Method for detecting content of organic matters in electrolytic manganese residues

Abstract

The invention belongs to the technical field of environmental monitoring and material analysis, and discloses a method for detecting the content of organic matters in electrolytic manganese residues. The method comprises the following steps: weighing the electrolytic manganese residues, then accurately adding a potassium dichromate-sulfuric acid solution, heating and digesting in an oil bath pan, adding a phenanthroline indicator at a constant volume after heating and digesting, then titrating by using a ferrous sulfate standard solution, and stopping titrating when the color of the solution is sequentially changed to be orange yellow, blue green and brownish red; and calculating the content of organic matters in the electrolytic manganese residues according to a formula. According to the method, through accurate volume and mass measurement, the measurement precision of the organic matter content is improved, and the influence of crystal water in the electrolytic manganese residues on a detection result is avoided; the detection process of the adopted volume-weight method is simple and rapid, and the detection time is greatly shortened; meanwhile, the dependence on expensive equipment is reduced, and the detection cost is reduced. According to the method, heating and firing are not needed in the detection process, the influence on the environment is reduced, and meanwhile carbon emission is reduced.

Description

Technical Field

[0001] The present invention relates to the technical fields of environmental monitoring and material analysis, and particularly relates to a method for detecting the organic matter content in electrolytic manganese slag. Background Art

[0002] At present, the "Pollution Control Standards for Storage and Landfilling of General Industrial Solid Wastes" (GB18599) limits the organic matter content standard for the admission of general industrial solid wastes, and stipulates the admission requirements for organic matter to Class I and Class II sites. The admission requirement for organic matter to enter Class I sites is that the organic matter content is less than 2% (except coal gangue), and the admission requirement for organic matter to enter Class II sites is that the organic matter content is less than 5% (except coal gangue). The determination method of organic matter is carried out in accordance with HJ761 (ignition loss method). This method has a high measured value of organic matter content for solid wastes containing non-organic matter components such as crystal water, such as electrolytic manganese slag and other tailings. In step 7.2 of the analysis procedure in HJ761 (ignition loss method), when the sample is dried at 105°C for 1 h, the crystal water in electrolytic manganese slag and other tailings cannot be completely removed. Therefore, in step 7.3 of the analysis procedure, the weight loss during the calcination process at 600°C for electrolytic manganese slag and other tailings is not only from organic matter, but also includes the crystal water in electrolytic manganese slag, resulting in an incorrect determination result of organic matter. The calculation result is as follows in formula (1):

[0003]

[0004] In the formula:

[0005] w—the organic matter content, %;

[0006] m 0 —the dry weight of the container and the sample, g;

[0007] m 1 —the mass of the container and the sample after calcination, g;

[0008] m—the dry weight of the sample, g;

[0009] 100—the unit conversion factor.

[0010] Through preliminary research and a large number of literature investigations, it is known that the main component of electrolytic manganese slag is raw gypsum (CaSO 4 ·2H 2O), when detecting the organic matter in electrolytic manganese slag by the ignition loss method (HJ 761-2015) for the determination of organic matter in solid waste, a large amount of crystal water in the electrolytic manganese slag will be lost during the high-temperature ignition process, resulting in the loss of weight not only from the organic matter in the electrolytic manganese slag, and finally making the test result much higher than the actual percentage content of organic matter. It should be noted that at present, China has promulgated a national standard (GB / T 17669.2-1999) for the determination of crystal water content in building gypsum. It can be directly seen from the operation procedure for the detection of crystal water in this standard that it is heated in an oven or high-temperature furnace at 230°C for 45 minutes until constant weight, and the weight of the crystal water is obtained by subtracting the weight before heating. Thus, it can be seen that the national standard measurement method for crystal water stipulates that crystal water will decompose at 230°C. This also means that the first-step heating treatment (105°C) in HJ761 cannot effectively remove crystal water, and the loss of organic matter obtained in the second-step ignition treatment (600°C) includes the loss of the weight of crystal water, ultimately resulting in a significantly higher determination result of organic matter.

[0011] As can be seen from the above, when determining the organic matter content in electrolytic manganese slag, due to the influence of crystal water and the limitation of the detection method, the test result of organic matter is quite different from the actual data, and the content of organic matter in electrolytic manganese slag cannot be correctly evaluated. Therefore, it is very necessary to propose a more suitable method for determining the organic matter in general industrial solid waste. Whether the test result of organic matter in electrolytic manganese slag is correct has a decisive effect on the harmless treatment and resource utilization of electrolytic manganese slag. Summary of the Invention

[0012] The purpose of the present invention is to provide a method for detecting the organic matter content in electrolytic manganese slag, so as to solve the problem that the test result of organic matter is quite different from the actual data due to the interference of crystal water in the existing measurement method.

[0013] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0014] The present invention provides a method for detecting the organic matter content in electrolytic manganese slag, including the following steps:

[0015] Wash the electrolytic manganese slag, conduct primary drying, grinding, screening, cooling, and secondary drying, and then conduct checking drying until constant weight to obtain an air-dried sample;

[0016] Accurately weigh the air-dried sample and place it in a test tube. Then, accurately add the potassium dichromate-sulfuric acid solution. After mixing evenly, place the test tube in an oil bath and heat it. Start timing when the solution in the test tube begins to boil. After the timing ends, take out the test tube, transfer the solid and liquid in the test tube to a conical flask, make up the volume, add o-phenanthroline indicator, and then titrate with a ferrous sulfate standard solution. The color of the solution in the conical flask changes successively from orange-yellow to blue-green until it turns brown-red and stops titration. Calculate the content of organic matter in the electrolytic manganese slag according to the formula.

[0017] Preferably, in the above method for detecting the content of organic matter in electrolytic manganese slag, the temperature of the first drying and the second drying is independently 100-110°C; the time of the first drying and the second drying is independently 2 h; the temperature of the checking drying is 100-110°C; the time of the checking drying is 30 min each time.

[0018] Preferably, in the above method for detecting the content of organic matter in electrolytic manganese slag, the aperture of the sieve for screening is 0.25 mm.

[0019] Preferably, in the above method for detecting the content of organic matter in electrolytic manganese slag, the mass ratio of the air-dried sample to the volume of the potassium dichromate-sulfuric acid solution is 0.05-0.5 g:10 mL; the concentration of the potassium dichromate-sulfuric acid solution is 0.4 mol / L.

[0020] Preferably, in the above method for detecting the content of organic matter in electrolytic manganese slag, the oil bath is preheated before use; the preheating temperature is 185-190°C.

[0021] Preferably, in the above method for detecting the content of organic matter in electrolytic manganese slag, the temperature for heating the test tube in the oil bath is 170-180°C.

[0022] Preferably, in the above method for detecting the content of organic matter in electrolytic manganese slag, the timing time is 4.5-5.5 min.

[0023] Preferably, in the above method for detecting the content of organic matter in electrolytic manganese slag, the addition amount of the o-phenanthroline indicator is 0.15 mL.

[0024] Preferably, in the above method for detecting the content of organic matter in electrolytic manganese slag, the formula is as follows:

[0025]

[0026] In the formula:

[0027] Q—the content of organic matter in the electrolytic manganese slag, unit: %;

[0028] V 0 — Volume of the ferrous sulfate standard solution consumed in the blank test, unit: mL;

[0029] V — Volume of the ferrous sulfate standard solution consumed in the determination of the air-dried sample, unit: mL;

[0030] C — Concentration of the ferrous sulfate standard solution, unit: mol / L;

[0031] 0.003 — Millimolar mass of 1 / 4 carbon atom, unit: g / mmol;

[0032] 1.724 — Coefficient for converting organic carbon to organic matter;

[0033] 1.10 — Oxidation correction coefficient;

[0034] m — Mass of the air-dried sample, unit: g.

[0035] As can be seen from the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0036] The detection method of the present invention includes: under the condition of external heating, oxidizing the organic matter (carbon) in the electrolytic manganese slag with a potassium dichromate-sulfuric acid solution of a certain concentration, and titrating the remaining potassium dichromate with ferrous sulfate. The content of organic carbon is calculated from the consumed potassium dichromate. At the beginning of the titration, the orange-yellow color of potassium dichromate is dominant. During the titration process, the green color of Cr 3+ gradually appears. When it is almost at the end point, it turns blue-green. When half a drop of the standard ferrous sulfate solution is in excess, it turns brown-red, indicating that the end point has been reached. Its essence is an oxidation-reduction and color reaction. The present invention improves the measurement accuracy of the organic matter content through precise volume and mass measurement, and avoids the influence of crystal water in the electrolytic manganese slag on the detection result; the bulk density method adopted has a simple and rapid detection process, greatly shortens the detection time, and increases the efficiency; at the same time, it reduces the dependence on expensive equipment and lowers the detection cost. The detection process of the present invention does not require heating and burning, reduces the impact on the environment, and reduces carbon emissions. Specific Embodiments

[0037] The present invention provides a method for detecting the organic matter content in electrolytic manganese slag, including the following steps:

[0038] Wash the electrolytic manganese slag, conduct primary drying, grinding, screening, cooling, and secondary drying, and then conduct checking drying until constant weight to obtain an air-dried sample;

[0039] Accurately weigh the air-dried sample and place it in a test tube. Then, accurately add the potassium dichromate-sulfuric acid solution. After mixing evenly, place the test tube in an oil bath and heat it. Start timing when the solution in the test tube begins to boil. After the timing ends, take out the test tube, transfer the solid and liquid in the test tube to a conical flask, make up the volume, add the o-phenanthroline indicator, and then titrate with the ferrous sulfate standard solution. The color of the solution in the conical flask changes successively from orange-yellow to blue-green until it turns brown-red and stops titration. Calculate the organic matter content in the electrolytic manganese slag according to the formula.

[0040] In the present invention, the liquid-solid ratio of the water washing is preferably 2:1; the number of times of the water washing is preferably 4 times.

[0041] In the present invention, the temperatures of the first drying and the second drying are independently preferably 100-110 °C, more preferably 105 °C; the times of the first drying and the second drying are independently preferably 2 h.

[0042] In the present invention, the aperture of the sieve mesh for screening is preferably 0.25 mm.

[0043] In the present invention, the cooling is preferably cooling to room temperature in a desiccator.

[0044] In the present invention, the temperature of the checking drying is preferably 100-110 °C, more preferably 105 °C; the time of the checking drying is preferably 30 min each time.

[0045] In the present invention, the mass of the air-dried sample is accurate to 0.0001 g.

[0046] In the present invention, the mass ratio of the air-dried sample to the volume of the potassium dichromate-sulfuric acid solution is preferably 0.05-0.5 g:10 mL, more preferably 0.5 g:10 mL; the concentration of the potassium dichromate-sulfuric acid solution is preferably 0.4 mol / L.

[0047] In the present invention, before placing the test tube in the oil bath for heating, a glass funnel is further placed at the mouth of the test tube.

[0048] In the present invention, the oil bath is preheated before use; the preheating temperature is preferably 185-190 °C, more preferably 190 °C.

[0049] In the present invention, the temperature for placing the test tube in the oil bath for heating is preferably 170-190 °C, more preferably 180 °C.

[0050] In the present invention, the timing time is preferably 4.5-5.5 min, more preferably 5 min.

[0051] In the present invention, the liquid level of the test tube is lower than the oil level of the oil bath.

[0052] In the present invention, after taking out the test tube, it further includes wiping the oil liquid on the outer wall of the test tube.

[0053] In the present invention, after transferring the solid and liquid in the test tube to the Erlenmeyer flask, it further includes washing the test tube and the glass funnel with water, and combining the washing liquid and adding it to the Erlenmeyer flask.

[0054] In the present invention, the volume of constant volume is preferably 50 - 60 mL, more preferably 50 mL.

[0055] In the present invention, the addition amount of the phenanthroline indicator is preferably 0.15 mL.

[0056] In the present invention, the preparation method of the phenanthroline indicator is as follows: Weigh 1.49 g of phenanthroline and 0.7 g of ferrous sulfate, dissolve them in 100 mL of pure water, and store them sealed in a brown bottle to obtain the phenanthroline indicator.

[0057] In the present invention, the formula is as follows:

[0058]

[0059] In the formula:

[0060] Q—the content of organic matter in electrolytic manganese residue, unit: %;

[0061] V 0 —the volume of the ferrous sulfate standard solution consumed in the blank test, unit: mL;

[0062] V—the volume of the ferrous sulfate standard solution consumed in the determination of the air-dried sample, unit: mL;

[0063] C—the concentration of the ferrous sulfate standard solution, unit: mol / L;

[0064] 0.003—the millimolar mass of 1 / 4 carbon atom, unit: g / mmol;

[0065] 1.724—the coefficient for converting organic carbon to organic matter;

[0066] 1.10—the oxidation correction coefficient;

[0067] m—the mass of the air-dried sample, unit: g.

[0068] In the present invention, the blank test is carried out under the condition of not containing the air-dried sample.

[0069] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0070] Example 1

[0071] This example provides a method for detecting the organic matter content in electrolytic manganese residue, including the following steps:

[0072] Wash the No. 1 electrolytic manganese residue 4 times according to a liquid-solid ratio of 2:1, filter it, dry it in an electric heating drying oven at 105°C for 2 h, then grind it until it all passes through a sieve with a pore diameter of 0.25 mm, put it into a sample bag, place the sample bag in a desiccator and cool it to room temperature, and then conduct a checking drying according to the above conditions, 30 min each time, until constant weight is achieved to obtain an air-dried sample;

[0073] Precisely weigh 0.5000 g of the air-dried sample and place it in a test tube. Then, accurately measure 10.00 mL of a potassium dichromate-sulfuric acid solution with a concentration of 0.4 mol / L using an automatic zero-adjusting burette and add it to the test tube. Mix it evenly. Place a glass funnel at the mouth of the test tube, place the test tube in an oil bath pot for heating. The oil bath pot is preheated to 190°C on an electric furnace. The liquid level in the test tube is lower than the oil level in the oil bath pot. After putting the test tube in, control the temperature of the oil bath pot at 180°C. Start timing when the solution in the test tube begins to boil. After timing for 5 min, take out the test tube and wipe off the oil stains on the outer wall of the test tube with a clean cloth. Transfer the solid and liquid in the test tube to a conical flask, wash the test tube and the glass funnel with water, and pour the washed liquid into the conical flask together. Make the total volume of the solution in the conical flask accurately controlled at 50 mL by volume fixing. Then add 0.15 mL of o-phenanthroline indicator, and finally titrate it with a ferrous sulfate standard solution. The color change of the solution shows orange-yellow, blue-green, and finally stops titrating when it turns brown-red. Calculate the organic matter content in the electrolytic manganese residue according to the formula, and the results are shown in Table 1.

[0074] Example 2

[0075] This example provides a method for detecting the organic matter content in electrolytic manganese residue. Specifically refer to Example 1, the difference is that the No. 1 electrolytic manganese residue is replaced with the No. 2 electrolytic manganese residue. The calculation results of the organic matter content in the electrolytic manganese residue are shown in Table 1.

[0076] Example 3

[0077] This example provides a method for detecting the organic matter content in electrolytic manganese residue. Specifically refer to Example 1, the difference is that the No. 1 electrolytic manganese residue is replaced with the No. 3 electrolytic manganese residue. The calculation results of the organic matter content in the electrolytic manganese residue are shown in Table 1.

[0078] Example 4

[0079] This example provides a method for detecting the organic matter content in electrolytic manganese residue. For details, refer to Example 1. The difference is that the 1# electrolytic manganese residue is replaced by the 4# electrolytic manganese residue. The calculation results of the organic matter content in the electrolytic manganese residue are shown in Table 1.

[0080] Example 5

[0081] This example provides a method for detecting the organic matter content in electrolytic manganese residue. For details, refer to Example 1. The difference is that the 1# electrolytic manganese residue is replaced by the 5# electrolytic manganese residue. The calculation results of the organic matter content in the electrolytic manganese residue are shown in Table 1.

[0082] Table 1 Results of the organic matter content in the electrolytic manganese residue obtained by the methods of Examples 1 - 5

[0083] Sample Name Air-dried Specimen Mass g Calculation Result % No. 1 Electrolytic Manganese Residue 0.5000 1.826 No. 2 Electrolytic Manganese Residue 0.5000 1.402 No. 3 Electrolytic Manganese Residue 0.5000 1.794 No. 4 Electrolytic Manganese Residue 0.5000 3.036 No. 5 Electrolytic Manganese Residue 0.5000 1.398

[0084] Comparative Example 1

[0085] This comparative example uses the standard ignition loss method of HJ 761 - 2015 to detect the organic matter content in electrolytic manganese residue, including the following steps:

[0086] Pre - burn the porcelain crucible in a muffle furnace at 600 °C until it reaches a constant weight (the difference between two consecutive weighings is not greater than 0.001 g), and set it aside for use;

[0087] Wash the 1# electrolytic manganese residue 4 times according to a liquid - to - solid ratio of 2:1, filter it, dry it in an electric drying oven at 105 °C for 2 h, then grind it until it all passes through a sieve with a pore size of 0.25 mm, put it into a sample bag, place the sample bag in a desiccator and cool it to room temperature, and then conduct a check - drying under the above conditions, 30 min each time, until it reaches a constant weight to obtain an air - dried sample;

[0088] Accurately weigh 0.5000 g of the air - dried sample and spread it flat in the porcelain crucible, cover the crucible, then put it into the muffle furnace. After the temperature rises to 600 °C, burn it at 600 °C for 3 h. Take it out, cool it in the air for 5 min first, then transfer it to a desiccator and cool it to room temperature, and weigh it; repeat the above steps for check - burning, 30 min each time, until it reaches a constant weight. Calculate the organic matter content in the electrolytic manganese residue according to the formula in the standard, and the results are shown in Table 2.

[0089] Comparative Examples 2 - 5

[0090] In Comparative Examples 2 - 5, the 1# electrolytic manganese residue in Comparative Example 1 is replaced by the 2# electrolytic manganese residue, 3# electrolytic manganese residue, 4# electrolytic manganese residue, and 5# electrolytic manganese residue respectively, and the rest refers to Comparative Example 1. The results are shown in Table 2.

[0091] Table 2 Content results of organic matter in electrolytic manganese slag obtained by the methods of Comparative Examples 1-5

[0092] Sample Name Air-dried Specimen Mass g Calculation Result % No. 1 Electrolytic Manganese Residue 0.5000 5.148 No. 2 Electrolytic Manganese Residue 0.5000 5.547 No. 3 Electrolytic Manganese Residue 0.5000 5.689 No. 4 Electrolytic Manganese Residue 0.5000 6.670 No. 5 Electrolytic Manganese Residue 0.5000 5.531

[0093] Examples 6-10

[0094] Examples 6-10 provide a method for determining the crystal water in 1-5# electrolytic manganese slag, including the following steps:

[0095] Accurately weigh 0.5000 g of air-dried sample and spread it flat in a weighing bottle with a ground glass stopper that has been dried to a constant weight. Place the ground glass stopper diagonally on the weighing bottle. Put the weighing bottle containing the sample in a drying oven at 230 °C and dry it for 1 h. Take out the weighing bottle and place it in a desiccator. Close the ground glass stopper tightly, cool it to room temperature, and weigh it. Repeat the above drying and cooling steps until a constant weight is reached. The content of crystal water is the difference between the total mass of the weighing bottle and the air-dried sample before and after drying divided by the mass of the air-dried sample weighed before drying. The results are shown in Table 3.

[0096] Table 3 Determination results of crystal water in 1-5# electrolytic manganese slag

[0097] Sample Name Air-dried Specimen Mass g Calculation Result % No. 1 Electrolytic Manganese Residue 0.5000 3.432 No. 2 Electrolytic Manganese Residue 0.5000 4.263 No. 3 Electrolytic Manganese Residue 0.5000 3.985 No. 4 Electrolytic Manganese Residue 0.5000 3.734 No. 5 Electrolytic Manganese Residue 0.5000 4.197

[0098] Compare the content of organic matter in electrolytic manganese slag determined by the ignition loss method in Comparative Examples 1-5 (Table 2) with the content of organic matter in electrolytic manganese slag determined by the bulk density method in Examples 1-5 (Table 1). The differences between the two methods for 1-5# electrolytic manganese slag are 3.322%, 4.145%, 3.895%, 3.634%, and 4.133% respectively, indicating that there are significant differences in the analysis results between the ignition loss method and the bulk density method.

[0099] After deducting the content of crystal water (Table 3) from the content of organic matter in electrolytic manganese slag determined by the ignition loss method in Comparative Examples 1-5 (Table 2), and comparing it with the content of organic matter in electrolytic manganese slag determined by the bulk density method in Examples 1-5 (Table 1), the differences between the two methods for 1-5# electrolytic manganese slag are -0.11%, -0.118%, -0.09%, -0.1%, and -0.064% respectively. The difference between the two is no more than 0.12%, indicating that the determination result of the bulk density method is not affected by crystal water.

[0100] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for detecting the content of organic matter in electrolytic manganese slag, characterized in that: The following steps are involved: The electrolytic manganese slag is washed, dried once, ground, screened, cooled, dried twice, and then dried to constant weight to obtain an air-dried sample; Accurately weigh the air-dried sample and place it in a test tube, then accurately add potassium dichromate-sulfuric acid solution, mix well and place the test tube in an oil bath for heating, start timing when the solution in the test tube begins to boil; after the timing ends, take out the test tube, transfer the solid and liquid in the test tube to a conical flask, add o-phenanthroline indicator after constant volume, and then use ferrous sulfate standard solution for titration, the color of the solution in the conical flask changes to orange-yellow, blue-green until brown-red, and then stop titration; calculate the content of organic matter in the electrolytic manganese slag according to the formula.

2. The method for detecting the organic matter content in electrolytic manganese slag according to claim 1, characterized in that: The temperature of the primary drying and the secondary drying are independently 100-110° C.; the time of the primary drying and the secondary drying are independently 2 hours; the temperature of the inspection drying is 100-110° C.; the time of the inspection drying is 30 minutes each time.

3. The method for detecting the organic matter content in electrolytic manganese slag according to claim 2, characterized in that: The sieve mesh size for screening is 0.25 mm.

4. The method for detecting the organic matter content in electrolytic manganese slag according to claim 3, characterized in that: The volume ratio of the mass of the air-dried sample to the potassium dichromate-sulfuric acid solution is 0.05-0.5 g:10 mL; the concentration of the potassium dichromate-sulfuric acid solution is 0.4 mol / L.

5. A method for detecting the content of organic matter in electrolytic manganese slag according to claim 1 or 4, characterized in that: The oil bath pot is preheated before use; the preheating temperature is 185-190°C.

6. The method for detecting the organic matter content in electrolytic manganese slag according to claim 5, characterized in that: The test tube is placed in an oil bath and heated at a temperature of 170-180°C.

7. A method for detecting the content of organic matter in electrolytic manganese slag according to claim 1 or 6, characterized in that: The timing time is 4.5 to 5.5 minutes.

8. The method for detecting the organic matter content in electrolytic manganese slag according to claim 7, characterized in that: The amount of the o-phenanthroline indicator added is 0.15 mL.

9. The method for detecting the organic matter content in electrolytic manganese slag according to claim 8, characterized in that: The formula is as follows: Where: Q—the content of organic matter in electrolytic manganese slag, in %; V0—the volume of ferrous sulfate standard solution consumed in the blank test, in mL; V—the volume of ferrous sulfate standard solution consumed in the air-dried sample determination, in mL; C—the concentration of ferrous sulfate standard solution, in mol / L; 0.003—1 / 4 of the millimolar mass of a carbon atom, in g / mmol; 1.724—The coefficient for converting organic carbon into organic matter; 1.10—Oxidation correction factor; m—The mass of the air-dried sample, in g.

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