Method for determining trace elements in sodium metaaluminate solution

Abstract

The invention provides a method for determining trace elements in a sodium metaaluminate solution, and relates to the technical field of chemical analysis. The method comprises the following steps: S1, measuring the content of sodium hydroxide in a sodium metaaluminate solution, and adding acid for acidizing for later measurement; s2, mixing the high-purity aluminum solution and the sodium hydroxide reference reagent solution, and adding the standard solutions of the elements to prepare a standard solution; s3, detecting the standard solution obtained in the step S2 by using an inductively coupled plasma emission spectrometer, and determining the wavelength, the detection mode and the analysis line of each element; and S4, according to a result obtained in the step S3, detecting the sodium metaaluminate solution obtained after neutralization treatment in the step S1, measuring the strength of each element analysis line, and calculating the element content. According to the method, the sodium metaaluminate solution is acidized, so that the solution is in a weakly acidic state, the influence of an alkaline environment on detection is eliminated, and the detection is more accurate and reliable.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analysis, in particular to a method for determining trace elements in a sodium aluminate solution. Background Art

[0002] Alumina is a very important fine chemical, which is used in sapphire single crystal, fine ceramics, high-pressure sodium lamp transparent tube, refractory materials and high-end abrasives. The production methods of high-purity alumina include alcohol salt hydrolysis method, metal aluminum hydration method, ammonium aluminum sulfate thermal decomposition method and modified Bayer process. At present, in the domestic alumina production process, most of them use the modified Bayer process to dissolve aluminum hydroxide into sodium aluminate solution with concentrated alkali, and then re-precipitate aluminum hydroxide by dilution and seeding. The obtained aluminum hydroxide of different purities is calcined to obtain alumina products.

[0003] In order to obtain aluminum hydroxide of different purities, the sodium aluminate solution needs to be purified to different degrees. Therefore, it is very important to master the impurities and purity of sodium aluminate in the production process of high-purity alumina. However, sodium aluminate solution is a relatively complex salt solution, which is mainly composed of caustic soda components, aluminum oxide components and carbonate components, and the solution contains various elements such as Li, K, Na, Ca, Si, Fe, Cr, etc. The conventional method is to use a single element analysis method, each time one of the elements is determined, the analysis cycle is long, and the detection of each element requires a large amount of organic reagents, and the production consumption is large. And the strong alkalinity and sodium ions and aluminum ions in the solution of sodium aluminate may interfere with the elements to be detected during the detection process, resulting in inaccurate detection results when detecting other elements. Therefore, how to detect the purity of sodium aluminate solution is a difficult problem in the industry at present. Summary of the invention

[0004] The purpose of the present invention is to provide a method for determining trace elements in a sodium aluminate solution in view of the deficiencies of the prior art, thereby at least solving some of the problems existing in the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for determining trace elements in a sodium aluminate solution comprises the following steps:

[0007] S1, determining the sodium hydroxide content in the sodium aluminate solution, adding acid for acidification, and testing;

[0008] S2, mixing high purity aluminum solution and sodium hydroxide reference reagent solution, adding standard solutions of various elements to prepare standard solutions;

[0009] S3, using an inductively coupled plasma emission spectrometer to detect the standard solution obtained in step S2, and determine the wavelength, detection method and analysis line of each element;

[0010] S4. According to the result obtained in step S3, the sodium aluminate solution obtained after the neutralization treatment in step S1 is tested, the intensity of each element analysis line is measured, and the element content is calculated.

[0011] Furthermore, in step S1, the method for determining the sodium hydroxide content in the sodium aluminate solution is a conventional method in the art, including but not limited to a titration method.

[0012] Furthermore, in step S1, the acid is a combination of any one of sulfuric acid and nitric acid and hydrochloric acid in a volume ratio of (1-3):1.

[0013] Furthermore, in step S1, the amount of the acid used is: based on the sodium hydroxide content in the sodium aluminate solution, the mass volume ratio of sodium hydroxide to acid is 1:(10-30) g / ml, preferably 1:20 g / ml.

[0014] Further, in step S2, the step of preparing the standard solution includes:

[0015] (1) Take 1.8722 g of high-purity aluminum, add 20 ml of concentrated sulfuric acid or concentrated nitric acid, heat until completely dissolved, add water to make the volume 100 ml, and obtain a high-purity aluminum solution;

[0016] (2) dissolving 2.7526 g of sodium hydroxide working standard reagent in water, and adding water to make the volume to 100 ml to obtain a sodium hydroxide standard reagent solution;

[0017] (3) Accurately pipette high-purity aluminum solution and sodium hydroxide standard reagent solution, mix them, add the standard solutions of each element into a volumetric flask, and prepare 5 standard solutions with different gradients for use.

[0018] Furthermore, in step (1), the mass volume ratio of the high purity aluminum to concentrated sulfuric acid or concentrated nitric acid is 1: (20-50) g / ml.

[0019] Furthermore, in step (3), the standard solutions of the elements are Li, K, Na, Ca, Si, Fe, Cr, Mg, Zn, Mn, and Ga standard solutions; and the concentration of the standard solutions is 1000 μg / ml.

[0020] Furthermore, in step (3), the volume ratio of the high purity aluminum solution to the sodium hydroxide reference reagent solution is 1:(1-2).

[0021] Furthermore, in step (3), the concentrations of the five standard solutions with different gradients are: 1 μg / ml, 2 μg / ml, 5 μg / ml, 10 μg / ml, and 20 μg / ml, respectively.

[0022] Further, in step S4, the calculated element content c is calculated according to the following formula (I):

[0023] c=C×V1 / V2(I)

[0024] In formula (I), C represents the concentration of the standard solution, V1 represents the volume of the standard solution, and V2 represents the constant volume.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention provides a method for determining trace elements in a sodium aluminate solution. By acidifying the sodium aluminate solution, the solution is placed in a weakly acidic state, thereby eliminating the influence of an alkaline environment on the detection, and the detection is more accurate and reliable.

[0027] 2. The method for determining trace elements in a sodium aluminate solution provided by the present invention comprises adding appropriate amounts of sodium salt and aluminum salt to the prepared standard solution so that the content of sodium ions and aluminum ions in the standard solution matches the amount of sodium ions and aluminum ions in the sodium aluminate solution to be detected, so as to reduce the influence of the presence of sodium ions and aluminum ions on other elements to be detected during the detection process, thereby improving the detection accuracy.

[0028] 3. The method for determining trace elements in a sodium aluminate solution provided by the present invention uses an inductively coupled plasma emission spectrometer for detection, and different wavelengths and observation methods are selected for different elements, thereby avoiding the influence of a high-salt environment and improving detection accuracy.

[0029] 4. The method provided by the present invention for determining trace elements in sodium aluminate solution has a detection limit of less than 1 ppm for multiple elements, high sensitivity, high repeatability and high recovery rate. DETAILED DESCRIPTION

[0030] The following non-limiting examples can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. The following content is only an exemplary description of the scope of the present invention, and those skilled in the art can make various changes and modifications to the invention of the present invention based on the disclosed content, and they should also fall within the scope of the present invention.

[0031] The present invention is further described below by way of specific examples. Unless otherwise specified, the various chemical reagents used in the examples of the present invention are obtained through conventional commercial channels.

[0032] Example 1

[0033] A method for determining trace elements in a sodium aluminate solution comprises the following steps:

[0034] S1, adopt titration method to measure the sodium hydroxide content in sodium aluminate solution, according to the mass volume ratio of sodium hydroxide to acid is 1:20g / ml, after sodium aluminate solution and acid (nitric acid and sulfuric acid with a volume ratio of 3:1) are mixed, water is added to make up to 100ml, to be measured;

[0035] S2. Prepare standard solution:

[0036] (1) Take 1.8722 g of high-purity aluminum, add 20 ml of concentrated nitric acid, heat until completely dissolved, and add water to make the volume 100 ml to obtain a high-purity aluminum solution;

[0037] (2) dissolving 2.7526 g of sodium hydroxide working standard reagent in water, and adding water to make the volume to 100 ml to obtain a sodium hydroxide working standard reagent solution;

[0038] (3) Accurately pipette high-purity aluminum solution and sodium hydroxide working reference reagent solution in a volume ratio of 1:2, mix them, add the standard solution of each element into a volumetric flask (the standard solution is the national standard solution of Li, K, Na, Ca, Si, Cu, Fe, Cr, Mg, Zn, Mn, and Ga with a concentration of 1000 μg / ml), and prepare 5 standard solutions with different gradients (1 μg / ml, 2 μg / ml, 5 μg / ml, 10 μg / ml, and 20 μg / ml) for use.

[0039] S3. The above standard solution was tested using an inductively coupled plasma emission spectrometer to determine the wavelength, detection method and analysis line of each element; the results are shown in Table 1 below:

[0040] Table 1

[0041]

[0042]

[0043] S4, according to the wavelength, detection method and analysis line result of each element obtained in step S3, the sodium aluminate solution obtained after the neutralization treatment in step S1 is detected, the intensity of the analysis line of each element is measured, and the element content is calculated according to the following formula (II);

[0044] c=C×V1 / V2(II)

[0045] In formula (II), C represents the concentration of the standard solution, V1 represents the volume of the standard solution, and V2 represents the constant volume.

[0046] According to the above method, the determination was repeated 20 times, and the detection limits were shown in Table 2 below.

[0047] Table 2. Detection limit test results

[0048] element Detection limit ppm element Detection limit ppm Li 1.0 Fe 0.3 K 0.5 Cr 1.0 Na 0.5 Mg 1.0 Ca 0.3 Zn 0.5 Si 0.3 Mn 1.0 Cu 1.0 Ga 0.5

[0049] Take 100ml of the solution prepared in step S1, add standard solutions with a concentration of 1000μg / ml respectively: 20μl Si standard solution, 5μl Fe standard solution, 10μl Ca standard solution, 20μl Ga standard solution, 1μl Cu standard solution, 1μl Zn standard solution, and mix well. Perform the test according to the detection method of step S4, measure each spiked sample three times in parallel and take the average value, measure the spiked recovery rate and repeatability, and the spiked recovery rate is calculated by subtracting the test result of each element in the solution obtained in S1 from the test result, and dividing the difference by the known amount of standard solution added.

[0050] The measured recovery and repeatability results are shown in Table 3 below.

[0051] Table 3. Spike recovery and repeatability results

[0052] element Spiked recovery % Repeatability (RSD) % element Spiked recovery % Repeatability (RSD) % Li 96.1 0.21 Fe 98.9 0.1 K 96.4 0.18 Cr 101.2 0.03 Na 98.4 0.18 Mg 97.8 0.03 Ca 97.2 0.17 Zn 99.3. 0.16 Si 97.6 0.15 Mn 101.6 0.02 Cu 100.5 0.05 Ga 100.5 0.04

[0053] As shown in the results of Table 2 and Table 3 above, the method for determining trace elements in sodium aluminate solution provided by the present invention has low detection limits for various elements, high sensitivity, a spike recovery rate of 96-101.6%, high detection accuracy and good repeatability.

[0054] Example 2

[0055] In order to investigate the influence of the acid composition during the acidification process of the sodium aluminate solution on its detection method, the acid composition in step S1 was changed, as shown in Table 4 below, and the sodium aluminate solution was not acidified for comparison (Group 9#); according to the method provided in Example 1, the detection limit and standard deviation were determined, and the results are shown in Table 5 below.

[0056] Table 4. Composition of acids

[0057]

[0058]

[0059] Table 5. Detection limit and standard deviation results (ppm)

[0060]

[0061] As shown in the table, compared with other groups, Example 1 and Group 1# have lower detection limits, better sensitivity, low standard deviation and high accuracy. It can also be seen that the choice of acid in the acidification process of sodium aluminate solution has a certain influence on the detection limit and accuracy of the detection method.

[0062] Comparative Example 1

[0063] Another method for determining trace elements in a sodium aluminate solution is different from Example 1 in that no sodium hydroxide working reference reagent solution is added during the preparation of the standard solution in step S2.

[0064] Comparative Example 2

[0065] Another method for determining trace elements in sodium aluminate solution is different from Example 1 in that high-purity aluminum solution is not added during the preparation of the standard solution in step S2.

[0066] In order to investigate the influence of sodium salt and aluminum salt in the preparation process of standard solution, the detection limit and standard deviation were determined according to the method provided in Comparative Examples 1 and 2. It can be seen that the detection limits of Comparative Examples 1 and 2 are higher than those of Example 1, the standard deviation is large, and the sensitivity and accuracy are relatively poor. The specific results are shown in Table 6 below.

[0067] Table 6. Detection limit and standard deviation results (ppm)

[0068]

[0069] Test example

[0070] The concentration of trace elements in the sodium aluminate solution was measured according to the method provided in the above examples and comparative examples and the results are shown in Table 7 below.

[0071] Table 7. Concentration of trace elements (ppm)

[0072]

[0073] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for determining trace elements in a sodium aluminate solution, characterized in that: The following steps are involved: S1, determining the sodium hydroxide content in the sodium aluminate solution, adding acid for acidification, and testing; S2, mixing the high purity aluminum solution and the sodium hydroxide reference reagent solution, adding the standard solutions of each element to prepare a standard solution; S3, using an inductively coupled plasma emission spectrometer to detect the standard solution obtained in step S2, and determine the wavelength, detection method and analysis line of each element; S4. According to the result obtained in step S3, the sodium aluminate solution obtained after the neutralization treatment in step S1 is tested, the intensity of each element analysis line is measured, and the element content is calculated.

2. The method for measuring trace elements in sodium aluminate solution according to claim 1, characterized in that: In step S1, the acid is a combination of any one of sulfuric acid and nitric acid and hydrochloric acid in a volume ratio of (1-3):

1.

3. The method for measuring trace elements in sodium aluminate solution according to claim 1, characterized in that: In step S1, the amount of the acid used is: based on the sodium hydroxide content in the sodium aluminate solution, the mass volume ratio of sodium hydroxide to acid is 1: (10-30) g / ml.

4. The method for measuring trace elements in sodium aluminate solution according to claim 1, characterized in that: In step S2, the preparation step of the standard solution includes: (1) Take 1.8722 g of high-purity aluminum, add 20 ml of concentrated sulfuric acid or concentrated nitric acid, heat until completely dissolved, add water to make the volume 100 ml, and obtain a high-purity aluminum solution; (2) dissolving 2.7526 g of sodium hydroxide working standard reagent in water, and adding water to make the volume to 100 ml to obtain a sodium hydroxide standard reagent solution; (3) Accurately pipette high-purity aluminum solution and sodium hydroxide standard reagent solution, mix them, add the standard solutions of each element into a volumetric flask, and prepare 5 standard solutions with different gradients for use.

5. The method for measuring trace elements in sodium aluminate solution according to claim 4, characterized in that: In step (1), the mass volume ratio of the high purity aluminum to concentrated sulfuric acid or concentrated nitric acid is 1: (20-50) g / ml.

6. The method for determining trace elements in sodium aluminate solution according to claim 4, characterized in that: In step (3), the standard solutions of the elements are Li, K, Na, Ca, Si, Fe, Cr, Mg, Zn, Mn, and Ga standard solutions; the concentration of the standard solutions is 1000 μg / ml.

7. The method for determining trace elements in sodium aluminate solution according to claim 4, characterized in that: In step (3), the volume ratio of the high purity aluminum solution to the sodium hydroxide reference reagent solution is 1:(1-2).

8. The method for determining trace elements in a sodium aluminate solution according to claim 4, characterized in that: In step (3), the concentrations of the five standard solutions with different gradients are: 1 μg / ml, 2 μg / ml, 5 μg / ml, 10 μg / ml, and 20 μg / ml, respectively.

9. The method for determining trace elements in a sodium aluminate solution according to claim 1, wherein: In step S4, the calculated element content c is calculated according to the following formula (I): c=C×V1 / V2(I) In formula (I), C represents the concentration of the standard solution, V1 represents the volume of the standard solution, and V2 represents the constant volume.

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