A method for detecting ammonia nitrogen content in alkaline vanadium-containing solution

Abstract

The present invention provides a method for detecting the ammonia nitrogen content in an alkaline vanadium-containing solution. The method comprises: (1) pre-treating the vanadium-containing solution to obtain a colorless vanadium-containing solution treatment solution, wherein the pre-treatment comprises adjusting the pH value of the vanadium-containing solution to 8-9 and heating the solution at 40-65 degrees Celsius; (2) filtering the vanadium-containing solution treatment solution to obtain a purified solution, and selectively diluting the purified solution according to the concentration of the purified solution to obtain a diluted solution; (3) uniformly mixing the solution obtained in step (2) with ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution, and Nessler's reagent, using ammonia-free water as a reference reagent, and measuring the absorbance of the mixed solution at a wavelength of 420 nm; and calculating the ammonia nitrogen content in the vanadium-containing solution based on the absorbance value and a standard curve. The method can achieve rapid and accurate analysis of the ammonia nitrogen content in the vanadium-containing solution by Nessler's reagent colorimetry.

Description

Technical Field

[0001] The present invention relates to the technical field of analysis and detection, and in particular to a method for detecting the ammonia nitrogen content in an alkaline vanadium-containing solution. Background Art

[0002] With the development of energy storage industry, vanadium battery plays an increasingly important role in the energy storage industry. The preparation technology of high-purity V2O5, the main raw material of vanadium battery, is generally to use crude V2O5 or finished ammonium polyvanadate (or ammonium metavanadate) to dissolve in alkali and then remove impurities to obtain pure vanadium-rich solution, and then precipitate vanadium with ammonium salt, and obtain high-purity V2O5 after calcination. During the dissolution of ammonium polyvanadate (or ammonium metavanadate), NH4 + It will have a great impact on the subsequent impurity removal. At the same time, in the process of using ammonium salt precipitation method, NH4 + Most of it is transferred to vanadium precipitation wastewater and generates a large amount of production wastewater, the ammonia nitrogen concentration of which can reach more than 3000 mg / L.

[0003] Conventional ammonium ion detection methods use distillation or ion chromatography. However, ion chromatography can affect the determination of trace ammonium ions due to high vanadium ion concentrations and the presence of vanadium ions of varying valences in vanadium-containing solutions. Distillation can eliminate the effects of vanadium ion concentration and color on ammonia nitrogen content, but it is more complex and consumes more electricity.

[0004] The analysis and detection of ammonia nitrogen content in vanadium-containing solutions still need further improvement. Summary of the Invention

[0005] To address the above technical problems, the present invention has developed an analytical method suitable for determining the ammonia nitrogen content in vanadium-containing solutions using the Nessler reagent method, thereby enabling accurate and efficient analysis of the ammonia nitrogen content in vanadium-containing solutions. The present invention provides a method for detecting the ammonia nitrogen content in vanadium-containing solutions, which is suitable for detecting the ammonia nitrogen content in vanadium-containing solutions under alkaline conditions. The method provided by the present invention utilizes the colorless nature of vanadium (V) in alkaline solutions, allowing direct detection of the ammonia nitrogen content without removing the vanadium from the vanadium-containing solution. Furthermore, the method utilizes Nessler's reagent colorimetry to achieve rapid and accurate analysis of the ammonia nitrogen content in the vanadium-containing solution.

[0006] Specifically, the present invention provides the following technical solutions:

[0007] In a first aspect of the present invention, a method for detecting the ammonia nitrogen content in a vanadium-containing solution is provided, comprising:

[0008] (1) pre-treating the vanadium-containing solution to obtain a colorless vanadium-containing solution treatment solution, wherein the pre-treatment comprises adjusting the pH value of the vanadium-containing solution to 8 to 9 and heating the solution at 40 to 65 degrees Celsius;

[0009] (2) filtering the vanadium-containing solution treatment liquid to obtain a purified liquid, and selectively diluting the purified liquid to obtain a diluted liquid;

[0010] (3) uniformly mixing the solution obtained in step (2) with ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution, and Nessler's reagent, using ammonia-free water as a reference reagent, and measuring the absorbance of the solution at a wavelength of 420 nm;

[0011] Calculating the ammonia nitrogen content in the vanadium-containing solution to be tested based on the absorbance value and in combination with a standard curve;

[0012] The standard curve is obtained by uniformly mixing ammonia nitrogen standard solution, ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution and Nessler's reagent, standing, using ammonia-free water as a reference reagent, and measuring the absorbance at a wavelength of 420 nm.

[0013] The method provided by the present invention utilizes the colorless nature of vanadium (V) in alkaline solutions. By adjusting the pH of the vanadium-containing solution to 8-9, the solution becomes colorless, and then measuring the absorbance of the solution using Nessler colorimetry, it is possible to directly detect the ammonia nitrogen content in the vanadium-containing solution without removing the vanadium from the solution. The method provided by the present invention converts the colored vanadium-containing solution to colorless by adjusting the pH and heating it at elevated temperatures. Then, using Nessler's reagent colorimetry, the ammonia nitrogen content in the vanadium-containing solution can be rapidly and accurately analyzed.

[0014] According to an embodiment of the present invention, the above-mentioned method for detecting the ammonia nitrogen content in the vanadium-containing solution may further include the following technical features:

[0015] According to an embodiment of the present invention, the time of the heating treatment in step (1) does not exceed 20 minutes.

[0016] According to an embodiment of the present invention, the filtration treatment in step (2) is performed using a 0.22 micron filter membrane.

[0017] According to an embodiment of the present invention, the ammonia nitrogen standard solution is prepared by dissolving ammonium chloride dried to a constant weight in pure water and then further diluting the solution. The mass volume ratio of the ammonium chloride to the pure water is 0.382 g:100 ml.

[0018] According to an embodiment of the present invention, the concentration of the sodium hydroxide solution is 200-400 g / L, and the concentration of the potassium sodium tartrate solution is 400-600 g / L.

[0019] According to an embodiment of the present invention, the standard curve is prepared by the following method:

[0020] Place various volumes of ammonia nitrogen standard solution in a 100ml volumetric flask and add ammonia-free water to approximately 75ml. Continue adding 2ml of potassium sodium tartrate solution, 3ml of sodium hydroxide solution, and 2ml of Nessler's reagent. Dilute to the mark with ammonia-free water and shake well. After standing for 10 minutes, measure the absorbance at 420nm using ammonia-free water as a reference to generate a standard curve.

[0021] According to an embodiment of the present invention, the ammonia nitrogen standard working solution is prepared by dissolving 0.382 g of ammonium chloride dried to constant weight in 100 ml of pure water and then diluting it 100 times. The volumes of the ammonia nitrogen standard working solution are 1 ml, 5 ml, 10 ml, 15 ml, and 20 ml, respectively.

[0022] According to an embodiment of the present invention, the concentration of the sodium hydroxide solution is 320 g / L, and the concentration of the potassium sodium tartrate solution is 500 g / L.

[0023] According to an embodiment of the present invention, the concentration range of the standard curve is 0.1-2 mg / L.

[0024] In a second aspect of the present invention, a method for detecting the ammonia nitrogen content in a vanadium-containing solution is provided, comprising:

[0025] (1) pre-treating the vanadium-containing solution to obtain a colorless vanadium-containing solution treatment solution, wherein the pre-treatment comprises adjusting the pH value of the vanadium-containing solution to 8-9 and heating the solution at 40-65 degrees Celsius for no more than 20 minutes;

[0026] (2) filtering the vanadium-containing solution treatment liquid to obtain a purified liquid;

[0027] (3) diluting the purified liquid to obtain a diluted liquid;

[0028] (4) The diluent is mixed evenly with ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution, and Nessler's reagent, and the absorbance of the solution is measured at a wavelength of 420 nm using ammonia-free water as a reference reagent;

[0029] Calculating the ammonia nitrogen content in the vanadium-containing solution to be tested based on the absorbance value and in combination with a standard curve;

[0030] The standard curve is obtained by uniformly mixing ammonia nitrogen standard solution, ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution and Nessler's reagent, and then allowing the mixture to stand. The ammonia-free water is used as a reference reagent, and the absorbance is measured at a wavelength of 420 nm. The concentration of the standard curve is 0.1 to 2 mg / L.

[0031] The concentration of the sodium hydroxide solution is 320 g / L, and the concentration of the potassium sodium tartrate solution is 500 g / L.

[0032] The method for detecting the ammonia nitrogen content in a vanadium-containing solution provided by the present invention has at least the following beneficial effects:

[0033] (1) The method provided by the present invention has a wider detection range. The method provided by the present invention can achieve a wider detection range by diluting the vanadium-containing solution.

[0034] (2) The method provided by the present invention is safe and convenient. The method provided by the present invention is simple and convenient, involving basic operations such as weighing, heating, dilution, and absorbance measurement. These operations are simple, non-hazardous, easy to operate, and easy to master.

[0035] (3) The method provided by the present invention has accurate results. The present invention uses Nessler's reagent for color development and then uses a spectrophotometer to measure absorbance, which is not only fast but also provides accurate and reliable data.

[0036] (4) The method provided by the present invention is fast and efficient. Once the standard curve is drawn, only the sample to be tested needs to be diluted and injected, and a single sample can be completed within 10 minutes.

[0037] (5) The method provided by the present invention can save reagents. The samples prepared by the present invention can be directly tested without pH adjustment, and only a small amount of reagents is needed for subsequent masking and color development. Compared with the distillation method that uses a large amount of high-concentration alkali solution to neutralize concentrated sulfuric acid, which is more expensive, the method provided by the present invention is very low-cost. DETAILED DESCRIPTION

[0038] The following describes in detail embodiments of the present invention. The embodiments are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0039] The present invention provides a method for detecting the ammonia nitrogen content in a vanadium-containing solution, comprising:

[0040] (1) Perform appropriate pretreatment according to the state of the vanadium-containing solution to be tested to obtain a colorless vanadium-containing solution treatment solution.

[0041] The vanadium-containing solution is pretreated by adjusting its pH to 8-9. A sample is placed in a 10ml centrifuge tube and sealed and heated at 40-65°C to fade its color. According to specific embodiments, the heating time should be controlled within 20 minutes (according to a preferred embodiment, the heating time is 5-10 minutes at 40-65°C). Excessive heating time can lead to inaccurate test results.

[0042] By adjusting the pH value, vanadium (V) becomes pentavalent in alkaline solutions, and the solution becomes colorless, resulting in a colorless vanadium-containing solution treatment liquid. During the research process, it was found that if the pH value is not properly controlled, ammonia will easily volatilize, affecting the accuracy of the test results. Therefore, it is necessary to adjust the pH value of the vanadium-containing solution to 8-9 through pretreatment. During the experiment, it is imperative to ensure that the vanadium-containing solution treatment liquid is colorless. Heating treatment can effectively ensure this. The heating temperature should not be too high or too low. If it is too low, the vanadium-containing solution treatment liquid will not be colorless and may still have a faint color, affecting the subsequent absorbance measurement and thus affecting the accuracy of the test results. If it is too high, ammonia will easily volatilize, affecting the accuracy of the test results.

[0043] (2) filtering the vanadium-containing solution treatment liquid to obtain a purified liquid;

[0044] The filtration process can be performed using a 0.22 micron filter membrane, for example, a 0.22 micron PES filter head.

[0045] (3) diluting the purified liquid to obtain a diluted liquid;

[0046] For example, the purification solution can be diluted with distilled water to make NH 4+ The concentration is within the detection range and a dilution solution is obtained;

[0047] (4) The dilution solution is mixed evenly with ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution, and Nessler's reagent, and the absorbance of the solution is measured at a wavelength of 420 nm using ammonia-free water as a reference reagent; based on the absorbance value, the ammonia nitrogen content in the vanadium-containing solution is calculated in combination with a standard curve.

[0048] The vanadium-containing solutions mentioned include but are not limited to homemade vanadium-containing solutions, or any other vanadium-containing solutions to be tested. These solutions can be in liquid form themselves, or can be prepared from solid form into liquid form, including but not limited to ammonium metavanadate, ammonium polyvanadate, ammonium vanadate, ammonium sulfate, vanadyl sulfate, etc.

[0049] Depending on the specific embodiment, pipette an appropriate amount of the dilution into a 100 mL volumetric flask, add ammonia-free water to 75 mL, add 2 mL of potassium sodium tartrate solution, 3 mL of sodium hydroxide solution, and 2 mL of Nessler's reagent, dilute to the mark with ammonia-free water, and shake well. After standing for 10 minutes, measure the absorbance at a wavelength of 420 nm, using ammonia-free water as a reference.

[0050] The standard curve can be drawn as follows:

[0051] Take a series of different volumes of ammonia nitrogen standard working solution in a 100ml volumetric flask, add ammonia-free water to about 75ml, continue to add 2ml of potassium sodium tartrate solution, 3ml of sodium hydroxide solution and 2ml of Nessler's reagent and dilute it to the scale with ammonia-free water, and shake well. After standing for 10 minutes, measure the absorbance at a wavelength of 420nm with water as the reference to obtain a standard curve. The ammonia nitrogen standard working solution used is prepared by dissolving 0.382g of ammonium chloride dried to constant weight in 100ml of pure water and then diluting it 100 times;

[0052] The series of ammonia nitrogen standard working solutions with different volumes are 1 ml, 5 ml, 10 ml, 15 ml and 20 ml respectively.

[0053] The sodium hydroxide solution used is 320 g / L, the potassium sodium tartrate solution is 500 g / L, and the Nessler's reagent can be prepared by yourself or purchased. The Nessler's reagent used in the examples was purchased from Hunan Huihong Reagent Co., Ltd.

[0054] The concentration range of the standard curve used is 0.1 to 2 mg / L. When measuring absorbance, a 2 cm cuvette can be used.

[0055] The technical solutions of the present invention are described below by means of specific examples. It should be noted that these examples are only intended to facilitate the understanding of those skilled in the art and should not be regarded as limiting the scope of protection of the present invention. The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0056] Example 1

[0057] In order to verify whether the pretreatment has an effect on the detection of ammonia nitrogen content, an ammonium chloride solution of about 1 mg / L (the pH of the ammonium chloride solution at this time is 6) was prepared to detect the ammonia nitrogen content, and then the pH was adjusted to 8.5 and tested again. Four groups of pH-adjusted solutions (10 ml each) were taken and sealed and heated in a 60°C water bath for 10 min, 20 min, 30 min, and 40 min to detect the ammonia nitrogen content. The results are shown in Table 1.

[0058] As shown in Table 1 below, by adjusting the solution pH and heating it, the ammonia nitrogen content decreases with increasing heating time. The error is particularly large when heating for more than 30 minutes because ammonium ions evaporate easily with increasing alkalinity and heating. However, the relative error remains within 2.5% within 20 minutes of heating. Adjusting the pH to 8.5 and heating for less than 10 minutes has minimal impact on ammonia nitrogen detection.

[0059] Table 1 Test results

[0060] Ammonia nitrogen content (g / L) pH = 6 1.0079 pH=8.5 1.0066 pH 8.5, heating for 10 minutes 1.0009 pH 8.5, heating for 20 minutes 0.9865 pH 8.5, heating for 30 minutes 0.9134 pH 8.5, heating for 40 minutes 0.8456

[0061] Example 2

[0062] Example 2 The method provided by the present invention was used to determine the ammonia nitrogen content in an ammonia nitrogen simulation solution prepared with distilled water, wherein the ammonia nitrogen concentration in the ammonia nitrogen simulation solution was 1 mg / L, and the total vanadium concentration in the ammonia nitrogen simulation solution was set to 30, 50, and 90 g / L (calculated as V2O5), respectively. The results are shown in Table 2 below. The results show that the vanadium concentration does not affect the detection of the ammonia nitrogen content in the solution, and the relative error does not exceed 3%.

[0063] Table 2 Test results

[0064]

[0065] Example 3

[0066] Example 3 The ammonia nitrogen content in a vanadium-containing solution prepared with 98% purity ammonium metavanadate was measured using the method provided by the present invention. 18 g of 98% purity ammonium metavanadate raw material was dissolved in 100 ml of 84 g / L NaOH solution. + Ammonia gas is easily generated and released in high alkalinity conditions. Therefore, after heating at 90°C for one hour and then cooling, a fixed amount of ammonium chloride was added to verify the accuracy of the experiment. After removing ammonia at 90°C for one hour, the ammonia nitrogen content measured using this method was 0.22 g / L. Ammonium chloride was added at room temperature to adjust the ammonia nitrogen content of the solution to 1.22 g / L, 2.22 g / L, 3.22 g / L, and 5.22 g / L, respectively. The results showed a maximum error of no more than 3%.

[0067] Table 3 Test results

[0068] Theoretical ammonia nitrogen concentration (g / L) Measured ammonia nitrogen concentration (g / L) Relative error 1.22 1.20 1.6％ 2.22 2.19 1.4％ 3.22 3.18 1.2％ 5.22 5.10 2.3％

[0069] Example 4

[0070] The vanadium-containing solution used for testing in Example 4 was taken from the experimental group in which the heating time affected the ammonia nitrogen content during the experimental process of Example 3. 18g of 98% pure ammonium metavanadate raw material was dissolved in 100ml of 84g / L NaOH solution. The solution was then divided into four groups of experiments, with samples taken after heating for 0 min, 20 min, 40 min, and 60 min, respectively. Ammonia nitrogen content was detected according to the method of the present invention and the distillation method (the distillation method detects ammonia nitrogen content by releasing the ammonia nitrogen in the solution through distillation, then absorbing the released ammonia nitrogen with an absorbent such as boric acid solution, and finally measuring the absorbed ammonia nitrogen amount by titration or colorimetry, thereby calculating the ammonia nitrogen content in the original solution). The results showed that the ammonia nitrogen content measured by the distillation method and the method of the present invention was similar, with a relative standard deviation of no more than 3%.

[0071] Table 4 Test results

[0072]

[0073]

[0074] Example 5

[0075] The vanadium-containing solution used in Example 5 was obtained from the experimental group used in Example 3 to investigate the effect of heating temperature on ammonia nitrogen content. 18 g of 98% pure ammonium metavanadate was dissolved in 100 ml of 84 g / L NaOH solution. The prepared samples were then divided into three groups for testing. The samples were reacted at 70°C, 80°C, and 90°C for 1 hour, respectively. The samples were then sampled and tested for ammonia nitrogen content using the method of the present invention and the distillation method. The results showed that the ammonia nitrogen content measured by the distillation method and the present invention were similar, with a relative standard deviation of no more than 4%.

[0076] Table 5 Test results

[0077]

[0078] Example 6

[0079] The vanadium-containing solution used in Example 6 was obtained from the experimental group used in Example 3 to investigate the effect of alkali addition on ammonia nitrogen content. 18g of 98% pure ammonium metavanadate was dissolved in 100ml of NaOH solution and reacted at 90°C for 1 hour. The experiment was divided into three groups, with NaOH concentrations of 68g / L, 74g / L, and 84g / L, respectively. Samples were taken and tested for ammonia nitrogen content using both the present method and the distillation method. The results showed that the distillation and present methods produced similar ammonia nitrogen content, with a relative standard deviation of no more than 5%.

[0080] Table 6 Test results

[0081]

[0082]

[0083] It can be seen from the above embodiments that the method provided by the present invention is simple to operate, and the results are accurate and the data are reliable.

[0084] In this specification, reference to terms such as "one embodiment," "some embodiments," "example," and "specific implementation" means that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example.

[0085] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for detecting ammonia nitrogen content in a vanadium-containing solution, characterized in that: include: (1) pre-treating the vanadium-containing solution to obtain a colorless vanadium-containing solution treatment solution, wherein the pre-treatment comprises adjusting the pH value of the vanadium-containing solution to 8.5 to 9 and heating the solution at 40 to 65 degrees Celsius for no more than 20 minutes; (2) filtering the vanadium-containing solution treatment liquid to obtain a purified liquid, and selectively diluting the purified liquid to obtain a diluted liquid; (3) uniformly mixing the solution obtained in step (2) with ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution, and Nessler's reagent, using ammonia-free water as a reference reagent, and measuring the absorbance of the solution at a wavelength of 420 nm; Based on the absorbance value and combined with the standard curve, the ammonia nitrogen content in the vanadium-containing solution to be tested is calculated; The standard curve is obtained by uniformly mixing ammonia nitrogen standard solution, ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution and Nessler's reagent, standing, using ammonia-free water as a reference reagent, and measuring the absorbance at a wavelength of 420 nm.

2. The method according to claim 1, characterized in that The filtration treatment in step (2) is performed using a 0.22 micron filter membrane.

3. The method according to claim 1, characterized in that The ammonia nitrogen standard solution is prepared by dissolving ammonium chloride dried to a constant weight in pure water and then continuously diluting the solution. The mass-to-volume ratio of the ammonium chloride to the pure water is 0.382 g:100 ml.

4. The method according to claim 1, wherein The concentration of the sodium hydroxide solution is 200-400 g / L, and the concentration of the potassium sodium tartrate solution is 400-600 g / L.

5. The method according to claim 1, wherein The standard curve was prepared by the following method: Take a series of different volumes of ammonia nitrogen standard working solution into a 100ml volumetric flask, add ammonia-free water to 75ml, continue to add 2ml of potassium sodium tartrate solution, 3ml of sodium hydroxide solution and 2ml of Nessler's reagent, dilute to the scale with ammonia-free water, shake well, let it stand for 10 minutes, and measure the absorbance at a wavelength of 420nm with ammonia-free water as a reference to obtain a standard curve.

6. The method according to claim 5, characterized in that The ammonia nitrogen standard working solution is prepared by dissolving 0.382 g of ammonium chloride dried to a constant weight in 100 ml of pure water and then diluting it 100 times. The volumes of the ammonia nitrogen standard working solution are 1 ml, 5 ml, 10 ml, 15 ml, and 20 ml, respectively.

7. The method according to claim 5, characterized in that The concentration of the sodium hydroxide solution is 320 g / L, and the concentration of the potassium sodium tartrate solution is 500 g / L.

8. The method according to claim 5, characterized in that The concentration range of the standard curve is 0.1-2 mg / L.

9. A method for detecting ammonia nitrogen content in a vanadium-containing solution, characterized in that: include: (1) pre-treating the vanadium-containing solution to obtain a colorless vanadium-containing solution treatment solution, wherein the pre-treatment comprises adjusting the pH value of the vanadium-containing solution to 8.5 to 9 and heating the solution at 40 to 65 degrees Celsius for no more than 20 minutes; (2) filtering the vanadium-containing solution treatment liquid to obtain a purified liquid; (3) diluting the purified liquid to obtain a diluted liquid; (4) The diluent is mixed evenly with ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution, and Nessler's reagent, and the absorbance of the solution is measured at a wavelength of 420 nm using ammonia-free water as a reference reagent; Calculating the ammonia nitrogen content in the vanadium-containing solution based on the absorbance value and in combination with a standard curve; The standard curve is obtained by uniformly mixing ammonia nitrogen standard solution, ammonia-free water, potassium sodium tartrate solution, sodium hydroxide solution and Nessler's reagent, and then measuring the absorbance at a wavelength of 420 nm with ammonia-free water as a reference reagent. The concentration range of the standard curve is 0.1 to 2 mg / L. The concentration of the sodium hydroxide solution is 320 g / L, and the concentration of the potassium sodium tartrate solution is 500 g / L.

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