GB/T 15076.7-2020Methods for chemical analysis of tantalum and niobium—Part 7:Determination of phospherus content in niobium—4-Formyloxy-pentyl ketone-2 extraction separation phosphomolybdate blue spectrophotometry and inductively coupled plasma atomic emission spectrometry (English PDF)

3.1 Principle

The sample is dissolved with nitric acid and hydrofluoric acid, and niobium and potassium nitrate form potassium fluoroniobate. Phosphorus is formed with ammonium molybdate in a medium containing nitric acid and hydrofluoric acid Phosphomolybdic heteropoly acid, extracted with 4-methyl-pentanone-[2], reduced to phosphomolybdenum blue with stannous chloride, measured at a wavelength of 725nm with a spectrophotometer Absorbance.

3.2 Reagents and materials

Unless otherwise stated, only reagents and laboratory secondary water confirmed to be analytically pure are used in the analysis.

3.2.1 Hydrofluoric acid (rho=1.14g/mL), excellent grade pure.

3.2.2 Hydrochloric acid (rho=1.18g/mL), excellent grade pure.

3.2.3 Nitric acid (rho=1.42g/mL), excellent grade pure.

3.2.4 Nitric acid-hydrofluoric acid leaching solution. Take 60 mL of nitric acid (3.2.3) in a plastic bottle, add 6 mL of hydrofluoric acid (3.2.1), and add water to 1000mL.

3.2.5 4-Methyl-pentanone-[2] (MIBK).

3.2.6 Potassium permanganate.

3.2.7 Potassium nitrate.

3.2.8 Sodium nitrite.

3.2.9 Ammonium molybdate.

3.2.10 Stannous chloride (SnCl2·2H2O).

3.2.11 Potassium permanganate solution (20g/L).

3.2.12 Potassium nitrate solution (200g/L).

3.2.13 Sodium nitrite solution (100g/L).

3.2.14 Ammonium molybdate solution (100g/L).

3.2.15 Stannous chloride solution (20g/L). Weigh 1g stannous chloride (3.2.10) into a 100mL beaker, add 25mL hydrochloric acid (2 1) Heat to dissolve, cool, add water to 50mL, and mix well. Equipped when used.

3.2.16 Niobium metal (wNb>=99.99%, wP<=0.0001%).

3.2.17 Phosphorus standard storage solution. Weigh 4.2636g of diammonium hydrogen phosphate that has been baked at 105°C for 1 hour and placed in a desiccator to cool to room temperature (Reference reagent) placed in a.200mL beaker, add 50mL of water to dissolve, transfer to a 1000mL volumetric flask, dilute to the mark with water, mix uniform. This solution 1mL contains 1mg phosphorus.

3.2.18 Phosphorus standard solution A. Pipette 10.00mL phosphorus standard stock solution (3.2.17) into a 100mL volumetric flask, dilute with water to Degree, mix well. This solution 1mL contains 100µg phosphorus.

3.2.19 Phosphorus standard solution B. Pipette 10.00mL phosphorus standard solution A (3.2.18) into a 100mL volumetric flask, dilute to the mark with water, Mix well. This solution 1mL contains 10µg phosphorus.

3.3 Equipment

Spectrophotometer.

3.4 Test procedure

3.4.1 Sample

Weigh 0.10g sample (Chapter 2), accurate to 0.0001g.

3.4.2 Parallel test

Do two tests in parallel and take the average value.

3.4.3 Blank test

Do a blank test with the sample.

3.4.4 Determination

3.4.4.1 Place the sample (3.4.1) in a 30mL platinum crucible, add 1mL nitric acid (3.2.3), and add 0.5mL hydrofluoric acid dropwise (3.2.1) After the violent reaction stops, place the crucible on a boiling water bath, heat it until the sample is completely dissolved, and add potassium permanganate solution (3.2.11) to The solution was purplish red, and continued heating for 1 min. Remove, add 2mL potassium nitrate solution (3.2.12), add sodium nitrite solution dropwise (3.2.13) Until the test solution is colorless, continue to evaporate the test solution on a water bath until there is just no mobile phase, and the salt is transparent and crystalline. Remove.

3.4.4.2 Add 10 mL of nitric acid-hydrofluoric acid leaching solution (3.2.4) to the crucible, stir with a plastic rod to completely dissolve the salts, and transfer the test solution into In a 25mL volumetric flask, wash the crucible twice with 10mL nitric acid-hydrofluoric acid leaching solution (3.2.4), and merge the washing solution into the 25mL volumetric flask to Dilute the nitric acid-hydrofluoric acid extract (3.2.4) to the mark and mix. According to Table 1, pipette the test solution into a 60mL separatory funnel, add nitric acid-hydrofluoric acid Extract the solution (3.2.4) to 17mL.

3.4.4.3 Add 6 mL of ammonium molybdate solution (3.2.14) to the separatory funnel, mix well, let stand for 5 minutes, add 10.00 mL MIBK (3.2.5), shake Shake for 1 min, stand for stratification, discard the water phase, add 5mL nitric acid-hydrofluoric acid extract (3.2.4), shake for 30s, stand for stratification, and discard the water phase. To The next operation (3.4.4.4~3.4.4.5) must be performed below 25°C.

3.4.4.4 Add 5mL of stannous chloride solution (3.2.15) in the separatory funnel, shake 30 times, after the organic phase turns sky blue, discard the water phase.

3.4.4.5 Immediately transfer part of the organic phase to a 1cm dry cuvette, use MIBK as a reference, and use a spectrophotometer with a wavelength of 725nm Measure its absorbance.

3.4.4.6 Subtract the absorbance of the blank solution accompanying the sample, and find the corresponding phosphorus amount from the working curve.

3.4.5 Drawing of working curve

3.4.5.1 Pipette 0mL, 0.10mL, 0.30mL, 0.50mL, 0.70mL, 1.00mL of phosphorus standard solution B (3.2.19), and place them in a Group 60mL separatory funnel, weigh the metal niobium equivalent to the sample (3.2.16). The remaining operations are carried out according to 3.4.4.1~3.4.4.5.

3.4.5.2 Subtract the absorbance of the reagent blank, take the amount of phosphorous as the abscissa and absorbance as the ordinate to draw a working curve.

3.5 Test data processing

Phosphorus content is calculated as the mass fraction of phosphorus wP, calculated according to formula (1).

3.6 Precision

3.6.1 Repeatability

The measured values of two independent test results obtained under repeatability conditions are within the average range given in Table 2. These two test results The absolute difference does not exceed the repeatability limit (r), and the case of exceeding the repeatability limit (r) does not exceed 5%. Repeatability limit (r) adopts the line according to the data in Table 2 Obtained by sexual interpolation or extension method.

3.6.2 Reproducibility

The measured values of two independent test results obtained under reproducibility conditions are within the range of the average value given in Table 3.

The absolute difference does not exceed the reproducibility limit (R), and does not exceed 5% in the case of exceeding the reproducibility limit (R). Reproducibility limit (R) is adopted according to the data in Table 3 Obtained by linear interpolation or extension method.

4.1 Principle

The sample is dissolved in nitric acid and hydrofluoric acid, in a dilute acid medium, using argon plasma as the ionization source, and direct inductively coupled plasma Atomic emission spectrometry.

4.2 Reagents and materials

Unless otherwise specified, only reagents and laboratory secondary water confirmed to be pure superior grade are used in the analysis.

4.2.1 Hydrofluoric acid (rho=1.14g/mL).

4.2.2 Nitric acid (rho=1.42g/mL).

4.2.3 Niobium metal. wNb>=99.99%, wP<=0.0001%.

4.2.4 Phosphorus standard storage solution. Weigh 4.2636g of diammonium hydrogen phosphate that has been pre-baked at 105°C for 1 hour and placed in a desiccator to cool to room temperature (Reference reagent) placed in a.200mL beaker, add 50mL of water to dissolve, transfer to a 1000mL volumetric flask, dilute to the mark with water, mix uniform. This solution 1mL contains 1mg phosphorus.

4.2.5 Phosphorus standard solution. Pipette 10.00mL phosphorus standard stock solution (4.2.4) into a 100mL volumetric flask, dilute to the mark with water, and mix uniform. This solution 1mL contains 100µg phosphorus.

4.2.6 Argon. The volume fraction is not less than 99.99%.

4.3 Equipment

4.3.1 Inductively coupled plasma atomic emission spectrometer, equipped with hydrofluoric acid resistant sampling system, the resolution at 200nm is less than 0.006nm.

4.3.2 The recommended phosphorus analysis line is 178.221nm.

4.4 Test procedure

4.4.1 Sample

Weigh 1.00g sample (Chapter 2), accurate to 0.0001g.

4.4.2 Parallel test

Do two tests in parallel and take the average value.

4.4.3 Blank test

Weigh niobium metal equivalent to the sample (4.2.3), and do a blank test with the sample.

4.4.4 Preparation of analysis test solution

4.4.4.1 Place the sample (4.4.1) in a 100mL polyethylene beaker and moisten it with a little water.

4.4.4.2 Slowly add 2 mL of nitric acid (4.2.2), and 4 mL of hydrofluoric acid (4.2.1) dropwise. After the violent reaction stops, heat it in a boiling water bath to Dissolve completely, remove and cool, add 2mL nitric acid (4.2.2). Transfer the solution into a 100mL polyethylene volumetric flask and dilute to the mark with water. Mix well.

4.4.5 Drawing of working curve

Weigh 6 parts of 1.000g metal niobium (4.2.3) into a 100mL polyethylene beaker, add 0mL, 0.10mL, 0.50mL, 1.00mL, 4.00mL, 8.00mL phosphorus standard solution (4.2.5), and then press 4.4.4.2.

4.4.6 Determination

After the instrument is optimized, according to the recommended analysis line, measure the emitted light intensity of the measured element in the standard series of the working curve drawn from low to high.

Taking the mass concentration as the abscissa and the intensity of the emitted light from the analysis line as the ordinate, the computer automatically draws the working curve. When the linear relationship of the working curve When it reaches above 0.999, measure the emitted light intensity of the measured element in the sample blank solution (4.4.3) and the sample solution (4.4.4), and the computer will automatically Calculate the mass concentration of the measured element from the working curve.

4.5 Test data processing

The phosphorus content is calculated as the mass fraction wP of phosphorus and calculated according to formula (2).

4.6 Precision

4.6.1 Repeatability

The measured values of two independent test results obtained under repeatability conditions are within the average range given in Table 4, and the two test results The absolute difference does not exceed the repeatability limit (r), and the case of exceeding the repeatability limit (r) does not exceed 5%. Repeatability limit (r) adopts the line according to the data in Table 4 Obtained by sexual interpolation or extension method.

4.6.2 Reproducibility

The measured values of two independent test results obtained under reproducibility conditions are within the range of the average value given in Table 5.

The absolute difference does not exceed the reproducibility limit (R), and does not exceed 5% in the case of exceeding the reproducibility limit (R). Reproducibility limit (R) is adopted according to the data in Table 5 Obtained by linear interpolation or extension method.