication number: CN109678379B
Application number: CN201710971778.0A
Authority: CN
Inventors: 封丽娟
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-10-18
Filing date: 2017-10-18
Publication date: 2021-07-06
Anticipated expiration: 2037-10-18
Also published as: CN109678379A

Abstract

The invention provides modified titanium dioxide applied to mortar and a preparation method thereof, wherein the preparation method comprises the following steps: (1) pretreating an industrial titanium dioxide raw material;(2) for the TiO obtained in the step (1)₂Carrying out pore-forming treatment; (3) coating a layer of TiO on the outer layer of the silicon dioxide inner core in the step (2)₂(ii) a (4) TiO obtained in the step (3)₂An outer layer is coated with a layer of Cr₂O₃(ii) a (5) Coating a layer of TiO on the outer layer of the titanium dioxide obtained in the step (4)₂. The titanium dioxide finished product prepared by the method has the characteristics of good mechanical strength, strong photocatalytic activity and the like, and can effectively prevent the coating from being polluted when being applied to mortar.

Description

Modified titanium dioxide and preparation method thereof

Technical Field

The invention belongs to the field of industrial titanium dioxide, and particularly relates to titanium dioxide used in lime mortar.

Background

Titanium dioxide is considered as a white pigment with the best performance in the world, has high covering power, weather resistance, color reducing power and the like, and is widely applied to fine chemical industries such as coatings, plastics, papermaking, printing ink, chemical fibers, rubber, ceramics, cosmetics, food, medicines and the like.

In previous studies, it was found that titanium dioxide has strong photocatalytic properties, such as purifying air, treating wastewater and the like (nano TiO)₂Preparation and photocatalytic performance research, Liyidong, etc.). When the titanium dioxide is applied to coatings or used as additives of food, medicine and the like, the strong photocatalytic activity of the titanium dioxide can adversely affect the performance of the product, and the titanium dioxide needs to be coated to avoid the aging of the product (orthogonal experiment for optimizing ZrO)₂Titanium dioxide coating process research, baiting, etc.). Therefore, how to apply the photocatalytic activity of titanium dioxide is an important research topic in the field.

Titanium dioxide is used as an additive in mortar, has the effect of enhancing the whiteness of the mortar, and is widely applied to industrial production. CN105565736A discloses a mortar with ultraviolet-resistant function, and nano titanium dioxide added in the mortar can improve the self-cleaning performance of the product. However, how to further improve the self-cleaning performance and ensure the whiteness of the titanium dioxide is a difficulty in related researches.

Disclosure of Invention

The invention is provided in view of the above.

The invention provides modified titanium dioxide, which comprises four layers and is characterized in that the modified titanium dioxide core is silicon dioxide (SiO)₂) The second layer is titanium dioxide (TiO)₂) The third layer is chromium oxide (Cr)₂O₃) The outermost layer is titanium dioxide (TiO)₂）。

In the modified titanium dioxide, SiO₂10-30% of Cr₂O₃5-20% of TiO₂The content is 50-85%.

The modified titanium dioxide is applied to mortar, and the mortar is one or more of lime mortar, cement mortar and mixed mortar.

The invention provides a preparation method of the modified titanium dioxide, which comprises the following steps: (1) pretreating an industrial titanium dioxide raw material; (2) for the TiO obtained in the step (1)₂Carrying out pore-forming treatment; (3) coating a layer of TiO on the outer layer of the silicon dioxide inner core₂(ii) a (4) TiO obtained in the step (3)₂An outer layer is coated with a layer containing Cr₂O₃An outer layer of (a); (5) coating a layer of TiO-containing titanium dioxide outer layer obtained in the step (4)₂An outer layer of (a).

Preferably, in step (3), the TiO coated on the outer layer₂For the TiO obtained in step (2)₂。

Preferably, in step (5), the TiO coated on the outer layer₂For the TiO obtained in step (2)₂。

Preferably, in the step (4), Cr is contained₂O₃In the outer layer of (2), Cr₂O₃The content of (B) is 100%.

Preferably, in step (5), the TiO-containing compound₂In the outer layer of (2), TiO₂The content of (B) is 100%.

In the step (4), Cr is contained₂O₃The outer layer of (2) may be made of Cr₂O₃And TiO₂Composition of, wherein Cr₂O₃The content is 60-90%. TiO 2₂Preferably TiO obtained in step (2)₂。

In the step (5), TiO is contained₂The outer layer of (2) may be made of Cr₂O₃And TiO₂Composition of, wherein TiO₂The content is 60-90%. TiO 2₂Preferably TiO obtained in step (2)₂。

In the step (1), the pretreatment step is preferably: putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the titanium dioxide raw material to the deionized water is 2-4:6-8, preferably 3: 7; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 1.0-2.0, continuously dropwise adding dithiocarbamate derivative solution into the reactor until no solid suspended matter is generated, continuously stirring for 15-25min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content.

Preferably, the dithiocarbamate derivative is one or more of sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, sodium dibutyldithiocarbamate and sodium ethylphenyldithiocarbamate.

The preparation step (2) is as follows: a. firstly, respectively grinding the titanium dioxide and the pore-forming agent obtained in the step (1) until the granularity is below 50 mu m, then uniformly mixing the ground titanium dioxide and the pore-forming agent powder, and performing compression molding under the pressure of 100-250 MPa; b. heating the material pressed and formed in the step a to 600-1100 ℃ at the heating rate of 5-10 ℃/min, and sintering for 3-6 h to obtain the porous titanium precursor after removing the pore-forming agent; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of calcium to titanium dioxide of more than or equal to 2:1, then performing calcium thermal reduction for 24-60 h under the conditions that the pressure in the furnace is less than or equal to 5Pa, the heating rate is 5-10 ℃/min and the reduction temperature is 1000-1100 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and performing vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm.

Preferably, the pore-forming agent is ammonium bicarbonate, high-purity graphite or starch, and the addition amount of the pore-forming agent is 3-15% of the mass of titanium dioxide.

Preferably, in the step a, the mixture is pressed and formed under the pressure of 200 MPa.

Preferably, in the step b, the material which is pressed and formed in the step a is heated to 800 ℃ at the heating rate of 6 ℃/min and sintered for 4 hours to obtain the porous titanium precursor after the pore-forming agent is removed.

Preferably, in the step c, the mass ratio of calcium to titanium dioxide is 5: 1.

Preferably, in the step c, the vacuum is performed until the pressure in the furnace is 2 Pa.

The preparation step (3) is as follows: a. taking SiO with the weight portion of 0.05-0.1₂Suspending the mixture in 5 to 15 parts by weight of ethanol under the ultrasonic condition; b. adding 0.05-0.1 weight part of 90% Hexadecylamine (HDA) and 0.1-0.4 weight part of ammonia water into the solution, and stirring at room temperature for 0.5-5 minutes; c. adding 0.1-1.0 weight part of tetraisopropyl Titanate (TIP) into the step b under the condition of stirring, and reacting for 5-20 minutes; d. centrifuging to obtain precipitate, and washing the precipitate with water and ethanol; e. burning the precipitate at 450 deg.C for 1-4 hr, washing with 10% hydrofluoric acid to obtain SiO as core₂Of TiO 2₂And (3) granules.

The preparation step (4) is as follows: a. subjecting the TiO obtained in step (3)₂Dispersing the granules in ethanol, and performing ultrasonic treatment for 10-15min per g TiO₂Adding organic chromium compound into the particles according to the proportion of 0.02-1mmol to form suspension; b. taking enough water, adjusting the pH value to 4-6, respectively heating the water and the suspension obtained in the step a to 80-95 ℃, and simultaneously adding the water and the suspension into a stirrer for hydrolysis reaction; c, after the reaction is finished after 10-30min, collecting the precipitate, and burning for 1 hour at the temperature of 450-₂O₃Of TiO 2₂And (3) granules.

The ultrasonic frequency is 30-80 KHz.

The pH adjusting agent is preferably HCl.

The organic chromium compound is Cr (OMe)₃、Cr（OEt）₃、Cr（O·n-Pr）₃、Cr（O·n-Bu）₃Preferably one or more of Cr (O-i-H)₃C₇)₃Or Cr₃O（O₂CCH₃）·7H₂O。

The preparation step (5) is as follows: a. taking 1-10 parts by weight of the titanium dioxide obtained in the step (4), taking 5-20 parts by weight of the titanium dioxide obtained in the step (2), dispersing the titanium dioxide in sufficient Decamethylcyclopentasiloxane (DMCPSI), adding 1-5 parts by weight of octyl p-methoxycinnamate (OPMC), and uniformly mixing to obtain a suspension A; b. pressing and coating the suspension A; c. heating the pressed suspension A at 60-120 deg.C for 10 min-3 hr to volatilize DMCPSI.

Preferably, in the step b, the pressing is performed by using a coating device manufactured by the self-made method of the present application, and the structure of the step b is shown in the attached figures 1 and 2 of the specification. Firstly, placing suspension A on a flat plate, uniformly spreading the suspension A on the flat plate by an applicator at a constant speed under the drive of a linear motor, wherein the coating speed is 1.0 multiplied by 10^-2m/s to 1 m/s. And pressing and coating the suspension A while coating, wherein the pressure is between 10Pa and 1000Pa, and the temperature is adjusted to be between 30 and 40 ℃. After coating, adjusting the temperature to 60-70 ℃, and drying for 10-30 min.

The present invention seeks to improve the photocatalytic activity of titanium dioxide in order to prevent the coating of mortar from being contaminated, in particular by soot-type contaminants, after its application in mortar. As titanium oxide is known to have a strong light absorption ability in the ultraviolet region and also a strong photocatalytic activity, the present invention attempts to increase the wavelength region of its light absorption by coating the outer layer of titanium oxide with a metal oxide, thereby increasing its photocatalytic activity. However, the whiteness of the titanium dioxide coated with the metal oxide is inevitably affected, so that the research on the method for coating the titanium dioxide on the metal oxide outer layer is carried out in the invention, and a preparation method capable of enhancing the photocatalytic activity of the titanium dioxide without reducing the whiteness is explored.

The invention surprisingly discovers that when the outermost layer is coated with titanium dioxide with a certain thickness, the whiteness of the finished product can be improved, and even the photocatalytic activity of the product can be further improved.

The invention has the beneficial effects that:

1. the titanium dioxide inner layer prepared by the preparation method provided by the invention has a silicon dioxide inner core, so that the whole powder has better mechanical properties.

2. The titanium dioxide inner layer prepared by the preparation method is coated with chromium sesquioxide, so that the light absorption capacity of the titanium dioxide powder is improved.

3. The outer titanium dioxide coated by the preparation method of the invention ensures that the final product has good whiteness without influencing the light absorption capacity of the titanium dioxide powder.

Description of the drawings:

in order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a front view of the cladding apparatus of the present invention

FIG. 2 is a side view of the cladding apparatus of the present invention

Description of the reference numerals

1. A linear motor driver; 11. a connecting arm; 12. a glass plate support; 13. a moving groove; 2. a glass plate; 3. an applicator; 31. a gap; 32. a coating roller; 4. heating plates; 5. and (3) suspension.

The technical scheme of the invention can be more clearly understood and explained by combining the embodiment of the invention through the reference sign description.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, these information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present invention. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.

The present invention will be described in detail below by way of examples.

Experimental example 1

In this experimental example, the method of coating chromium with titanium dioxide was investigated.

The chromium coating method commonly used in the art is as follows: weighing TiO according to the mass ratio of 9:1₂And Cr₂O₃Mixing the two, adding into a planetary ball mill, ball milling for 4h, drying for 12h, taking out the powder, placing in a muffle furnace, and keeping the temperature at 1000 deg.C for 70h to obtain the final product coated with Cr₂O₃Of TiO 2₂. Experiments were performed in parallel 5 times according to the method.

In this experiment, the following procedure was used for the preparation of TiO₂Carrying out Cr₂O₃Coating: dispersing titanium dioxide particles in sufficient ethanol, performing ultrasonic treatment at 40KHz frequency for 15min, and adding Cr in an amount of 0.04 mmol/g titanium dioxide particles₃O（O₂CCH₃）·7H₂O, forming a suspension, and heating to 90 ℃; adding HCl to regulate pH to 5, heating to 90 deg.C,adding the suspension and the purified water into a stirrer at the same time, and carrying out hydrolysis reaction; after 30min, the reaction is finished, the precipitate is collected and burned for 1 hour at 700 ℃, and the titanium dioxide particles coated with the chromium sesquioxide are obtained. Experiments were performed in parallel 5 times according to the method.

The titanium dioxide prepared by the two methods was subjected to absorbance tests at different wavelengths, and the results are shown in table 1. The ultraviolet-visible diffuse reflectance spectra (UV-VIS DRS) of the samples were measured using a Perkin Elmer-Lambda 35 UV-Vis Spectrometer.

According to the results in Table 1, the TiO coated by the process of the invention₂Has TiO coated in the visible light region (400-550 nm) compared with the TiO coated by the conventional ball milling method₂Greater absorbance (P < 0.01).

TABLE 1 absorbance of titanium dioxide at different wavelengths before and after coating

Wavelength (nm)	TiO before coating₂	The method of the invention is adopted to coat Cr₂O₃Of TiO 2₂	Coating Cr by ball milling₂O₃Of TiO 2₂
				300	1.2	1.4	1.2
350	1.0	1.2	1.1
				400	0.2	1.0	0.4
450	0.1	0.8	0.2
				500	0.03	0.5	0.05
550	0.02	0.1	0.04

Experimental example 2

In the coating process of the invention, a coating device is used. The coating equipment consists of a linear motor driver 1, a glass plate 2, a coater 3 and a heating plate 4. The connecting arm 11 is fixedly connected to the applicator 3 and can be moved in the moving slot 13 by the motor, thereby pushing the applicator 3 to move on the glass plate 2. The height of the gap 31 between the applicator 3 and the glass plate 2 is 5-30 μm, preferably 15 μm, and the size of the gap 31 can be controlled by adjusting the height of the application roller 32. The linear motor driver 1 is provided with a glass plate support 12 for supporting the glass plate 3, and a heating plate 4 is fixedly arranged below the glass plate 3.

Weighing a steel plate coated with Cr₂O₃Of TiO 2₂500g of industrial titanium dioxide and 500g of industrial titanium dioxide are dispersed in 1L of DMCPSI, stirred evenly and added with 100g ofOPMC, mixed well to give suspension 5.

A certain amount of suspension 5 is taken and placed on a glass plate 2 of the coating equipment, a linear motor driver 1 is started, and a coater 3 is pushed to move on the glass plate at a constant speed through conduction of a connecting arm 11. The gap between the applicator 3 and the glass plate 2 was 15 μm, and the moving speed of the applicator 3 on the glass plate 2 was 0.02 m/s.

When a homogeneous spreading of the suspension 5 onto the glass plate 2 was observed, the heating plate 4 was opened and the temperature was adjusted to 35 ℃. The linear motor driver 1 is then controlled to move in the opposite direction until the starting point, thus reciprocating 1 h. Stopping the linear motor driver 1, adjusting the temperature of the heating plate 4 to 70 ℃, and drying for 30 min.

After coating was complete, the experiment was repeated five times.

For comparison, the coating was applied by ball milling. The experimental method is as follows: weighing industrial titanium dioxide and Cr-coated industrial titanium dioxide according to the mass ratio of 9:1₂O₃Of TiO 2₂Mixing the two, adding into a planetary ball mill, performing ball milling reaction for 4h, drying for 12h, taking out the powder, placing in a muffle furnace, and keeping the temperature at 1000 ℃ for 70h to obtain Cr₂O₃Coated with TiO on the outer layer₂Titanium dioxide particles of (2). The above experiment was repeated five times.

The whiteness of the titanium dioxide was measured by a whiteness measuring instrument, and the results are shown in table 2.

As can be seen from the results in Table 2, the titanium dioxide was coated with Cr before the coating₂O₃The whiteness of the titanium dioxide particles is improved to a certain extent by adopting the conventional technology in the field, namely, after the titanium dioxide particles are coated by the ball milling method, compared with the whiteness before the coating, and the data of the titanium dioxide particles have statistical significance (P is less than 0.01). After the method is adopted to coat the titanium dioxide, the whiteness of the titanium dioxide is obviously improved (P is less than 0.01) compared with the whiteness before coating, and the whiteness reaches the level of industrial titanium dioxide (P is more than 0.05).

TABLE 2 whiteness values (%)

Before coating	After being coated by the method of the invention	After being coated by ball milling method	Industrial titanium dioxide
				75.1	90.0	89.2	90.2

The absorbance of titanium dioxide in this example was measured by the method of example 1, and the measurement results are shown in table 3. The inventors have surprisingly found that by using the coating method of the present invention, Cr is coated₂O₃Coating a layer of TiO outside the layer₂Then, the absorbance in the visible light region was also increased, and the absorbance at 550nm was significantly different (P < 0.05) from that before coating, and Cr was added by ball milling₂O₃Coating a layer of TiO outside the layer₂Then, the absorbance in the visible light region was significantly reduced compared to that before coating (P < 0.01).

The coating of the outer TiO layer cannot be controlled by adopting a ball milling method₂Resulting in Cr₂O₃Coated with a thick layer of TiO₂Therefore, the light absorption capability in the visible light region cannot be exhibited. By the coating method of the present invention, Cr₂O₃Coated TiO layer₂The layer is very thin, not only has little influence on the light absorption capability of the layer in a visible light region, but also has Cr₂O₃Visible light absorbed by the layer can simultaneously improve TiO of the inner layer and the outer layer₂Photocatalytic activity of (1). It can be seen that the coating method of the present invention is adoptedThe absorbance of titanium dioxide in the visible light range, particularly at 500-550nm, can be increased.

TABLE 3 absorbance of titanium dioxide at different wavelengths before and after coating

Wavelength (nm)	Before coating	The method of the invention is adopted to coat TiO₂	Coating TiO by ball milling method₂	Industrial titanium dioxide
					300	1.4	1.4	1.2	1.2
350	1.2	1.2	1.1	1.0
					400	1.0	1.0	0.5	0.2
450	0.8	0.9	0.4	0.1
					500	0.5	0.6	0.08	0.03
550	0.1	0.3	0.03	0.02

Experimental example 3

This example explores the pretreatment of titanium dioxide coated with Cr₂O₃Influence of the outer layer. Coated with Cr₂O₃The procedure of (3) is as described in experimental example 2.

Scheme a: (1) weighing a steel plate coated with Cr₂O₃500g of titanium dioxide (A) and 1kg of industrial titanium dioxide (B) were dispersed in 1L of DMCPSI, stirred uniformly, added with 100g of OPMC, and mixed uniformly to obtain a suspension. A certain amount of suspension is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. The gap between the coater and the glass plate was 15 μm, and the moving speed of the coater on the glass plate was 0.02 m/s. When uniform spreading of the suspension onto the glass plate was observed, the heating plate was opened and the temperature was adjusted to 35 ℃. Then the linear motor driver is controlled to move in the opposite direction until the starting point, and thus the linear motor driver reciprocates for 1 h. And after the coating is finished, stopping the linear motor driver, adjusting the temperature of the heating plate to 70 ℃, and drying for 30 min.

Experiments were performed in parallel 5 times according to the method.

Scheme b: (1) firstly, respectively grinding titanium dioxide and a pore-forming agent ammonium bicarbonate until the granularity is below 50 mu m, wherein the mass of the ammonium bicarbonate is 5 percent of that of the titanium dioxide, then uniformly mixing the ground titanium dioxide and the ammonium bicarbonate, and performing compression molding under the pressure of 200 MPa; b. b, heating the material pressed and formed in the step a to 800 ℃ at the heating rate of 6 ℃/min, and sintering for 4h to obtain a porous titanium precursor after removing the pore-forming agent; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of calcium to titanium dioxide of 5:1, then carrying out calcium thermal reduction for 50h under the conditions of vacuumizing until the pressure in the furnace is 2Pa, the heating rate is 5 ℃/min and the reduction temperature is 1000 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm.

(2) Weighing a steel plate coated with Cr₂O₃500g of the titanium dioxide and 1kg of the porous titanium dioxide prepared in the previous step were dispersed in 1L of DMCPSI, stirred uniformly, added with 100g of OPMC, and mixed uniformly to obtain a suspension. A certain amount of suspension is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. The gap between the coater and the glass plate was 15 μm, and the moving speed of the coater on the glass plate was 0.02 m/s. When uniform spreading of the suspension onto the glass plate was observed, the heating plate was opened and the temperature was adjusted to 35 ℃. Then the linear motor driver is controlled to move in the opposite direction until the starting point, and thus the linear motor driver reciprocates for 1 h. And after the coating is finished, stopping the linear motor driver, adjusting the temperature of the heating plate to 70 ℃, and drying for 30 min.

Experiments were performed in parallel 5 times according to the method.

Scheme c: (1) putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the titanium dioxide raw material to the deionized water is 3:7 by weight; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 2.0, continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor until no solid suspended matter is generated, continuously stirring for 20min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content.

Experiments were performed in parallel 5 times according to the method.

Scheme d: scheme c: (1) putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the titanium dioxide raw material to the deionized water is 3:7 by weight; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 2.0, continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor until no solid suspended matter is generated, continuously stirring for 20min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content.

(2) Firstly, respectively grinding titanium dioxide and a pore-forming agent ammonium bicarbonate until the granularity is below 50 mu m, wherein the mass of the ammonium bicarbonate is 5 percent of that of the titanium dioxide, then uniformly mixing the ground titanium dioxide and the ammonium bicarbonate, and performing compression molding under the pressure of 200 MPa; b. b, heating the material pressed and formed in the step a to 800 ℃ at the heating rate of 6 ℃/min, and sintering for 4h to obtain a porous titanium precursor after removing the pore-forming agent; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of calcium to titanium dioxide of 5:1, then carrying out calcium thermal reduction for 50h under the conditions of vacuumizing until the pressure in the furnace is 2Pa, the heating rate is 5 ℃/min and the reduction temperature is 1000 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm.

(3) Weighing a steel plate coated with Cr₂O₃500g of the titanium dioxide and 1kg of the porous titanium dioxide prepared in the previous step were dispersed in 1L of DMCPSI, stirred uniformly, added with 100g of OPMC, and mixed uniformly to obtain a suspension. A certain amount of suspension is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. The gap between the coater and the glass plate was 15 μm, and the moving speed of the coater on the glass plate was 0.02 m/s. When uniform spreading of the suspension onto the glass plate was observed, the heating plate was opened and the temperature was adjusted to 35 ℃. Then the linear motor driver is controlled to move in the opposite direction until the starting point, and thus the linear motor driver reciprocates for 1 h. And after the coating is finished, stopping the linear motor driver, adjusting the temperature of the heating plate to 70 ℃, and drying for 30 min.

Experiments were performed in parallel 5 times according to the method.

And (3) detecting the whiteness and the absorbance of the titanium dioxide prepared by the scheme a-d. The detection method was as in experimental examples 1 and 2. The results of the experiment are shown in tables 4 and 5. According to the data in table 4, when the pretreatment and pore-forming treatment are simultaneously performed on the titanium dioxide raw material, the whiteness of the coated titanium dioxide particles is remarkably improved (P is less than 0.01) compared with other schemes (the pore-forming treatment is performed alone or the pretreatment is performed alone). In addition, the technical scheme that the titanium dioxide is subjected to pore-forming treatment alone or is coated after being subjected to pretreatment alone is different from the technical scheme that the titanium dioxide is directly coated without treatment, the whiteness of the finished product is not obviously different (P is more than 0.05), and the fact that the titanium dioxide is coated on the outer layer after being subjected to pretreatment and pore-forming proves that the technical effect which is unexpected by a person skilled in the art is achieved.

TABLE 4 whiteness values (%)% of titanium dioxide before and after coating

Scheme a	Scheme b	Scheme c	Scheme d	Industrial titanium dioxide
					90.0	90.1	90.4	92.2	90.2

According to the data in Table 5, the absorbance of the product obtained in the scheme b and the scheme c in the ultraviolet region (400 nm) and the visible region (400 nm) are not significantly different (P is more than 0.05) compared with the product obtained in the scheme a, but the product obtained in the scheme d has better absorbance (P is less than 0.05) in the visible region (500 nm and 550 nm) compared with the product obtained in the scheme a-c.

TABLE 5 absorbance of titanium dioxide at different wavelengths before and after coating

Wavelength (nm)	Scheme a	Scheme b	Scheme c	Scheme d	TiO before coating₂
						300	1.4	1.4	1.4	1.6	1.2
350	1.2	1.1	1.2	1.4	1.0
						400	1.0	1.0	1.1	1.3	0.2
450	0.9	0.9	0.8	0.9	0.1
						500	0.6	0.6	0.6	0.8	0.03
550	0.3	0.4	0.4	0.6	0.02

Experimental example 4

In the experimental example, the influence of the inner core of titanium dioxide, which is silicon dioxide, on the mechanical properties of the powder is researched.

Scheme 1: titanium dioxide was prepared according to the complete preparation process of the present invention. Specifically, (1) putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the titanium dioxide raw material to the deionized water is 2: 8; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 1.0, and continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor until the solution is completely dissolvedStopping the process without generating solid suspended matters, continuing stirring for 15min, and filtering and extracting titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content. (2) Firstly, respectively grinding the titanium dioxide obtained in the step (1) and a pore-forming agent ammonium bicarbonate until the granularity is below 50 mu m, then weighing the ground titanium dioxide and ammonium bicarbonate powder which is 3 percent of the mass of the titanium dioxide, uniformly mixing, and performing compression molding under the pressure of 100 MPa; b. b, heating the material pressed and formed in the step a to 600 ℃ at the heating rate of 5 ℃/min, and sintering for 3h to obtain a porous titanium precursor after the pore-forming agent is removed; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of calcium to titanium dioxide of 2:1, then carrying out calcium thermal reduction for 24 hours under the conditions of vacuumizing until the pressure in the furnace is 1Pa, the heating rate is 5 ℃/min and the reduction temperature is 1000 ℃, taking out the reduction product after cooling, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm. (3): a. taking 50g of SiO₂Suspended in 5000g of ethanol under ultrasonic conditions; b. to the above solution were added 50g of 90% Hexadecylamine (HDA) and 100g of aqueous ammonia, and stirred at room temperature for 0.5 minute; c. adding 100g of tetraisopropyl Titanate (TIP) into the step b under stirring, and reacting for 5 minutes; d. centrifuging to obtain precipitate, and washing the precipitate with water and ethanol; e. burning the precipitate at 450 deg.C for 1 hr, washing with 10% hydrofluoric acid to obtain SiO as core₂Of TiO 2₂And (3) granules. (4) a, mixing the TiO obtained in the step (3)₂Dispersing the granules in ethanol, and performing 30KHz ultrasonic treatment for 10min per g TiO₂Cr is added into the particles according to the proportion of 0.02mmol₃O（O₂CCH₃）·7H₂O, forming a suspension; b. taking enough water, adjusting the pH value to 4 by using HCl, respectively heating the water and the suspension obtained in the step a to 80 ℃, and simultaneously adding the water and the suspension into a stirrer for hydrolysis reaction; c.10min later, collecting precipitate, and burning at 450 deg.C for 1 hr to obtain coated Cr₂O₃Of TiO 2₂And (3) granules. (5) Taking 100g of the titanium dioxide obtained in the step (4), taking 2000g of the titanium dioxide obtained in the step (2), dispersing the titanium dioxide in 1L of Decamethylcyclopentasiloxane (DMCPSI), adding 100g of octyl p-methoxycinnamate (OPMC), and uniformly mixing to obtain a suspension A; b. a certain amount of suspension A is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. The gap between the coater and the glass plate was 15 μm, and the moving speed of the coater on the glass plate was 0.01 m/s; c. when a uniform spreading of suspension a on the glass plate was observed, the heating plate was opened and the temperature was adjusted to 30 ℃. Then the linear motor driver is controlled to move in the opposite direction until the starting point, and the linear motor driver reciprocates for 30 min. Stopping the linear motor driver, adjusting the temperature of the heating plate to 60 ℃, and drying for 30 min. The preparation was carried out 5 times in parallel according to the method.

Scheme 2: according to the step (3) of the preparation method of scheme 1, silica coated with titanium dioxide is prepared. The preparation was carried out 5 times in parallel according to the method.

Scheme 3: according to the steps (3) to (4) of the preparation method of the scheme 1, the powder with silicon dioxide-titanium dioxide-chromium sesquioxide respectively from the inside to the outside is prepared. The preparation was carried out 5 times in parallel according to the method.

Scheme 4: the coating method of the step (3) in the scheme 1 is changed into the conventional ball milling method in the field to coat titanium dioxide, and the titanium dioxide is obtained in the step (2). The preparation was carried out 5 times in parallel according to the method.

The Mohs hardness of the finished products of schemes 1-4 was measured, and the results are shown in Table 6. As shown in the data in Table 6, the hardness of the products prepared by the schemes 1-3, namely, after the titanium dioxide is wrapped on the silicon dioxide by the method of the invention is obviously improved (P is less than 0.01) compared with the hardness of the titanium dioxide raw material. Moreover, after coating the titanium dioxide on the silica by the conventional method (scheme 4), the mechanical strength of the product is significantly lower than that of the product coated by the method of the present invention (schemes 1-3) (P < 0.01).

TABLE 6 Mohs hardness of finished products of schemes 1-4

	Scheme 1	Scheme 2	Scheme 3	Scheme 4	Industrial titanium dioxide	Titanium dioxide produced by the steps (1) to (2)
							Mohs hardness	7.4	7.3	7.3	6.1	5.9	6.0

Comparative example 1

CN102641220A discloses a titanium dioxide having a strong ultraviolet absorption ability. The method for preparing the titanium dioxide product comprises the following specific operation steps: 1) amphiphilic triblock polymer PEO-b-PDMA-b-synthesis of PS: using 0.500g of brominated polyoxyethylene (PEO-Br) as a macroinitiator, 0.036g of cuprous bromide (CuBr) as a catalyst, 0.044g of the ligand PMDETA, 1.580g of monomeric Dimethylaminoethyl Methacrylate (DMA) and 4mL of solvent were added to 50mL of a round-bottomed flaskIn a bottle, Atom Transfer Radical Polymerization (ATRP) was carried out at a temperature of 30 deg.C^oC, after 6 hours of reaction, 3.800g of styrene was diluted and added to the reaction flask to continue the reaction for 24 hours. The obtained polymer is subject to rotary evaporation, silica gel column chromatography, concentration, precipitation and pumping, and finally is put into a vacuum oven for 24 hours to obtain the block polymer PEO₄₃-b-PDMA₄₀-b-PS₁₄₀. 2) Self-assembly of polymers to form micelles: the polymer was dissolved in Tetrahydrofuran (THF) to prepare a 20mg/mL solution, methanol was added dropwise to the THF solution at a rate of 10d/min with stirring, and the solution was stirred for 24 hours to obtain a milky white solution. 3) Depositing a titanium source on the surface of the polymer micelle: tetrabutyl titanate (TBT) was dissolved in ethanol at a concentration of 10mg/mL using tetrabutyl titanate as a titanium source, and TBT and DMA were dropped into the micellar solution at a molar ratio of 0.2:1, and vigorously stirred for 24 hours to give a milky white solution. 4) And drying the obtained organic-inorganic hybrid nano-particle solution to obtain the required product.

Comparative example 2

CN1454939A discloses a titanium dioxide product with strong ultraviolet shielding ability. The method for preparing the titanium dioxide product comprises the following specific operation steps: 250gTi (OC)₄H₉)₄Dissolving in 2500ml ethanol to obtain Ti (OC)₄H₉)₄Solution A; 1320ml of ethanol is dissolved in 1320ml of water to obtain solution B; preparing sodium aluminate alkali solution C (mass percentage concentration: Al)₂O₃0.28% and 0.45% NaOH), solution a was pumped into vigorously stirred solution B over 50 minutes at room temperature, stirred for a further 15 minutes, filtered off with suction and dried at 110 ℃ for 15 hours. And grinding the xerogel, sieving by a 80-mesh micro-sieve, and roasting at 500 ℃ for 1 hour to obtain the anatase type nano titanium dioxide. Dispersing 10g of the nano titanium dioxide in 300ml of water according to the proportion of P₂O₅∶TiO₂Sodium hexametaphosphate as a dispersant was added at 0.1%, and the pH was adjusted to 10 with 1M NaOH, and the mixture was ultrasonically dispersed for 50 minutes. Mixing nanometer TiO₂The slurry was heated to 85 ℃ with stirring, the pH was then adjusted to 8.5, and solution C, Al, was added over 40 minutes₂O₃By weight, Al₂O₃∶TiO₂Aging for 3 hours at 10%. The pH of the slurry was adjusted to 7.0 with a sulfuric acid solution and then stirred for 30 minutes. Filtering, washing with deionized water for the second time until no SO is detected₄ ^2-And drying at 120 ℃ for 15 hours to obtain the monodisperse surface coating aluminum oxide nano titanium dioxide particles.

Comparative example 3

CN105565736A discloses an anti-ultraviolet mortar, which is prepared into a titanium dioxide product according to the method, and the concrete operation steps are as follows: (1) preparing modified diatomite: respectively taking diatomite, chitin, water, a coupling agent and nano titanium dioxide according to the mass ratio of 10: 1: 20: 0.5: 1; then, adding the diatomite, the chitin, the water and the coupling agent into a stirrer, and uniformly mixing at a stirring speed of 3000 r/min; then, reducing the rotating speed of the stirrer to 500r/min, slowly adding the nano titanium dioxide, and stirring for 30min at the stirring speed of 500r/min to prepare slurry; and drying the prepared slurry in a drying oven at 100 ℃, and grinding into powder to obtain the high-performance high-temperature-resistant high-temperature. (2) Adding 45kg of quartz sand powder, 30kg of P.O42.5 ordinary portland cement, 10kg of desulfurized gypsum, 5kg of fly ash, 1kg of anti-crack fiber, 2kg of cellulose ether, 5kg of modified diatomite and 2kg of lithium bentonite into a dry powder stirrer with the volume weight of 100kg in sequence, and stirring for 15min until the components are uniformly mixed to obtain the powder A. (3) 13kg of methyl acrylate emulsion, 0.1kg of alcohol ester dodeca film-forming additive, 0.1kg of defoaming agent and 0.5kg of dispersing agent are sequentially added into a stirrer with the volume weight of 50kg and the rotating speed of 30r/min, and the mixture is stirred for 15min until the components are uniformly mixed to obtain the emulsion material B. (4) The powder A component and the emulsion material B component are mixed and stirred uniformly in the mass ratio of 1: 1-2 on site during construction.

Example 1

Titanium dioxide was prepared as follows: (1) putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the titanium dioxide raw material to the deionized water is 2: 8; stirring and pulping by a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering titanium dioxideExtracting; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 1.0, continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor till no solid suspended matter is generated, continuously stirring for 15min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content. (2) Firstly, respectively grinding the titanium dioxide obtained in the step (1) and a pore-forming agent ammonium bicarbonate until the granularity is below 50 mu m, then weighing the ground titanium dioxide and ammonium bicarbonate powder which is 3 percent of the mass of the titanium dioxide, uniformly mixing, and performing compression molding under the pressure of 100 MPa; b. b, heating the material pressed and formed in the step a to 600 ℃ at the heating rate of 5 ℃/min, and sintering for 3h to obtain a porous titanium precursor after the pore-forming agent is removed; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of calcium to titanium dioxide of 2:1, then carrying out calcium thermal reduction for 24 hours under the conditions of vacuumizing until the pressure in the furnace is 1Pa, the heating rate is 5 ℃/min and the reduction temperature is 1000 ℃, taking out the reduction product after cooling, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm. (3): a. taking 50g of SiO₂Suspended in 5000g of ethanol under ultrasonic conditions; b. to the above solution were added 50g of 90% Hexadecylamine (HDA) and 100g of aqueous ammonia, and stirred at room temperature for 0.5 minute; c. adding 100g of tetraisopropyl Titanate (TIP) into the step b under stirring, and reacting for 5 minutes; d. centrifuging to obtain precipitate, and washing the precipitate with water and ethanol; e. burning the precipitate at 450 deg.C for 1 hr, washing with 10% hydrofluoric acid to obtain SiO as core₂Of TiO 2₂And (3) granules. (4) a, mixing the TiO obtained in the step (3)₂Dispersing the granules in ethanol, and performing 30KHz ultrasonic treatment for 10min per g TiO₂Cr is added into the particles according to the proportion of 0.02mmol₃O（O₂CCH₃）·7H₂O, forming a suspension; b. taking a sufficient amount of water, adjusting the pH to 4 with HCl, and heating the suspension obtained in a toAdding the two into a stirrer at the same time at 80 ℃ for hydrolysis reaction; c.10min later, collecting precipitate, and burning at 450 deg.C for 1 hr to obtain coated Cr₂O₃Of TiO 2₂And (3) granules. (5) Taking 100g of the titanium dioxide obtained in the step (4), taking 2000g of the titanium dioxide obtained in the step (2), dispersing the titanium dioxide in 1L of Decamethylcyclopentasiloxane (DMCPSI), adding 100g of octyl p-methoxycinnamate (OPMC), and uniformly mixing to obtain a suspension A; b. a certain amount of suspension A is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. The gap between the coater and the glass plate was 15 μm, and the moving speed of the coater on the glass plate was 0.01 m/s; c. when a uniform spreading of suspension a on the glass plate was observed, the heating plate was opened and the temperature was adjusted to 30 ℃. Then the linear motor driver is controlled to move in the opposite direction until the starting point, and the linear motor driver reciprocates for 30 min. Stopping the linear motor driver, adjusting the temperature of the heating plate to 60 ℃, and drying for 30 min.

Example 2

Titanium dioxide was prepared as follows: (1) putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the titanium dioxide raw material to the deionized water is 4: 6; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 2.0, continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor till no solid suspended matter is generated, continuously stirring for 25min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content. (2) a, firstly, respectively grinding the titanium dioxide obtained in the step (1) and a pore-forming agent ammonium bicarbonate until the granularity is below 50 mu m, then weighing the ground titanium dioxide and ammonium bicarbonate powder which is 3 percent of the mass of the titanium dioxide, uniformly mixing the titanium dioxide and the ammonium bicarbonate powder at 250MPa, pressing and forming under pressure; b. b, heating the material pressed and formed in the step a to 1100 ℃ at a heating rate of 10 ℃/min, and sintering for 6h to obtain a porous titanium precursor after removing the pore-forming agent; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of the calcium to the titanium dioxide of 10:1, then carrying out calcium thermal reduction for 60 hours under the conditions of vacuumizing until the pressure in the furnace is 5Pa, the heating rate is 10 ℃/min and the reduction temperature is 1100 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm. (3): a. take 100g of SiO₂Suspended in 15000g of ethanol under ultrasonic conditions; b. 100g of 90% Hexadecylamine (HDA) and 400g of ammonia water were added to the above solution, and stirred at room temperature for 5 minutes; c. adding 1000g of tetraisopropyl Titanate (TIP) into the step b under stirring, and reacting for 20 minutes; d. centrifuging to obtain precipitate, and washing the precipitate with water and ethanol; e. burning the precipitate at 450 deg.C for 4 hr, washing with 10% hydrofluoric acid to obtain SiO as core₂Of TiO 2₂And (3) granules. (4) a, mixing the TiO obtained in the step (3)₂Dispersing the granules in ethanol, and performing 80KHz ultrasonic treatment for 15min per g TiO₂Adding Cr into the particles according to the proportion of 1mmol₃O（O₂CCH₃）·7H₂O, forming a suspension; b. taking enough water, adjusting the pH value to 6 by using HCl, respectively heating the water and the suspension obtained in the step a to 95 ℃, and simultaneously adding the water and the suspension into a stirrer for hydrolysis reaction; c.30min later, collecting precipitate, burning at 750 deg.c for 1 hr to obtain coated Cr₂O₃Of TiO 2₂And (3) granules. (5) Taking 1000g of the titanium dioxide obtained in the step (4), taking 500g of the titanium dioxide obtained in the step (2), dispersing the titanium dioxide in 10L of Decamethylcyclopentasiloxane (DMCPSI), adding 500g of octyl p-methoxycinnamate (OPMC), and uniformly mixing to obtain a suspension A; b. a certain amount of suspension A is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. Coating ofThe gap between the applicator and the glass plate was 50 μm, and the moving speed of the applicator on the glass plate was 1 m/s; c. when a uniform spreading of suspension a on the glass plate was observed, the heating plate was opened and the temperature was adjusted to 40 ℃. The linear motor drive is then controlled to move in the opposite direction until the starting point, thus reciprocating for 2 h. Stopping the linear motor driver, adjusting the temperature of the heating plate to 70 ℃, and drying for 30 min.

Example 3

Titanium dioxide was prepared as follows: (1) putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the titanium dioxide raw material to the deionized water is 3:7 by weight; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 1.5, continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor till no solid suspended matter is generated, continuously stirring for 20min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content. (2) Firstly, respectively grinding the titanium dioxide obtained in the step (1) and a pore-forming agent ammonium bicarbonate until the granularity is below 50 mu m, then weighing the ground titanium dioxide and ammonium bicarbonate powder which is 3 percent of the mass of the titanium dioxide, uniformly mixing, and performing compression molding under the pressure of 200 MPa; b. b, heating the material pressed and formed in the step a to 800 ℃ at the heating rate of 6 ℃/min, and sintering for 4h to obtain a porous titanium precursor after removing the pore-forming agent; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of calcium to titanium dioxide of 5:1, then carrying out calcium thermal reduction for 48h under the conditions of vacuumizing until the pressure in the furnace is 5Pa, the heating rate is 6 ℃/min and the reduction temperature is 1050 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm. (3): a. 80g of SiO are taken₂Suspending in 10000g of ethanol under ultrasonic conditions; b. 80g of 90% Hexadecylamine (HDA) and 200g of ammonia water were added to the above solution, and stirred at room temperature for 2 minutes; c. adding 500g of tetraisopropyl Titanate (TIP) into the step b under stirring, and reacting for 10 minutes; d. centrifuging to obtain precipitate, and washing the precipitate with water and ethanol; e. burning the precipitate at 450 deg.C for 2 hr, washing with 10% hydrofluoric acid to obtain SiO as core₂Of TiO 2₂And (3) granules. (4) a, mixing the TiO obtained in the step (3)₂Dispersing the granules in ethanol, and performing 50KHz ultrasonic treatment for 10min per g TiO₂Cr is added into the particles according to the proportion of 0.1mmol₃O（O₂CCH₃）·7H₂O, forming a suspension; b. taking enough water, adjusting the pH value to 5 by using HCl, respectively heating the water and the suspension obtained in the step a to 90 ℃, and simultaneously adding the water and the suspension into a stirrer for hydrolysis reaction; c.20min later, collecting precipitate, and burning at 600 deg.C for 1 hr to obtain coated Cr₂O₃Of TiO 2₂And (3) granules. (5) Taking 500g of the titanium dioxide obtained in the step (4), taking 1000g of the titanium dioxide obtained in the step (2), dispersing the titanium dioxide in 5L of Decamethylcyclopentasiloxane (DMCPSI), adding 200g of octyl p-methoxycinnamate (OPMC), and uniformly mixing to obtain a suspension A; b. a certain amount of suspension A is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. The gap between the coater and the glass plate was 30 μm, and the moving speed of the coater on the glass plate was 0.1 m/s; c. when a uniform spreading of suspension a on the glass plate was observed, the heating plate was opened and the temperature was adjusted to 35 ℃. Then the linear motor driver is controlled to move in the opposite direction until the starting point, and thus the linear motor driver reciprocates for 1 h. Stopping the linear motor driver, adjusting the temperature of the heating plate to 65 ℃, and drying for 20 min.

Example 4

Titanium dioxide was prepared as follows: (1) putting industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the titanium dioxide raw material and the deionized water are mixed according to the weight ratio3: 7; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 1.5, continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor till no solid suspended matter is generated, continuously stirring for 20min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content. (2) Firstly, respectively grinding the titanium dioxide obtained in the step (1) and a pore-forming agent ammonium bicarbonate until the granularity is below 50 mu m, then weighing the ground titanium dioxide and ammonium bicarbonate powder which is 3 percent of the mass of the titanium dioxide, uniformly mixing, and performing compression molding under the pressure of 200 MPa; b. b, heating the material pressed and formed in the step a to 800 ℃ at the heating rate of 6 ℃/min, and sintering for 4h to obtain a porous titanium precursor after removing the pore-forming agent; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of calcium to titanium dioxide of 5:1, then carrying out calcium thermal reduction for 48h under the conditions of vacuumizing until the pressure in the furnace is 5Pa, the heating rate is 6 ℃/min and the reduction temperature is 1050 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm. (3): a. 80g of SiO are taken₂Suspending in 10000g of ethanol under ultrasonic conditions; b. 80g of 90% Hexadecylamine (HDA) and 200g of ammonia water were added to the above solution, and stirred at room temperature for 2 minutes; c. adding 500g of tetraisopropyl Titanate (TIP) into the step b under stirring, and reacting for 10 minutes; d. centrifuging to obtain precipitate, and washing the precipitate with water and ethanol; e. burning the precipitate at 450 deg.C for 2 hr, washing with 10% hydrofluoric acid to obtain SiO as core₂Of TiO 2₂And (3) granules. (4) a, mixing the TiO obtained in the step (3)₂Dispersing the granules in ethanol, and performing 50KHz ultrasonic treatment for 10min per g TiO₂Cr (O-i-H) is added into the particles according to the proportion of 0.1mmol₃C₇)₃Forming a suspension; b. taking enough water, adjusting the pH value to 5 by using HCl, respectively heating the water and the suspension obtained in the step a to 90 ℃, and simultaneously adding the water and the suspension into a stirrer for hydrolysis reaction; c.20min later, collecting precipitate, and burning at 600 deg.C for 1 hr to obtain coated Cr₂O₃Of TiO 2₂And (3) granules. (5) Taking 500g of the titanium dioxide obtained in the step (4), taking 1000g of the titanium dioxide obtained in the step (2), dispersing the titanium dioxide in 5L of Decamethylcyclopentasiloxane (DMCPSI), adding 200g of octyl p-methoxycinnamate (OPMC), and uniformly mixing to obtain a suspension A; b. a certain amount of suspension A is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. The gap between the coater and the glass plate was 30 μm, and the moving speed of the coater on the glass plate was 0.1 m/s; c. when a uniform spreading of suspension a on the glass plate was observed, the heating plate was opened and the temperature was adjusted to 35 ℃. Then the linear motor driver is controlled to move in the opposite direction until the starting point, and thus the linear motor driver reciprocates for 1 h. Stopping the linear motor driver, adjusting the temperature of the heating plate to 65 ℃, and drying for 20 min.

Example 5

Titanium dioxide was prepared as follows: (1) putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the titanium dioxide raw material to the deionized water is 3:7 by weight; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 1.5, continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor till no solid suspended matter is generated, continuously stirring for 20min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content. (2) Firstly, respectively grinding the titanium dioxide obtained in the step (1) and a pore-forming agent ammonium bicarbonate until the particle size is 50 muBelow m, weighing the ground titanium dioxide and ammonium bicarbonate powder which is 3 percent of the titanium dioxide in mass, uniformly mixing, and performing compression molding under the pressure of 200 MPa; b. b, heating the material pressed and formed in the step a to 800 ℃ at the heating rate of 6 ℃/min, and sintering for 4h to obtain a porous titanium precursor after removing the pore-forming agent; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of calcium to titanium dioxide of 5:1, then carrying out calcium thermal reduction for 48h under the conditions of vacuumizing until the pressure in the furnace is 5Pa, the heating rate is 6 ℃/min and the reduction temperature is 1050 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm. (3): a. 80g of SiO are taken₂Suspending in 10000g of ethanol under ultrasonic conditions; b. 80g of 90% Hexadecylamine (HDA) and 200g of ammonia water were added to the above solution, and stirred at room temperature for 2 minutes; c. adding 500g of tetraisopropyl Titanate (TIP) into the step b under stirring, and reacting for 10 minutes; d. centrifuging to obtain precipitate, and washing the precipitate with water and ethanol; e. burning the precipitate at 450 deg.C for 2 hr, washing with 10% hydrofluoric acid to obtain SiO as core₂Of TiO 2₂And (3) granules. (4) a, mixing the TiO obtained in the step (3)₂Dispersing the granules in ethanol, and performing 50KHz ultrasonic treatment for 10min per g TiO₂Cr is added into the particles according to the proportion of 0.1mmol₃O（O₂CCH₃）·7H₂O, forming a suspension; b. taking enough water, adjusting the pH value to 5 by using HCl, respectively heating the water and the suspension obtained in the step a to 90 ℃, and simultaneously adding the water and the suspension into a stirrer for hydrolysis reaction; c.20min later, collecting precipitate, and burning at 600 deg.C for 1 hr to obtain coated Cr₂O₃Of TiO 2₂And (3) granules. (5) Taking 500g of the titanium dioxide obtained in the step (4), taking 1000g of the titanium dioxide obtained in the step (2), dispersing the titanium dioxide in 5L of Decamethylcyclopentasiloxane (DMCPSI), adding 200g of octyl p-methoxycinnamate (OPMC), and uniformly mixing to obtain a suspension A; b. pressing and coating the suspension A at the pressure of 500 Pa; c. to pressingThe latter suspension A was heated at 80 ℃ for 2 hours to volatilize DMCPSI.

Example 6

In the step (5), TiO is contained₂Outer layer of (2) consisting of Cr₂O₃And TiO₂And (4) forming.

The preparation method specifically comprises the following steps: (1) putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the titanium dioxide raw material to the deionized water is 4: 6; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 2.0, continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor till no solid suspended matter is generated, continuously stirring for 25min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content. (2) Firstly, respectively grinding the titanium dioxide obtained in the step (1) and a pore-forming agent ammonium bicarbonate until the granularity is below 50 mu m, then weighing the ground titanium dioxide and ammonium bicarbonate powder which is 3 percent of the mass of the titanium dioxide, uniformly mixing, and performing compression molding under the pressure of 250 MPa; b. b, heating the material pressed and formed in the step a to 1100 ℃ at a heating rate of 10 ℃/min, and sintering for 6h to obtain a porous titanium precursor after removing the pore-forming agent; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of the calcium to the titanium dioxide of 10:1, then carrying out calcium thermal reduction for 60 hours under the conditions of vacuumizing until the pressure in the furnace is 5Pa, the heating rate is 10 ℃/min and the reduction temperature is 1100 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm. (3): a. take 100g of SiO₂Suspended in 15000g of ethanol under ultrasonic conditions; b. to the above solution were added 100g of 90% Hexadecylamine (HDA), and 400g of aqueous ammonia inStirring for 5 minutes at room temperature; c. adding 1000g of tetraisopropyl Titanate (TIP) into the step b under stirring, and reacting for 20 minutes; d. centrifuging to obtain precipitate, and washing the precipitate with water and ethanol; e. burning the precipitate at 450 deg.C for 4 hr, washing with 10% hydrofluoric acid to obtain SiO as core₂Of TiO 2₂And (3) granules. (4) a, mixing the TiO obtained in the step (3)₂Dispersing the granules in ethanol, and performing 80KHz ultrasonic treatment for 15min per g TiO₂Adding Cr into the particles according to the proportion of 1mmol₃O（O₂CCH₃）·7H₂O, forming a suspension; b. taking enough water, adjusting the pH value to 6 by using HCl, respectively heating the water and the suspension obtained in the step a to 95 ℃, and simultaneously adding the water and the suspension into a stirrer for hydrolysis reaction; c.30min later, collecting precipitate, burning at 750 deg.c for 1 hr to obtain coated Cr₂O₃Of TiO 2₂And (3) granules. (5) Taking 600g of titanium dioxide obtained in the step (4); taking 300g of titanium dioxide obtained in the step (2) and 200g of Cr₂O₃Dispersing in 10L Decamethylcyclopentasiloxane (DMCPSI), adding 500g octyl p-methoxycinnamate (OPMC), and mixing to obtain suspension A; b. a certain amount of suspension A is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. The gap between the coater and the glass plate was 50 μm, and the moving speed of the coater on the glass plate was 1 m/s; c. when a uniform spreading of suspension a on the glass plate was observed, the heating plate was opened and the temperature was adjusted to 40 ℃. The linear motor drive is then controlled to move in the opposite direction until the starting point, thus reciprocating for 2 h. Stopping the linear motor driver, adjusting the temperature of the heating plate to 70 ℃, and drying for 30 min.

Example 7

The preparation method specifically comprises the following steps: (1) putting industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the titanium dioxide raw materialThe mixing ratio of the deionized water to the deionized water is 4: 6; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 2.0, continuously dropwise adding a sodium dimethyldithiocarbamate solution into the reactor till no solid suspended matter is generated, continuously stirring for 25min, and filtering to extract the titanium dioxide; and washing the titanium dioxide after being filtered and extracted by using water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content. (2) Firstly, respectively grinding the titanium dioxide obtained in the step (1) and a pore-forming agent ammonium bicarbonate until the granularity is below 50 mu m, then weighing the ground titanium dioxide and ammonium bicarbonate powder which is 3 percent of the mass of the titanium dioxide, uniformly mixing, and performing compression molding under the pressure of 250 MPa; b. b, heating the material pressed and formed in the step a to 1100 ℃ at a heating rate of 10 ℃/min, and sintering for 6h to obtain a porous titanium precursor after removing the pore-forming agent; c. and c, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of the calcium to the titanium dioxide of 10:1, then carrying out calcium thermal reduction for 60 hours under the conditions of vacuumizing until the pressure in the furnace is 5Pa, the heating rate is 10 ℃/min and the reduction temperature is 1100 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, and carrying out vacuum drying to obtain the porous titanium dioxide. And grinding the obtained porous titanium dioxide to a particle size of less than 5 μm. (3): a. take 100g of SiO₂Suspended in 15000g of ethanol under ultrasonic conditions; b. 100g of 90% Hexadecylamine (HDA) and 400g of ammonia water were added to the above solution, and stirred at room temperature for 5 minutes; c. adding 1000g of tetraisopropyl Titanate (TIP) into the step b under stirring, and reacting for 20 minutes; d. centrifuging to obtain precipitate, and washing the precipitate with water and ethanol; e. burning the precipitate at 450 deg.C for 4 hr, washing with 10% hydrofluoric acid to obtain SiO as core₂Of TiO 2₂And (3) granules. (4) a, mixing the TiO obtained in the step (3)₂Dispersing the granules in ethanol, and performing 80KHz ultrasonic treatment for 15min per g TiO₂Adding Cr into the particles according to the proportion of 1mmol₃O（O₂CCH₃）·7H₂O, forming a suspension; b. taking enough water, adjusting the pH value to 6 by using HCl, respectively heating the water and the suspension obtained in the step a to 95 ℃, and simultaneously adding the water and the suspension into a stirrer for hydrolysis reaction; c.30min later, collecting precipitate, burning at 750 deg.c for 1 hr to obtain coated Cr₂O₃Of TiO 2₂And (3) granules. (5) Taking 600g of titanium dioxide obtained in the step (4); taking 450g of titanium dioxide obtained in the step (2) and 50g of Cr₂O₃Dispersing in 10L Decamethylcyclopentasiloxane (DMCPSI), adding 500g octyl p-methoxycinnamate (OPMC), and mixing to obtain suspension A; b. a certain amount of suspension A is taken and placed on a glass plate of the coating equipment, a linear motor driver is started, and the coater is pushed to move on the glass plate at a constant speed through conduction of a connecting arm. The gap between the coater and the glass plate was 50 μm, and the moving speed of the coater on the glass plate was 1 m/s; c. when a uniform spreading of suspension a on the glass plate was observed, the heating plate was opened and the temperature was adjusted to 40 ℃. The linear motor drive is then controlled to move in the opposite direction until the starting point, thus reciprocating for 2 h. Stopping the linear motor driver, adjusting the temperature of the heating plate to 70 ℃, and drying for 30 min.

Example 8

The titanium dioxide prepared in comparative examples 1 to 2 and examples 1 to 7 was subjected to the absorbance test as described in Experimental example 1. As can be seen from the results in Table 7, the titanium dioxide prepared by the method of the present invention has a strong ability to absorb light in both the ultraviolet region and the visible region, especially in the visible region (400-550 nm), the titanium dioxide of examples 1-7 has higher absorbance than that of comparative examples 1 and 2, and the results have statistical significance (P < 0.01). Wherein, in the 500nm and 550nm position of the embodiment 5, the absorbance is less (P is less than 0.05) than that in the embodiments 1 to 4, which shows that the device provided by the invention has better effect in the coating process of the step (5).

TABLE 7 absorbance of titanium dioxide at different wavelengths

Wavelength (nm)	Comparative example 1	Comparative example 2	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7
										300	1.3	1.0	1.6	1.6	1.7	1.6	1.6	1.5	1.6
350	1.0	0.8	1.4	1.4	1.4	1.3	1.2	1.2	1.2
										400	0.3	0.2	1.3	1.2	1.3	1.1	1.0	0.9	0.8
450	0.1	0.1	1.1	1.1	1.1	0.9	0.8	0.8	0.7
										500	0.02	0.04	0.8	0.7	0.9	0.7	0.5	0.5	0.5
550	0.01	0.02	0.6	0.5	0.7	0.5	0.3	0.3	0.3

Placing titanium dioxide and NO gas in a quartz reactor, and irradiating with light with the wavelength of 300nm or light with the wavelength of 500nm for 8 hours, wherein the following reactions are carried out in the reactor: 3NO + hv → (1/2) N₂+N₂O+O₂. Determination of the decomposition product N by gas chromatography₂Amount of O, N₂The larger the amount of O produced, the stronger the photocatalytic activity of titanium dioxide, and the results are shown in Table 8. As shown by the results in Table 8, comparative examples 1-2, examples 1-7, N at 300nm₂The O generation amount is very close, and the data has no significant difference (P is more than 0.05), which indicates that the photocatalytic activity of the titanium dioxide at 300nm is not greatly different; however, at a wavelength of 500nm, the titanium dioxide of examples 1-7 has a significantly higher catalytic activity than comparative examples 1 and 2 (P < 0.01), demonstrating that the titanium dioxide provided in the present invention has a stronger catalytic activity under visible light.

TABLE 8N₂Amount of O produced

Wavelength of light	Comparative example 1 （mmol/ gTiO₂）	Comparative example 2 （mmol/ gTiO₂）	Example 1 （mmol/ gTiO₂）	Example 2 （mmol/ gTiO₂）	Example 3 （mmol/ gTiO₂）	Example 4 （mmol/ gTiO₂）	Example 5 （mmol/ gTiO₂）	Example 6 （mmol/ gTiO₂）	Example 7 （mmol/gTiO₂）
										300nm	1.9	1.8	1.7	1.9	2.0	1.9	2.0	1.7	2.0
500nm	0.4	0.1	1.8	1.7	1.8	2.0	1.5	0.9	1.3

Example 9

The titanium dioxide prepared in comparative examples 1 to 2 and examples 1 to 7 was used to prepare mortars according to the methods of comparative examples 1 to 3. Mixing the powder A component and the emulsion B component according to a mass ratio of 1: 2, uniformly stirring, coating on a 10cm × 10cm flat plate, controlling the thickness to be 1.8-2.2cm, coating 30 sample plates on each sample, and dividing into an ultraviolet experiment group and a visible light experiment group, wherein each group comprises 15 flat plates. Each sample panel was coated with 1g of soot uniformly.

Different mortars were tested for their resistance to soot contamination under ultraviolet (300 nm), and visible (500 nm) light. The detection method is as follows: respectively irradiating the sample with ultraviolet rays and visible light for 30 days, detecting the color of the sample by using a portable spectrocolorimeter, and calculating the sample color change condition of the sample, wherein the calculation formula is as follows: delta E^* _ab=［（ΔL^*）²+（Δa^*）²+（Δb^*）²］^1/2Wherein L is whiteness (0 is black, 100 is white), Δ L^*=L^* _f-L^* ₀；a^*Is the red and green region (+ a)^*Is red, -a^*Green), Δ a^*=a^* _f-a^* ₀；b^*Is a yellow-blue region (+ b)^*Is yellow, -b^*Blue), Δ b)^*=b^* _f-b^* ₀。ΔE^* _abThe larger the value, the more the sample is in the experimentThe darker the product becomes, i.e. the less resistant to contamination. The results of the experiment are shown in tables 9 and 10.

According to the results of tables 9 and 10, the mortars prepared in examples 1 to 5 can prevent the soot from being continuously contaminated (P < 0.01) and prevent the coating from being further blackened in the visible light region better than those prepared in comparative examples 1 to 3, which is also consistent with the result that the titanium dioxide of examples 1 to 5 has a strong absorbance in the visible light region in example 8. However, in the ultraviolet region, comparative examples 1 and 2 have similar absorbance and photocatalytic activity to those of examples 1 to 5 (see example 8), and surprisingly, as shown in table 9, the ability of examples 1 to 5 to prevent the continuous contamination of the coating by soot is significantly stronger than that of comparative examples 1 and 2 (P < 0.01) and comparative example 3 (P < 0.01) at 300nm, which proves that the titanium dioxide prepared by the present invention has unexpectedly better technical effect in preventing the mortar coating from being contaminated, especially from being contaminated by soot.

TABLE 9 color change of samples after UV treatment

	Comparative example 1	Comparative example 2	Comparative example 3	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7
											ΔE^* _ab	41.5	55.2	35.3	28.1	29.0	25.2	26.6	30.1	32.2	31.3

TABLE 10 color change of samples after visible light treatment

	Comparative example 1	Comparative example 2	Comparative example 3	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7
											ΔE^* _ab	33.2	30.8	28.9	20.1	20.5	17.6	18.9	22.1	18.4	20.8

It should be noted that, for those skilled in the art, it is possible to make several improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. The preparation method of the modified titanium dioxide comprises four layers, and is characterized in that the modified titanium dioxide comprises a silicon dioxide inner core, a titanium dioxide second layer, a chromium oxide third layer and a titanium dioxide outermost layer;

the preparation method of the modified titanium dioxide comprises the following steps: (1) pretreating an industrial titanium dioxide raw material; (2) for the TiO obtained in the step (1)₂Carrying out pore-forming treatment; (3) coating a layer of TiO on the outer layer of the silicon dioxide inner core₂(ii) a (4) TiO obtained in the step (3)₂An outer layer is coated with a layer of Cr₂O₃(ii) a (5) TiO obtained in the step (2)₂Coating the titanium dioxide obtained in the step (4) with an outer layer;

in the step (1), the pretreatment step is as follows: putting an industrial titanium dioxide raw material and deionized water into a beating tank of an impurity removal device, wherein the mixing ratio of the industrial titanium dioxide raw material to the deionized water is 2-4:6-8 according to weight; stirring and pulping by using a stirring device to form slurry, injecting the slurry into a first ultrasonic vibration sieve for ultrasonic vibration filtration, and filtering and extracting titanium dioxide; adding ammonia water into the extracted titanium dioxide, adjusting the pH value of the solution to 1.0-2.0, continuously dropwise adding dithiocarbamate derivative solution into the reactor until no solid suspended matter is generated, continuously stirring for 15-25min, and filtering to extract the titanium dioxide; washing the titanium dioxide after being filtered and extracted by water, filtering the titanium dioxide by ultrasonic vibration after washing, and drying the titanium dioxide in a drying device to obtain the titanium dioxide with low impurity content;

the step (2) is as follows: a. firstly, respectively grinding the titanium dioxide and the pore-forming agent obtained in the step (1) until the granularity is below 50 mu m, then uniformly mixing the ground titanium dioxide and the pore-forming agent powder, and performing compression molding under the pressure of 100-250 MPa; b. heating the material pressed and formed in the step a to 600-1100 ℃ at the heating rate of 5-10 ℃/min, and sintering for 3-6 h to prepare the porous titanium precursor without the pore-forming agent; c. b, adding metal calcium into the porous titanium precursor obtained in the step b according to the mass ratio of calcium to titanium dioxide of more than or equal to 2:1, then performing calcium thermal reduction for 24-60 h under the conditions that the pressure in the furnace is less than or equal to 5Pa, the heating rate is 5-10 ℃/min and the reduction temperature is 1000-1100 ℃, cooling, taking out the reduction product, leaching the reduction product by using dilute hydrochloric acid, washing by using distilled water and absolute ethyl alcohol after leaching, performing vacuum drying to obtain porous titanium dioxide, and grinding the obtained porous titanium dioxide until the particle size is less than 5 mu m;

in the coating process, a coating device is used, and the coating device consists of a linear motor driver (1), a glass plate (2), a coater (3) and a heating plate (4); the connecting arm (11) is fixedly connected with the coating device (3) and can move in the moving groove (13) under the driving of the motor, so that the coating device (3) is pushed to move on the glass plate (2); a glass plate support (12) is arranged on the linear motor driver (1) and used for supporting the glass plate (2), and a heating plate (4) is fixedly arranged below the glass plate (2); the height of the gap (31) between the applicator (3) and the glass plate (2) is 5-30 μm.

2. The process for producing a modified titanium dioxide according to claim 1, wherein: in the modified titanium dioxide, SiO₂10-30% of Cr₂O₃5-20% of TiO₂The content is 50-85%.

3. The method for producing a modified titanium dioxide according to claim 1 or 2, characterized in that: the modified titanium dioxide is applied to mortar, and the mortar is one or more of lime mortar, cement mortar and mixed mortar.

4. The production method according to claim 1, characterized in that: the pore-forming agent is ammonium bicarbonate, high-purity graphite or starch, and the addition amount of the pore-forming agent is 3-15% of the mass of titanium dioxide.

5. The production method according to claim 1, characterized in that: in the step c, the mass ratio of the calcium to the titanium dioxide is 5: 1.

6. The production method according to claim 1, characterized in that: the preparation step (4) is as follows: a. subjecting the TiO obtained in step (3)₂Dispersing the granules in ethanol, and performing ultrasonic treatment for 10-15ming TiO₂Adding organic chromium compound into the particles according to the proportion of 0.02-1mmol to form suspension; b. b, taking enough water, adjusting the pH value to 4-6, respectively heating the water and the suspension obtained in the step a to 80-95 ℃, and simultaneously adding the water and the suspension into a stirrer for hydrolysis reaction; c, after the reaction is finished after 10-30min, collecting the precipitate, and burning for 1 hour at the temperature of 450-₂O₃Of TiO 2₂And (3) granules.

7. The production method according to claim 1, characterized in that: the preparation step (5) is as follows: a. taking 1-10 parts by weight of the titanium dioxide obtained in the step (4), taking 5-20 parts by weight of the titanium dioxide obtained in the step (2), dispersing the titanium dioxide in sufficient decamethylcyclopentasiloxane, adding 1-5 parts by weight of octyl p-methoxycinnamate, and uniformly mixing to obtain a suspension A; b. pressing and coating the suspension A; c. heating the pressed suspension A at 60-120 deg.C for 1-3 hr to volatilize decamethylcyclopentasiloxane.