Calibration device and method of methylene blue standard solution for machine-made sand MB value test

Abstract

The invention belongs to the technical field of material performance detection, and discloses a calibration device and method of a methylene blue standard solution for a machine-made sand MB value test, which can quickly judge the deviation degree of the concentration of the methylene blue solution, improve the accuracy of the concentration of the methylene blue solution and improve the accuracy of the MB value test. The stable property of the standard substance for calibration can ensure that the detection result of the engineering sand is accurate in a long time span, so that the engineering quality is ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of material performance detection, and particularly relates to a calibration device and method for methylene blue standard solution for machine-made sand MB value test. BACKGROUND

[0002] The methylene blue value (MB value) of machine-made sand is an index for judging the adsorption performance of machine-made sand, and is helpful for distinguishing whether the particles smaller than 0.075 mm in the machine-made sand are useful stone powder or harmful mud powder. Methylene blue is a water-soluble dye, and its molecules can be dissociated into cations in water. The microstructure of mud powder in machine-made sand is a loose and porous layered structure, and the surface is negatively charged in the aqueous solution, having a strong adsorption capacity for methylene blue cations; while the stone powder is a small particle produced by mechanical crushing of parent rock, and the surface is dense and has weak adsorption capacity. Therefore, the content of mud powder in machine-made sand can be judged by the color change of the suspension liquid and the consumption of methylene blue solution in the titration process.

[0003] The shelf life of methylene blue solution for machine-made sand MB value determination should not exceed 28 days, but the shelf life of methylene blue reagent purchased on the market is usually much longer than that of methylene blue solution. It is not clear whether the methylene blue reagent or methylene blue solution can be used for MB value determination when the shelf life is approaching. Due to the long time span of engineering projects, the methylene blue reagent is replaced or its shelf life is approaching during the engineering cycle. At this time, it is not clear whether the prepared methylene blue solution can continue to be used, and whether the difference between the MB value determined by the initial methylene blue solution is acceptable. Therefore, if the methylene blue solution is not calibrated, it will affect the MB value determination results, and further affect the concrete quality and even the engineering quality.

[0004] At present, the calibration of methylene blue solution includes spectrophotometric analysis, high liquid chromatography analysis, chemical titration (iodine method), etc. Among them, the spectrophotometric analysis of the suspension liquid is easy to settle, which has an impact on the test results, and the operation is complex and the preparation of standard sample requires high requirements; the high liquid chromatography analysis has high accuracy, but the instrument is expensive; the chemical titration (iodine method) is complex in operation and requires high professional ability of the test personnel in chemical analysis; all these are not conducive to the calibration in the engineering project site laboratory.

[0005] In addition, the machine-made sand methylene blue test device and method steps have defects affecting the calibration accuracy, such as: there are stirring dead angles, the bottom of the suspension liquid cannot be stirred; the diameter range of the titration precipitate is large and inconsistent, and the color halo width measurement method is not clearly specified; the manual pipette has low accurate suction efficiency and slow speed; the glass rod dipped in the methylene blue solution has inconsistent amount, resulting in inconsistent diameter and irregular shape of the titration precipitate, so the calibration appliance needs to be improved and new devices need to be added.

[0006] CN119269426A discloses a test mechanism sand MB value detection with methylene blue solution reagent concentration and MB value result correction method, using spectrophotometry to compare the absorbance difference of copper sulfate pentahydrate solution and methylene blue solution whether in the range of ±0.02, within the range, the methylene blue solution can be directly used for MB value test, but the copper sulfate pentahydrate will slowly lose crystallization water, and will be converted into copper sulfate trihydrate when the temperature is 45℃, the property is relatively unstable, that is, the reference standard may change, in addition, the spectrophotometry itself has the disadvantages of complex operation and low precision, and the three-step dilution method of standard solution is difficult to configure and is easy to produce deviation. In addition, the main purpose of CN119269426A is to correct the MB value, the purpose of detection is to find the influencing factors and then improve the detection method to directly judge whether the product is qualified, but it is unreasonable to correct the MB value of the product by using the reagent with unstable property in the later period.

[0007] Therefore, it is necessary to develop a new type of methylene blue standard solution calibration device and method for machine-made sand MB value test. SUMMARY

[0008] The purpose of the present application is to solve the problems of the prior art, and provide a methylene blue standard solution calibration device and method for machine-made sand MB value test, which can quickly judge the deviation degree of the concentration of the methylene blue solution, improve the accuracy of the concentration of the methylene blue solution, and ensure that the engineering sand maintains accurate detection results for a long time, thereby ensuring the engineering quality.

[0009] In order to solve the technical problem, the technical scheme of the present application is: a methylene blue standard solution calibration method for machine-made sand MB value test, comprising the following steps: Step 1: using anhydrous methylene blue reagent with a purity of not less than 98.0%, preparing a methylene blue standard solution with a concentration of 10 g / L, and using the reagent to be calibrated or newly purchased to prepare a methylene blue solution with a theoretical concentration of 10 g / L; Step 2: weighing at least three portions of dry kaolin with a mass gradient of Ag, slowly adding them into a water-containing beaker placed on a magnetic stirrer, fully mixing with water, and then stopping stirring to obtain a kaolin suspension; Step 3: titrate the kaolin suspension of step 2 with the methylene blue standard solution, stir the kaolin suspension with a magnetic stirrer until the end of the test, take the methylene blue standard solution with a digital pipette and add it to the kaolin suspension, after stirring for 1-5 min, use an electric micro-adjustable pipette to take the suspension, adjust the amount of suspension to form a 10 mm ± 1 mm diameter precipitate, calibrate with a calibration device, clamp the fast quantitative filter paper with a magnetic filter clamp and place it on a special titration table, so that the fast quantitative filter paper is suspended and flat, cover the color halo test plate above the magnetic filter clamp to form a calibration device; drop the suspension from the center of the color halo titration hole of the color halo test plate, observe whether a color halo appears, if the width of the color halo is ≥1 mm, stop, record the cumulative amount of methylene blue standard solution consumed; linear fitting to obtain the slope and intercept, calculate the MB value corresponding to different mass of kaolin, and take the average value MB0 as the MB value of the batch of kaolin. Step 4: titrate the kaolin suspension of step 2 with the methylene blue solution, record the consumption of the methylene blue solution, linear fitting to obtain the slope and intercept, calculate the average value MB1 corresponding to the methylene blue solution, compare it with the average value MB0, and determine whether the methylene blue solution is continued to be used.

[0010] Preferably, the methylene blue standard solution with a concentration of 10 g / L prepared in step 1 is specifically prepared as follows: weigh anhydrous methylene blue reagent with a purity of not less than 98.0%, pour it into a beaker containing distilled water, stir with a magnetic stirrer until completely dissolved, naturally cool to room temperature 25±5℃, pour the solution into a volumetric flask, rinse the beaker with a small amount of distilled water several times and supplement distilled water to the specified scale, move the solution in the volumetric flask into a dark storage bottle, label the preparation information, and obtain a methylene blue standard solution with a concentration of 10 g / L.

[0011] Preferably, the kaolin in step 2 contains kaolinite with a mass fraction of not less than 90.0%, with a specification of chemical purity, a SiO2 mass fraction of not less than 46.5%, an Al2O3 mass fraction of not less than 36.5%, a mass loss on ignition of not more than 15.0%, a 45 μm sieve residue of not more than 0.1%, and a specific surface area of 20000-50000 m 2 / kg; dry the kaolin in an oven at 100±5℃ to a constant weight, and cool it in a desiccator. The mass of kaolin is weighed to an accuracy of 0.1 g.

[0012] Preferably, in step 3, if the precipitate does not appear color halo or less than 1 mm, continue to repeat the titration step until a stable light blue color halo with a width of ≥1 mm appears around the precipitate. At this time, continue to stir and do not add methylene blue standard solution. Take the suspension every 1 min for dyeing test. Observe whether the color halo is stable at the 5th min. If it is stable, the sample titration is finished. If it is not stable, this kaolin cannot be used as a calibration material.

[0013] Preferably, the working temperature of the magnetic stirrer is set to 20-30℃, the magnetic stirrer is stirred at a speed of 600±60 r / min for 5-8 min, and then continuously stirred at a speed of 400±40 r / min, and the temperature of the kaolin suspension is kept at 25±5℃.

[0014] Preferably, the range of the digital pipettor is 10 mL, and the accuracy is 1 mL; and the range of the electric micro-adjustable pipettor is 30-300 μL.

[0015] Preferably, the specific requirements for determining whether the methylene blue solution can continue to be used in step 4 are as follows: the deviation distance of the corresponding vertical intercept of the methylene blue solution and the methylene blue standard solution from the origin is not greater than 3.0, the difference between the corresponding slopes of the consumption of the methylene blue solution and the methylene blue standard solution is not greater than 0.10, and the deviation amplitude of the corresponding MB1 value of the methylene blue solution from the corresponding MB0 value of the methylene blue standard solution is not greater than 1.0 g / kg, and then it is determined that the methylene blue solution can continue to be used; otherwise, it cannot continue to be used.

[0016] Preferably, a methylene blue standard solution calibration device for a machine-made sand MB value test is used for the calibration method of the methylene blue standard solution for the machine-made sand MB value test, the calibration device comprises a special titration table, a magnetic filter paper clamp, a color halo test plate and a rapid quantitative filter paper, the magnetic filter paper clamp is composed of two mutually magnetic circular rings, the two magnetic circular rings are respectively placed on the front and back of the rapid quantitative filter paper to clamp the rapid quantitative filter paper, the magnetic filter paper clamp with the clamped rapid quantitative filter paper is placed on the special titration table, and the color halo test plate is placed above the magnetic filter paper clamp with the clamped rapid quantitative filter paper.

[0017] Preferably, the special titration table is in a cylindrical structure, the bottom of the special titration table is sealed, the inside of the top of the special titration table is provided with a step for placing the magnetic filter paper clamp, and a notch is formed in the top of the special titration table close to the step.

[0018] Preferably, a plurality of color halo rings are arranged on the color halo test plate, the plurality of color halo rings are uniformly distributed in a rice-shaped manner, a color halo titration hole is arranged at the center position of each color halo ring, the diameter of the color halo titration hole is 5 mm, each color halo ring comprises 10 measuring rings from inside to outside, the diameter of each measuring ring increases by 1 mm, and the diameter of the outermost ring is 15 mm; the diameter of the color halo test plate is 150 mm, the color halo test plate is provided with measuring rings from inside to outside, the diameter of each measuring ring increases by 40 mm, the diameter of the outermost ring is 120 mm, and the center of each color halo ring is on the measuring ring of the color halo test plate.

[0019] Compared with the prior art, the application has the following advantages: (1) The application has stable and accurate calibration results: due to the long time period of the engineering project, kaolin is used as the calibration object, which has stable chemical properties, is not sensitive to environmental moisture, is easy to obtain, store and has high safety, can ensure that the properties do not change within the engineering period, and only needs to be accurately calibrated once using methylene blue reagent with purity detected and corresponding test report, which can eliminate the influence of methylene blue solution replacement or property change on MB value determination; (2) The application enhances error control: through the longitudinal intercept deviation distance, slope difference and MB value deviation amplitude, the fitting accuracy and secondary screening of the solution to be calibrated are realized, and through the judgment of the three-step numerical relationship, it is finally confirmed whether the methylene blue solution is usable, which reduces the influence of calibration operation on the results; (3) The application establishes a stable value transfer relationship: a value transfer relationship of "methylene blue standard solution-kaolin-to-be-calibrated methylene blue solution" is formed with kaolin MB value as the reference, a 10 g / L methylene blue standard solution is prepared by using anhydrous methylene blue reagent with a purity of more than 98% detected, kaolin suspension is titrated to obtain the inherent property MB0 value of kaolin, the MB0 value of kaolin is stable and uniform, and it is compared with the MB1 value measured by the newly purchased or to-be-calibrated methylene blue solution to determine whether it can be used continuously, which simplifies the calibration procedure of methylene blue solution and improves the calibration efficiency; (4) The application improves the MB value test device, uses a digital display pipettor to make the accurate absorption speed of the methylene blue standard solution or the methylene blue solution faster; uses a heating magnetic stirrer to stir the bottom of the suspension, so that the mixing of kaolin and the methylene blue standard solution or the methylene blue solution is more uniform, and the solution / suspension temperature is controllable and will not break the beaker; uses an electric micro-adjustable pipettor to accurately absorb the amount of suspension, and the diameter of the precipitate formed by titration is more accurate and controllable, which is accurately controlled at (10±1) mm; (5) The calibration device of the application clamps the rapid quantitative filter paper with a magnetic filter paper clamp and places it on a special titration table, so that the rapid quantitative filter paper is suspended and flat, covers the color halo test plate above the magnetic filter paper clamp, so that the rapid quantitative filter paper is placed horizontally and flat on the special titration table; the color halo titration hole of the color halo test plate serves as a reference standard for vertical titration, improves the circularity of the titration precipitate, and the measurement ring of the color halo test plate can accurately measure the diameter of the precipitate and the width of the light blue halo, providing a reference standard for the uniformity of the precipitate diameter, improving the measurement accuracy and efficiency, and ultimately improving the detection accuracy of the MB value. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a flowchart of a method for calibrating a methylene blue standard solution for machine-made sand MB value test according to the application; Figure 2 is a flowchart of a method for calibrating a methylene blue standard solution for machine-made sand MB value test according to the application; Figure 3 is a calibration device structure diagram of methylene blue standard solution for machine-made sand MB value test of the application; Figure 4 is a structure diagram of a special titration table of the application; Figure 5 is a structure diagram of a magnetic filter paper clamp of the application; Figure 6 is a structure diagram of a color halo test plate of the application; Figure 7 is a relationship diagram between methylene blue solution consumption and kaolin mass of example 1 of the application; Figure 8 is a result diagram of MB value determination of methylene blue solutions of different sources of example 1 of the application.

[0021] BRIEF DESCRIPTION OF DRAWINGS: 1, special titration table, 2, magnetic filter paper clamp, 3, color halo test plate, 4, rapid quantitative filter paper; 3-1, color halo ring, 3-1-1, color halo titration hole. DETAILED DESCRIPTION

[0022] The application will be described in detail below in conjunction with the drawings and specific examples, but the application is not limited to only these examples. The application covers any substitutions, modifications, equivalent methods and schemes made on the essence and scope of the application. In order to make the public have a thorough understanding of the application, specific details are described in detail in the following examples of the application, and the application can also be completely understood without the description of these details for those skilled in the art.

[0023] As shown in Figure 1 , the application discloses a calibration method of methylene blue standard solution for machine-made sand MB value test, comprising the following steps: Step 1: using anhydrous methylene blue reagent with a purity of not less than 98.0%, prepare a methylene blue standard solution with a concentration of 10 g / L, and use the reagent to be calibrated or newly purchased to prepare a methylene blue solution with a theoretical concentration of 10 g / L; For example: prepare a methylene blue standard solution with a concentration of 10 g / L: weigh 5.00±0.01 g of anhydrous methylene blue, pour it into a beaker containing 300 mL of distilled water, and use a magnetic stirrer to stir until completely dissolved. Pour the solution into a 500 mL volumetric flask, use distilled water to rinse the beaker a few times and supplement distilled water to the 500 mL mark of the volumetric flask. Move the solution in the volumetric flask to a dark storage bottle, and label the preparation information.

[0024] Step 2: Take at least three portions of dry kaolin with mass gradient A g, slowly add them into a water-containing beaker placed on a magnetic stirrer, stop stirring after fully mixing with water, and obtain a kaolin suspension; Step 3: Titrate the kaolin suspension of Step 2 using the methylene blue standard solution, use the magnetic stirrer to stir the kaolin suspension until the end of the test, use a digital pipette to take the methylene blue standard solution and add it to the kaolin suspension, stir for 1-5 min, use an electric micro-adjustable pipette to take the suspension, adjust the amount of the suspension to form a 10 mm ± 1 mm precipitate diameter, calibrate using a calibration device, clamp the fast quantitative filter paper 4 with the magnetic filter paper clamp 2 and place it on the special titration table 1, so that the fast quantitative filter paper 4 is suspended and flat, cover the color halo test plate 3 above the magnetic filter paper clamp 2 to form a calibration device, drop the suspension from the center of the color halo titration hole 3-1-1 of the color halo test plate 3, and observe whether a color halo appears, if the width of the color halo is ≥1 mm, stop, and record the cumulative amount of methylene blue standard solution consumed; linear fitting obtains the slope and intercept, calculates the MB value corresponding to different mass of kaolin, and takes the average value MB0 as the MB value of the batch of kaolin; For example: Take dry kaolin with mass of 15 g, 30 g, and 45 g respectively and count as M 15 , M 30 , and M 45 , accurate to 0.01 g. Dissolve the samples in 500 mL of distilled water respectively, and use a magnetic stirrer to stir until the end of the test. Use a digital pipette to take 2 mL of standard methylene blue solution and add it to the kaolin suspension, stir for 1 min, use an electric micro-adjustable pipette to take an appropriate amount of suspension, adjust the amount of the suspension to form a 10 mm ± 1 mm precipitate diameter, first clamp the fast quantitative filter paper of 150 mm model 201 with the magnetic filter paper clamp and place it on the special titration table, so that the filter paper is suspended and flat, cover the color halo measurement plate above the magnetic filter paper clamp, drop the suspension from the center of the suspension titration hole, observe whether a color halo appears, if the width of the color halo is ≥1 mm, stop, and record the cumulative amount of methylene blue solution consumed. M 30 The first titration amount can refer to the final methylene blue solution consumption total amount of M 15 , M 45 The first titration amount is the same as above. Titration obtains M 15 , M 30 , and M 45 corresponding to the cumulative volume V 15 , V 30 , and V 45 of methylene blue solution, accurate to 1 mL. Linear fitting obtains the slope a0 and intercept b0, calculates the MB value corresponding to different mass of kaolin, and takes the average value MB0 as the MB value of the batch of kaolin, which is used for calibration of other methylene blue solution concentrations; Step 4: titrate the kaolin suspension of Step 2 with methylene blue solution, record the consumption of methylene blue solution, linear fitting to get the slope and intercept, calculate the average value MB1 corresponding to the methylene blue solution, compare with the average value MB0, and determine whether the methylene blue solution can continue to be used.

[0025] For example: use the reagent to be calibrated or newly purchased to prepare a methylene blue solution with a theoretical concentration of 10 g / L, titrate at least three portions of dry kaolin with a mass gradient of 15.00 g that have been assigned values, the test steps are the same as in Step 3, record the consumption of methylene blue solution for each kaolin sample, and through linear fitting, obtain the slope a1 and the intercept b1, calculate the average value MB1 corresponding to the methylene blue reagent, compare it with MB0, and determine whether the methylene blue reagent can continue to be used.

[0026] Preferably, the preparation of a methylene blue standard solution with a concentration of 10 g / L in Step 1 is specifically as follows: weigh anhydrous methylene blue reagent with a purity of not less than 98.0%, pour it into a beaker containing distilled water, use a magnetic stirrer to stir until completely dissolved, naturally cool to room temperature 25±5℃, pour the solution into a volumetric flask, use distilled water to rinse the beaker a few times and supplement distilled water to the specified scale, move the solution in the volumetric flask to a dark storage bottle, label the preparation information, and obtain a methylene blue standard solution with a concentration of 10 g / L.

[0027] Preferably, the kaolin in Step 2 contains kaolinite with a mass fraction of not less than 90.0%, with a specification of chemical purity, a SiO2 mass fraction of not less than 46.5%, an Al2O3 mass fraction of not less than 36.5%, a mass loss on ignition of not more than 15.0%, a 45 μm sieve residue of not more than 0.1%, and a specific surface area of 20000~ 50000 m2 / kg; dry the kaolin in an oven at 100±5℃ to a constant weight, and cool it in a desiccator. The mass of the kaolin is weighed to an accuracy of 0.1 g.

[0028] Preferably, in Step 3, if the precipitate does not appear color halo or is less than 1 mm, continue to repeat the titration step until a stable light blue color halo with a width ≥1 mm appears around the precipitate. At this time, continue to stir and do not add methylene blue standard solution. Every 1 min, take a sample of the suspension for dyeing test. By the 5th min, observe whether the color halo is stable. If it is stable, the titration of this sample is complete. If it is not stable, this kaolin cannot be used as a calibration material.

[0029] Preferably, the working temperature of the magnetic stirrer is set to 20℃~30℃, the magnetic stirrer is stirred at a speed of 600±60 r / min for 5~8 min, and then continuously stirred at a speed of 400±40 r / min, and the temperature of the kaolin suspension is maintained at 25±5℃.

[0030] Preferably, the range of the digital display pipette is 10 mL, and the precision is 1 mL; the range of the electric micro-adjustable pipette is 30 μL~300 μL. The heating magnetic stirrer is adjustable in heating temperature, and the stirring speed is adjustable in the range of 200~1500 rpm, and the maximum stirring capacity is 2 L, and the snowflake type four-fluorine magnetic stirring rotor is adopted.

[0031] Preferably, the specific requirements for judging whether the methylene blue solution can continue to be used in step 4 are as follows: the deviation distance of the corresponding vertical intercepts of the methylene blue solution and the methylene blue standard solution from the origin is not greater than 3.0, the difference between the corresponding slopes of the consumption amounts of the methylene blue solution and the methylene blue standard solution is not greater than 0.10, and the deviation amplitude of the MB1 value corresponding to the methylene blue solution from the MB0 value corresponding to the methylene blue standard solution is not greater than 1.0 g / kg, and then it is judged that the methylene blue solution can continue to be used; otherwise, it cannot continue to be used.

[0032] For example: the deviation distance of the vertical intercepts b0 and b1 from the origin should not be greater than 3.0, the difference between the corresponding slopes a1 and a0 of the consumption amounts of the methylene blue solution to be calibrated or newly purchased reagent prepared methylene blue solution and the methylene blue standard solution should not be greater than 0.10; the MB value is calculated according to 10 × (V / m), wherein V is the volume (mL) of the consumed methylene blue solution, and m is the mass (g) of the kaolin; the deviation amplitude of the MB1 value corresponding to the methylene blue solution to be calibrated from the MB0 value corresponding to the methylene blue standard solution should not be greater than 1.0 g / kg.

[0033] As shown in Figure 3 Preferably, a methylene blue standard solution calibration device for the manufactured sand MB value test is used for the calibration method of the methylene blue standard solution for the manufactured sand MB value test, the calibration device comprises a special titration table 1, a magnetic filter paper clamp 2, a color halo test plate 3 and a rapid quantitative filter paper 4, the magnetic filter paper clamp 2 is composed of two mutually magnetically attracted magnetic circular rings, the two magnetic circular rings are respectively placed on the front and back surfaces of the rapid quantitative filter paper 4 to clamp the rapid quantitative filter paper 4, the magnetic filter paper clamp 2 clamping the rapid quantitative filter paper 4 is placed on the special titration table 1, and the color halo test plate 3 is placed above the magnetic filter paper clamp 2 clamping the rapid quantitative filter paper 4.

[0034] For example: the special titration table 1 is transparent organic glass with a thickness of 3 mm, and the inner diameter of the special titration table 1 is 140 / 150 mm; the inner diameter of the magnetic filter paper clamp 2 is 140 mm, and the rapid quantitative filter paper 4 can be fixed; the filter paper has a specification of 150 mm; the color halo test plate 3 is made of transparent organic glass with a thickness of 3 mm, and the diameter of the measurement plate is 150 mm; a plurality of color halo rings 3-1 are uniformly distributed on the measurement plate, the color halo titration hole 3-1-1 of the color halo ring 3-1 has a diameter of 5 mm, the measurement ring around the titration hole is distributed with concentric circle diameter scales, the diameter scale graduation value is 1 mm, and the maximum scale diameter of the measurement ring is 15 mm.

[0035] AsFigure 4 , 5 As shown, preferably, the dedicated titration stage 1 has a cylindrical structure, the bottom of the dedicated titration stage 1 is sealed, a step is provided on the inner side of the top of the dedicated titration stage 1 for placing the magnetic filter paper clip 2, and a slot is opened on the top of the dedicated titration stage 1 near the step.

[0036] like Figure 6 As shown, preferably, the color halo test plate 3 is provided with multiple color halo rings 3-1, which are evenly distributed in a star shape. A color halo titration hole 3-1-1 with a diameter of 5 mm is provided at the center of the color halo ring 3-1. The color halo ring 3-1 has 10 measuring rings from the inside out, with the diameter increasing by 1 mm each time, and the outermost ring having a diameter of 15 mm. The diameter of the color halo test plate 3 is 150 mm. The color halo test plate 3 has 3 measuring rings from the inside out, with the diameter increasing by 40 mm each time, and the outermost ring having a diameter of 120 mm. The center of the color halo ring 3-1 is located on the measuring ring of the color halo test plate 3.

[0037] Example 1 like Figure 2 As shown, this application provides a method for calibrating a methylene blue standard solution for testing the MB value of manufactured sand. It is recommended to use the improved MB value testing and calibration apparatus of this application during titration to improve calibration accuracy. The method includes the following specific steps: First, a 10 g / L methylene blue standard solution GY-10 was prepared using anhydrous methylene blue reagent with tested purity and corresponding test reports. Prepare a methylene blue solution with a theoretical concentration of 10 g / L using reagents to be calibrated or newly purchased. Information on methylene blue reagents is shown in Table 1.

[0038] The kaolin clay had a 45 μm sieve residue of 0.03% and a specific surface area of ​​35.6 m². 2 / g, dried to constant weight in an oven at (100 ± 5) ℃ and cooled in the oven, weighed 15.00g, 30.00g and 45.00g of kaolin respectively, with the mass accurate to 0.01g, and placed on a magnetic stirrer at 600 r / min and stirred continuously for 5 min to prepare a uniform kaolin suspension; The kaolin suspension is stirred using a magnetic stirrer until the end of the test, the methylene blue standard solution is added to the kaolin suspension using a digital pipette, and after stirring for 1-5 min, the suspension is taken up using an electrically powered micro-adjustable pipette, the amount of suspension is adjusted to form a 10 mm ± 1 mm diameter precipitate, and calibration is performed using a calibration device. The rapid quantitative filter paper 4 is clamped using the magnetic filter paper clamp 2 and placed on the special titration table 1, so that the rapid quantitative filter paper 4 is suspended and flat, and the color halo test plate 3 is placed above the magnetic filter paper clamp 2 to form the calibration device. The suspension is dropped from the center of the color halo titration hole 3-1-1 of the color halo test plate 3, and whether a color halo appears is observed. If the width of the color halo is ≥1 mm, the test is terminated, and the amount of methylene blue standard solution consumed is recorded. The slope and the vertical intercept are obtained by linear fitting, the MB values corresponding to different mass of kaolin are calculated, and the average value MB0 is taken as the MB value of the batch of kaolin. The amount of methylene blue standard solution consumed is recorded as shown in Table 2, and the relationship curve between the amount of methylene blue standard solution consumed and the mass of kaolin is plotted as shown in Figure 2 The fitting results obtained by linear fitting are shown in Table 3.

[0039] where the coefficient of the first term and the vertical intercept are a and b, respectively. Since the termination condition specified in the standard is the appearance of a stable blue color halo in the suspension, the vertical intercept b of the fitting curve should not deviate too much from the origin. When the offset distance b is not greater than 3.0, it is considered that the fitting curve is accurate. At this time, if the slope difference is not greater than 0.10, it is considered that the concentration of the methylene blue solution to be calibrated or prepared from newly purchased reagents is the same as that of the reference solution, and can be used for MB value calculation. If the difference is greater than 0.10, it is considered that the concentration of the methylene blue solution to be calibrated or prepared from newly purchased reagents is significantly different from that of the methylene blue standard solution, and cannot be used for MB value calculation.

[0040] Table 1 Methylene blue reagent information Table 2 Amount of methylene blue solution consumed at different mass of kaolin (unit: ml) R 2The deviation distance of the longitudinal intercept b is not greater than 3.0, indicating that the linear fitting effect is good and the fitting curve is accurate; compared with the slope a of the reference solution GY-10 which is 0.57, the difference 0.10 is in the range [0.47, 0.67], and from Table 3, it can be seen that CD-01, YF-02, SM-03, XY-08 and GY-09 are all in the slope difference range, so it can be considered that the concentration of the methylene blue solution prepared by the reagent to be calibrated or newly purchased is the same as that of the methylene blue standard solution; while GS-04, YK-05, XY-06 and XY-07 are not in the slope difference range, it is considered that the concentration of the methylene blue solution prepared by the reagent to be calibrated or newly purchased is significantly different from that of the methylene blue standard solution.

[0041] Table 3 Fitting results of methylene blue solution consumption and kaolin mass The MB value is calculated by the formula MB = V / m x 10, wherein V (ml) is the consumption of methylene blue solution, m (g) is the sample mass, and 10 is the coefficient for converting the volume of methylene blue solution to mass. The acceptable deviation of the MB value of machine-made sand is 0.1-0.2 g / kg, while the clay content of kaolin is significantly higher than that of machine-made sand, and the MB value is usually 5-10 times that of machine-made sand, so the acceptable deviation of the MB value of kaolin is set to 1.0 g / kg. When the average value of the MB value is compared with the methylene blue standard solution, the deviation is not greater than 1.0 g / kg, it can be considered that the current methylene blue reagent has not changed in nature and can continue to be used, otherwise if the deviation is greater than 1.0 g / kg, the methylene blue reagent cannot be used. The MB value calculation results corresponding to different kaolin masses are shown in Table 4, and the range, median and average of the MB value corresponding to the methylene blue reagent produced by different manufacturers are shown in the box plot as Figure 3 The results show that the MB value of the GY-10 methylene blue standard solution is 6.22, so the value range of the MB value is [5.22, 7.22], the MB value determination results of CD-01, YF-02, SM-03 and GY-09 are within the reasonable range, and can continue to be used for the determination of the MB value of construction sand, while the MB value determination results of GS-04, YK-05, XY-06, XY-07 and XY-08 are not within the reasonable range, and cannot continue to be used.

[0042] Table 4 MB value (unit: g / kg) corresponding to different kaolin masses Comparative Example 1 The reference solution with a concentration of 10 g / L was prepared using anhydrous methylene blue solution, 15.00 g of kaolin, illite and montmorillonite were weighed and placed in an oven at a temperature of 100±5 ℃ to dry to constant weight and cool to room temperature in the oven. The kaolin was made into a suspension and placed on a magnetic stirrer to stir at a speed of 600 r / min for 5 min, and the titration experiment started after the magnetic stirrer stopped working. The appearance of blue halo in the suspension was the termination condition of the experiment, and the results were as shown in Table 5.

[0043] Table 5: Calibration experiment results of different objects (unit: g / kg) Through the methylene blue MB value test, the MB values of 15 g samples were respectively: kaolin 6.22 g / kg, illite 15.49 g / kg, and montmorillonite 59.56 g / kg. The consumption of kaolin methylene blue reagent and the titration time were relatively the shortest. The MB value calibration deviation ranges of kaolin, illite and montmorillonite were [-0.22, 0.45], [-0.80, 0.84] and [-2.89, 3.77] respectively. It can be found that the deviation range of MB value gradually expands, the sensitivity gradually increases, that is, the error of single experiment increases, and the repeatability becomes poor. The adsorption capacity of kaolin is much lower than that of montmorillonite, and its sensitivity to methylene blue solution consumption is lower, which will not produce large experimental errors due to sample differences. The uniformity of the standard sample is much better than that of montmorillonite, and kaolin is not hydrophilic, has low environmental sensitivity, and is more helpful to keep the standard sample stable under normal storage conditions.

[0044] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application.

[0045] Many other changes and modifications can be made without departing from the concept and scope of the present application. It should be understood that the present application is not limited to the specific embodiments, and the scope of the present application is defined by the appended claims.

Claims

1. A calibration method of methylene blue standard solution for machine-made sand MB value test, characterized in that, The method comprises the following steps: Step 1: using anhydrous methylene blue reagent with a purity of not less than 98.0%, prepare a methylene blue standard solution with a concentration of 10 g / L, use the reagent to be calibrated or newly purchased to prepare a methylene blue solution with a theoretical concentration of 10 g / L; Step 2: weigh at least three portions of dry kaolin with a mass gradient of A g, slowly add them into a water-containing beaker placed on a magnetic stirrer, stop stirring after fully mixing with water, and obtain a kaolin suspension; Step 3: use the methylene blue standard solution to titrate the kaolin suspension of step 2, use the magnetic stirrer to stir the kaolin suspension until the end of the test, use a digital pipette to add the methylene blue standard solution into the kaolin suspension, stir for 1-5 min, then use an electric micro-adjustable pipette to suck the suspension, adjust the amount of the suspension to form a 10 mm±1 mm diameter precipitate, use a calibration device to calibrate, clamp the rapid quantitative filter paper (4) with a magnetic filter paper clamp (2) and place it on a special titration table (1), so that the rapid quantitative filter paper (4) is suspended and flat, cover the color halo test plate (3) above the magnetic filter paper clamp (2) to form a calibration device, drop the suspension from the center of the color halo titration hole (3-1-1) of the color halo test plate (3), and observe whether a color halo appears, if the width of the color halo is ≥1 mm, stop, and record the cumulative consumption of the methylene blue standard solution; linear fitting obtains the slope and intercept, calculates the MB value corresponding to different mass of kaolin, and takes the average value MB0 as the MB value of the batch of kaolin; Step 4: use the methylene blue solution to titrate the kaolin suspension of step 2, record the consumption of the methylene blue solution, linear fitting obtains the slope and intercept, calculates the average value MB1 of the methylene blue solution, compares it with the average value MB0, and determines whether the methylene blue solution can be used continuously.

2. The calibration method of methylene blue standard solution for machine-made sand MB value test according to claim 1, characterized in that, The preparation of the methylene blue standard solution with a concentration of 10 g / L in step 1 specifically comprises the following steps: weighing anhydrous methylene blue reagent with a purity of not less than 98.0%, pouring it into a beaker containing distilled water, stirring with a magnetic stirrer until completely dissolved, naturally cooling to room temperature 25±5℃, pouring the solution into a volumetric flask, rinsing the beaker with distilled water and supplementing distilled water to the specified scale, transferring the solution in the volumetric flask into a dark storage bottle, marking the preparation information, and obtaining a methylene blue standard solution with a concentration of 10 g / L.

3. The method for calibrating a methylene blue standard solution for testing the MB value of manufactured sand according to claim 1, characterized in that, The kaolin in step 2 contains kaolinite with a mass fraction of not less than 90.0 %, a specification of chemical purity, a SiO2 mass fraction of not less than 46.5 %, an Al2O3 mass fraction of not less than 36.5 %, a mass loss on ignition of not more than 15.0 %, a 45 μm sieve residue of not more than 0.1 %, and a specific surface area of 20,000-50,000 m 2 / kg; the kaolin is dried to a constant weight in an oven at 100±5 ℃ and cooled in a desiccator, and the mass of the kaolin is weighed to an accuracy of 0.1 g.

4. The method for calibrating a methylene blue standard solution for testing the MB value of manufactured sand according to claim 1, characterized in that, In step 3, if the precipitate does not appear color halo or the width of the color halo is less than 1 mm, continue to repeat the titration step until a stable light blue color halo with a width of ≥1 mm appears around the precipitate, at this time, continue to stir and do not add methylene blue standard solution, every 1 min, suck the suspension for titration test, until the 5th min, observe whether the color halo is stable, if stable, the sample titration is completed, if not stable, the kaolin cannot be used as a calibration material.

5. The calibration method of methylene blue standard solution for testing the MB value of machine-made sand according to claim 4, characterized in that, The working temperature of the magnetic stirrer is set to 20-30℃, the magnetic stirrer is stirred at a speed of 600±60 r / min for 5-8 min, and then continuously stirred at a speed of 400±40 r / min, and the temperature of the kaolin suspension is maintained at 25±5℃.

6. The method for calibrating a methylene blue standard solution for testing the MB value of manufactured sand according to claim 4, characterized in that, The digital display pipette has a range of 10 mL and a precision of 1 mL; and the electric micro-adjustable pipette has a range of 30 μL-300 μL.

7. The method for calibrating a methylene blue standard solution for testing the MB value of manufactured sand according to claim 4, characterized in that, The specific requirement for determining whether the methylene blue solution can continue to be used in the step 4 is that the deviation distance of the vertical intercepts corresponding to the methylene blue solution and the methylene blue standard solution from the origin is not greater than 3.0, the difference between the slopes corresponding to the consumption of the methylene blue solution and the methylene blue standard solution is not greater than 0.10, and the deviation range of the MB1 value corresponding to the methylene blue solution from the MB0 value corresponding to the methylene blue standard solution is not greater than 1.0 g / kg, so that it is determined that the methylene blue solution can continue to be used; otherwise, it cannot continue to be used.

8. A calibration device for methylene blue standard solution for machine-made sand MB value test, characterized in that, The calibration method of the methylene blue standard solution for the machine-made sand MB value test according to any one of claims 1-7, wherein the calibration device comprises a special titration table (1), a magnetic filter paper clamp (2), a color halo test plate (3), and a rapid quantitative filter paper (4); the magnetic filter paper clamp (2) is composed of two mutually magnetic circular rings, and the two magnetic circular rings are placed on the front and back surfaces of the rapid quantitative filter paper (4) to clamp the rapid quantitative filter paper (4); the magnetic filter paper clamp (2) clamping the rapid quantitative filter paper (4) is placed on the special titration table (1); and the color halo test plate (3) is placed above the magnetic filter paper clamp (2) clamping the rapid quantitative filter paper (4).

9. The calibration device for methylene blue standard solution for testing the MB value of manufactured sand according to claim 8, characterized in that, The special titration table (1) has a cylindrical structure, the bottom of the special titration table (1) is sealed, the top inner side of the special titration table (1) is provided with a step for placing the magnetic filter paper clamp (2), and a notch is formed in the top of the special titration table (1) close to the step.

10. The calibration device for methylene blue standard solution for testing the MB value of manufactured sand according to claim 8, characterized in that, The color halo test plate (3) is provided with a plurality of color halo rings (3-1), the plurality of color halo rings (3-1) are uniformly distributed in a rice-shaped manner, the center of each color halo ring (3-1) is provided with a color halo titration hole (3-1-1) with a diameter of 5 mm, and the color halo ring (3-1) has 10 measuring rings from inside to outside with an increasing diameter of 1 mm, and the outermost ring has a diameter of 15 mm; the diameter of the color halo test plate (3) is 150 mm, the color halo test plate (3) is provided with 3 measuring rings from inside to outside with an increasing diameter of 40 mm, and the outermost ring has a diameter of 120 mm, and the center of the color halo ring (3-1) is located on the measuring ring of the color halo test plate (3).

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