Method for rapidly determining molybdenum content in ferromolybdenum

Abstract

The invention relates to a method for rapidly determining the content of molybdenum in ferromolybdenum, and belongs to the field of measurement of metal molybdenum. The method comprises the following steps: 1) dissolving a sample: weighing a ferromolybdenum sample in a beaker, adding a dissolving acid, covering a watch glass, and heating to completely dissolve the ferromolybdenum sample; 2) interference ion masking: adding water and a masking agent into the solution; 3) pH adjustment: adjusting the solution to weak acidity, and adding a buffer solution to maintain the pH value of the solution; 4) precipitating and aging: heating the solution to near boiling, adding a precipitating agent to precipitate the molybdenum element, and aging; 5) filtering and firing: after the solution is cooled, filtering the solution with quantitative filter paper, washing the precipitate, adding ammonium oxalate as a stabilizer, carbonizing with a constant-weight platinum crucible, and firing to constant weight; the method is simple in step and convenient to operate, and compared with an existing gravimetric method (the analysis period is shortened by at least 4 hours, the accuracy is higher, and the precision is better.

Description

Technical Field

[0001] The invention relates to a method for determining molybdenum in ferromolybdenum. Background Art

[0002] Ferromolybdenum is often used as an alloy additive for steel smelting. It can improve the strength, toughness and creep resistance of steel, improve the welding performance and heat resistance of steel, and enhance the corrosion resistance of steel in acid and alkali solutions. Ferromolybdenum is an alloy mainly composed of molybdenum and iron. Generally, the molybdenum content is between 50% and 70%. The molybdenum element needs to be accurately added during the smelting process. In addition, during the procurement process, the molybdenum content is used as an economic value for the acceptance of ferromolybdenum raw materials. Therefore, its accurate and rapid determination is obviously very important. It can not only guide production and ensure the quality of steel products. It is also extremely important for other scientific research.

[0003] At present, there are two methods for determining the molybdenum content in ferromolybdenum: melting sample preparation-X-ray fluorescence spectrometry and inductively coupled plasma atomic emission spectrometry. These two methods have low accuracy, high testing costs, and control of production costs; the lead molybdate weight method and 8-hydroxyquinoline weight method have complicated operating steps and long inspection cycles and cannot meet the needs of zero inventory and rapid production.

[0004] Developing a low-cost detection method that is easy to operate, accurate, reliable, produces results on the same day, and is suitable for batch determination has become an urgent development goal for the determination of molybdenum content in ferromolybdenum. Summary of the invention

[0005] In view of the shortcomings of the existing method for detecting the molybdenum content in ferromolybdenum, the present invention proposes a method for determining the molybdenum content in ferromolybdenum with strong operability, short detection time and high detection accuracy.

[0006] The technical solution adopted by the present invention to solve the above problem is: a method for quickly determining the molybdenum content in ferromolybdenum, comprising the following steps: 1) Sample dissolution: weigh the ferromolybdenum sample into a beaker, add the dissolving acid, cover with a watch glass and heat to dissolve completely; 2) Masking of interfering ions: adding water and masking agent to the solution; 3) pH adjustment: adjust the solution to weak acidity, and then add buffer solution to maintain the pH value of the solution; 4) Precipitation and aging: Heat the solution to near boiling, add a precipitant to precipitate the molybdenum element and age it; 5) Filtration and calcination: After the solution is cooled, filter the solution with quantitative filter paper, wash the precipitate, add ammonium oxalate as a stabilizer, carbonize it with a constant weight platinum crucible and calcine it to constant weight; 6) Calculate the molybdenum content in the sample by the formula ω( For )(%)=(( m 1-m 2)*0.6665) / m *100 Where m1: mass of constant weight platinum crucible, g; m2: mass of constant weight molybdenum trioxide and platinum crucible, g; 0.6665: Conversion factor of molybdenum trioxide to molybdenum content; m: sample weight, g.

[0007] Preferably, in step 1), the dissolving acid is a nitric acid solution with a mass fraction of 20-30%, and the heating temperature for dissolving is 300-330°C.

[0008] Preferably, in step 2), the masking agent is a disodium ethylenediaminetetraacetic acid solution; in step 3), ammonia water is added to the solution to adjust the pH to 4-5, and an acetic acid-ammonium acetate buffer solution of pH 4-5 is added.

[0009] Preferably, in step 4), the solution is heated to a temperature of 85°C to 95°C, the precipitant is a 3% by mass 8-hydroxyquinoline solution, the molybdenum element is fully precipitated, and the aging is performed for more than 30 minutes.

[0010] Preferably, in step 5), the calcination temperature is 600° C. and the calcination time is 30 min.

[0011] Compared with the prior art, the advantages of the present invention are: The principle of the method for determining the molybdenum content in ferromolybdenum of the present invention is as follows: a single dilute nitric acid is used to quickly decompose the sample, EDTA masks all interfering elements, a buffer solution ensures that the pH value of the solution is stable at 4-5, 8-hydroxyquinoline is used to precipitate molybdenum in a slightly boiling state, and after aging, it is filtered with medium-speed filter paper, the precipitate is rinsed and ammonium oxalate is added as a stabilizer, and carbonization is burned to constant weight.

[0012] The method has simple steps and is easy to operate, shortens the analysis cycle by at least 4 hours compared with the existing weight method (lead acetate precipitation carbonization ignition weight method and 8-hydroxyquinoline precipitation drying weight method), and has higher accuracy and better precision.

[0013] In the present application, ammonium oxalate is added to the precipitate before carbonization and burning. The gas generated during the burning process envelops the product, making the burning product molybdenum trioxide more stable, so that the calculated result is more accurate. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below in conjunction with examples. The examples are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0015] A method for detecting the molybdenum content in ferromolybdenum comprises the following steps: In order to verify the accuracy and precision of the determination results of the method of the present invention: 2 standard substances were selected as test objects, and precision experiments were performed respectively. The specific steps of the determination method are as follows: A Weigh 0.2000g of ferromolybdenum sample, put it into a 300mL beaker, add 30mL of 30% nitric acid solution, cover it with a watch glass, and heat until the sample is completely dissolved. Remove and rinse the watch glass.

[0016] Add 50 mL of water to B, add 20 mL of 10% disodium ethylenediaminetetraacetate, add ammonia water until the pH value of the solution is approximately 4.5, and add 5 mL of pH 4.5 acetic acid-ammonium acetate solution.

[0017] Heat the solution to C until it is almost boiling and quickly add 25 mL of 3% by mass 8-hydroxyquinoline solution as a precipitant. The aging time is 30 min.

[0018] D. Use medium-speed quantitative filter paper to filter the lukewarm solution and rinse the precipitate, add 1g of ammonium oxalate, carbonize it in a constant-weight platinum crucible, and then calcine it at 600℃ to constant weight.

[0019] E Calculate the molybdenum content in the sample through the formula.

[0020] The following data were obtained by experiments using two standard substances, wherein Table 1 is the experimental result without adding ammonium oxalate in step D, and Table 2 is the experimental result with adding ammonium oxalate, and the other steps are the same.

[0021] Table 1: Precision test results of samples without ammonium oxalate addition (result: %) .

[0022] Precision: The actual RSD is greater than the specified value of 0.5% by the weight method, indicating that the precision of the sample not burned with ammonium oxalate is not high and the dispersion of the parallel measurement values ​​is large.

[0023] Accuracy: Check the t-test critical value table, t0.05=2.365, t calculated <2.365, although there is no significant difference, but ferromolybdenum is a precious substance, the measured value is directly used for economic settlement, and high accuracy is required. The measurement results without ammonium oxalate can only be used for reference.

[0024] Table 2: Precision test results of samples with ammonium oxalate added (result: %) .

[0025] Precision: The actual RSD is less than 0.5% of the specified value of the weight method. After adding ammonium oxalate, the precision of the parallel data is high and the ignition product is stable.

[0026] Accuracy: Check the t-test critical value table, t 0.05 =2.365, t 计算<2.365 indicates that there is no significant difference in the results obtained, and the method for detecting the molybdenum content in ferromolybdenum of the present invention is reliable.

[0027] In addition to the above embodiments, the present invention also includes other implementation modes. Any technical solutions formed by equivalent transformation or equivalent replacement should fall within the protection scope of the claims of the present invention.

Claims

1. A method for rapidly determining the molybdenum content in ferromolybdenum, characterized in that: The following steps are included 1) Sample dissolution: weigh the ferromolybdenum sample into a beaker, add the dissolving acid, cover with a watch glass and heat to dissolve completely; 2) Masking of interfering ions: adding water and masking agent to the solution; 3) pH adjustment: adjust the solution to weak acidity, and then add buffer solution to maintain the pH value of the solution; 4) Precipitation and aging: Heat the solution to near boiling, add a precipitant to precipitate the molybdenum element and age it; 5) Filtration and calcination: After the solution is cooled, filter the solution with quantitative filter paper, wash the precipitate, add ammonium oxalate as a stabilizer, carbonize it with a constant weight platinum crucible and calcine it to constant weight; 6) Calculate the molybdenum content in the sample by the formula oh( Mo )(%)=(( m 1- m 2)*0.6665) / m *100 Where m1: mass of constant weight platinum crucible, g; m2: mass of constant weight molybdenum trioxide and platinum crucible, g; 0.6665: Conversion factor of molybdenum trioxide to molybdenum content; m: sample weight, g.

2. The method according to claim 1, characterized in that: Step 1), the dissolving acid is a nitric acid solution with a mass fraction of 20-30%, and the heating temperature for dissolving is 300-330°C.

3. The method according to claim 1, characterized in that: Step 2), the masking agent is a disodium ethylenediaminetetraacetic acid solution; Step 3), ammonia water is added to the solution to adjust the pH to 4-5, and an acetic acid-ammonium acetate buffer solution of pH 4-5 is added.

4. The method according to claim 1, characterized in that: Step 4), heating the solution to a temperature of 85°C to 95°C, using a 3% by mass 8-hydroxyquinoline solution as the precipitant, fully precipitating the molybdenum element, and aging for more than 30 minutes.

5. The method according to claim 1, characterized in that: Step 5), the calcination temperature is 600°C and the calcination time is 30 minutes.