A method for analyzing effective acid in titanium liquid during the production of titanium dioxide using hydrochloric acid

Abstract

The present invention discloses a method for analyzing the effective acid of titanium liquid in the production process of titanium dioxide by hydrochloric acid method. The method comprises the following steps: accurately drawing a certain volume of titanium liquid into a triangular flask, adding a certain volume of deionized water to dilute it, and in order to avoid Fe 2+ The hydrolysis of methyl violet is carried out by using methyl violet as an indicator, and 2 drops of methyl violet ethanol solution are added, shaken, and the solution to be measured is titrated with a sodium hydroxide standard solution. When the solution is purple-red, it is near the titration end point. Insert an acidity meter to detect the pH value of the titrated solution, and carefully add sodium hydroxide standard solution until the pH value of the titrated solution is 2.15, which is the end point. Compared with the acid-base neutralization methyl orange indicator titration method, the present invention eliminates the defects and errors existing in the traditional titanium liquid determination method, is not limited by the turbidity of the solution, etc., the end point is easy to judge, the test result is objective and reliable, and the influence of human errors is reduced, and satisfactory results are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of titanium dioxide and titanium dioxide production, in particular to a method for analyzing effective acid in titanium liquid during the production of titanium dioxide using a hydrochloric acid process. Background Art

[0002] Titanium dioxide for pigments, commonly known as titanium dioxide, is the world's best white pigment. It is widely used in coatings, plastics, papermaking, rubber, ink, chemical fiber, electronics, ceramics and other industrial fields. It is one of the most important inorganic chemical products. The mature technology for wet production of titanium dioxide is sulfuric acid titanium dioxide production technology, and the hydrochloric acid titanium dioxide production technology is being developed. The titanium raw materials for the production of sulfuric acid titanium dioxide and hydrochloric acid titanium dioxide are mainly acid-soluble titanium slag and ilmenite. The decomposition acids used are sulfuric acid and hydrochloric acid, respectively. The acid decomposition of titanium-containing minerals obtains titanium oxysulfate, titanium sulfate mixed solution and titanium oxychloride solution, respectively. Other acid-soluble impurities are decomposed into soluble sulfates and chlorides, such as divalent iron salts, calcium salts, magnesium salts, etc. Undecomposed minerals are mixed in the solution in the form of solid impurities, which can be removed by filtration. The solution is called titanium liquid. The titanium liquid is subjected to the process of impurity removal, concentration increase, hydrolysis to prepare hydrated titanium dioxide, filtration, washing, calcination, post-treatment, etc. to obtain pigment-grade titanium dioxide. In titanium liquid, acid exists in three forms, namely, acid combined with titanium, acid combined with other impurity elements and free acid. Free acid refers to acid not combined with other elements. The sum of free acid and acid combined with titanium is called effective acid. The detection of effective acid plays an important role in determining the hydrolysis performance and stability of titanium liquid. The determination of effective acid is generally carried out by chemical titration. The current method for determining effective acid in the production of titanium dioxide by sulfuric acid method is: use a pipette to draw a certain volume of titanium liquid into a volumetric flask, and add distilled water to dilute to the scale. After shaking well, draw a certain volume of diluted titanium liquid into a conical flask, add ammonium chloride and barium chloride mixed solution to precipitate barium sulfate to release sulfuric acid, drop methyl orange as an indicator, and use sodium hydroxide standard solution to titrate to orange and stabilize for 30 seconds without fading, which is the end point. However, this method is not suitable for the determination of effective acid of titanium liquid produced in the production of titanium dioxide by hydrochloric acid method. At present, it is particularly important to establish a practical method for determining effective acid of titanium liquid for the development of hydrochloric acid method titanium dioxide production technology. Summary of the invention

[0003] The purpose of the present invention is to provide a method for analyzing the effective acid of titanium liquid in the production process of titanium dioxide by hydrochloric acid method. In the conventional chemical analysis method, a standard alkaline titrant is used to titrate the acidic solution that is quantitatively absorbed and diluted with deionized water, and a specific acid-base indicator is used to indicate the titration end point by color development, or a pH meter is used to measure the pH change value of the titrated acidic solution, or a potentiometric titrator is used to measure the potential change value of the titrated acidic solution to determine the titration end point, and the acidity of the measured acidic solution is determined by concentration and volume conversion; the present invention is aimed at the titanium liquid having a large amount of Fe that is easily hydrolyzed.2+ , Ca 2+ Mg 2+ Such as metal cations, such as simple acid-base titration solution to a neutral pH to determine the endpoint, due to Fe 2+ , Ca 2+ Mg 2+ The hydrolysis of metal cations releases H + Therefore, in order to determine the effective acidity of titanium liquid in the production process of titanium dioxide by hydrochloric acid method, it is necessary to ensure that Fe 2+ , Ca 2+ Mg 2+ The effective acid is tested under the premise that the metal ions are not hydrolyzed; in order to correctly determine the effective acidity of the titanium liquid in the production process of titanium dioxide by the hydrochloric acid method, methyl violet with a pH value of 2.0-3.0 in the third color change range is selected as the indicator. The test method is to titrate the diluted titanium liquid to be tested with a standard sodium hydroxide solution. The titration is near the end point when the solution turns purple-red. Then insert a pH meter into the solution titrated to the purple-red solution to measure the pH value of the solution, carefully add sodium hydroxide standard solution until the pH value of the solution to be tested is 2.15, and the titration end point is reached. The effective acidity of the titanium liquid is calculated according to the calculation formula. Ti in the diluted titanium liquid to be tested 4+ The slight turbidity and color caused by the hydrolysis of Fe does not affect the determination of the titration endpoint and can effectively prevent Fe 2+ , Ca 2+ Mg 2+ Hydrolysis of metal cations and reliable determination of effective acidity of titanium liquid.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problem is to use the following analytical steps to determine the effective acidity of titanium liquid: use an acid-base indicator and a pH value determination method to determine the titration end point, the steps comprising: diluting the titanium liquid, dripping methyl violet with a pH value of 2.0-3.0 in the third color change range as an acid-base indicator, dripping a standard sodium hydroxide solution, starting to measure the pH value of the solution when the titration is close to the end point, adding additional sodium hydroxide solution until the pH value of the solution being tested is 2.15, and the titration end point is reached, and calculating the effective acidity of the titanium liquid according to the calculation formula.

[0005] The titanium liquid is taken from the titanium liquid storage tanks with different concentrations in each production step of the hydrochloric acid method titanium dioxide production line.

[0006] Preparation method of the solution to be measured: Use an automatic sampler to take 5-20ml of titanium liquid into a 100ml volumetric flask, add deionized water to the scale. Take 5-50ml of the fixed solution into a 300ml conical flask, add 50-100ml of deionized water to obtain a standard solution of sodium hydroxide of 0.1-0.6mol / L.

[0007] Add 2 drops of 0.1% methyl violet solution to the diluted titanium solution to be tested, and add sodium hydroxide standard solution while shaking evenly. When the solution turns purple-red, the titration is close to the endpoint. Then insert the pH meter glass electrode into the solution that has been titrated to purple-red to measure the pH value of the solution, and carefully add sodium hydroxide standard solution until the pH value of the solution to be tested is 2.15. When the titration endpoint is reached, calculate the effective acidity of the titanium solution according to the calculation formula.

[0008] Analysis result calculation formula:

[0009]

[0010] Where: C(HCl)—effective acid concentration in titanium liquid, g / L

[0011] C 1 ——Concentration of NaOH standard solution, mol / L;

[0012] V 1 ——Volume of NaOH standard solution, ml;

[0013] M – molecular weight of HCl, 36.45;

[0014] V 2 ——The volume of the solution to be tested, ml;

[0015] V 3 ——The volume of the solution to be tested, ml;

[0016] V 4 ——The volume of the solution to be tested after being fixed to volume, ml;

[0017] The beneficial effect of the present invention is that it can effectively determine the effective acid in various titanium liquids in the production and research of titanium dioxide by hydrochloric acid method, and can effectively prevent Fe 2+ , Ca 2+ Mg 2+ The hydrolysis of metal cations such as Ti and Mg will affect the determination of effective acidity of titanium liquid. 4+ The slight turbidity and original color caused by the hydrolysis do not affect the judgment of the titration end point. The test results are objective and reliable, reducing the influence of human errors. A reliable detection method for effective acid in various titanium liquids has been invented for the actual industrial production application of the hydrochloric acid method of titanium dioxide. DETAILED DESCRIPTION

[0018] The preferred embodiments of the present invention are described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0019] The embodiments of the present invention include:

[0020] A method for analyzing the effective acidity of titanium liquid in the production process of titanium dioxide by the hydrochloric acid method. The test method is to titrate the diluted titanium liquid to be tested with a standard sodium hydroxide solution, using methyl violet as an indicator, and titrating until the solution turns purple-red as the near end point, then inserting a pH meter into the solution to measure the pH value of the solution, carefully adding sodium hydroxide standard solution until the pH value of the tested solution reaches 2.15, and the titration end point is reached, and the effective acidity of the titanium liquid is calculated according to the calculation formula. Ti in the diluted titanium liquid to be tested 4+ The slight turbidity and color caused by the hydrolysis of Fe does not affect the determination of the titration endpoint and can effectively prevent Fe 2+ , Ca 2+ Mg 2+ Hydrolysis of metal cations and reliable determination of effective acidity of titanium liquid.

[0021] Embodiments of the present invention include:

[0022] Example 1

[0023] Use a pipette to draw 10 ml of the acid solution into a 100 ml volumetric flask, add deionized water to the mark and shake well.

[0024] Take 20ml of the solution in a 300ml conical flask and add 100ml of deionized water;

[0025] Add 2 drops of methyl violet indicator and titrate with 0.5017 mol / L NaOH standard solution until the solution turns purple-red, which is the near end point of the titration.

[0026] Then insert the pH meter glass electrode into the solution that is titrated until the solution turns purple-red to measure the pH value of the solution;

[0027] Carefully add more sodium hydroxide standard solution until the pH value of the solution to be tested reaches 2.15. When the titration endpoint is reached, read the volume of the sodium hydroxide standard solution V = 23.65 ml.

[0028] After calculation, the effective acid in the acid hydrolyzate is 216.24 g / L.

[0029] Example 2

[0030] Use a pipette to draw 10 ml of clear titanium solution into a 100 ml volumetric flask, add deionized water to the mark and shake well.

[0031] Take 20ml of the solution in a 300ml conical flask and add 100ml of deionized water;

[0032] Add 2 drops of methyl violet indicator and titrate with 0.5017 mol / L NaOH standard solution until the solution turns purple-red, which is the near end point of the titration.

[0033] Then insert the pH meter glass electrode into the solution that is titrated until the solution turns purple-red to measure the pH value of the solution;

[0034] Carefully add more sodium hydroxide standard solution until the pH value of the solution to be tested reaches 2.15. When the titration endpoint is reached, read the volume of the sodium hydroxide standard solution V = 26.20 ml.

[0035] After calculation, the effective acid in the titanium clearing solution is 239.56 g / L.

[0036] Example 3

[0037] Use a pipette to draw 10 ml of concentrated titanium solution into a 100 ml volumetric flask, add deionized water to the mark and shake well.

[0038] Take 20ml of the solution in a 300ml conical flask and add 100ml of deionized water;

[0039] Add 2 drops of methyl violet indicator and titrate with 0.5017 mol / L NaOH standard solution until the solution turns purple-red, which is the near end point of the titration.

[0040] Then insert the pH meter glass electrode into the solution that is titrated until the solution turns purple-red to measure the pH value of the solution;

[0041] Carefully add more sodium hydroxide standard solution until the pH value of the solution to be tested reaches 2.15. When the titration endpoint is reached, read the volume of the sodium hydroxide standard solution V = 21.30 ml.

[0042] After calculation, the effective acid in the concentrated titanium solution is 194.76g / L.

[0043] Example 4

[0044] Use a pipette to draw 5 ml of the hydrolysis mother solution into a 300 ml conical flask, and add 100 ml of deionized water;

[0045] Add 2 drops of methyl violet indicator and titrate with 0.5017 mol / L NaOH standard solution until the solution turns purple-red, which is the near end point of the titration.

[0046] Then insert the pH meter glass electrode into the solution that is titrated until the solution turns purple-red to measure the pH value of the solution;

[0047] Carefully add sodium hydroxide standard solution until the pH value of the solution to be tested reaches 2.15. When the titration endpoint is reached, read the volume of sodium hydroxide standard solution V = 35.85 ml.

[0048] The calculation showed that the effective acid in the hydrolysis mother liquor was 131.11 g / L.

[0049] By measuring the mass of steam added to the hydrolysis mother liquor and measuring the volume and concentration of the condensed acid in the hydrolysis tail gas, it was calculated that the yield of HCl during the hydrolysis process was 99.64%.

[0050] The titanium liquids used in Example 1, Example 2, Example 3, and Example 4 are titanium-containing and effective acid solutions obtained in different process steps during the production process. The titanium liquid in Example 1 is an acidolysis liquid, the titanium liquid in Example 2 is a clear titanium liquid, the titanium liquid in Example 3 is a concentrated titanium liquid, and the titanium liquid in Example 4 is a hydrolysis mother liquid.

[0051] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent process changes made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for analyzing the effective acid in titanium liquid during the production of titanium dioxide by the hydrochloric acid method, using an acid-base indicator and a pH value determination method to determine the titration endpoint, the steps of which are: include: Dilute the titanium liquid, drop methyl violet with a pH value of 2.0-3.0 in the third color change range as an acid-base indicator, drop sodium hydroxide standard solution, start measuring the solution pH value when the titration is close to the endpoint, add sodium hydroxide standard solution until the pH value of the measured solution is 2.15, and the titration endpoint is reached. Calculate the effective acidity of the titanium liquid according to the calculation formula, which is: Where: C(HCl)—effective acid concentration in titanium liquid, g / L C 1 ——Concentration of NaOH standard solution, mol / L; V 1 ——Volume of NaOH standard solution, ml; M – molecular weight of HCl, 36.45; V 2 ——The volume of the solution to be tested, ml; V 3 ——The volume of the solution to be tested, ml; V 4 ——The volume of the solution to be tested after it is fixed to volume, ml.

2. The method for analyzing effective acid in titanium liquid during the production of titanium dioxide by the hydrochloric acid method according to claim 1, Features The standard solution of sodium hydroxide is 0.1-0.6 mol / L.

3. The method for analyzing effective acid in titanium liquid during the production of titanium dioxide by the hydrochloric acid method according to claim 1, Features The titanium liquid comes from titanium liquid storage tanks with different concentrations in each production step of the hydrochloric acid method titanium dioxide production line; the preparation method of the solution to be measured is to take 5-20ml of titanium liquid in a 100ml volumetric flask, rinse the pipette with deionized water and transfer it into the volumetric flask, add deionized water to make up to the scale; take 5-50ml of the fixed solution in a 300ml conical flask, add 50-100ml of deionized water to obtain.

4. The method for analyzing effective acid in titanium liquid during the production of titanium dioxide by the hydrochloric acid method according to claim 1, Features The titration is near the end point when the solution turns purple-red.

5. The method for analyzing effective acid in titanium liquid during the production of titanium dioxide by the hydrochloric acid method according to claim 4, Features Insert a pH meter into the solution that has been titrated until it turns purple-red to measure the pH value of the solution, and carefully add more sodium hydroxide standard solution until the pH value of the solution being tested reaches 2.

15.

6. According to the method for analyzing the effective acid of titanium liquid in the production process of titanium dioxide by the hydrochloric acid method as described in claim 5, 2 drops of 0.1% methyl violet solution are dripped into the diluted titanium liquid to be tested, and a standard sodium hydroxide solution is dripped into the diluted titanium liquid under uniform shaking.

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