HG/T 4701-2021Iron phosphate for batteries (English PDF)

2.940 Report the measurement results as D50

7.3.2 Reagents or materials

7.3.2.1 Hydrogen peroxide.

7.3.2.2 Hydrochloric acid.

7.3.2.3 Sulfuric acid-phosphoric acid mixed solution

Slowly add 15 mL of sulfuric acid to 70 mL water; cool it; add 15 mL of phosphoric acid; mix well.

7.3.2.4 Stannous chloride solution. 100 g/L

Weigh 10.0 g of stannous chloride (SnCl2·2H2O); place in a dry beaker; dissolve in 40 mL of hydrochloric acid; use water to dilute to 100 mL; add 1 tin particle; store in a brown bottle.

7.3.2.5 Titanium trichloride solution. 2%

Pipette 10 mL of titanium trichloride solution (15% ~ 20%); use hydrochloric acid solution (1 + 9) to dilute to 100 mL; store in a brown bottle. It can be prepared before use.

Prepare and process the test data according to the following steps.

a) Preparation. Weigh 2.45 g ± 0.2 g of the standard potassium dichromate (accurate to 0.0001 g), which was dried at 120 °C ± 2 °C to a constant mass; dissolve it in water; transfer all to a 1000 mL volumetric flask; use water to dilute to the mark; shake well;

b) Test data processing. The concentration of the standard potassium dichromate titration solution is expressed in moles per liter (mol/L), which is calculated according to formula (1).

V - The volume of the standard potassium dichromate titration solution, in milliliters (mL);

M - The molar mass of potassium dichromate, in grams per mole (g/mol)

7.3.2.6 Potassium dichromate standard titration solution

Where. m - The mass of the standard potassium dichromate weighed, in grams (g);

7.3.2.7 Sodium tungstate indicator solution. 10%

Weigh 10.0 g of sodium tungstate (NaWO4·2H2O); dissolve in 85 mL of water; add 5.0 mL of phosphoric acid; mix well; store in a brown bottle.

7.3.2.8 Sodium diphenylamine sulfonate indicator solution. 5 g/L.

7.3.3 Instruments and equipment

Test sieve. phi200 × 50 - 0.1/0.071 GB/T 6003.1-2012.

7.3.4 Test steps

7.3.4.1 Preparation of test solution A Weigh 4 g of the sieved specimen (accurate to 0.0002 g); place it in a 250 mL beaker; moisten it with a small amount of water. Add 25 mL of hydrochloric acid; cover with a watch glass; heat at low temperature in a fume hood to dissolve. Rinse the watch glass with a small amount of water; cool it (filter if necessary); transfer it to a 250 mL volumetric flask; dilute to the mark; shake well. This is test solution A, which is used for the determination of iron and phosphorus content.

7.3.4.2 Test

Use a pipette to transfer 10 mL of test solution A into a 250 mL conical flask. Add 5 mL of hydrochloric acid; heat to near boiling. While hot, shake the conical flask and add stannous chloride solution drop by drop, until the solution changes from brown to light yellow (if the solution becomes colorless after adding too much stannous chloride, add hydrogen peroxide until the solution turns light yellow). Add 4 ~ 5 drops of sodium tungstate indicator solution; add titanium trichloride solution drop by drop while shaking the conical flask, until the solution turns light blue. Immediately cool with running water; add 50 mL of water; titrate with potassium dichromate standard titration solution, until the blue color just fades (usually 1 ~ 2 drops, do not record the reading).

Add water to dilute it to 100 mL. Add 10 mL of sulfuric acid-phosphoric acid mixed solution, 3 ~ 4 drops of sodium diphenylamine sulfonate indicator solution; titrate with potassium dichromate standard titration solution until a stable purple-red color appears (does not disappear in 30 s), which is the end point.

At the same time, perform a blank test. Except for not adding the specimen (except the standard titration solution), the types and amounts of other reagents added to the blank

7.4.4 Test procedure

Use a pipette to transfer 25 mL of test solution A (see 7.3.4.1) into a 250 mL volumetric flask; dilute to the mark with water; shake well. Use a pipette to transfer 10 mL of this test solution into a 250 mL beaker; add 10 mL of nitric acid solution; add water to about 100 mL. Cover with a watch glass; slowly heat to boil; keep it at a slight boil for 5 minutes. Add 50 mL of quinoline molybdate solution; keep it warm for 30 seconds (do not use open flame when adding reagents or heating; do not stir when adding reagents or heating to avoid the formation of clots). Cool to room temperature and stir 3 ~ 4 times during the cooling process. Use a glass crucible that has been dried to constant mass at 180 °C ± 5 °C to filter the upper clear liquid; wash the precipitate 5 ~ 6 times by decantation, using about 20 mL of water each time. Transfer the precipitate to a glass crucible and continue washing with water 3 ~ 4 times. Place the glass crucible and the precipitate in an electric constant temperature drying oven at 180 °C ± 5 °C; dry for 45 minutes. Take it out; cool it slightly; place it in a dryer; cool it to room temperature. Weigh it to an accuracy of 0.0002 g.

At the same time, do a blank test. Except for not adding the sample to the blank test solution, the types and amounts of other reagents added are the same as those of the test solution.

7.4.5 Test data processing

The phosphorus content is calculated as the mass fraction w2 of phosphorus (P), according to formula (3).

Wherein. m1 - The mass of quinoline phosphomolybdic acid precipitate generated by the test solution, in grams (g); m2 - The mass of quinoline phosphomolybdic acid precipitate generated by the blank test solution, in grams (g); m - The mass of the sample, in grams (g);

0.0140 - The coefficient for converting quinoline phosphomolybdic acid into phosphorus.

The arithmetic mean of the parallel determination results is taken as the determination result. The absolute difference between the two parallel determination results is not Inductively coupled plasma emission spectrometer.

7.6.4 Test steps

7.6.4.1 Drawing of working curve

Pipette 0.00 mL, 1.00 mL, 2.00 mL, 4.00 mL, 6.00 mL, 8.00 mL, 10.00 mL of standard solution (see 7.6.2.2) respectively; place in seven 100 mL volumetric flasks; add 2 mL of hydrochloric acid to each; dilute to the mark with water; shake well. Introduce into inductively coupled plasma emission spectrometer for measurement. The wavelength of the analysis spectrum and instrument working conditions are shown in Appendix A.

Draw the working curve, using the mass concentration (µg/mL) of the standard solution as the abscissa and the corresponding emission intensity value as the ordinate.

7.6.4.2 Test

Weigh 1 g of specimen (accurate to 0.0002 g); place in a 250 mL beaker; moisten with a small amount of water; add 20 mL of hydrochloric acid. Cover with a watch glass and heat at low temperature in a fume hood until almost dry. After cooling, transfer to a 100 mL volumetric flask; dilute to the mark; shake well. Introduce into the inductively coupled plasma emission spectrometer; measure the emission intensity value of the corresponding element to be tested under the same conditions as 7.6.4.1. If the spectral intensity of the test solution exceeds the range of the working curve, the test solution shall be appropriately diluted and the acidity shall be kept consistent with that before dilution. Find the mass concentration of the element to be tested in the test solution from the standard curve.

At the same time, perform a blank test. Except for not adding the sample to the blank test solution, the type and amount of other reagents added are the same as those of the test solution.

7.6.5 Test data processing

The content of the elements to be tested (calcium, magnesium, sodium, potassium, copper, zinc, nickel, manganese, aluminum, titanium, cobalt, lead, chromium) is calculated as the mass fraction wi of the elements to be tested (Ca, Mg, Na, K, Cu, Zn, Ni, Mn, Al, Ti, Co, Pb, Cr), according to formula (5). Where.

rhoi - The mass concentration of the element to be tested in the test solution, as found from the working curve, in micrograms per milliliter (µg/mL);

rho0 - The mass concentration of the element to be tested in the blank test solution, as found from the working curve, in micrograms per milliliter (µg/mL); m - The mass of the sample, in grams (g); k - The dilution factor of the test solution.

The arithmetic mean of the parallel determination results is taken as the test result. The absolute difference between the two parallel determination results shall not exceed 10% of the arithmetic mean.

7.7 Determination of sulfur content

7.7.1 Principle

The specimen is heated and burned in the oxygen flow of a high-frequency induction furnace. The generated sulfur dioxide is carried by oxygen to the measuring chamber of the infrared analyzer. Sulfur dioxide absorbs infrared energy of a certain wavelength; its absorption energy is proportional to its concentration. The sulfur content can be measured according to the change in the energy received by the detector.

7.7.2 Reagents or materials

According to the provisions of Chapter 4 of GB/T 6730.61-2005.

7.7.3 Instruments and equipment

According to the provisions of Chapter 5 of GB/T 6730.61-2005.

7.7.4 Test steps

Weigh 0.2 g of the specimen burned according to 7.9 (accurate to 0.0002 g); measure according to the provisions of Chapter 7 of GB/T 6730.61-2005.

7.7.5 Test data processing

According to the provisions of Chapter 8 of GB/T 6730.61-2005.

7.8 Determination of magnetic substance content

7.8.1 Principle

The magnetic substance in the specimen is adsorbed by a magnetic rod and then dissolved with aqua regia. The intensity of the characteristic spectral lines of the magnetic substance elements (iron, zinc, nickel, chromium) is determined by an inductively coupled plasma emission spectrometer; the working curve method is used for quantification. The content of the magnetic substance is obtained by calculation.

7.8.2 Reagents or materials

Add 150 mL of anhydrous ethanol and 300 mL of water; put in a clean magnetic bar; cover the bottle cap and tighten it; roll it with a jar mill (speed 110 r/min) for 30 min.

After the mixed adsorption is completed, use a magnet to adsorb the magnetic bar on the outside of the container; pour out the solution; rinse the magnetic bar with water (ultrasonic cleaning for 30 seconds if necessary). Transfer the magnetic bar to a 250 mL beaker; add 15 mL of aqua regia; then add 40 mL of water; cover with a watch glass; heat to a slight boil on a heating plate. Remove it when it reaches about 10 mL ~ 20 mL; cool to room temperature. Transfer all the solution to a 100 mL volumetric flask; wash the magnetic bar 3 times with a small amount of water; pour it into the volumetric flask; finally dilute it to the scale with water; shake it well. Introduce it into the inductively coupled plasma emission spectrometer; determine the emission intensity value of the corresponding element to be measured under the same conditions as 7.8.4.1. Find the mass concentration of the element to be measured in the test solution from the standard curve.

At the same time, a blank test is also performed. Except for not adding the sample to the blank test solution, the types and amounts of other reagents added are the same as those of the test solution.

7.8.5 Test data processing

The content of the elements to be tested (iron, zinc, nickel, chromium, phosphorus) is calculated as the mass fraction wj of the elements to be tested (Fe, Zn, Ni, Cr, P), according to formula (6).

The content of magnetic substances is calculated as the mass fraction w3 according to formula (7). In formula (6) and formula (7).

rhoj - The mass concentration of the element to be tested in the test solution found from the working curve, in micrograms per milliliter (µg/mL);

rho0 - The mass concentration of the element to be tested in the blank test solution found from the working curve, in micrograms per milliliter (µg/mL); m - The mass of the sample, in grams (g); wFe - The iron content of the magnetic substance, calculated according to formula (6); wP - The phosphorus (P) content in the iron phosphate adsorbed by the magnetic rod, The arithmetic mean of the parallel determination results is taken as the determination result. The absolute difference between the two parallel determination results is not greater than 0.2%.

7.10 Determination of tap density

The determination shall be carried out according to the method specified in GB/T 5162.

7.11 Determination of particle size

7.11.1 Reagents or materials

Anhydrous ethanol.

7.11.2 Instruments and equipment

7.11.2.1 Laser particle size analyzer. The measuring range shall meet the particle size range to be detected.

7.11.2.2 Ultrasonic disperser. Power greater than 100 W

7.11.3 Test steps

According to the requirements of the laser particle size analyzer, weigh a certain amount of specimen; add 100 mL of water; then add 1.0 mL ~ 1.5 mL of anhydrous ethanol dispersant; place the specimen solution on the ultrasonic disperser; perform ultrasonic dispersion for 3 minutes. According to the operating steps of the laser particle size analyzer, measure the particle size distribution of the specimen; the refractive index is […]

7.12 Determination of specific surface area

The measurement is carried out according to the method specified in GB/T 19587. The adsorption gas is nitrogen; the degassing conditions are 180 °C, 1 h.

8.3

Determine the number of sampling units according to the provisions of GB/T 6678. When sampling, insert the sampler vertically from the top of the packaging bag to 3/4 of the depth of the material layer. The sample taken from each bag is not less than 50 g.

Mix the collected samples; reduce them to about 1000 g by quartering method; pack them into two dry, clean wide-mouth bottles or plastic bags; seal them; stick labels on them, indicating the manufacturer name, product name, model, batch number, sampling date, name of the sampler. One bottle (bag) is used for inspection; the other bottle (bag) is kept for reference; the storage time is determined by the manufacturer based on actual conditions.