Method for measuring content of nickel element in ferronickel

Abstract

The invention discloses a method for determining the content of a nickel element in ferronickel, which mainly comprises the following steps: dissolving a ferronickel sample with hydrochloric acid, nitric acid and hydrofluoric acid under the condition of microwave digestion, firstly determining the content of the cobalt element in a test solution by adopting inductively coupled plasma emission spectrometry, secondly taking the test solution and adding a masking agent to mask interference elements, a copper ion selective electrode is used as an indicator electrode, an Ag / AgCl electrode is used as a reference electrode, a Cu-EDTA solution is used as an indicator, EDTA is used as a titrant, the content of nickel and cobalt elements in a sample is calculated according to the consumption of an EDTA standard titration solution, and finally the content of the nickel element can be obtained by deducting the content of the cobalt element from the content of the nickel and cobalt elements. The method solves the problem of determination of the nickel element in ferronickel, improves the precision and accuracy of analysis and measurement, and is rapid in measurement and simple and convenient to operate.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical analysis and detection, and particularly relates to a method for determining the nickel content in ferronickel. Background Art

[0002] Ferronickel is a nickel-iron alloy containing 15% to 80% nickel. It is primarily used as a nickel substitute in stainless steel furnace feedstock. It is an alloy of nickel and iron containing carbon, silicon, cobalt, copper, and other elements. In the steelmaking industry, it is used as an alloying element additive to increase the bending strength and hardness of steel. In cast iron, it can also provide a uniform structure and increase density. Ferronickel is also used as an additive in nickel- or nickel-chromium-containing cast iron rolls and other casting alloys.

[0003] In the existing technology, the standard detection methods for determining nickel in nickel iron include dimethylglyoxime gravimetric method, EDTA titration method, X-ray fluorescence spectrometry, and spark source atomic emission spectrometry. Among them, the dimethylglyoxime gravimetric method is time-consuming and complicated to operate; the EDTA titration method is interfered by cobalt and copper elements, and the dissolution method is time-consuming; X-ray fluorescence spectrometry and spark source atomic emission spectrometry are conventional detection methods. The methods are simple to operate, but have high requirements for sample preparation. For nickel beans or granular samples, it is difficult to meet the sample preparation requirements for sample testing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for determining nickel in ferronickel, which has high sensitivity and high accuracy, and the instrument is easy to operate and has a wide range of applications, thereby improving the applicability of the analytical method and the convenience of operation.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for measuring the nickel content in ferronickel, characterized in that it comprises the following steps:

[0007] (1) Weigh the nickel-iron test sample and digest it;

[0008] After the digestion process is completed, cool it down and transfer the digestion solution to a plastic beaker. Wash the inner cover and the digestion inner tank with water. Combine the washings and transfer them to a plastic volumetric flask. Dilute with water to the mark and mix well to obtain the sample solution.

[0009] (2) using an inductively coupled plasma emission spectrometer to sequentially measure a series of standard solutions and a sample solution, using the concentration of cobalt in the series of standard solutions as the abscissa and the intensity as the ordinate, and using a linear intercept calculation method to draw a series of standard curves, and calculating the cobalt content in the sample solution based on the series of standard curves;

[0010] (3) Pipette the sample solution into a conical flask, adjust the solution pH to 10, add ammonia-ammonium chloride buffer solution, add Cu-EDTA solution, use a copper ion selective electrode as the indicator electrode, and EDTA standard solution as the titrant. Automatic potentiometric titrator automatically records the potential change. When the potential jump occurs, i.e., the titration endpoint, record the total amount of nickel and cobalt elements.

[0011] (4) The calculated total amount of nickel and cobalt elements in the nickel-iron test sample minus the calculated cobalt content in the nickel-iron test sample is the nickel element in the nickel-iron test sample.

[0012] Preferably, the specific steps of digestion in step (1) are: weighing the nickel-iron test sample, placing it in a digestion tank, adding water to moisten it, adding hydrochloric acid and nitric acid until the violent reaction is completed, adding drops of hydrofluoric acid, covering the digestion cover, and placing it in a microwave digestion instrument to heat and digest.

[0013] Preferably, the microwave digestion power in step (1) is 1000W to 1600W, the temperature is raised to a target temperature of 180°C to 210°C, and then kept warm until complete digestion.

[0014] Preferably, in step (1), the mass ratio of the nickel-iron test sample to the wetting water is 1:25;

[0015] The volume ratio of water, hydrochloric acid and nitric acid used for wetting is 5:5-9:3-8;

[0016] Add 1 to 3 drops of hydrofluoric acid to 1 ml of moistening water;

[0017] Use a 100 mL plastic volumetric flask to make up to volume for every 0.1 g of nickel-iron test sample.

[0018] Preferably, the temperature in step (1) is cooled to below 50°C.

[0019] Preferably, the preparation method of the series standard solution in step (2) is as follows: 6 parts of 0.1000g high-purity nickel and 0.1000g high-purity iron are weighed into a 150mL beaker, 8mL of hydrochloric acid and 8mL of nitric acid are added, and the mixture is heated to a slight boil until the sample is completely dissolved, then removed and cooled, and transferred to a 200mL volumetric flask. 0mL, 200μL, 400μL, 1.00mL, 4.00mL, and 4.00mL of 1000μg / mL cobalt standard solution are respectively pipetted into corresponding volumetric flasks, diluted to the scale line with water, and mixed to obtain a series of standard solutions.

[0020] Preferably, the concentration of the cobalt standard solution used to draw the series of standard curves in step (2) is 1 μg / mL to 20 μg / mL, and the mass content detection range of the cobalt element in the nickel iron test sample is 0.1% to 2%.

[0021] Preferably, in step (3), the solution used to adjust the pH value of the solution to 10 is composed of 1+1 triethanolamine and 1+1 ammonia water.

[0022] Preferably, in step (3), the volume ratio of the sample solution to the volume of the conical flask is 1:10;

[0023] Sample solution: 1+1 triethanolamine: ammonia-ammonium chloride buffer solution: Cu-EDTA solution, volume ratio is 10:2~3:2~3:0.1~0.4.

[0024] Preferably, the content of nickel in the nickel-iron test sample in step (4) is expressed as mass fraction ω B The value is expressed in %, calculated according to formula (1):

[0025]

[0026] Where:

[0027] C—actual concentration of EDTA standard solution, in moles per liter (moL / L);

[0028] V—the volume of EDTA standard solution added to the sample solution, in milliliters (mL);

[0029] 58.69—Molar mass of nickel in grams per mole (g / moL);

[0030] m—mass of nickel-iron test sample, in grams;

[0031] r—dilution ratio of the sample solution;

[0032] 58.93—Molar mass of cobalt in grams per mole (g / moL);

[0033] w Co —Mass fraction of cobalt in the sample solution.

[0034] The beneficial technical effects of the present invention are:

[0035] The present invention uses hydrochloric acid, nitric acid, and hydrofluoric acid to dissolve a sample under microwave digestion conditions, and then determines the cobalt content in ferronickel by inductively coupled plasma emission spectrometry. Potentiometric titration is used to determine the total amount of nickel and cobalt in the sample, and mathematical correction is used to deduct the cobalt content to calculate the nickel content in the sample. The present invention is applicable to ferronickel alloys with a nickel content of 5.00% to 90.00% (with a maximum detection error of ±0.40%). Practice has shown that the method is simple to operate, has high accuracy in measurement results, and has good repeatability. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to specific embodiments.

[0037] Example 1

[0038] The method for measuring nickel content in ferronickel in the present embodiment comprises the following steps:

[0039] (1) Sample dissolution

[0040] Weigh 0.2g of nickel-iron test sample, place it in a digestion tank, add 5ml of water to moisten it, then add 9ml of hydrochloric acid and 3ml of nitric acid. After the violent reaction is completed, add 10 drops of hydrofluoric acid, cover the digestion cover, and place it in a microwave digestion instrument according to the set program (digestion power is 1200w, heating to the target temperature of 200℃). After the digestion program is completed, cool it to below 50℃, transfer the digestion solution to a plastic beaker, clean the inner cover and digestion inner tank with water in small amounts several times, combine the washings and transfer them to a 200ml plastic volumetric flask, dilute with water to the scale, and mix to obtain the sample solution.

[0041] (2) Determination of cobalt content

[0042] Weigh 6 portions of 0.1000g high-purity nickel and 0.1000g high-purity iron respectively into a 150mL beaker, add 8mL of hydrochloric acid and 8mL of nitric acid, heat to a slight boil until the sample is completely dissolved, remove and cool, transfer to a 200mL volumetric flask, pipette 0mL, 200μL, 400μL, 1.00mL, 2.00mL, and 4.00mL of cobalt standard solution (1000μg / mL) into the corresponding volumetric flask, dilute to the scale with water, and mix well to obtain a series of standard solutions;

[0043] A series of standard solutions and a sample solution were measured sequentially using an inductively coupled plasma emission spectrometer. A standard curve was plotted using the cobalt concentration in the standard solutions as the abscissa and the intensity as the ordinate, using a linear intercept calculation method. The cobalt content in the sample solution was calculated based on the standard curve. The cobalt content was determined to be 0.254%.

[0044] (1) Determination of nickel and cobalt content

[0045] Pipette 50.00mL of test solution into a 500mL conical flask, add 15mL of 1+1 triethanolamine, add 1+1 ammonia water dropwise to adjust the pH value of the solution to 10, add 10mL of ammonia water-ammonium chloride buffer solution, add 1mL of Cu-EDTA solution, use a copper ion selective electrode as the indicator electrode and EDTA standard solution as the titrant, and use an automatic potentiometric titrator to automatically record the potential change. Record the total amount of nickel and cobalt elements when the potential jumps (i.e., the titration end point).

[0046] (2) Calculation of nickel content in ferronickel

[0047] The calculation formula for the nickel content in ferronickel is as follows:

[0048]

[0049] Where:

[0050] C—actual concentration of EDTA standard solution, in moles per liter (moL / L);

[0051] V—the volume of EDTA standard solution added to the sample solution, in milliliters (mL);

[0052] 58.69 — molar mass of nickel in grams per mole (g / moL);

[0053] m—mass of nickel-iron test sample, in grams (g);

[0054] r—dilution ratio of the sample solution;

[0055] 58.93 — Molar mass of cobalt in grams per mole (g / moL);

[0056] w Co —Mass fraction of cobalt in the sample solution.

[0057] The concentration of EDTA standard solution added to sample 1 is 0.02004moL / L. The volume of EDTA standard solution added to the sample solution is mL. Substitute it into the formula to calculate:

[0058]

[0059] After calculation, the mass content of nickel in the measured sample was 23.62%, and the result determined by standard titration method was 23.43%. The range of the two results was less than the allowable difference requirement in GB / T 30072-2013, and the result was satisfactory.

[0060] Example 2

[0061] The method for measuring nickel content in ferronickel in the present embodiment comprises the following steps:

[0062] (1) Sample dissolution

[0063] Weigh 0.2g of nickel-iron test sample, place it in a digestion tank, add 5ml of water to moisten it, then add 5ml of hydrochloric acid and 5ml of nitric acid. After the violent reaction is completed, add 10 drops of hydrofluoric acid, cover the digestion cover, and place it in a microwave digester according to the set program (digestion power is 1400w, heating to the target temperature of 190℃). After the digestion program is completed, cool it to below 50℃, transfer the digestion solution to a plastic beaker, wash the inner cover and digestion inner tank with water in small amounts several times, combine the washings and transfer them to a 200ml plastic volumetric flask, dilute with water to the scale, and mix to obtain the sample solution.

[0064] (2) Determination of cobalt content

[0065] Weigh 6 portions of 0.1000g high-purity nickel and 0.1000g high-purity iron respectively into a 150mL beaker, add 8mL of hydrochloric acid and 8mL of nitric acid, heat to a slight boil until the sample is completely dissolved, remove and cool, transfer to a 200mL volumetric flask, pipette 0mL, 200μL, 400μL, 1.00mL, 2.00mL, and 4.00mL of cobalt standard solution (1000μg / mL) into the corresponding volumetric flask, dilute to the scale with water, and mix well to obtain a series of standard solutions;

[0066] A series of standard solutions and a sample solution were measured sequentially using an inductively coupled plasma emission spectrometer. A standard curve was plotted using the cobalt concentration in the standard solutions as the abscissa and the intensity as the ordinate, using a linear intercept calculation method. The cobalt content in the sample solution was calculated based on the standard curve. The cobalt content was determined to be 0.347%.

[0067] (3) Determination of nickel and cobalt content

[0068] Pipette 50.00mL of test solution into a 500mL conical flask, add 12mL of 1+1 triethanolamine, add 1+1 ammonia water dropwise to adjust the pH value of the solution to 10, add 15mL of ammonia water-ammonium chloride buffer solution, add 1.5mL of Cu-EDTA solution, use a copper ion selective electrode as the indicator electrode and EDTA standard solution as the titrant, and use an automatic potentiometric titrator to automatically record the potential change. Record the total amount of nickel and cobalt elements when the potential jumps (i.e., the titration end point).

[0069] (4) Calculation of nickel content in ferronickel

[0070] The calculation formula for the nickel content in ferronickel is as follows:

[0071]

[0072] Where:

[0073] C—actual concentration of EDTA standard solution, in moles per liter (moL / L);

[0074] V—the volume of EDTA standard solution added to the sample solution, in milliliters (mL);

[0075] 58.69 — molar mass of nickel in grams per mole (g / moL);

[0076] m—mass of nickel-iron test sample, in grams (g);

[0077] r—dilution ratio of the sample solution;

[0078] 58.93 — Molar mass of cobalt in grams per mole (g / moL);

[0079] w Co —Mass fraction of cobalt in the sample solution.

[0080] The concentration of EDTA standard solution added to sample 2 is 0.02004moL / L. The volume of EDTA standard solution added to the sample solution is mL. Substitute it into the formula to calculate:

[0081]

[0082] After calculation, the mass content of nickel in the measured sample was 58.77%, and the result determined by standard titration method was 58.83%. The range of the two results was less than the allowable difference requirement in GB / T 30072-2013, and the result was satisfactory.

[0083] Example 3

[0084] The method for measuring nickel content in ferronickel in the present embodiment comprises the following steps:

[0085] (1) Sample dissolution

[0086] Weigh 0.2g of nickel-iron test sample, place it in a digestion tank, add 5ml of water to moisten it, then add 8ml of hydrochloric acid and 4ml of nitric acid. After the violent reaction is completed, add 5 drops of hydrofluoric acid, cover the digestion cover, and place it in a microwave digestion instrument according to the set program (digestion power is 1000w, heating to the target temperature of 180℃). After the digestion program is completed, cool it to below 50℃, transfer the digestion solution to a plastic beaker, clean the inner cover and digestion inner tank with water in small amounts several times, combine the washings and transfer them to a 200ml plastic volumetric flask, dilute with water to the scale, and mix to obtain the sample solution.

[0087] (2) Determination of cobalt content

[0088] Weigh 6 portions of 0.1000g high-purity nickel and 0.1000g high-purity iron respectively into a 150mL beaker, add 8mL of hydrochloric acid and 8mL of nitric acid, heat to a slight boil until the sample is completely dissolved, remove and cool, transfer to a 200mL volumetric flask, pipette 0mL, 200μL, 400μL, 1.00mL, 2.00mL, and 4.00mL of cobalt standard solution (1000μg / mL) into the corresponding volumetric flask, dilute to the scale with water, and mix well to obtain a series of standard solutions;

[0089] A series of standard solutions and a sample solution were measured sequentially using an inductively coupled plasma emission spectrometer. A standard curve was plotted using the cobalt concentration in the standard solutions as the abscissa and the intensity as the ordinate, using a linear intercept calculation method. The cobalt content in the sample solution was calculated based on the standard curve. The cobalt content was determined to be 1.37%.

[0090] (5) Determination of nickel and cobalt content

[0091] Pipette 50.00mL of test solution into a 500mL conical flask, add 12mL of 1+1 triethanolamine, add 1+1 ammonia water dropwise to adjust the pH value of the solution to 10, add 12mL of ammonia water-ammonium chloride buffer solution, add 2mL of Cu-EDTA solution, use a copper ion selective electrode as the indicator electrode and EDTA standard solution as the titrant, and use an automatic potentiometric titrator to automatically record the potential change. Record the total amount of nickel and cobalt elements when the potential jumps (i.e., the titration end point).

[0092] (6) Calculation of nickel content in ferronickel

[0093] The calculation formula for the nickel content in ferronickel is as follows:

[0094]

[0095] Where:

[0096] C—actual concentration of EDTA standard solution, in moles per liter (moL / L);

[0097] V—the volume of EDTA standard solution added to the sample solution, in milliliters (mL);

[0098] 58.69 — molar mass of nickel in grams per mole (g / moL);

[0099] m—mass of nickel-iron test sample, in grams (g);

[0100] r—dilution ratio of the sample solution;

[0101] 58.93 — Molar mass of cobalt in grams per mole (g / moL);

[0102] w Co —Mass fraction of cobalt in the sample solution.

[0103] The cobalt content of sample 3 was determined by inductively coupled plasma method to be 0.182%. The concentration of EDTA standard solution was 0.02004 mol / L. The volume of EDTA standard solution added to the sample solution was mL. Substitute it into the formula to calculate:

[0104]

[0105] After calculation, the mass content of nickel in the measured sample was 78.26%, and the result determined by standard titration method was 78.37%. The range of the two results was less than the allowable difference requirement in GB / T 30072-2013, and the result was satisfactory.

[0106] Example 4

[0107] The method for measuring nickel content in ferronickel in the present embodiment comprises the following steps:

[0108] (1) Sample dissolution

[0109] Weigh 0.2g of nickel-iron test sample, place it in a digestion tank, add 5ml of water to moisten it, then add 5ml of hydrochloric acid and 8ml of nitric acid. After the violent reaction is completed, add 15 drops of hydrofluoric acid, cover the digestion cover, and place it in a microwave digester according to the set program (digestion power is 1500w, heating to the target temperature of 210℃). After the digestion program is completed, cool it to below 50℃, transfer the digestion solution to a plastic beaker, clean the inner cover and digestion inner tank with water in small amounts several times, combine the washings and transfer them to a 200ml plastic volumetric flask, dilute with water to the scale, and mix to obtain the sample solution.

[0110] (2) Determination of cobalt content

[0111] Weigh 6 portions of 0.1000g high-purity nickel and 0.1000g high-purity iron respectively into a 150mL beaker, add 8mL of hydrochloric acid and 8mL of nitric acid, heat to a slight boil until the sample is completely dissolved, remove and cool, transfer to a 200mL volumetric flask, pipette 0mL, 200μL, 400μL, 1.00mL, 2.00mL, and 4.00mL of cobalt standard solution (1000μg / mL) into the corresponding volumetric flask, dilute to the scale with water, and mix well to obtain a series of standard solutions;

[0112] A series of standard solutions and a sample solution were measured sequentially using an inductively coupled plasma emission spectrometer. A standard curve was plotted using the cobalt concentration in the standard solutions as the abscissa and the intensity as the ordinate, using a linear intercept calculation method. The cobalt content in the sample solution was calculated based on the standard curve. The cobalt content was determined to be 0.145%.

[0113] (7) Determination of nickel and cobalt content

[0114] Pipette 50.00mL of test solution into a 500mL conical flask, add 12mL of 1+1 triethanolamine, add 1+1 ammonia water dropwise to adjust the pH value of the solution to 10, add 10mL of ammonia water-ammonium chloride buffer solution, add 0.5mL of Cu-EDTA solution, use a copper ion selective electrode as the indicator electrode and EDTA standard solution as the titrant, and use an automatic potentiometric titrator to automatically record the potential change. Record the total amount of nickel and cobalt elements when the potential jumps (i.e., the titration end point).

[0115] (8) Calculation of nickel content in ferronickel

[0116] The calculation formula for the nickel content in ferronickel is as follows:

[0117]

[0118] Where:

[0119] C—actual concentration of EDTA standard solution, in moles per liter (moL / L);

[0120] V—the volume of EDTA standard solution added to the sample solution, in milliliters (mL);

[0121] 58.69 — molar mass of nickel in grams per mole (g / moL);

[0122] m—mass of nickel-iron test sample, in grams (g);

[0123] r—dilution ratio of the sample solution;

[0124] 58.93 — Molar mass of cobalt in grams per mole (g / moL);

[0125] w Co —Mass fraction of cobalt in the sample solution.

[0126] The concentration of the EDTA standard solution added to sample 4 is 0.02004 mol / L. The volume of the EDTA standard solution added to the sample solution is mL. Substitute it into the formula to calculate:

[0127]

[0128] After calculation, the mass content of nickel in the measured sample was 15.50%, and the result determined by standard titration method was 15.42%. The range of the two results was less than the allowable difference requirement in GB / T 30072-2013, and the result was satisfactory.

[0129] It can be seen from the above experimental results that the method provided by the present invention can accurately determine the content of nickel in nickel iron and has good test precision and accuracy.

[0130] Comparative Example 1

[0131] The method for measuring the nickel content in ferronickel in this comparative example comprises the following steps:

[0132] (1) Sample dissolution

[0133] Weigh 0.2g of nickel-iron test sample, place it in a digestion tank, add 5ml of water to moisten it, then add 5ml of hydrochloric acid and 8ml of nitric acid. After the violent reaction is completed, add 15 drops of hydrofluoric acid, cover the digestion cover, and place it in a microwave digester according to the set program (digestion power is 1500w, heating to the target temperature of 140℃). After the digestion program is completed, cool it to below 50℃, transfer the digestion solution to a plastic beaker, clean the inner cover and digestion inner tank with water in small amounts several times, combine the washings and transfer them to a 200ml plastic volumetric flask, dilute with water to the scale, and mix to obtain the sample solution.

[0134] (2) Determination of cobalt content

[0135] Weigh 6 portions of 0.1000g high-purity nickel and 0.1000g high-purity iron respectively into a 150mL beaker, add 8mL of hydrochloric acid and 8mL of nitric acid, heat to a slight boil until the sample is completely dissolved, remove and cool, transfer to a 200mL volumetric flask, pipette 0mL, 200μL, 400μL, 1.00mL, 2.00mL, and 4.00mL of cobalt standard solution (1000μg / mL) into the corresponding volumetric flask, dilute to the scale with water, and mix well to obtain a series of standard solutions;

[0136] A series of standard solutions and a sample solution were measured sequentially using an inductively coupled plasma emission spectrometer. A standard curve was plotted using the cobalt concentration in the standard solutions as the abscissa and the intensity as the ordinate, using a linear intercept calculation method. The cobalt content in the sample solution was calculated based on the standard curve. The cobalt content was determined to be 0.115%.

[0137] (9) Determination of nickel and cobalt content

[0138] Pipette 50.00mL of test solution into a 500mL conical flask, add 12mL of 1+1 triethanolamine, add 1+1 ammonia water dropwise to adjust the pH value of the solution to 10, add 10mL of ammonia water-ammonium chloride buffer solution, add 0.5mL of Cu-EDTA solution, use a copper ion selective electrode as the indicator electrode and EDTA standard solution as the titrant, and use an automatic potentiometric titrator to automatically record the potential change. Record the total amount of nickel and cobalt elements when the potential jumps (i.e., the titration end point).

[0139] (10) Calculation of nickel content in ferronickel

[0140] The calculation formula for the nickel content in ferronickel is as follows:

[0141]

[0142] Where:

[0143] C—actual concentration of EDTA standard solution, in moles per liter (moL / L);

[0144] V—the volume of EDTA standard solution added to the sample solution, in milliliters (mL);

[0145] 58.69 — molar mass of nickel in grams per mole (g / moL);

[0146] m—mass of nickel-iron test sample, in grams (g);

[0147] r—dilution ratio of the sample solution;

[0148] 58.93 — Molar mass of cobalt in grams per mole (g / moL);

[0149] w Co —Mass fraction of cobalt in the sample solution.

[0150] The concentration of the EDTA standard solution added to sample 4 is 0.02004 mol / L. The volume of the EDTA standard solution added to the sample solution is mL. Substitute it into the formula to calculate:

[0151]

[0152] Calculation showed that the mass content of nickel in the sample was 12.07%, and the result determined by standard titration was 15.42%. The range of the two results was greater than the allowable difference requirement in GB / T 30072-2013, indicating that incomplete digestion had a significant impact on the experimental results.

[0153] Comparative Example 2

[0154] The method for measuring the nickel content in ferronickel in this comparative example comprises the following steps:

[0155] (1) Sample dissolution

[0156] Weigh 0.2g of nickel-iron test sample, place it in a digestion tank, add 5ml of water to moisten it, then add 5ml of hydrochloric acid and 8ml of nitric acid. After the violent reaction is completed, add 15 drops of hydrofluoric acid, cover the digestion cover, and place it in a microwave digester according to the set program (digestion power is 1500w, heating to the target temperature of 210℃). After the digestion program is completed, cool it to below 50℃, transfer the digestion solution to a plastic beaker, clean the inner cover and digestion inner tank with water in small amounts several times, combine the washings and transfer them to a 200ml plastic volumetric flask, dilute with water to the scale, and mix to obtain the sample solution.

[0157] (2) Determination of cobalt content

[0158] Weigh 6 portions of 0.1000g high-purity nickel and 0.1000g high-purity iron respectively into a 150mL beaker, add 8mL of hydrochloric acid and 8mL of nitric acid, heat to a slight boil until the sample is completely dissolved, remove and cool, transfer to a 200mL volumetric flask, pipette 0mL, 200μL, 400μL, 1.00mL, 2.00mL, and 4.00mL of cobalt standard solution (1000μg / mL) into the corresponding volumetric flask, dilute to the scale with water, and mix well to obtain a series of standard solutions;

[0159] A series of standard solutions and a sample solution were measured sequentially using an inductively coupled plasma emission spectrometer. A standard curve was plotted using the cobalt concentration in the standard solutions as the abscissa and the intensity as the ordinate, using a linear intercept calculation method. The cobalt content in the sample solution was calculated based on the standard curve. The cobalt content was determined to be 0.145%.

[0160] (11) Determination of nickel and cobalt content

[0161] Pipette 50.00mL of test solution into a 500mL conical flask, add 12mL of 1+1 triethanolamine, add 1+1 ammonia water dropwise to adjust the pH value of the solution to 10, add 10mL of ammonia water-ammonium chloride buffer solution, add 0.2mL of Cu-EDTA solution, use a copper ion selective electrode as the indicator electrode and EDTA standard solution as the titrant, and use an automatic potentiometric titrator to automatically record the potential change. Record the total amount of nickel and cobalt elements when the potential jumps (i.e., the titration end point).

[0162] (12) Calculation of nickel content in ferronickel

[0163] The calculation formula for the nickel content in ferronickel is as follows:

[0164]

[0165] Where:

[0166] C—actual concentration of EDTA standard solution, in moles per liter (moL / L);

[0167] V—the volume of EDTA standard solution added to the sample solution, in milliliters (mL);

[0168] 58.69 — molar mass of nickel in grams per mole (g / moL);

[0169] m—mass of nickel-iron test sample, in grams (g);

[0170] r—dilution ratio of the sample solution;

[0171] 58.93 — Molar mass of cobalt in grams per mole (g / moL);

[0172] w Co —Mass fraction of cobalt in the sample solution.

[0173] The concentration of the EDTA standard solution added to sample 4 is 0.02004 mol / L. The volume of the EDTA standard solution added to the sample solution is mL. Substitute it into the formula to calculate:

[0174]

[0175] Calculation showed that the nickel content in the sample was 14.02% by mass, and the result determined by standard titration was 15.42%. The range of the two results was greater than the allowable difference requirement in GB / T 30072-2013. The amount of Cu-EDTA solution added had a significant impact on the result.

[0176] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring nickel content in ferronickel, characterized in that, The following steps are involved: (1) Weigh the nickel-iron test sample and digest it; After the digestion process is completed, cool it down and transfer the digestion solution to a plastic beaker. Wash the inner cover and the digestion inner tank with water. Combine the washings and transfer them to a plastic volumetric flask. Dilute with water to the mark and mix well to obtain the sample solution. (2) using an inductively coupled plasma emission spectrometer to sequentially measure a series of standard solutions and a sample solution, using the concentration of cobalt in the series of standard solutions as the abscissa and the intensity as the ordinate, and using a linear intercept calculation method to draw a series of standard curves, and calculating the cobalt content in the sample solution based on the series of standard curves; (3) Pipette the sample solution into a conical flask, adjust the solution pH to 10, add ammonia-ammonium chloride buffer solution, add Cu-EDTA solution, use a copper ion selective electrode as the indicator electrode, and EDTA standard solution as the titrant. Automatic potentiometric titrator automatically records the potential change. When the potential jump occurs, i.e., the titration endpoint, record the total amount of nickel and cobalt elements. (4) The calculated total amount of nickel and cobalt elements in the nickel-iron test sample minus the calculated cobalt content in the nickel-iron test sample is the nickel element in the nickel-iron test sample.

2. A method for measuring nickel content in ferronickel according to claim 1, characterized in that, The specific steps of digestion in step (1) are as follows: weigh the nickel-iron test sample, place it in a digestion tank, add water to moisten it, add hydrochloric acid and nitric acid until the violent reaction ends, add hydrofluoric acid, cover the digestion cover, and place it in a microwave digester to heat and digest it.

3. A method for measuring nickel content in ferronickel according to claim 2, characterized in that, The microwave digestion power in step (1) is 1000W to 1600W, the temperature is raised to a target temperature of 180°C to 210°C, and then kept warm until complete digestion.

4. A method for measuring nickel content in ferronickel according to claim 3, characterized in that, In step (1), the mass ratio of the nickel-iron test sample to the water used for wetting is 1:25; The volume ratio of water, hydrochloric acid and nitric acid used for wetting is 5:5-9:3-8; Add 1 to 3 drops of hydrofluoric acid to 1 ml of moistening water; Use a 100 mL plastic volumetric flask to make up to volume for every 0.1 g of nickel-iron test sample.

5. A method for measuring nickel content in ferronickel according to claim 1, characterized in that, In step (1), the mixture is cooled to below 50°C.

6. A method for measuring nickel content in ferronickel according to claim 1, characterized in that, The preparation method of the series standard solution in step (2) is as follows: 6 parts of 0.1000g high-purity nickel and 0.1000g high-purity iron are weighed into a 150mL beaker, 8mL of hydrochloric acid and 8mL of nitric acid are added, and the mixture is heated to a slight boil until the sample is completely dissolved, then removed and cooled, and transferred to a 200mL volumetric flask. 0mL, 200μL, 400μL, 1.00mL, 4.00mL, and 4.00mL of 1000μg / mL cobalt standard solution are respectively pipetted into corresponding volumetric flasks, diluted to the scale with water, and mixed to obtain a series of standard solutions.

7. A method for measuring nickel content in ferronickel according to claim 1, characterized in that, The concentration of the cobalt standard solution used to draw the series of standard curves in step (2) is 1 μg / mL to 20 μg / mL, and the mass content detection range of the cobalt element in the nickel iron test sample is 0.1% to 2%.

8. A method for measuring nickel content in ferronickel according to claim 1, characterized in that, In step (3), the solution used to adjust the pH value of the solution to 10 is 1+1 triethanolamine and 1+1 ammonia water.

9. A method for measuring nickel content in ferronickel according to claim 1, characterized in that, In step (3), the volume ratio of the sample solution to the volume of the conical flask is 1:10; Sample solution: 1+1 triethanolamine: ammonia-ammonium chloride buffer solution: Cu-EDTA solution, volume ratio is 10:2~3:2~3:0.1~0.

4.

10. A method for measuring nickel content in ferronickel according to claim 1, characterized in that, The content of nickel in the nickel-iron test sample in step (4) is expressed as mass fraction ω B The value is expressed in %, calculated according to formula (1): Where: C—actual concentration of EDTA standard solution, in moles per liter (moL / L); V—the volume of EDTA standard solution added to the sample solution, in milliliters (mL); 58.69—Molar mass of nickel in grams per mole (g / moL); m—mass of nickel-iron test sample, in grams; r—dilution ratio of the sample solution; 58.93—Molar mass of cobalt in grams per mole (g / moL); w Co —Mass fraction of cobalt in the sample solution.

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