Method for measuring vanadium content in sodium aluminate solution

Abstract

The invention relates to the technical field of analytical chemistry, in particular to a method for determining the content of vanadium in a sodium aluminate solution, and the method realizes rapid and accurate determination of vanadium in the sodium aluminate solution by optimizing a reagent system and an operation process. The method is easy and convenient to operate, low in cost and particularly suitable for quality control in the aluminum oxide production process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of analytical chemistry, and particularly relates to a method for determining the content of vanadium in a sodium aluminate solution. BACKGROUND

[0002] Vanadium is widely used in the fields of steel, chemical industry, energy, etc. At present, the methods for determining the content of vanadium mainly include instrumental analysis methods such as spectrophotometry, ICP-AES / X-ray fluorescence method, and a traditional oxidation-reduction titration method.

[0003] However, the existing determination methods have the following problems: the instrumental analysis method has high equipment cost, while the traditional titration method is complicated, is easily interfered by Cr 6+ and other oxidizing substances, and has unclear end point (such as color lag when using sodium diphenylamine sulfonate indicator), and has subjective error. In addition, the current methods often need to use toxic reagents (such as mercury salt) for determination, which does not meet the requirements of green analysis.

[0004] Therefore, it is of great significance to develop a vanadium content determination method which is rapid, strong in anti-interference, and has obvious end point. SUMMARY

[0005] In view of the above, it is necessary to provide a method for determining the content of vanadium in a sodium aluminate solution, which significantly improves the anti-interference and end point judgment accuracy by optimizing the reagent system and titration process, and is suitable for industrial process control and laboratory analysis.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is:

[0007] A method for determining the content of vanadium in a sodium aluminate solution, the method comprising the following steps:

[0008] (1) sample pretreatment: put the sodium aluminate solution into a conical flask, dilute with water, add sulfuric acid solution while shaking, until the precipitate is completely dissolved, then add sulfuric acid solution and phosphoric acid solution again, shake well, and reserve;

[0009] (2) drop potassium permanganate: drop potassium permanganate solution into the product of step (1) while shaking, until a stable red color appears, stand for 4-6 min, and reserve;

[0010] (3) urea-sodium nitrite treatment: continue to add urea solution to the product of step (2), drop sodium nitrite solution, after the red color disappears, drop 2 drops of excess, shake until small bubbles appear, and stand for 2-4 min;

[0011] (4) Calibration: pipette the potassium dichromate standard solution, place it in a conical flask, add sulfuric acid solution, phosphoric acid solution and water, drop 2-3 drops of N-phenyl o-amino benzoic acid indicator, titrate with the ferrous ammonium sulfate standard solution until the solution changes from purple red to bright yellow green as the end point, do not count the volume of the consumed ferrous ammonium sulfate standard titration solution, then add the potassium dichromate standard solution again, and titrate with the ferrous ammonium sulfate standard solution until the solution changes from purple red to bright yellow green as the end point, record the volume of the consumed ferrous ammonium sulfate standard solution as V1;

[0012] The concentration of the ferrous ammonium sulfate standard titration solution is calculated according to the following formula:

[0013] c(Fe 2+ ) = c*10 / V1;

[0014] In the formula,

[0015] c(Fe 2+ ) is the concentration of the ferrous ammonium sulfate solution, with the unit of mol / L;

[0016] c is the concentration of the potassium dichromate standard solution, with the unit of mol / L;

[0017] V1 is the volume of the consumed ferrous ammonium sulfate standard solution during titration, with the unit of mL;

[0018] (5) Ferrous ammonium sulfate titration determination: add 2-3 drops of N-phenyl o-amino benzoic acid indicator to the product of step (3), titrate with the ferrous ammonium sulfate standard solution until the purple red changes to bright yellow green as the end point; record the volume of the consumed ferrous ammonium sulfate standard solution during titration as V2;

[0019] The content of vanadium is calculated according to the following formula:

[0020] ρ(V2O5)(g / L) = c(Fe 2+ )*V2*90.94*100 / 1000;

[0021] In the formula,

[0022] c(Fe 2+ ) is the concentration of the ferrous ammonium sulfate solution calculated in step (4), with the unit of mol / L;

[0023] V2 is the volume of the consumed ferrous ammonium sulfate standard solution during titration, with the unit of mL.

[0024] In the present application, further, the water added in step (1) is 2 times the amount of the sodium aluminate solution.

[0025] Further, in the application, the sulfuric acid solution is obtained by mixing concentrated sulfuric acid with equal volume of water; and the phosphoric acid solution is obtained by mixing concentrated phosphoric acid with equal volume of water.

[0026] Further, in the application, the volume ratio of the sulfuric acid solution, the phosphoric acid solution and the sodium aluminate solution added again in step (1) is 0.5:0.5:1.

[0027] Further, in the application, the concentration of the potassium permanganate solution (2g of potassium permanganate is weighed and dissolved in 100mL of water) is 2%, the concentration of the urea solution (10g of urea is weighed and dissolved in 100mL of water) is 10%, and the concentration of the sodium nitrite solution (1g of sodium nitrite is weighed and dissolved in 100mL of water) is 1%.

[0028] Further, in the application, in step (4), the volume ratio of the potassium dichromate standard solution, the sulfuric acid solution, the phosphoric acid solution and water is 2:1:1:2.5, and when operating, half amount of the potassium dichromate standard solution is first taken and placed in a conical flask, and then the other half amount of the potassium dichromate standard solution is added dropwise.

[0029] The preparation method of the N-phenyl anthranilic acid indicator is as follows: 0.2g of N-phenyl anthranilic acid is weighed and dissolved in 100mL of ethanol (or in 0.2% of sodium carbonate solution).

[0030] The potassium dichromate standard solution, C(1 / 6K2Cr2O7=0.01mol / L): 0.4903g of reference potassium dichromate dried at 150°C to constant weight is weighed and placed in a 300mL beaker, dissolved with water, transferred into a 1000mL volumetric flask, diluted to the scale, and used after shaking.

[0031] The preparation method of the ammonium ferrous sulfate standard solution is as follows: 3.9214g of ammonium ferrous sulfate hexahydrate is weighed and dissolved in 300mL of water, 100mL of sulfuric acid solution is added, diluted to a 1000mL volumetric flask with water, and used after shaking.

[0032] The application has the following beneficial effects:

[0033] The application provides a novel method for determining the content of vanadium in a sodium aluminate solution, which comprises the following steps: pretreating a sample, treating the sample in a sulfuric acid-phosphoric acid mixed acid medium, inhibiting Fe 3+ hydrolysis, and eliminating Cr 6+Interference, then combined with potassium permanganate selective oxidation of vanadium, vanadium oxidation into pentavalent, and then through the urea and sodium nitrite synergistic elimination of excess oxidant, with N-phenyl anthranilic acid as indicator, titrated with ferrous ammonium sulfate standard solution to bright yellow green is the end point, and finally according to the consumption of ferrous ammonium sulfate standard solution, the conversion of vanadium content. The end point of the method is sharp, high accuracy, relative error <0.5%, single sample analysis time <20 min, suitable for rapid detection in production site; in addition, the method of the application is green and safe, avoiding the use of mercury salt and other toxic reagents, meeting the environmental protection requirements, its cost is low, without large instrument, reagent is easy to get and has high stability, it is worth popularizing in industrial production, has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Vanadium content determination operation flow field diagram.

[0035] Figure 2 Vanadium content determination operation flow field diagram. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned purpose, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application are described in detail below. In the following description, a lot of specific details are set forth in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the scope of the present application, therefore the present application is not limited to the specific implementation disclosed below.

[0037] Implementation example:

[0038] The embodiment provides a method for determining the vanadium content in sodium aluminate solution, which comprises the following materials and steps:

[0039] (I) reagents and materials:

[0040] (1) sulfuric acid (1+1): slowly add concentrated sulfuric acid to equal volume of water, cool and reserve.

[0041] (2) phosphoric acid (1+1): mix concentrated phosphoric acid with equal volume of water.

[0042] (3) potassium permanganate solution (2%): weigh 2g of potassium permanganate and dissolve in 100mL of water, store in a brown bottle.

[0043] (4) sodium nitrite solution (1%): weigh 1g of sodium nitrite and dissolve in 100mL of water, prepare and use immediately.

[0044] (5) urea solution (10%): weigh 10g of urea and dissolve in 100mL of water.

[0045] (6) N-phenylanthranilic acid indicator (0.2%): weigh 0.2 g of the indicator into 100 mL of ethanol.

[0046] (7) Potassium dichromate standard solution (0.01 mol / L): weigh 0.4903 g of reference potassium dichromate (150°C oven dried to constant weight), dissolve and make up to 1000 mL.

[0047] (8) Preparation of ferrous ammonium sulfate standard solution (≈0.01 mol / L): weigh 3.9214 g of (NH4)2Fe(S04)2·6H20, dissolve in 300 mL of water, add 100 mL of sulfuric acid (1+1), and make up to 1000 mL.

[0048] (B) Calibration:

[0049] The calibration flow chart of the ferrous ammonium sulfate standard solution is shown in Figure 1 , which includes the following steps:

[0050] 1) Take 10.00 mL of potassium dichromate standard solution into a conical flask, add 10 mL of sulfuric acid (1+1), 10 mL of phosphoric acid (1+1), 25 mL of water, and 2-3 drops of indicator;

[0051] 2) titrate with ferrous ammonium sulfate solution to bright yellow-green (not counting the volume);

[0052] 3) add another 10.00 mL of potassium dichromate standard solution, titrate to the end point when the solution changes from purple red to bright yellow-green, record the volume of ferrous ammonium sulfate standard solution consumed, denoted as V1 (three parallel times, with a range of ≤0.05 mL);

[0053] 4) calculate the concentration of the ferrous ammonium sulfate standard titration solution according to the following formula:

[0054] c(Fe 2+ ) = c*10 / V1;

[0055] In the formula,

[0056] c(Fe 2+ ) is the concentration of the ferrous ammonium sulfate solution, with units of mol / L;

[0057] c is the concentration of the potassium dichromate standard solution, with units of mol / L;

[0058] V1 is the volume of ferrous ammonium sulfate standard solution consumed during titration, with units of mL;

[0059] (III) Determination:

[0060] The operation flow chart for the determination of vanadium content is shown in Figure 2 , which includes the following steps:

[0061] (1) Sample pretreatment: Put the sodium aluminate solution into a conical flask, dilute with water, add sulfuric acid solution while shaking, until the precipitate is completely dissolved, then add sulfuric acid solution and phosphoric acid solution again, shake well, and reserve;

[0062] (2) Drop potassium permanganate: drop potassium permanganate solution into the product of step (1) while shaking, until a stable red color appears, stand for 5 min, and reserve;

[0063] (3) Urea-sodium nitrite treatment: continue to add urea solution to the product of step (2), drop sodium nitrite solution, until the red color disappears, then drop 2 more drops, shake until small bubbles appear, and stand for 3 min;

[0064] (4) Ammonium ferrous sulfate titration determination: add 2 drops of N-phenyl o-aminobenzoic acid indicator to the product of step (3), titrate with ammonium ferrous sulfate standard solution until the purple red color changes to bright yellow green, which is the end point; record the volume of ammonium ferrous sulfate standard solution consumed during titration as V2;

[0065] The content of vanadium is calculated according to the following formula:

[0066] ρ(V2O5)(g / L) = c(Fe 2+ )*V2*90.94*100 / 1000;

[0067] In the formula,

[0068] c(Fe 2+ ) is the concentration of the ammonium ferrous sulfate solution calibrated in step, with a unit of mol / L;

[0069] V2 is the volume of ammonium ferrous sulfate standard solution consumed during titration, with a unit of mL.

[0070] (Note: 90.94 is the molar mass conversion coefficient of V2O5).

[0071] (Four) Result calculation:

[0072] In order to illustrate the reliability of the test results of the present application, the applicant detected the vanadium content of multiple sodium aluminate solution samples, and compared the traditional ICP analysis method, calculated the error of the two, and the results are shown in Table 1:

[0073] Table 1 Comparison of the test method of the present application and the traditional method (ICP)

[0074]

[0075]

[0076] According to the test result comparison of Table 1, the data obtained by the method of the present application and the traditional icp analysis method have little error, wherein sample A and sample E are vanadium standard samples, and other samples are sodium aluminate solution samples of an alumina plant, whether the sample is a standard sample or a conventional sample, the test result obtained by the method of the present application is consistent with the existing ICP-OES result, the error is small, and the test result is reliable. The present application provides a rapid and accurate vanadium content determination method, by optimizing the reagent system and titration process, the anti-interference and end point judgment accuracy are significantly improved, and the method is suitable for industrial process control and laboratory analysis.

[0077] The above-described embodiments only express several embodiments of the present application, which are described in detail, but should not be understood as limiting the scope of the present application.

Claims

1. A method for determining the vanadium content in a sodium aluminate solution, characterized in that: The method comprises the following steps: (1) Sample pretreatment: Place sodium aluminate solution in a conical flask, dilute with water, add sulfuric acid solution while shaking until the precipitate is completely dissolved, then add sulfuric acid solution and phosphoric acid solution again, shake thoroughly, and set aside; (2) Add potassium permanganate dropwise: Add potassium permanganate solution dropwise to the product of step (1) while shaking until a stable red color appears, let it stand for 4-6 minutes, and set aside; (3) Urea-sodium nitrite treatment: Continue to add urea solution to the product of step (2), add sodium nitrite solution dropwise until the red color disappears, then add 2 drops in excess, shake until small bubbles appear, and let it stand for 2-4 minutes; (4) Calibration: Pipette potassium dichromate standard solution into a conical flask, add sulfuric acid solution, phosphoric acid solution and water, add 2-3 drops of N-phenylanthranilic acid indicator, and titrate with ammonium ferrous sulfate standard solution until the solution changes from purple-red to bright yellow-green. Ignore the volume of ammonium ferrous sulfate standard solution consumed. Then, add potassium dichromate standard solution and titrate with ammonium ferrous sulfate standard solution until the solution changes from purple-red to bright yellow-green. Record the volume of ammonium ferrous sulfate standard solution consumed as V1. Calculate the concentration of the standard titration solution of ammonium ferrous sulfate according to the following formula: c(Fe 2+ )=c*10 / V1; Where, c(Fe 2+ ) is the concentration of ammonium ferrous sulfate solution, in mol / L; c is the concentration of potassium dichromate standard solution, in mol / L; V1 is the volume of ammonium ferrous sulfate standard solution consumed during titration, in mL; (5) Ammonium ferrous sulfate titration determination: Add 2-3 drops of N-phenylated anthranilic acid indicator to the product of step (3) and titrate with ammonium ferrous sulfate standard solution until the purple-red color changes to bright yellow-green. The volume of ammonium ferrous sulfate standard solution consumed during the titration is recorded as V2. The vanadium content was calculated according to the following formula: ρ(V2O5)(g / L)=c(Fe 2+ )*V2*90.94*100 / 1000; Where, c(Fe 2+ ) is: the concentration of the ammonium ferrous sulfate solution calculated in step (4), in mol / L; V2 is the volume of ammonium ferrous sulfate standard solution consumed during titration, in mL.

2. The method according to claim 1, characterized in that The amount of water added in step (1) is twice that of the sodium aluminate solution.

3. The method according to claim 1, characterized in that The sulfuric acid solution is obtained by mixing concentrated sulfuric acid with an equal volume of water; the phosphoric acid solution is obtained by mixing concentrated phosphoric acid with an equal volume of water.

4. The method according to claim 1, wherein The volume ratio of the sulfuric acid solution, phosphoric acid solution and sodium aluminate solution added again in step (1) is 0.5:0.5:

1.

5. The method according to claim 1, characterized in that The concentration of the potassium permanganate solution is 2%, the concentration of the urea is 10%, and the concentration of the sodium nitrite solution is 1%.

6. The method according to claim 1, characterized in that In the step (4), the volume ratio of the potassium dichromate standard solution, the sulfuric acid solution, the phosphoric acid solution and the water is 2:1:1:2.

5. During the operation, firstly, half of the potassium dichromate standard solution is drawn into a conical flask, and then the other half of the potassium dichromate standard solution is added dropwise.

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