A method for evaluating the effective amount of hydrolyzed seed crystals

Abstract

This invention relates to the field of titanium dioxide production technology, and in particular to a method for evaluating the effective amount of hydrolyzed seed crystals. The proposed method includes the following steps: S1: Preparing a hydrolyzed seed crystal solution, and detecting the titanium concentration C of the hydrolyzed seed crystal solution using a method for detecting titanium content; S2: Mixing a volume V of the hydrolyzed seed crystal solution with an acid solution to obtain a mixed liquid, allowing the mixed liquid to stand until stable stratification occurs, measuring the volume V1 of the upper clear liquid, and detecting the titanium concentration C1 of the upper clear liquid using a method for detecting titanium content; S3: Calculating the effective amount of hydrolyzed seed crystals: The effective amount of hydrolyzed seed crystals is: C*V - C1*V1. This method can separate excess titanium liquid from the hydrolyzed seed crystal solution, thereby achieving the purpose of evaluating the actual effective amount of hydrolyzed seed crystals. This greatly helps in controlling the amount of hydrolyzed seed crystals during the actual production process of titanium dioxide, and improves the yield of titanium dioxide.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide production, and in particular to a method for evaluating the effective amount of hydrolyzed seed crystals. Background Technology

[0002] The hydrolysis process in titanium dioxide production involves adding hydrolytic seed crystals of a certain quantity and size, which cause the titanium liquid to hydrolyze at a certain temperature. The quantity and quality of the hydrolytic seed crystals determine the composition of the hydrolyzed precipitate and also the performance of the final product.

[0003] The method for preparing hydrolyzed seed crystals used in titanium dioxide production involves neutralizing titanium oxysulfate and liquid alkali (NaOH) to prepare H4TiO4 seed crystals, i.e., TiOSO4 + NaOH → H4TiO4 + Na2SO4. The process involves taking a certain amount of titanium liquid and liquid alkali, heating them to a specific temperature, then pouring the titanium oxysulfate solution into the alkali within a specified time, continuing heating to 96°C, and maintaining this temperature for maturation. The stability of the seed crystal solution is then tested. Once the stability of the prepared hydrolyzed seed crystals meets the requirements, the preparation of the hydrolyzed seed crystals is considered complete.

[0004] In existing technologies, the content of hydrolyzed seed crystals is generally determined by detecting the TiO2 content. This method characterizes the content of hydrolyzed seed crystals by measuring the TiO2 content in the prepared seed solution. However, this method cannot accurately represent the actual content of the prepared hydrolyzed seed crystals. Because the titanium solution is often in excess during the preparation process, residual titanium solution (TiOSO4) in the prepared seed solution can also be detected by the TiO2 content detection method. This affects the accuracy of determining the content of hydrolyzed seed crystals by measuring the TiO2 content in the prepared seed solution, thus increasing the perceived amount of hydrolyzed seed crystals. Therefore, this method cannot truly represent the effective amount of hydrolyzed seed crystals prepared.

[0005] Therefore, this invention proposes a method for evaluating the effective amount of hydrolyzed seed crystals. Summary of the Invention

[0006] To address the problems in the prior art, this invention proposes a method for evaluating the effective amount of hydrolyzed seed crystals.

[0007] In existing technologies, the total titanium content in titanium dioxide production lines is characterized by measuring the TiO2 content. Similarly, the prepared hydrolyzed seed crystals are also characterized by measuring the TiO2 content. However, such characterization methods cannot represent the actual amount of seed crystals prepared. This is because, in the process of preparing hydrolyzed seed crystals, after adding alkali to the titanium liquid, a certain amount of seed crystals are formed. Since the titanium liquid is in excess, further heating causes the previously formed seed crystals to induce the formation of new seed crystals in the titanium liquid. However, not all TiOSO4 in the titanium liquid forms seed crystals. In other words, the hydrolyzed seed crystal solution consists of three parts: one part is the H4TiO4 seed crystals formed by the direct reaction of the titanium liquid and alkali; another part is the new H4TiO4 seed crystals induced by the previously formed H4TiO4 seed crystals, the new seed crystals formed being related to seed crystal stability; and the third part is the TiOSO4 in the titanium liquid that has not formed seed crystals. The actual effective seed content refers to the H4TiO4 seed crystals formed and the new seed crystals formed on the basis of the H4TiO4 seed crystals. Therefore, the existing technology is inaccurate to directly use the method of detecting TiO2 content to detect the hydrolyzed seed content in the hydrolyzed seed solution. The characterization results make the effective amount of hydrolyzed seed crystals too large.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention proposes a method for evaluating the effective amount of hydrolyzed seed crystals, comprising the following steps:

[0010] S1: Prepare a hydrolyzed seed solution, and determine the titanium concentration C of the hydrolyzed seed solution using a method for detecting titanium content;

[0011] S2: Under certain seed stability conditions, measure the titanium concentration in the hydrolyzed seed solution: Take volume V of the hydrolyzed seed solution and mix it evenly with the acid solution to obtain a mixed liquid. After standing for the mixed liquid to form a stable layer, measure the volume V1 of the upper clear liquid and use the method of detecting titanium content to detect the titanium concentration C1 of the upper clear liquid.

[0012] S3: Calculate the effective amount of hydrolyzed seed crystals: The effective amount of hydrolyzed seed crystals is: C*V-C1*V1.

[0013] Preferably, the acid solution is a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 18-36%.

[0014] Preferably, the volume ratio of the hydrolyzed seed solution to hydrochloric acid is 1:(2-3).

[0015] Preferably, the stirring time of the hydrolyzed seed solution and the acid solution in S2 is 5-10 minutes, and the standing time of the mixed liquid is 60-90 minutes.

[0016] Preferably, the method for preparing the hydrolyzed seed solution in S1 includes: placing titanium oxysulfate solution and NaOH solution in separate containers, heating the titanium oxysulfate solution and NaOH solution to 75℃-85℃ respectively, and adding the heated titanium oxysulfate solution to the heated NaOH solution within 2-4 minutes while stirring.

[0017] Preferably, the volume ratio of the titanium oxysulfate solution to the NaOH solution is 50:(18-25).

[0018] Preferably, the concentration of the titanium oxysulfate solution is 200 g / L, and the concentration of the NaOH solution is 98 g / L-100 g / L.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention has discovered that the existing evaluation methods for the effective amount of hydrolyzed seed crystals have the problem of inaccurate evaluation results. That is, the evaluation methods of the existing technology increase the content of hydrolyzed seed crystals, and this method cannot truly characterize the effective amount of hydrolyzed seed crystals prepared.

[0021] 2. In this invention, a hydrolyzed seed solution is first prepared using a titanium oxysulfate solution. Then, the titanium concentration C of the hydrolyzed seed solution is determined by detecting the titanium content. Under certain seed stability conditions, a certain volume V of the hydrolyzed seed solution is taken and mixed with hydrochloric acid solution for acid dissolution, i.e., HCl + H4TiO4 → TiO2Cl2 + H2O. After acid dissolution, the titanium oxychloride in the hydrolyzed seed solution gradually precipitates from a diffuse sol-like state to a gel state. After standing and settling, the solution separates into layers. The unreacted titanium oxysulfate in the hydrolyzed seed solution is dispersed in the upper clear liquid, thereby separating the residual titanium oxysulfate in the hydrolyzed seed solution from the hydrolyzed seed. That is, the upper clear liquid V1 is a residual titanium oxysulfate solution containing titanium oxysulfate. Then, the titanium concentration C1 in the residual titanium oxysulfate solution is determined by detecting the titanium content. According to the calculation formula C*V-C1*V1, the result is the actual effective amount of the prepared hydrolyzed seed crystals. The method of the present invention can separate the residual titanium oxysulfate in the hydrolyzed seed crystal solution from the obtained hydrolyzed seed crystals in order to evaluate the actual effective amount of the hydrolyzed seed crystals.

[0022] 3. The characterization method of the actual effective amount of seed crystals has greatly helped to accurately control the amount of hydrolyzed seed crystals added in the actual production process of titanium dioxide, thus improving the yield of titanium dioxide. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0025] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field can be followed.

[0026] The method for determining the stability of seed crystals in this invention is as follows: 10 mL of seed crystals is measured into an Erlenmeyer flask, the flask is shaken and water is continuously added. Hydrolysis is indicated by the appearance of a white liquid. Water addition and shaking are stopped, and the volume of the liquid in the flask is measured. The volume (mL) represents the stability of the seed crystals. This method is only used to determine the effective amount of hydrolyzed seed crystals at a certain state during the preparation of hydrolyzed seed crystals. The method for determining stability is not limited to this.

[0027] The method for detecting titanium content in this invention includes a method for detecting liquid TiO2.

[0028] The detection method for liquid TiO2 includes the following steps:

[0029] (1) Pipette 1 ml to 10 ml of titanium liquid sample into an Erlenmeyer flask, add 80 to 100 ml of sulfuric acid mixture and 2 g of aluminum sheet; (the sulfuric acid mixture is 98% concentrated sulfuric acid: 37% concentrated hydrochloric acid in a volume ratio of 1:1)

[0030] (2) Install the Geiger funnel and seal it with a rubber stopper. Add saturated sodium bicarbonate solution to the Geiger funnel until the container volume is 1 / 3. Heat it on an electric furnace with a small flame until the reaction begins. Remove it from the heat source. After the aluminum sheet has dissolved, heat it again to remove all the hydrogen gas from the solution. Remove it from the heat source when the solution is clear and cool it to room temperature with running water.

[0031] (3) During the cooling process, add a saturated sodium bicarbonate solution, add 2 ml of ammonium thiocyanate index reagent, and immediately titrate with ferric ammonium sulfate solution until a light red endpoint is reached; the titanium dioxide content A is expressed as:

[0032] A = (a * V * 79.9 / V1) in g / L;

[0033] Where a is the molar concentration of ferric ammonium sulfate standard solution (mol / L); V is the volume of ferric ammonium sulfate standard solution consumed (mL); and V1 is the volume of titanium oxysulfate absorbed (mL).

[0034] In the following examples, the titanium concentration was detected using a method for detecting liquid TiO2.

[0035] Example 1

[0036] S1: Preparation of hydrolysis seed solution: 500 mL of 200 g / L titanium oxysulfate solution and 250 mL of 98 g / L NaOH solution were placed in two separate beakers. The two beakers were placed in a water bath and heated to 75°C. The heated titanium oxysulfate solution was added to the heated NaOH solution over 2 minutes while stirring continuously at 500 rpm until homogeneous. After standing at a constant temperature for 4 minutes, the first hydrolysis seed solution was obtained. 10 mL of the first hydrolysis seed solution was taken to determine its titanium concentration C. 21 ;

[0037] S2: Take 10 mL of the first hydrolyzed seed crystal solution and test the initial stability of the seed crystals. The initial stability is 180 mL. Take 50 mL of the first hydrolyzed seed crystal solution and add 100 mL of 18% hydrochloric acid solution to dissolve the crystals while stirring for 5 minutes. Let it stand for 60 minutes. After the reaction, the titanium oxychloride in the hydrolyzed seed crystal solution gradually precipitates from a diffuse sol-like state to a gel-like state. Then, use the method for detecting titanium content to determine the total titanium content C of the supernatant. 11 Measure the volume V of the supernatant. 11 ;

[0038] S21: Continue heating the first hydrolyzed seed solution to 96℃ to mature, obtaining the second hydrolyzed seed solution. Take 10mL of the second hydrolyzed seed solution to test the stability of the seed crystals. When the seed crystal stability reaches 100mL, take 10mL of the second hydrolyzed seed solution to test its titanium concentration C. 22 Then, 50 mL of the second hydrolyzed seed solution was added to a beaker, and 100 mL of 18% hydrochloric acid solution was added while stirring. After the addition was complete, the mixture was allowed to stand for 60 minutes. The titanium oxychloride in the hydrolyzed seed solution gradually precipitated from a diffuse sol-like state to a gel-like state. The total titanium content C of the supernatant was then measured. 12 And measure the volume V of the supernatant. 12 .

[0039] S3: Substitute the above data into the formula for the effective amount of hydrolyzed seed crystals: C*V - C1*V1, where V = 50mL, and V1 represents the volume of the supernatant (V... 11 or V 12 C1 represents the titanium concentration in the supernatant (C 11 Or C 12 C represents the titanium concentration in the hydrolysis seed solution (C0). 21 Or C 22The results showed that the actual effective amount of hydrolyzed seed crystals was measured when the seed crystal stability was 180 mL and 100 mL, respectively.

[0040] Example 2

[0041] S1: Preparation of hydrolysis seed solution: 500 mL of 200 g / L titanium oxysulfate solution and 200 mL of 99 g / L NaOH solution were placed in two separate beakers. The two beakers were placed in a water bath and heated to 80 °C. The heated titanium oxysulfate solution was added to the heated NaOH solution over 3 min while stirring continuously at 500 rpm until homogeneous. After standing at a constant temperature for 4 min, the first hydrolysis seed solution was obtained. 10 mL of the first hydrolysis seed solution was taken to determine its titanium concentration C. 21 ;

[0042] S2: Take 10 mL of the first hydrolyzed seed crystal solution and test the initial stability of the seed crystals. The initial stability is 220 mL. Take 50 mL of the first hydrolyzed seed crystal solution and add 100 mL of 25% hydrochloric acid solution to dissolve it while stirring for 5 minutes. Let it stand for 75 minutes. After the reaction, the titanium oxychloride in the hydrolyzed seed crystal solution gradually precipitates from a diffuse sol-like state to a gel-like state. Then, use the method for detecting titanium content to determine the total titanium content C of the supernatant. 11 Measure the volume V of the supernatant. 11 ;

[0043] S21: Continue heating the first hydrolyzed seed solution to 96℃ to mature and obtain the second hydrolyzed seed solution. Take 10mL of the second hydrolyzed seed solution to test the stability of the seed crystals. When the seed crystal stability reaches 130mL, take 10mL of the second hydrolyzed seed solution to test its titanium concentration C. 22 Then, 50 mL of the second hydrolyzed seed solution was added to a beaker, and 100 mL of 25% hydrochloric acid solution was added while stirring. After the addition was complete, the mixture was allowed to stand for 75 minutes. The titanium oxychloride in the hydrolyzed seed solution gradually precipitated from a diffuse sol-like state to a gel-like state. The total titanium content C of the supernatant was then measured. 12 And measure the volume V of the supernatant. 12 .

[0044] S3: Substitute the above data into the formula for the effective amount of hydrolyzed seed crystals: C*V - C1*V1, where V = 50mL, and V1 represents the volume of the supernatant (V... 11 or V 12 C1 represents the titanium concentration in the supernatant (C 11 Or C 12 C represents the titanium concentration in the hydrolysis seed solution (C0). 21 Or C 22The results showed that the actual effective amount of hydrolyzed seed crystals was measured when the seed crystal stability was 180 mL and 100 mL, respectively.

[0045] Example 3

[0046] S1: Preparation of hydrolysis seed solution: 500 mL of 200 g / L titanium oxysulfate solution and 230 mL of 100 g / L NaOH solution were placed in two separate beakers. The two beakers were placed in a water bath and heated to 80°C. The heated titanium oxysulfate solution was added to the heated NaOH solution over 4 minutes while stirring continuously at 500 rpm until homogeneous. After standing at a constant temperature for 4 minutes, the first hydrolysis seed solution was obtained. 10 mL of the first hydrolysis seed solution was taken to determine its titanium concentration C. 21 ;

[0047] S2: Take 10 mL of the first hydrolyzed seed crystal solution to test the initial stability of the seed crystals (200 mL). Take 50 mL of the first hydrolyzed seed crystal solution in a beaker and add 100 mL of 36% hydrochloric acid solution to dissolve it while stirring for 5 minutes. Let it stand for 90 minutes. After the reaction, the titanium oxychloride in the hydrolyzed seed crystal solution gradually precipitates from a diffuse sol-like state to a gel-like state. Then, use the method for detecting titanium content to determine the total titanium content C of the supernatant. 11 Measure the volume V of the supernatant. 11 ;

[0048] S21: Continue heating the first hydrolyzed seed solution to 96℃ to mature, obtaining the second hydrolyzed seed solution. Take 10mL of the second hydrolyzed seed solution to test the stability of the seed crystals. When the seed crystal stability reaches 150mL, take 10mL of the second hydrolyzed seed solution to test its titanium concentration C. 22 Then, 50 mL of the second hydrolyzed seed solution was added to a beaker, and 100 mL of 36% hydrochloric acid solution was added while stirring. After the addition was complete, the mixture was allowed to stand for 90 minutes. The titanium oxychloride in the hydrolyzed seed solution gradually precipitated from a diffuse sol-like state to a gel-like state. The total titanium content C of the supernatant was then measured. 12 And measure the volume V of the supernatant. 12 .

[0049] S3: Substitute the above data into the formula for the effective amount of hydrolyzed seed crystals: C*V - C1*V1, where V = 50mL, and V1 represents the volume of the supernatant (V... 11 or V 12 C1 represents the titanium concentration in the supernatant (C 11 Or C 12 C represents the titanium concentration in the hydrolysis seed solution (C0). 21 Or C 22The results showed that the actual effective amount of hydrolyzed seed crystals was measured when the seed crystal stability was 180 mL and 100 mL, respectively.

[0050] Comparative Example 1 (as opposed to Example 1, during the preparation of seed crystals by hydrolysis in Example 1)

[0051] (1) In Example 1, when the initial stability of the seed crystal was 180 mL, the total titanium content in 50 mL of the first hydrolyzed seed crystal solution was calculated to be: 50 mL * C 21 This refers to the actual effective amount of hydrolyzed seed crystals as determined by existing technologies.

[0052] (2) In Example 1, when the initial stability of the seed crystal was 100 mL, the total titanium content in 50 mL of the second hydrolyzed seed crystal solution was calculated to be: 50 mL * C 22 This refers to the actual effective amount of hydrolyzed seed crystals as determined by existing technologies.

[0053] Comparative Example 2 (as opposed to Example 2, during the preparation of hydrolyzed seed crystals in Example 2)

[0054] (1) In Example 2, when the initial stability of the seed crystal was 220 mL, the total titanium content in 50 mL of the first hydrolyzed seed crystal solution was calculated to be: 50 mL * C 21 This refers to the actual effective amount of hydrolyzed seed crystals as determined by existing technologies.

[0055] (2) In Example 2, when the initial stability of the seed crystal was 130 mL, the total titanium content in 50 mL of the second hydrolyzed seed crystal solution was calculated to be: 50 mL * C 22 This refers to the actual effective amount of hydrolyzed seed crystals as determined by existing technologies.

[0056] Table 1 shows the calculated effective seed quantity data of the hydrolyzed seed solutions prepared in Examples 1-3 and Comparative Examples 1-2.

[0057]

[0058] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0059] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for evaluating the effective amount of hydrolyzed seed crystals, characterized in that, Includes the following steps: S1: Prepare a hydrolyzed seed solution, and determine the titanium concentration C of the hydrolyzed seed solution using a method for detecting titanium content; The method for preparing the hydrolyzed seed solution includes: placing titanium oxysulfate solution and NaOH solution in separate containers, heating the titanium oxysulfate solution and NaOH solution to 75℃-85℃ respectively, and adding the heated titanium oxysulfate solution to the heated NaOH solution within 2-4 minutes while stirring. The volume ratio of the titanium oxysulfate solution to the NaOH solution is 50:(18-25). The concentration of the titanium oxysulfate solution is 200 g / L, and the concentration of the NaOH solution is 98 g / L-100 g / L; S2: Under certain seed stability conditions, measure the titanium concentration in the hydrolyzed seed solution: Take volume V of the hydrolyzed seed solution and mix it evenly with the acid solution to obtain a mixed liquid. After standing for the mixed liquid to form a stable layer, measure the volume V1 of the upper clear liquid and use the method of detecting titanium content to detect the titanium concentration C1 of the upper clear liquid. The acid solution is a hydrochloric acid solution with a concentration of 18-36%. The volume ratio of the hydrolyzed seed solution to hydrochloric acid is 1:(2-3). S3: Calculate the effective amount of hydrolyzed seed crystals: The effective amount of hydrolyzed seed crystals is: C*V-C1*V1.

2. The method for evaluating the effective amount of hydrolyzed seed crystals as described in claim 1, characterized in that, The hydrolysis seed solution and acid solution in S2 are stirred and mixed for 5-10 minutes, and the mixed liquid is allowed to stand for 60-90 minutes.

Images