Automatic potentiometric titration detection method for analyzing content of sodium carbonate in alkali powder

Abstract

The invention discloses an automatic potentiometric titration detection method for analyzing the content of sodium carbonate in alkali powder. The reaction principle in the process of detecting the content of sodium carbonate in the alkali powder is an acid-base neutralization reaction, the pH value in the reaction cup can change along with the continuous reaction process, the corresponding pH value is identified through the potential change of the electrode on the automatic potentiometric titrator to indicate the titration end point, and the content of sodium carbonate in the alkali powder is detected and analyzed. According to the detection result, the poor accuracy of the manual titration detection result is eliminated, the operation is simple, the reagent consumption is low, the detection efficiency is high, and the detection analysis of the effective calcium oxide content in the lime can be accurately and quickly realized.

Description

Technical Field

[0001] The invention belongs to the technical field of analysis methods, and particularly relates to an automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the application, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Alkali powder (sodium hydroxide) is one of the raw materials used in the preparation of raw material slurry during alumina production. Industrial alkali powder requires a sodium carbonate mass fraction of 0.6% or less. Currently, the determination of sodium hydroxide and sodium carbonate content in industrial sodium hydroxide is generally based on the GB / T4348.1-2013 standard. This manual titration method is cumbersome, and the operator's proficiency significantly affects the accuracy of the test results. Summary of the Invention

[0004] In view of the technical problems of the manual titration analysis method used in the existing detection of sodium carbonate content in alkali powder, such as poor detection result accuracy, high reagent consumption, low detection efficiency, and cumbersome operation process, the present invention provides an automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: An automatic potentiometric titration method for analyzing the sodium carbonate content in alkali powder is provided. The method is based on the fact that the electrode potential on the automatic potentiometric titrator changes with the environment in the reaction cup to indicate the titration end point. The method is based on the automatic potentiometric titrator and includes the following steps: S1, create a dynamic titration method in the titration software; S2, determine the command parameters, which include: In the Stir command, the parameters include speed and time; In the EQP command, parameters include titrant type and concentration, electrode, and threshold; further, the EQP command also includes maximum volume and EQP points.

[0006] In the calculation command, the parameters include: in the calculation R1 Consumption command, set the formula R1=VEQ1 and the constant C to 1; in the calculation R2 Consumption command, set the formula R2=VEQ2 and the constant C to 1; R1 command VEQ1 is the equivalent volume of titrant consumed when the equivalence point is reached for the first time, and R2 command VEQ2 is the equivalent volume of titrant consumed when the equivalence point is reached for the second time; in the R3 Content command, set the formula R3=(Q1+Q2)*C / m and the constant C=M / (10*z).

[0007] Furthermore, the command parameters also include a flushing command to set the number of flushing times, volume per cycle, and time.

[0008] S3, sample detection: Based on the command parameters determined in step S2, the content of sodium carbonate in the sample is analyzed and detected.

[0009] Preferably, in step S1, the titration software is Mettler LabX Client titration software.

[0010] Preferably, in step S1, the dynamic titration method is the DET method.

[0011] Preferably, in step S2, the speed in the Stir command in the titration method is adjusted to 60%, and the time is 60s; in the EQP command, the titrant is selected as HCl:2mol / L, the electrode is DG115-SC1, the threshold is 1pH / ml, the maximum volume is set to 20ml, and the EQP point number is 2.

[0012] Preferably, step S3 includes calling a dynamic titration method that has been adjusted in the software, weighing the alkali powder sample on an electronic balance, and the system automatically uploading the sample weight; performing titration, and automatically uploading the result to the system after the titration is completed.

[0013] Furthermore, step S3 includes: weighing 1.500g to 2.000g of alkali powder sample into a 100mL dry reaction cup; placing the reaction cup on the sample rack of the automatic potentiometric titrator; calling the dynamic titration method that has been adjusted in the software, and selecting the sample weight transmitted by the electronic balance; performing the titration, and after the titration is completed, the results are automatically uploaded to the system.

[0014] Furthermore, step S3 includes the following stages: 1) Initial stage of titration: The starting point of the curve corresponds to the potential value before the titration begins; in the first reaction stage, as the titrant is continuously added, the strong base is completely neutralized and the titrant begins to react with the sodium carbonate; the first equivalence point is reached when all the sodium carbonate is converted into sodium bicarbonate, corresponding to the turning point of the curve where the potential changes sharply; 2) Second reaction stage: After the first equivalence point, the titrant is continued to be added, and the sodium bicarbonate further reacts with the titrant to produce carbon dioxide and water; Second equivalence point: When all the sodium bicarbonate reacts completely, the second equivalence point is reached, which is the turning point of the second sharp change in potential on the curve; By analyzing the titrant volume corresponding to the two equivalence points of the dynamic titration curve, combined with the titrant concentration and using the calculation formula, the sodium carbonate content in the alkali powder can be accurately calculated.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) According to the reaction principle of acid-base neutralization reaction in the process of detecting the sodium carbonate content in alkali powder, the pH value in the reaction cup will change as the reaction process continues. The corresponding pH value is identified by the change of electrode potential on the automatic potentiometric titrator to indicate the titration end point, thereby realizing the detection and analysis of the sodium carbonate content in alkali powder.

[0016] (2) The detection results of the present invention eliminate the poor accuracy of the detection results of manual titration, and are simple to operate, low in reagent consumption, high in detection efficiency, precise quantification, good in repeatability, and the results are independent of the operator; and can accurately and quickly realize the detection and analysis of the sodium carbonate content in alkali powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 Schematic diagram of sample analysis parameters.

[0019] Figure 2 Schematic diagram for setting the Stir parameter.

[0020] Figure 3 Schematic diagram for Titration parameter settings.

[0021] Figure 4 Schematic diagram for setting parameters of calculation formula R1.

[0022] Figure 5 Schematic diagram for setting parameters of calculation formula R2.

[0023] Figure 6 Schematic diagram for setting parameters of calculation formula R3.

[0024] Figure 7 Set up schematic for flush command parameters.

[0025] Figure 8 Schematic diagram for setting parameters for the dip command.

[0026] Figure 9 Schematic diagram for setting parameters for the electrode hold command.

[0027] Figure 10 This is a report diagram.

[0028] Figure 11 Schematic diagram of dynamic titration curve.

[0029] Figure 12 This is a comparison chart of the absolute difference between automatic potentiometric titration results and manual titration results. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] The present invention provides an automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder. The detection method is based on the fact that the potential of an electrode on an automatic potentiometric titrator changes with the environment in a reaction cup to indicate the titration end point. The method selectively creates a dynamic titration method (DET method) in Mettler LabX Client titration software, confirms optimal test parameters by continuously adjusting parameters in a Stir command, an EQP command, and a Calculate command in the method, weighs an alkali powder sample to collect experimental results, and aims to ensure that the absolute value of the error between the collected results and the manual measurement results is ≤0.2%. The optimal parameters in the command are selected, and the content is analyzed and detected. According to the reaction principle of the sodium carbonate content detection process in the alkali powder, which is an acid-base neutralization reaction, the pH value in the reaction cup changes with the continuation of the reaction process. The corresponding pH value indicating the titration end point is accurately identified by the change in the potential of the electrode on the automatic potentiometric titrator, thereby realizing automatic potentiometric titration instead of manual titration to detect and analyze the sodium carbonate content in the alkali powder, and obtaining a result consistent with the manual titration result.

[0033] Example 1, Automatic Potentiometric Titration Detection Method for Analysis of Sodium Carbonate Content in Alkali Powder During the potentiometric titration process, the potential of the solution will change with the change of hydrogen ion concentration. When all carbonate ions are converted into bicarbonate ions, it is the first equivalence point. Continue titration, the bicarbonate ions react completely with the hydrogen ions, and the potential shows a larger jump, which is the second equivalence point. The sodium carbonate content is calculated based on the volume of hydrochloric acid consumed at the two equivalence points.

[0034] 1. Preparation of reagents: Hydrochloric acid standard titration solution: c(HCl)=2.0000mol / L.

[0035] 2. Instruments and Equipment Mettler T9 potentiometric titrator.

[0036] Electronic balance: sensitivity 0.0001g.

[0037] Beaker: 100mL.

[0038] 3. Analysis Steps 3.1 Weigh approximately 1.500g to 2.000g of sample into a 100mL dry cuvette. Place the cuvette on the sample rack of the T9 automatic potentiometric titrator. Enter the sample number and sample weight in the analysis software, click OK, and the instrument will automatically analyze.

[0039] 3.2 The test results are displayed after completion.

[0040] 3.3 Two parallel samples should be weighed for measurement during analysis, and the average value should be taken.

[0041] 4 Allowable difference: The absolute value difference of parallel determination results shall not exceed the following values: Sodium carbonate (%): ≤0.05%.

[0042] The specific steps of the detection method provided by the present invention are as follows: like Figures 1 to 9 As shown, it includes the following settings or operations: In the first step, a dynamic titration method (DET method) is optionally created in the METTLER TOLEDO LabX Client titration software.

[0043] In the second step, adjust the speed in the Stir command within the titration method to 60% and the time to 60s. In the EQP command, select the titrant (HCl: 2mol / L), the electrode to be DG115-SC1, the threshold to be 1pH / ml, the maximum volume to be set to 20ml, and the number of EQP points to be 2. In the Calculate R1 (Consumption) command, set the formula R1=VEQ1 (i.e., the equivalent volume of titrant consumed when the equivalence point is reached for the first time) and the constant C to 1. In the Calculate R2 (Consumption) command, set the formula R2=VEQ2 (i.e., the equivalent volume of titrant consumed when the equivalence point is reached for the second time). =The equivalent volume of titrant consumed at the equivalence point) constant C is 1; in the R3 (content) command, set the formula R3=(Q1+Q2)*C / m and the constant C=M / (10*z) (where: Q1 is the titrant volume consumed at the first equivalence point; Q2 is the titrant volume consumed at the second equivalence point; C is a constant; M is the molecular weight of sodium carbonate; z represents the stoichiometric ratio of the reaction between hydrochloric acid and sodium carbonate, 1 sodium carbonate reacts with 2 hydrochloric acids, so z=2); in the flush command, set the number of flushes to 1, the volume of each cycle to 20 ml, and the time to 20 seconds.

[0044] The above parameters are the optimal conditions obtained from multiple tests. After adjusting the parameters for further tests, we found that: if the stirring speed is too slow, the reaction will be uneven, and if it is too fast, it will easily splash; if the titration time is too short, the reaction will be incomplete, and if the titration time is too long, side reactions will occur; if the threshold is too high, the determination of the titration endpoint will be delayed; if the threshold is too low, the titration endpoint will be determined too early.

[0045] The third step is to weigh about 1.500 g to 2.000 g of alkali powder sample into a 100 mL dry reaction cup.

[0046] Step 4: Place the reaction cup on the sample rack of the T9 automatic potentiometric titrator.

[0047] Step 5: Call the dynamic titration method that has been adjusted in the software, select the sample weight transmitted by the electronic balance, and the system will automatically upload the sample weight.

[0048] Step 6: Perform titration. Once titration is complete, the results are automatically uploaded to the system.

[0049] Dynamic titration curve Figure 11 As shown, we can see that: 1) Initial stage of titration: The starting point of the curve corresponds to the potential value before the titration begins; in the first reaction stage, as the titrant is continuously added, the strong base is completely neutralized and the titrant begins to react with the sodium carbonate; the first equivalence point is reached when all the sodium carbonate is converted into sodium bicarbonate, corresponding to the turning point of the curve where the potential changes sharply; 2) Second reaction stage: After the first equivalence point, the titrant is continued to be added, and the sodium bicarbonate further reacts with the titrant to produce carbon dioxide and water; Second equivalence point: When all the sodium bicarbonate reacts completely, the second equivalence point is reached, which is the turning point of the second sharp change in potential on the curve.

[0050] By analyzing the titrant volume corresponding to the two equivalence points of the dynamic titration curve, combined with the titrant concentration and using the calculation formula, the sodium carbonate content in the alkali powder can be accurately calculated.

[0051] Comparative Example 1, manual titration method: Weigh 2.0000 g (accurate to 0.01 g) of sample into a 250 mL conical flask. Add 50 mL of water and shake until dissolved. Add 10 drops of a mixed bromocresol green-methyl red indicator solution and titrate with 1 mol / L hydrochloric acid standard solution until the solution turns from green to dark red. Boil for 2 minutes, cool, and continue titrating until a dark red color is obtained. This is the endpoint.

[0052] The same sample was analyzed and tested by manual titration and automatic potentiometric titration respectively. The absolute difference of the test results was compared to verify whether the absolute difference between the automatic potentiometric titration result and the manual titration result was within the required range. The absolute difference comparison is shown in Figure 12 .

[0053] Depend on Figure 12 It can be seen that the absolute difference between the automatic potentiometric titration result and the manual titration result is in line with the required range, and the operation is simple, the reagent consumption is small, and the detection efficiency is high, which can replace the manual titration method.

[0054] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An automatic potentiometric titration method for analyzing the sodium carbonate content in alkali powder, characterized in that: The steps include: S1, create a dynamic titration method in the titration software; S2, determine the command parameters, which include: In the Stir command, the parameters include speed and time; In the EQP command, the parameters include titrant type and concentration, electrode, and threshold value; In the calculation command, the parameters include: in the calculation R1 Consumption command, set the formula R1=VEQ1 and the constant C to 1; in the calculation R2 Consumption command, set the formula R2=VEQ2 and the constant C to 1; where R1 command VEQ1 is the equivalent volume of titrant consumed when the equivalence point is reached for the first time, and R2 command VEQ2 is the equivalent volume of titrant consumed when the equivalence point is reached for the second time; In the R3 content command, set the formula R3 = (Q1 + Q2) * C / m, where the constant C = M / (10 * z); Q1 is the volume of titrant consumed at the first equivalence point, Q2 is the volume of titrant consumed at the second equivalence point, C is a constant, M is the molecular weight of sodium carbonate, and z represents the stoichiometric ratio of the reaction between hydrochloric acid and sodium carbonate, where z = 2. S3, sample detection: Based on the command parameters determined in step S2, the content of sodium carbonate in the sample is analyzed and detected.

2. The automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder according to claim 1, wherein In step S1, the titration software is Mettler LabX Client titration software.

3. The automatic potentiometric titration detection method for analyzing sodium carbonate content in alkali powder according to claim 1, wherein In step S1, the dynamic titration method is the DET method.

4. The automatic potentiometric titration detection method for analyzing sodium carbonate content in alkali powder according to claim 1, wherein In step S2, the command parameters also include maximum volume and EQP points.

5. The automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder according to claim 1, wherein In step S2, the command parameters also include a flushing command to set the number of flushing times, volume per cycle, and time.

6. The automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder according to claim 1, wherein In step S2, the speed in the Stir command within the titration method is adjusted to 60%, and the duration is 60 seconds. In the EQP command, the titrant is selected as HCl:2 mol / L, the electrode is DG115-SC1, the threshold is set to 1 pH / ml, the maximum volume is set to 20 ml, and the number of EQP points is set to 2.

7. The automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder according to claim 1, wherein In step S3, the dynamic titration method that has been adjusted in the software is called, the alkali powder sample is weighed on the electronic balance, and the system automatically uploads the sample weight; the titration is performed, and after the titration is completed, the result is automatically uploaded to the system.

8. The automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder according to claim 1, wherein Step S3 includes: weighing 1.500g to 2.000g of alkali powder sample into a 100mL dry reaction cup; placing the reaction cup on the sample rack of the automatic potentiometric titrator; calling the dynamic titration method that has been adjusted in the software and selecting the sample weight transmitted by the electronic balance; performing the titration, and when the titration is completed, the results are automatically uploaded to the system.

9. The automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder according to claim 1, wherein Step S3 includes the following stages: 1) Initial stage of titration: The starting point of the curve corresponds to the potential value before the titration begins; in the first reaction stage, as the titrant is continuously added, the strong base is completely neutralized and the titrant begins to react with the sodium carbonate; the first equivalence point is reached when all the sodium carbonate is converted into sodium bicarbonate, corresponding to the turning point of the curve where the potential changes sharply; 2) Second reaction stage: After the first equivalence point, the titrant is continued to be added, and the sodium bicarbonate further reacts with the titrant to produce carbon dioxide and water; Second equivalence point: When all the sodium bicarbonate reacts completely, the second equivalence point is reached, which is the turning point of the second sharp change in potential on the curve.

10. The automatic potentiometric titration detection method for analyzing the sodium carbonate content in alkali powder according to claim 1, characterized in that: In step S3, the sodium carbonate content in the alkali powder is calculated by analyzing the titrant volumes corresponding to the two equivalence points of the dynamic titration curve, combining the titrant concentration, and using a calculation formula.

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