Preparation method and application of high-dispersity food-grade titanium dioxide

Abstract

The invention provides a preparation method and application of high-dispersity food-grade titanium dioxide, and relates to the technical field of food additives. The preparation method comprises the following steps: S1, mixing a titanium dioxide crude product with concentrated sulfuric acid and deionized water, carrying out acid pickling, stirring for 20-40 minutes, adding deionized water, carrying out water washing, and carrying out filter pressing until filtrate is neutral, so as to obtain a filter cake; s2, filtering the filter cake through a sieve shaker, sanding, adding deionized water to dilute and wash until the conductivity of the slurry is stabilized below 400 [mu] S / cm, and grading to obtain slurry containing fine particles; s3, carrying out filter pressing on the slurry containing the fine particles, adding deionized water into an obtained filter cake, re-dispersing, and then carrying out spray drying and crushing to obtain food-grade titanium dioxide; the food-grade titanium dioxide obtained by the preparation method provided by the invention has excellent dispersity and long-term suspension stability, extremely high whiteness and extremely low color cast, the content of harmful heavy metals is reduced to an extremely low level, the particle size is controlled to be 0.3 mu m or below through fine processing steps of sanding, diluting and grading, the pore structure is larger than 50 nm, and the food-grade titanium dioxide has relatively good compactness and is suitable for industrial production. The agglomeration phenomenon is effectively reduced, and the method can be widely applied to food.

Description

Technical Field

[0001] This invention relates to the field of food additives technology, specifically to a method for preparing food-grade titanium dioxide and its applications. Background Technology

[0002] Food-grade titanium dioxide (scientific name: titanium dioxide) is a white inorganic pigment widely used in the food, pharmaceutical, and cosmetic industries, mainly as a whitening agent and colorant.

[0003] However, in applications, industrial-grade titanium dioxide often contains trace amounts of harmful heavy metal impurities (such as lead and arsenic), failing to meet the relevant standards for food-grade titanium dioxide. Furthermore, the dispersibility and agglomeration of titanium dioxide particles directly affect its application performance, leading to decreased product performance, reduced production efficiency, and higher safety risks.

[0004] Therefore, providing a method for preparing food-grade titanium dioxide that can improve dispersibility, reduce agglomeration, and lower the content of harmful heavy metal impurities, as well as its applications, is an urgent problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing highly dispersible food-grade titanium dioxide and its applications. The preparation method includes the following steps: S1, mixing crude titanium dioxide with concentrated sulfuric acid and deionized water, acid washing, stirring for 20-40 minutes, then adding deionized water for washing, and filtration until the filtrate is neutral to obtain a filter cake; S2, filtering the filter cake through a vibrating screen, then milling it, then adding deionized water for dilution and washing until the conductivity of the slurry stabilizes below 400 μS / cm, then classifying it to obtain a slurry containing fine particles; S3, filtration the slurry containing fine particles, adding deionized water to the obtained filter cake for redispersing, then spray drying and pulverizing to obtain food-grade titanium dioxide. The food-grade titanium dioxide prepared by the method of this invention has excellent dispersibility and long-term suspension stability, extremely high whiteness and extremely low color deviation, and the content of harmful heavy metals is reduced to extremely low levels. Through fine processing steps such as milling, dilution, and classification, the particle size is controlled below 0.3 μm and the pore structure is greater than 50. nm has good density, effectively reducing agglomeration, and can be widely used in food.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing highly dispersed food-grade titanium dioxide, the method comprising the following steps: S1. Mix crude titanium dioxide with concentrated sulfuric acid and deionized water, acid wash, stir for 20-40 minutes, then add deionized water for washing, filter until the filtrate is neutral, and obtain filter cake. S2. The filter cake is filtered through a vibrating screen, then milled, and then diluted and washed with deionized water until the conductivity of the slurry is stable below 400 μS / cm. Then it is classified to obtain a slurry containing fine particles. S3. The slurry containing fine particles is filtered by pressure, and the resulting filter cake is redispersed with deionized water, then spray-dried and pulverized to obtain food-grade titanium dioxide.

[0007] In some specific embodiments of the present invention, the food-grade titanium dioxide has a mercury content of 0.009 mg / kg, a lead content of 0.24 mg / kg, and an arsenic content of 0.91 mg / kg.

[0008] In some specific embodiments of the present invention, the food-grade titanium dioxide has a particle size of less than 0.3 μm, a specific surface area of ​​12.3 m² / g, and a pore structure of macropores greater than 50 nm.

[0009] In some specific embodiments of the present invention, the color value L of the food-grade titanium dioxide is 99.3, and the color deviation a is 0.07.

[0010] In some specific embodiments of the present invention, during the powder collection process of the spray drying in step S3, compressed air is used for pulse backflushing to remove dust, the air pressure of the air supply system is controlled at 90-110 Pa, and the backflushing pressure is controlled at 0.3-0.4 MPa; the equipment for collecting powder is a bag filter.

[0011] In some specific embodiments of the present invention, the weight ratio of crude titanium dioxide to concentrated sulfuric acid and deionized water in step S1 is 5:1:10.

[0012] In some specific embodiments of the present invention, the amount of deionized water added in step S1 for washing is 3 to 4 times the weight of crude titanium dioxide.

[0013] In some specific embodiments of the present invention, the equipment for sand grinding in step S2 is a sand mill, and the number of sand grinding cycles is 2 to 3.

[0014] In some specific embodiments of the present invention, the grading equipment in step S2 is a horizontal screw discharge sedimentation centrifuge; the crushing equipment in step S3 is a hammer mill.

[0015] Secondly, the present invention provides the use of food-grade titanium dioxide obtained by the preparation method described in the first aspect in food.

[0016] The beneficial effects achieved by this invention are as follows: The preparation method provided by this invention yields food-grade titanium dioxide with excellent dispersibility and long-term suspension stability, extremely high whiteness and extremely low color deviation, and the content of harmful heavy metals is reduced to extremely low levels. Through fine processing steps such as sand milling, dilution and grading, the particle size is controlled below 0.3 μm, the pore structure is greater than 50 nm, and it has good compactness, effectively reducing agglomeration. It can be widely used in food. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a method for preparing food-grade titanium dioxide. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are not intended to limit the present invention, but only to illustrate the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0020] Example 1 A method for preparing food-grade titanium dioxide, the flowchart of which is shown below. Figure 1 As shown, the specific steps include: (1) Coarse processing: By weight, crude titanium dioxide is mixed with concentrated sulfuric acid and deionized water in a ratio of 5:1:10 (corresponding to 20 tons of crude titanium dioxide, 4 tons of sulfuric acid, and 40 tons of deionized water), and acid-washed for 30 minutes. The acid-washed slurry is transferred to a mixing tank, diluted with 75 tons of deionized water, washed, and then pumped into a plate and frame filter press for filtration. The filter cake in the filter press is repeatedly washed and filtered with sufficient deionized water until the filtrate is neutral, i.e., the pH of the filtrate is 7.

[0021] (2) Fine processing: Take the filter cake from the previous step, add sufficient deionized water, and filter it through a vibrating screen. Then, use a sand mill to perform two cycles of sand milling on the slurry. Transfer the slurry to a mixing tank, add 75 tons of deionized water for dilution and washing until the slurry conductivity stabilizes below 400 μS / cm. The washed slurry is continuously pumped into a horizontal screw discharge sedimentation centrifuge for classification, separating and removing materials with larger particle sizes, and collecting the slurry containing fine particles for later use.

[0022] (3) Dispersion treatment: The fine slurry is fed into a plate and frame filter press for filtration to obtain a filter cake. The filter cake is transferred to a pulping tank for redispersing. The treated slurry is dried using a spray dryer, and the dried powder is collected in a bag filter. During the collection process, compressed air is used for pulse backflushing cleaning, with the air supply system pressure controlled at around 100 Pa and the backflushing pressure controlled at 0.3–0.4 MPa (approximately 3–4 kgf / cm²). Finally, the collected powder is lightly pulverized and deagglomerated using a hammer mill to obtain a food-grade titanium dioxide product with small particle size and excellent dispersibility.

[0023] The obtained food-grade titanium dioxide was subjected to full elemental analysis. The mercury content was 0.009 mg / kg, the lead content was 0.24 mg / kg, and the arsenic content was 0.91 mg / kg. The content of heavy metal harmful impurities in the titanium dioxide was significantly better than the national food-grade standard (GB 1886.341-2021: Pb≤10 mg / kg, As≤3 mg / kg), reducing the content of harmful heavy metals in the product to an extremely low level, reflecting the extremely high safety of the product.

[0024] The obtained food-grade titanium dioxide was subjected to particle size analysis. Through fine processing such as sand milling and grading, the particle size of the raw titanium dioxide was successfully controlled below 0.3 μm. Nitrogen adsorption-desorption tests further showed that the titanium dioxide had a specific surface area of ​​12.3 m² / g and a pore structure of macropores >50 nm. This dense microstructure and fine particle size are the basis for the product's excellent dispersibility and optical properties.

[0025] The obtained food-grade titanium dioxide was subjected to colorimetric testing, and its colorimetric values ​​were: L = 99.3 (extremely high brightness) and a = 0.07 (extremely low red-green deviation, presenting a pure white color). This indicates that the titanium dioxide has extremely high whiteness and extremely low color deviation. This optical performance ensures that it can provide a bright and pure visual appearance in the end product.

[0026] The obtained food-grade titanium dioxide was subjected to dispersion stability testing, specifically a quantitative sedimentation experiment: 25 g of the product was dispersed in 225 ml of deionized water to form a homogeneous slurry, which was then transferred to a 250 ml transparent graduated cylinder for observation. The results showed that the slurry particles settled slowly, and after standing for one week, the sediment was compact, with a height of only 2 mm. This result fully demonstrates that the product of this invention has excellent dispersibility and long-term suspension stability.

[0027] Comparative Example 1 Titanium dioxide was prepared according to the method of Example 1, the difference being that step (2) was omitted and the drying method in step (3) was oven drying. The titanium dioxide in Comparative Example 1 had a heavy metal harmful impurity arsenic content of 2 mg / Kg and a lead content as low as 6 mg / Kg.

[0028] Comparative Example 2 Titanium dioxide was obtained by referring to the preparation method of Example 1, except that step (2) was not performed. The particle size of the titanium dioxide in Comparative Example 1 was 100-150 nm.

[0029] In summary, the titanium dioxide prepared by the method of this application has a mercury content of 0.009 mg / kg, a lead content of 0.24 mg / kg, and an arsenic content of 0.91 mg / kg. In contrast, the titanium dioxide of Comparative Example 1 only has characterization results for arsenic and lead, and cannot characterize the mercury content. The titanium dioxide of Comparative Example 2 cannot characterize the contents of arsenic, lead, and mercury. This indicates that the titanium dioxide of this application can comprehensively characterize the contents of harmful heavy metals mercury, lead, and arsenic, and the contents of these harmful heavy metals are extremely low, exhibiting extremely high safety. At the same time, the titanium dioxide of this application also has extremely high whiteness and extremely low color deviation. Through fine processing steps such as sand milling, dilution, and classification, the particle size is controlled below 0.3 μm, the pore structure is greater than 50 nm, and it has good compactness, effectively reducing agglomeration and exhibiting excellent dispersibility and long-term suspension stability.

[0030] The above specific embodiments further illustrate the purpose, technical solution and beneficial effects of this application. It should be understood that the above are only specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing highly dispersed food-grade titanium dioxide, characterized in that, The preparation method includes the following steps: S1. Mix crude titanium dioxide with concentrated sulfuric acid and deionized water, acid wash, stir for 20-40 minutes, then add deionized water for washing, filter until the filtrate is neutral, and obtain filter cake. S2. The filter cake is filtered through a vibrating screen, then milled, and then diluted and washed with deionized water until the conductivity of the slurry is stable below 400 μS / cm. Then it is classified to obtain a slurry containing fine particles. S3. The slurry containing fine particles is filtered by pressure, and the resulting filter cake is redispersed with deionized water, then spray-dried and pulverized to obtain food-grade titanium dioxide.

2. The preparation method according to claim 1, characterized in that, The food-grade titanium dioxide has a mercury content of 0.009 mg / kg, a lead content of 0.24 mg / kg, and an arsenic content of 0.91 mg / kg.

3. The preparation method according to claim 1, characterized in that, The food-grade titanium dioxide has a particle size of less than 0.3 μm, a specific surface area of ​​12.3 m² / g, and a pore structure of macropores greater than 50 nm.

4. The preparation method according to claim 1, characterized in that, The food-grade titanium dioxide has a color value L of 99.3 and a color deviation a of 0.

07.

5. The preparation method according to claim 1, characterized in that, In step S3, during the powder collection process of spray drying, compressed air is used for pulse backflushing to remove dust. The air pressure of the air supply system is controlled at 90-110 Pa, and the backflushing pressure is controlled at 0.3-0.4 MPa. The equipment for collecting the powder is a bag filter.

6. The preparation method according to claim 1, characterized in that, The weight ratio of crude titanium dioxide to concentrated sulfuric acid and deionized water in step S1 is 5:1:

10.

7. The preparation method according to claim 1, characterized in that, The amount of deionized water added during the washing process in step S1 is 3 to 4 times the weight of the crude titanium dioxide.

8. The preparation method according to claim 1, characterized in that, The equipment used for sand grinding in step S2 is a sand mill, and the number of sand grinding cycles is 2 to 3.

9. The preparation method according to claim 1, characterized in that, The grading equipment mentioned in step S2 is a horizontal screw discharge sedimentation centrifuge; the crushing equipment mentioned in step S3 is a hammer mill.

10. Use of food-grade titanium dioxide obtained by any one of claims 1 to 9 in food.

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