Determination method of iodine adsorption value of coal-based activated carbon

Abstract

The invention relates to the technical field of activated carbon performance determination, and in particular to a method for determining the iodine adsorption value of coal-based activated carbon. The invention relates to a test method for an iodine adsorption value less than 600 mg / g in the current standard. Since the test result of a residual concentration c=0.02 mol / L cannot be obtained when the iodine adsorption value is less than 485 mg / g, the test result is not accurate, and the smaller the iodine adsorption value is, the greater the deviation of the test value is. The invention provides a method for determining the iodine adsorption value of coal-based activated carbon, which is simple and feasible, has more accurate measurement results, and can accurately obtain the iodine adsorption value of the coal-based activated carbon when the iodine adsorption value is less than 600 mg / g, thereby ensuring the uniformity of different activated carbon iodine value test methods, eliminating errors caused by different detection methods, improving detection efficiency, and ensuring the accuracy of detection results.

Description

Technical Field

[0001] The invention relates to the technical field of activated carbon performance determination, and in particular to a method for determining the iodine adsorption value of coal-based activated carbon. Background Art

[0002] Activated carbon is a type of microcrystalline carbon that is made from carbon-containing materials through processes such as carbonization and activation. It has a black appearance, a well-developed internal pore structure, a large specific surface area, and a strong adsorption capacity. It can be divided into powdered activated carbon, granular activated carbon, molded activated carbon, and activated carbon fiber according to its appearance. Due to its special physical and chemical properties, activated carbon can be used to treat wastewater (such as oily wastewater, dye wastewater, and mercury-containing wastewater), for catalysis and loading catalysts, for supercapacitor electrodes, for hydrogen storage, and for air pollutant control (such as volatile organic compounds and other waste gas treatment).

[0003] For the control of air pollutants, activated carbon is still the first choice because of its special structure, which can absorb odors, toxic gases, etc. However, the efficiency of activated carbon is not constant. With the increase of usage time and the increase of toxic emissions, its adsorption capacity will tend to saturation, which means that a new batch of activated carbon needs to be replaced. In order to give full play to the use value of activated carbon, the iodine adsorption value of activated carbon can be measured regularly to reduce the replacement frequency, thereby saving the cost of purchasing activated carbon and the cost of disposing of waste activated carbon.

[0004] The iodine adsorption value refers to the mass of iodine adsorbed per gram of activated carbon, and is one of the indicators used to evaluate the adsorption performance of activated carbon. The currently effective national standard of the People's Republic of China, Test method for granular activated carbon from coal-Part 7: Determination of iodine number (GB / T 7702.7-2023), describes the method for determining the iodine adsorption value of granular activated carbon from coal, including principles, reagents and materials, instruments and equipment, sample preparation, determination steps, determination data processing, precision and test reports. In this standard, a distinction is made between iodine adsorption values ​​≥ 600 mg / g and iodine adsorption values ​​< 600 mg / g, and the determination steps and data processing methods of the two are different. In the determination of iodine adsorption values ​​≥ 600 mg / g, three points need to be tested and the curve is fitted. For the determination of iodine adsorption values ​​< 600 mg / g, a fixed amount of 0.7500 g of sample is weighed for testing. Regardless of the concentration of the remaining filtrate, the calculated result is used as the final iodine value. The numerical value has low accuracy and cannot accurately represent the actual iodine value.

[0005] In the existing standards, when the iodine adsorption value is less than 600 mg / g, especially when the iodine adsorption value is less than 485 mg / g, 0.7500g of activated carbon is weighed, the filtrate concentration is not within the range of 0.008 mol / L to 0.040 mol / L, and the iodine adsorption value at the residual concentration of 0.02 mol / L cannot be obtained; when 485 mg / g≤iodine adsorption value is less than 600 mg / g, 0.7500g of activated carbon is weighed, although the filtrate concentration is within the range of 0.008 mol / L to 0.040 mol / L, the iodine adsorption value at the residual concentration of 0.02 mol / L cannot be obtained. Therefore, the method provided by the current standard cannot guarantee the uniformity of the test methods for activated carbons with different iodine values, resulting in errors caused by different detection methods, and cannot guarantee the accuracy of the results of the iodine value determination of activated carbon.

[0006] The invention patent application with application number 202410912507.8 and the invention name "A method for rapid determination of iodine adsorption value of activated carbon" (hereinafter collectively referred to as prior art 1) also mentioned the shortcomings of the current standards, and specifically provided a method for rapid determination of iodine adsorption value of activated carbon, firstly making an empirical estimate of the iodine adsorption value of the sample according to the sample morphology, taking the sample mass for the first estimated test according to the estimated residual filtrate concentration of 0.02 mol / L; according to the actual concentration of the residual filtrate of the first estimated test sample and the degree of deviation of 0.02 mol / L, increasing or decreasing a certain amount of iodine adsorption value by every change of 0.001 mol / L, and performing a second estimation test, and performing parallel tests to obtain a relatively accurate estimated value of iodine adsorption of activated carbon. If the concentration of the first filtrate is not within the range of 0.008 mol / L to 0.040 mol / L, if it is higher than this range, then increase the estimated sample mass and repeat the experiment; if it is lower than this range, then reduce the estimated sample mass and repeat the experiment; until the residual filtrate concentration is close to 0.02 mol / L.

[0007] Prior art 1 mentions in the abstract that a relatively accurate estimated value of activated carbon iodine adsorption is obtained by conducting parallel tests, and in the claims, it is mentioned that the constant a is taken as 5 mg / g, and in the specification, it is mentioned that through the study of a large amount of experimental data, the change in the iodine adsorption value corresponding to each change of 0.001 mol / L from the residual filtrate concentration of 0.02 mol / L is obtained, and the degree of deviation between the residual filtrate concentration and 0.02 mol / L can be quickly found, and a relatively accurate estimated iodine adsorption value can be quickly determined, and in the embodiment, an example is given to illustrate that when the second filtrate concentration c B=0.019mol / L≈0.02mol / L, the second iodine adsorption value at this time can represent the iodine adsorption value of activated carbon. However, the test method of prior art 1 has the following defects: (1) There is no experimental data for parallel testing in the embodiment. (2) The constant a is taken as 5mg / g without explaining how it is obtained, which is not rigorous. (3) A large number of experimental data studies are only verbally explained, without detailed experimental data support, which is not convincing and cannot effectively locate the residual filtrate concentration of 0.02mol / L. It is only an approximate value without accuracy and rigor. Moreover, it has been verified by experiments that this formula is extremely inaccurate. (4) "Test Method for Coal-Based Granular Activated Carbon Part 7: Determination of Iodine Adsorption Value" (GB / T 7702.7-2023) mentions that the adsorption capacity of activated carbon for any adsorbent is related to the concentration of the adsorbent in the solution. In order to obtain the iodine adsorption value at the residual concentration of 0.02mol / L, the filtrate concentration must be in the range of 0.008 mol / L~0.040 mol / L, otherwise the sample mass needs to be adjusted. The experimental data of <600 mg / g in the prior art 1 is the iodine adsorption value corresponding to the filtrate concentration of 0.02 mol / L in Example 3. The experimental data of <600 mg / g in the "Test Method for Coal Granular Activated Carbon Part 7: Determination of Iodine Adsorption Value" (GB / T 7702.7-2023) is the iodine adsorption value corresponding to the filtrate concentration obtained by taking a fixed mass of 0.7500g carbon sample. The filtrate concentrations of the two are different, and there is a large gap in the iodine adsorption value, and the data is extremely untrue. (5) The method of the prior art 1 requires two valuation tests and at least two repetitions of the experimental process. Compared with the test method of <600 mg / g in the "Test Method for Coal Granular Activated Carbon Part 7: Determination of Iodine Adsorption Value" (GB / T 7702.7-2023), it does not save experimental time. After a large number of experimental verifications, the iodine adsorption value obtained by the prior art 1 has a particularly large error with the true value, which is not practical.

[0008] In order to improve the convenience, timeliness and accuracy of iodine adsorption value determination, it is necessary to improve the iodine adsorption value determination method for activated carbon with iodine adsorption value <600 mg / g in the standard, and obtain a unified, simple and precise test method that can accurately obtain the iodine adsorption value at the residual concentration of 0.02 mol / L. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a method for determining the iodine adsorption value of coal-based activated carbon, which is simple and feasible, has more accurate measurement results and can accurately obtain the iodine adsorption value of the residual filtrate when the concentration is 0.02 mol / L.

[0010] In order to solve the above technical problems, the technical solution of the present invention is:

[0011] The method for determining the iodine adsorption value of coal-based activated carbon is characterized by comprising the following steps:

[0012] Step 1: Estimate the mass of the sample using the following formula:

[0013] In the formula,

[0014] c1 is the concentration of the iodine standard titration solution, 0.1000 mol / L;

[0015] V1 is the volume of the iodine standard titration solution added, 50 mL;

[0016] V2 is the volume of hydrochloric acid solution added, 10 mL;

[0017] M is the molar mass of iodine, 126.9 g / mol;

[0018] E0 is the estimated iodine adsorption value of the sample, in mg / g, E0<600mg / g;

[0019] Substitute the three values ​​of c into the above formula according to 0.01mol / L, 0.02mol / L and 0.03mol / L respectively to calculate the usage mass m of the three samples, in g, which are recorded as the first sample m1, the second sample m2 and the third sample m3 respectively;

[0020] Step 2: Weigh three portions of coal-based activated carbon samples with masses of m1, m2 and m3 respectively, accurate to 0.0001g;

[0021] Step 3, put the three weighed samples into a dry, stoppered ground-mouth conical flask with a capacity of 250 ml, use a single-line pipette to transfer 10 ml of hydrochloric acid solution, add it to the stoppered ground-mouth conical flask, plug the glass stopper, shake it to soak the sample; remove the stopper, heat it on a hot plate to a slight boil for 30 seconds, and cool it to room temperature; use a single-line pipette to transfer 50 ml of iodine standard titration solution to the above-mentioned ground-mouth conical flask, immediately plug the glass stopper, oscillate on an oscillator for 15 minutes, let it stand for 5 minutes, and filter it into a dry, stoppered ground-mouth conical flask with filter paper; rinse the single-line pipette with 10-15 ml of primary filtrate; use a single-line pipette to transfer 25 ml of filtrate, place it in a conical flask, and titrate it with a sodium thiosulfate standard titration solution; when the solution is light yellow, add 1-2 ml of starch indicator solution, and titrate until the blue color of the solution disappears;

[0022] Step 4: Calculate the filtrate concentrations of the first, second and third samples according to the following formulas:

[0023] Where:

[0024] c2 is the concentration of sodium thiosulfate standard titration solution, 0.1000ml / L;

[0025] V3 is the volume of sodium thiosulfate standard titration solution consumed, in mL;

[0026] V is the volume of filtrate transferred by a single-line pipette, 25 mL;

[0027] Step 5: Calculate the adsorbed iodine amount X according to the following formula:

[0028] Where:

[0029] c1 is the concentration of the iodine standard titration solution, 0.1000 mol / L;

[0030] V1 is the volume of the added iodine standard titration solution, 50 mL;

[0031] V2 is the volume of hydrochloric acid solution added, 10 mL;

[0032] V is the volume of filtrate transferred by a single-line pipette, 25 mL;

[0033] c2 is the concentration of sodium thiosulfate standard titration solution, 0.1056 mol / L;

[0034] V3 is the volume of sodium thiosulfate standard titration solution consumed, in mL;

[0035] M is the molar mass of iodine [M(1 / 2I2)=126.9], in g / mol;

[0036] Step 6: Calculate the adsorption iodine value E according to the following formula:

[0037] Where:

[0038] X is the amount of adsorbed iodine calculated in step 5, in mg;

[0039] m is the mass of the three samples, in g;

[0040] E is the iodine adsorption value, in mg / g;

[0041] Step 7, according to the filtrate concentration c of the three samples calculated in step 4 and the corresponding adsorption iodine value E calculated in step 6, a straight line of E (ordinate) versus c (abscissa) is given on a double logarithmic coordinate, and the fitting value of the three points and the straight line is calculated by the least squares method according to the following formula;

[0042] lgE=algc+b

[0043] Where:

[0044] E is the iodine adsorption value calculated in step 6, in mg / g;

[0045] a is the slope of the fitted line;

[0046] c is the filtrate concentration calculated in step 4, in mol / L;

[0047] b is the intercept of the fitting line;

[0048] Step 8. According to the adsorption isotherm fitted in step 7, when the correlation coefficient of the fitting is not less than 0.995, the E value when the residual concentration c=0.02 mol / L is taken as the iodine adsorption value obtained by the test.

[0049] As a preferred technical solution, E0 in the step 1 is <485 mg / g.

[0050] As a preferred technical solution, the mass fraction of the hydrochloric acid solution is 5%; the preparation method of the hydrochloric acid solution, the iodine standard titration solution and the sodium thiosulfate standard titration solution is prepared in accordance with the national standard GB / T 7702.7-2023.

[0051] Due to the adoption of the above technical scheme, the beneficial effect of the present invention is: the test method when the iodine adsorption value is less than 600 mg / g is improved with reference to the test method when the iodine adsorption value is ≥600 mg / g. Since the smaller the iodine adsorption value is, the larger the sample mass calculated according to the formula in step one is. When it is large to a certain extent, when 10 mL of hydrochloric acid is added according to the method of the iodine adsorption value ≥600 mg / g in the current standard, the sample cannot be completely immersed. Therefore, the present application reduces the volume V1 of the added iodine standard titration solution by half, thereby reducing the sample mass measured according to step one by half. About, so that the hydrochloric acid can completely immerse the sample, and then the volume of the filtrate transferred by the single-marked pipette is halved and the starch indicator solution is added for titration. After the measurement data is fitted to the curve, the E value when the residual concentration c=0.02mol / L is taken as the iodine adsorption value obtained by the test. The accuracy of the iodine adsorption value measured by the method provided by the present invention is greatly improved. Compared with the invention patent with application number 202410912507.8 and the invention name "A method for rapid determination of iodine adsorption value of activated carbon", the detection method provided by this application is supported by a large amount of experimental data, and all conclusions are true and reliable. The test method is simple and feasible, the measurement results are more accurate, and the iodine adsorption value of coal-based activated carbon can be accurately obtained for iodine adsorption values ​​<600mg / g when the residual filtrate concentration is 0.02mol / L, which ensures the uniformity of different activated carbon iodine value test methods, eliminates errors caused by different detection methods, improves detection efficiency, and ensures the accuracy of detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The following drawings are intended only to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0053] Figure 1 It is a flow chart of the method for determining the iodine adsorption value of coal-based activated carbon of the present invention;

[0054] Figure 2 1 is a curve fitting and value diagram of iodine adsorption value of Example 1 of the present invention;

[0055] Figure 3 : is a curve fitting and value diagram of diiodine adsorption value of an embodiment of the present invention;

[0056] Figure 4 It is a curve fitting and value diagram of triiodine adsorption value of an embodiment of the present invention. DETAILED DESCRIPTION

[0057] The present invention is further described below in conjunction with the accompanying drawings and examples. In the following detailed description, certain exemplary embodiments of the present invention are described only by way of illustration. Needless to say, those of ordinary skill in the art will recognize that the described embodiments may be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the drawings and description are illustrative in nature and are not intended to limit the scope of protection of the claims.

[0058] Embodiment 1, as Figure 1 As shown, the test method for the estimated iodine adsorption value of 230 mg / g is as follows:

[0059] Step 1: Estimate the mass of the sample using the following formula:

[0060] In the formula,

[0061] c1 is the concentration of the self-prepared iodine standard titration solution, 0.1054 mol / L, prepared according to the national standard GB / T 7702.7-2023;

[0062] V1 is the volume of the iodine standard titration solution added, 50 mL;

[0063] V2 is the volume of hydrochloric acid solution added, 10 mL, the mass fraction of hydrochloric acid is 5%, measure 70 mL of hydrochloric acid (analytical grade as specified in GB / T622), slowly inject it into 550 mL of water and mix well;

[0064] M is the molar mass of iodine, 126.9 g / mol;

[0065] E0 is the estimated iodine adsorption value of the sample, E0=230mg / g;

[0066] Substitute the three values ​​of c into the above formula according to 0.01mol / L, 0.02mol / L and 0.03mol / L to calculate the mass m of the three samples in g, which are recorded as m1=2.5764 for the first sample, m2=2.2486 for the second sample and m3=1.9148 for the third sample;

[0067] Step 2: weigh three coal-based activated carbon samples with masses of m1=2.5764g, m2=2.2486g and m3=1.9148g respectively;

[0068] Step 3, put the three weighed samples into a dry, stoppered ground-mouth conical flask with a capacity of 250 ml, use a single-line pipette to transfer 10 ml of hydrochloric acid solution, add it to the stoppered ground-mouth conical flask, plug the glass stopper, shake it to soak the sample; remove the stopper, heat it on a hot plate to a slight boil for 30 seconds, and cool it to room temperature; use a single-line pipette to transfer 50 ml of iodine standard titration solution to the above-mentioned ground-mouth conical flask, immediately plug the glass stopper, oscillate on an oscillator for 15 minutes, let it stand for 5 minutes, and filter it into a dry, stoppered ground-mouth conical flask with filter paper; rinse the single-line pipette with 10-15 ml of primary filtrate; use a single-line pipette to transfer 25 ml of filtrate, place it in a conical flask, and titrate it with a sodium thiosulfate standard titration solution; when the solution is light yellow, add 1-2 ml of starch indicator solution, and titrate until the blue color of the solution disappears;

[0069] Step 4: Calculate the filtrate concentrations of the first, second and third samples according to the following formulas:

[0070] Where:

[0071] c2 is the concentration of the self-prepared sodium thiosulfate standard titration solution, 0.1056 ml / L, prepared in accordance with the national standard GB / T 7702.7-2023;

[0072] V is the volume of filtrate transferred by a single-line pipette, 25 mL;

[0073] V3 is the volume of sodium thiosulfate standard titration solution consumed. The volumes of sodium thiosulfate standard titration solution consumed by the filtrates of the first, second and third samples are 4.00mL, 5.11mL and 6.61mL respectively.

[0074] Step 5: Calculate the adsorbed iodine amount X according to the following formula:

[0075] Where:

[0076] c1 is the concentration of the self-prepared iodine standard titration solution, 0.1054 mol / L, prepared according to the national standard GB / T 7702.7-2023;

[0077] V1 is the volume of the added iodine standard titration solution, 50 mL;

[0078] V2 is the volume of hydrochloric acid solution added, 10 mL; the mass fraction of hydrochloric acid is 5%, measure 70 mL of hydrochloric acid (analytical grade as specified in GB / T622), slowly inject it into 550 mL of water and mix well;

[0079] V is the volume of filtrate transferred by a single-line pipette, 25 mL;

[0080] c2 is the concentration of the self-prepared sodium thiosulfate standard titration solution, 0.1056 ml / L, prepared in accordance with the national standard GB / T 7702.7-2023;

[0081] V3 is the volume of sodium thiosulfate standard titration solution consumed, in mL;

[0082] M is the molar mass of iodine [M(1 / 2I2)=126.9], in g / mol;

[0083] Step 6: Calculate the adsorption iodine value E according to the following formula:

[0084] Where:

[0085] X is the amount of adsorbed iodine calculated in step 5, in mg;

[0086] m is the mass of the three samples, in g;

[0087] E is the iodine adsorption value, in mg / g;

[0088] It was found that the adsorbed iodine amounts of the first sample, the second sample and the third sample were 210 mg / g, 224 mg / g and 238 mg / g respectively.

[0089] See Table 1 for specific test data.

[0090]

[0091] Table 1 Relevant data of three samples measured when the estimated iodine adsorption value was 230 mg / g

[0092] Step 7, according to the filtrate concentration c of the three samples calculated in step 4 and the corresponding adsorption iodine value E calculated in step 6, a straight line of E (ordinate) versus c (abscissa) is given on a double logarithmic coordinate, and the fitting value of the three points and the straight line is calculated by the least squares method according to the following formula;

[0093] lgE=algc+b

[0094] Where:

[0095] E is the iodine adsorption value calculated in step 6, in mg / g;

[0096] a is the slope of the fitted line;

[0097] c is the filtrate concentration calculated in step 4, in mol / L;

[0098] b is the intercept of the fitting line;

[0099] Fitting curve see Figure 2 ;

[0100] Step 8. According to the adsorption isotherm fitted in step 7, when the correlation coefficient of the fitting is not less than 0.995, the E value when the residual concentration c=0.02 mol / L is taken as the iodine adsorption value obtained by the test.

[0101] according to Figure 2 The iodine adsorption value obtained in Example 1 when c=0.02 mol / L is 219 mg / g.

[0102] Comparative Example 1:

[0103] The iodine adsorption values ​​measured according to the test method disclosed in the existing national standard GB / T 7702.7-2023 are shown in Table 2

[0104]

[0105] Table 2 Relevant data measured by existing standards when the estimated iodine adsorption value is 230 mg / g

[0106] Table 3 shows the relative deviation of iodine adsorption values ​​measured by the test method of the present invention and the existing standard test method.

[0107]

[0108] Table 3 Relative deviations of iodine adsorption values ​​measured by the test method of the present invention and the existing standard test method.

[0109] This shows that the iodine adsorption value obtained by the test method of the present application is obviously more accurate than that obtained by the existing standard test method.

[0110] Embodiment 2: Figure 1 As shown, the test method for estimating the iodine adsorption value of 400 mg / g is as follows:

[0111] Step 1: Estimate the mass of the sample using the following formula:

[0112] In the formula,

[0113] c1 is the concentration of the self-prepared iodine standard titration solution, 0.1054 mol / L, prepared according to the national standard GB / T 7702.7-2023;

[0114] V1 is the volume of the iodine standard titration solution added, 50 mL;

[0115] V2 is the volume of hydrochloric acid solution added, 10 mL, the mass fraction of hydrochloric acid is 5%, measure 70 mL of hydrochloric acid (analytical grade as specified in GB / T622), slowly inject it into 550 mL of water and mix well;

[0116] M is the molar mass of iodine, 126.9 g / mol;

[0117] E0 is the estimated iodine adsorption value of the sample, E0=400mg / g;

[0118] Substitute the three values ​​of c into the above formula according to 0.01mol / L, 0.02mol / L and 0.03mol / L to calculate the mass m of the three samples in g, which are recorded as m1=1.4847g for the first sample, m2=1.2944g for the second sample and m3=1.1040g for the third sample;

[0119] Step 2: weigh three portions of coal-based activated carbon samples with masses of m1=1.4847g, m2=1.2944g and m3=1.1040g respectively;

[0120] Step 3, put the three weighed samples into a dry, stoppered ground-mouth conical flask with a capacity of 250 ml, use a single-line pipette to transfer 10 ml of hydrochloric acid solution, add it to the stoppered ground-mouth conical flask, plug the glass stopper, shake it to soak the sample; remove the stopper, heat it on a hot plate to a slight boil for 30 seconds, and cool it to room temperature; use a single-line pipette to transfer 50 ml of iodine standard titration solution to the above-mentioned ground-mouth conical flask, immediately plug the glass stopper, oscillate on an oscillator for 15 minutes, let it stand for 5 minutes, and filter it into a dry, stoppered ground-mouth conical flask with filter paper; rinse the single-line pipette with 10-15 ml of primary filtrate; use a single-line pipette to transfer 25 ml of filtrate, place it in a conical flask, and titrate it with a sodium thiosulfate standard titration solution; when the solution is light yellow, add 1-2 ml of starch indicator solution, and titrate until the blue color of the solution disappears;

[0121] Step 4: Calculate the filtrate concentrations of the first, second and third samples according to the following formulas:

[0122] Where:

[0123] c2 is the concentration of the self-prepared sodium thiosulfate standard titration solution, 0.1056 ml / L, prepared in accordance with the national standard GB / T 7702.7-2023;

[0124] V is the volume of filtrate transferred by a single-line pipette, 25 mL;

[0125] V3 is the volume of sodium thiosulfate standard titration solution consumed. The volumes of sodium thiosulfate standard titration solution consumed by the filtrates of the first, second and third samples are 3.10mL, 4.45mL and 6.05mL respectively.

[0126] Step 5: Calculate the adsorbed iodine amount X according to the following formula:

[0127] Where:

[0128] c1 is the concentration of the self-prepared iodine standard titration solution, 0.1054 mol / L, prepared according to the national standard GB / T 7702.7-2023;

[0129] V1 is the volume of the added iodine standard titration solution, 50 mL;

[0130] V2 is the volume of hydrochloric acid solution added, 10 mL; the mass fraction of hydrochloric acid is 5%, measure 70 mL of hydrochloric acid (analytical grade as specified in GB / T622), slowly inject it into 550 mL of water and mix well;

[0131] V is the volume of filtrate transferred by a single-line pipette, 25 mL;

[0132] c2 is the concentration of the self-prepared sodium thiosulfate standard titration solution, 0.1056 ml / L, prepared in accordance with the national standard GB / T 7702.7-2023;

[0133] V3 is the volume of sodium thiosulfate standard titration solution consumed, in mL;

[0134] M is the molar mass of iodine [M(1 / 2I2)=126.9], in g / mol;

[0135] Step 6: Calculate the adsorption iodine value E according to the following formula:

[0136] Where:

[0137] X is the amount of adsorbed iodine calculated in step 5, in mg;

[0138] m is the mass of the three samples, in g;

[0139] E is the iodine adsorption value, in mg / g;

[0140] It was found that the adsorbed iodine amounts of the first sample, the second sample and the third sample were 383 mg / g, 406 mg / g and 430 mg / g respectively.

[0141] See Table 4 for specific test data.

[0142]

[0143] Table 4 Relevant data of three samples measured when the estimated iodine adsorption value is 400 mg / g

[0144] Step 7, according to the filtrate concentration c of the three samples calculated in step 4 and the corresponding adsorption iodine value E calculated in step 6, a straight line of E (ordinate) versus c (abscissa) is given on a double logarithmic coordinate, and the fitting value of the three points and the straight line is calculated by the least squares method according to the following formula;

[0145] lgE=algc+b

[0146] Where:

[0147] E is the iodine adsorption value calculated in step 6, in mg / g;

[0148] a is the slope of the fitted line;

[0149] c is the filtrate concentration calculated in step 4, in mol / L;

[0150] b is the intercept of the fitting line;

[0151] Fitting curve see Figure 3 ;

[0152] Step 8. According to the adsorption isotherm fitted in step 7, when the correlation coefficient of the fitting is not less than 0.995, the E value when the residual concentration c=0.02 mol / L is taken as the iodine adsorption value obtained by the test.

[0153] according to Figure 3 The iodine adsorption value obtained in Example 2 when c=0.02 mol / L is 412 mg / g.

[0154] The iodine adsorption values ​​measured according to the test method disclosed in the existing national standard GB / T 7702.7-2023 are shown in Table 5.

[0155]

[0156] Table 5 Relevant data measured by existing standards when the estimated iodine adsorption value is 400 mg / g

[0157] Table 6 shows the relative deviation of iodine adsorption values ​​measured by the test method of the present invention and the existing standard test method.

[0158]

[0159] Table 6 Relative deviation of iodine adsorption values ​​measured by the test method of the present invention and the existing standard test method.

[0160] This shows that the iodine adsorption value obtained by the test method of the present application is obviously more accurate than that obtained by the existing standard test method.

[0161] Embodiment 3: Figure 1 As shown, the test method for estimating the iodine adsorption value of 500 mg / g is as follows:

[0162] Step 1: Estimate the mass of the sample using the following formula:

[0163] In the formula,

[0164] c1 is the concentration of the self-prepared iodine standard titration solution, 0.1054 mol / L, prepared according to the national standard GB / T 7702.7-2023;

[0165] V1 is the volume of the iodine standard titration solution added, 50 mL;

[0166] V2 is the volume of hydrochloric acid solution added, 10 mL, the mass fraction of hydrochloric acid is 5%, measure 70 mL of hydrochloric acid (analytical grade as specified in GB / T622), slowly inject it into 550 mL of water and mix well;

[0167] M is the molar mass of iodine, 126.9 g / mol;

[0168] E0 is the estimated iodine adsorption value of the sample, E0=500mg / g;

[0169] Substitute the three values ​​of c into the above formula according to 0.01mol / L, 0.02mol / L and 0.03mol / L to calculate the mass m of the three samples in g, which are recorded as m1=1.1878g for the first sample, m2=1.0355g for the second sample and m3=0.8830g for the third sample;

[0170] Step 2: weigh three portions of coal-based activated carbon samples with masses of m1=1.1878g, m2=1.0355g and m3=0.8830g respectively;

[0171] Step 3, put the three weighed samples into a dry, stoppered ground-mouth conical flask with a capacity of 250 ml, use a single-line pipette to transfer 10 ml of hydrochloric acid solution, add it to the stoppered ground-mouth conical flask, plug the glass stopper, shake it to soak the sample; remove the stopper, heat it on a hot plate to a slight boil for 30 seconds, and cool it to room temperature; use a single-line pipette to transfer 50 ml of iodine standard titration solution to the above-mentioned ground-mouth conical flask, immediately plug the glass stopper, oscillate on an oscillator for 15 minutes, let it stand for 5 minutes, and filter it into a dry, stoppered ground-mouth conical flask with filter paper; rinse the single-line pipette with 10-15 ml of primary filtrate; use a single-line pipette to transfer 25 ml of filtrate, place it in a conical flask, and titrate it with a sodium thiosulfate standard titration solution; when the solution is light yellow, add 1-2 ml of starch indicator solution, and titrate until the blue color of the solution disappears;

[0172] Step 4: Calculate the filtrate concentrations of the first, second and third samples according to the following formulas:

[0173] Where:

[0174] c2 is the concentration of the self-prepared sodium thiosulfate standard titration solution, 0.1056 ml / L, prepared in accordance with the national standard GB / T 7702.7-2023;

[0175] V is the volume of filtrate transferred by a single-line pipette, 25 mL;

[0176] V3 is the volume of sodium thiosulfate standard titration solution consumed. The volumes of sodium thiosulfate standard titration solution consumed by the filtrates of the first, second and third samples are 3.30mL, 4.85mL and 6.64mL respectively.

[0177] Step 5: Calculate the adsorbed iodine amount X according to the following formula:

[0178] Where:

[0179] c1 is the concentration of the self-prepared iodine standard titration solution, 0.1054 mol / L, prepared according to the national standard GB / T 7702.7-2023;

[0180] V1 is the volume of the added iodine standard titration solution, 50 mL;

[0181] V2 is the volume of hydrochloric acid solution added, 10 mL; the mass fraction of hydrochloric acid is 5%, measure 70 mL of hydrochloric acid (analytical grade as specified in GB / T622), slowly inject it into 550 mL of water and mix well;

[0182] V is the volume of filtrate transferred by a single-line pipette, 25 mL;

[0183] c2 is the concentration of the self-prepared sodium thiosulfate standard titration solution, 0.1056 ml / L, prepared in accordance with the national standard GB / T 7702.7-2023;

[0184] V3 is the volume of sodium thiosulfate standard titration solution consumed, in mL;

[0185] M is the molar mass of iodine [M(1 / 2I2)=126.9], in g / mol;

[0186] Step 6: Calculate the adsorption iodine value E according to the following formula:

[0187] Where:

[0188] X is the amount of adsorbed iodine calculated in step 5, in mg;

[0189] m is the mass of the three samples, in g;

[0190] E is the iodine adsorption value, in mg / g;

[0191] The results showed that the adsorbed iodine amounts of the first sample, the second sample and the third sample were 474 mg / g, 495 mg / g and 516 mg / g respectively.

[0192] See Table 7 for specific test data.

[0193]

[0194] Table 7 Relevant data of three samples measured when the estimated iodine adsorption value is 500 mg / g

[0195] Step 7, according to the filtrate concentration c of the three samples calculated in step 4 and the corresponding adsorption iodine value E calculated in step 6, a straight line of E (ordinate) versus c (abscissa) is given on a double logarithmic coordinate, and the fitting value of the three points and the straight line is calculated by the least squares method according to the following formula;

[0196] lgE=algc+b

[0197] Where:

[0198] E is the iodine adsorption value calculated in step 6, in mg / g;

[0199] a is the slope of the fitted line;

[0200] c is the filtrate concentration calculated in step 4, in mol / L;

[0201] b is the intercept of the fitting line;

[0202] Fitting curve see Figure 4 ;

[0203] Step 8. According to the adsorption isotherm fitted in step 7, when the correlation coefficient of the fitting is not less than 0.995, the E value when the residual concentration c=0.02 mol / L is taken as the iodine adsorption value obtained by the test.

[0204] according to Figure 4 The iodine adsorption value of Example 2 when c=0.02 mol / L was 495 mg / g.

[0205] Comparative Example 3:

[0206] The iodine adsorption values ​​measured according to the test method disclosed in the existing national standard GB / T 7702.7-2023 are shown in Table 8

[0207]

[0208] Table 8 Relevant data measured by existing standards when the estimated iodine adsorption value is 500 mg / g

[0209] Table 9 shows the relative deviation of iodine adsorption values ​​measured by the test method of the present invention and the existing standard test method.

[0210]

[0211] Table 9 Relative deviations of iodine adsorption values ​​measured by the test method of the present invention and the existing standard test method.

[0212] This shows that the iodine adsorption value obtained by the test method of the present application is obviously more accurate than that obtained by the existing standard test method.

[0213] It can be seen from the above three embodiments and three comparative examples that there is a significant deviation between the iodine adsorption value measured by the current standard method and the iodine adsorption value measured by the test method of this application, and as the estimated iodine adsorption value gradually decreases, the relative deviation of the actual iodine adsorption values ​​of the two gradually increases. This shows that the results of the existing standards for samples with smaller iodine adsorption values ​​are less accurate, and the present application has found through a large number of experiments that the test method of this application has high accuracy, good applicability, strong operability, and the test method of this application can accurately obtain the iodine adsorption value when the residual filtrate concentration is 0.02 mol / L, which ensures the uniformity of different activated carbon iodine value test methods, eliminates errors caused by different detection methods, improves detection efficiency, and ensures the accuracy of the detection results.

[0214] Comparative Example 4: Verify that the existing standard cannot obtain a filtrate concentration of 0.02 mol / L when the iodine adsorption value is less than 485 mg / g.

[0215] Weigh six portions of coal-based activated carbon samples with a mass of 0.7500g each. The estimated iodine adsorption values ​​of these six activated carbon samples are all less than 600mg / g. Put the weighed samples into a dry, stoppered ground-mouth conical flask with a capacity of 250ml, and use a single-marked pipette to transfer 10ml of hydrochloric acid solution to the conical flask, plug the glass stopper, and shake to soak the sample; remove the stopper, heat to a slight boil on a hot plate for 30s, and cool to room temperature; use a single-marked pipette to transfer 50mL of iodine standard titration solution to the above-mentioned ground-mouth conical flask, immediately plug the glass stopper, oscillate on an oscillator for 15min, let it stand for 5min, and filter the solution with filter paper. Rinse the single-marked pipette with 10mL~15mL of primary filtrate; use a single-marked pipette to transfer 25mL of filtrate, place it in a 250mL conical flask, and titrate with sodium thiosulfate standard titration solution; when the solution turns light yellow, add 1mL~2mL starch indicator solution and titrate until the blue color of the solution disappears.

[0216] The adsorbed iodine amount X is calculated according to the following formula:

[0217] Where:

[0218] c1 is the concentration of the self-prepared iodine standard titration solution, 0.1054 mol / L, prepared according to the national standard GB / T 7702.7-2023;

[0219] V1 is the volume of the added iodine standard titration solution, 50 mL;

[0220] V2 is the volume of hydrochloric acid solution added, 10 mL; the mass fraction of hydrochloric acid is 5%, measure 70 mL of hydrochloric acid (analytical grade as specified in GB / T622), slowly inject it into 550 mL of water and mix well;

[0221] V is the volume of filtrate transferred by a single-line pipette, 25 mL;

[0222] c2 is the concentration of the self-prepared sodium thiosulfate standard titration solution, 0.1056 ml / L, prepared in accordance with the national standard GB / T 7702.7-2023;

[0223] V3 is the volume of sodium thiosulfate standard titration solution consumed, in mL;

[0224] M is the molar mass of iodine [M(1 / 2I2)=126.9], in g / mol;

[0225] The adsorption iodine value E is calculated according to the following formula:

[0226] Where:

[0227] X is the amount of adsorbed iodine, in mg;

[0228] m is 0.7500g;

[0229] E is the iodine adsorption value, in mg / g;

[0230] The specific test data of the above six samples are shown in Table 10

[0231]

[0232] Table 10 Relevant data of six samples measured when the estimated iodine adsorption value is less than 600 mg / g

[0233] In order to ensure the accuracy of the test results, sample 3# in Table 10 was taken for repeated experiments. The experimental results are shown in Table 11.

[0234]

[0235] Table 11 Relevant data of five samples measured with existing standards at an estimated iodine adsorption value of 485 mg / g

[0236] It can be seen from Table 10 and Table 11 that when the iodine adsorption value is less than 485 mg / g, the filtrate concentration is not in the range of 0.008 mol / L to 0.040 mol / L, so it is impossible to take the iodine adsorption value when the filtrate concentration is 0.02 mol / L. Therefore, the existing standard is not applicable when the iodine adsorption value is less than 485 mg / g, and the test result is not accurate. When the iodine adsorption value is 485 mg / g≤iodine adsorption value<600 mg / g, the concentration of the filtrate is in the range of 0.008 mol / L to 0.040 mol / L, but it is impossible to take the iodine adsorption value when the filtrate concentration is 0.02 mol / L. Therefore, the existing standard is not applicable when the iodine adsorption value is less than 600 mg / g.

[0237] The test methods of Examples 1 to 3 of the present invention are universal for iodine adsorption values ​​less than 600 mg / g, and accurate iodine adsorption values ​​can be obtained by uniformly adopting this method.

[0238] The present invention makes an empirical estimate of the iodine adsorption value of the sample according to the existing information and morphological characteristics of the sample, takes different sample masses for experiments according to the estimated residual filtrate concentration of 0.01 mol / L, 0.02 mol / L and 0.03 mol / L, estimates the actual concentration c of the residual filtrate of the test sample and the corresponding iodine adsorption value E, and gives a straight line of E (ordinate) to c (abscissa) on a double logarithmic coordinate according to the results of three samples. The fitting value of the three points and the straight line is calculated by the least squares method. According to the adsorption isotherm, when the correlation coefficient of the fitting is not less than 0.995, E when the residual concentration c=0.02 mol / L is taken as the iodine adsorption value. The adsorption capacity of activated carbon for any adsorbate is related to the concentration of the adsorbate in the solution. In order to obtain the iodine adsorption value when the residual concentration is 0.02 mol / L, the filtrate concentration must be within the range of 0.008 mol / L~0.040 mol / L, otherwise, the sample mass needs to be adjusted. When the iodine adsorption value of coal-based activated carbon is less than 600 mg / g, the iodine adsorption value at the residual concentration of 0.02 mol / L cannot be obtained, while the iodine adsorption value of coal-based activated carbon detection method with an iodine adsorption value greater than 600 mg / g is the iodine adsorption value at the residual concentration of 0.02 mol / L. The method of the present invention ensures the uniformity of the test methods of activated carbon with different iodine values, eliminates the errors caused by different detection methods, improves the detection efficiency, and ensures the accuracy of the detection results.

[0239] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for determining the iodine adsorption value of coal-based activated carbon, characterized in that: The steps include: Step 1: Estimate the mass of the sample using the following formula: ； In the formula, c1 is the concentration of the iodine standard titration solution, 0.1000 mol / L; V1 is the volume of the iodine standard titration solution added, 50 mL; V2 is the volume of hydrochloric acid solution added, 10 mL; M is the molar mass of iodine, 126.9 g / mol; E0 is the estimated iodine adsorption value of the sample, in mg / g, E0<600mg / g; Substitute the three values ​​of c into the above formula according to 0.01mol / L, 0.02mol / L and 0.03mol / L respectively to calculate the usage mass m of the three samples, in g, which are recorded as the first sample m1, the second sample m2 and the third sample m3 respectively; Step 2: Weigh three portions of coal-based activated carbon samples with masses of m1, m2 and m3 respectively, accurate to 0.0001g; Step 3, put the three weighed samples into a dry, stoppered ground-mouth conical flask with a capacity of 250 ml, use a single-line pipette to transfer 10 ml of hydrochloric acid solution, add it to the stoppered ground-mouth conical flask, plug the glass stopper, shake it to soak the sample; remove the stopper, heat it on a hot plate to a slight boil for 30 seconds, and cool it to room temperature; use a single-line pipette to transfer 50 ml of iodine standard titration solution to the above-mentioned ground-mouth conical flask, immediately plug the glass stopper, oscillate on an oscillator for 15 minutes, let it stand for 5 minutes, and filter it into a dry, stoppered ground-mouth conical flask with filter paper; rinse the single-line pipette with 10-15 ml of primary filtrate; use a single-line pipette to transfer 25 ml of filtrate, place it in a conical flask, and titrate it with a sodium thiosulfate standard titration solution; when the solution is light yellow, add 1-2 ml of starch indicator solution, and titrate until the blue color of the solution disappears; Step 4: Calculate the filtrate concentrations of the first, second and third samples according to the following formulas: ； Where: c2 is the concentration of sodium thiosulfate standard titration solution, 0.1000ml / L; V3 is the volume of sodium thiosulfate standard titration solution consumed, in mL; V is the volume of filtrate transferred by a single-line pipette, 25 mL; Step 5: Calculate the adsorbed iodine amount X according to the following formula: ； Where: c1 is the concentration of the iodine standard titration solution, 0.1000 mol / L; V1 is the volume of the added iodine standard titration solution, 50 mL; V2 is the volume of hydrochloric acid solution added, 10 mL; V is the volume of filtrate transferred by a single-line pipette, 25 mL; c2 is the concentration of sodium thiosulfate standard titration solution, 0.1000 mol / L; V3 is the volume of sodium thiosulfate standard titration solution consumed, in mL; M is the molar mass of iodine [M(1 / 2I2)=126.9], in g / mol; Step 6: Calculate the adsorption iodine value E according to the following formula: ； Where: X is the amount of adsorbed iodine calculated in step 5, in mg; m is the mass of the three samples, in g; E is the iodine adsorption value, in mg / g; Step 7: According to the filtrate concentration c of the three samples calculated in step 4 and the corresponding adsorption iodine value E calculated in step 6, a straight line of the vertical coordinate E against the horizontal coordinate c is given on a double logarithmic coordinate, and the fitting value of the three points and the straight line is calculated by the least square method according to the following formula; lgE=algc+b Where: E is the iodine adsorption value calculated in step 6, in mg / g; a is the slope of the fitted line; c is the filtrate concentration calculated in step 4, in mol / L; b is the intercept of the fitting line; Step 8. According to the adsorption isotherm fitted in step 7, when the correlation coefficient of the fitting is not less than 0.995, the E value when the residual concentration c=0.02 mol / L is taken as the iodine adsorption value obtained by the test.

2. The method for determining the iodine adsorption value of coal-based activated carbon according to claim 1, characterized in that , E0 in the step one is <485 mg / g.

3. The method for determining the iodine adsorption value of coal-based activated carbon according to any one of claims 1 to 2, characterized in that , The mass fraction of the hydrochloric acid solution is 5%; The hydrochloric acid solution, the iodine standard titration solution and the sodium thiosulfate standard titration solution are prepared in accordance with the national standard GB / T7702.7-2023.

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