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GB/T 14635-2020 English PDF (GBT14635-2020)

GB/T 14635-2020 English PDF (GBT14635-2020)

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GB/T 14635-2020: Rare earth metals and their compounds -- Determination of total rare earth content

This Standard specifies the determination method of total rare earth content in the rare earth metals and their compounds. This Standard is applicable to the determination of the total rare earth content in rare earth metals and their compounds. This Standard contains two methods: Method-1 is oxalate gravimetric method, and Method-2 is EDTA titration method. Method-1 is applicable to the determination of the total rare earth content in single and mixed rare earth metals and their compounds; the determination range is shown in Table 1; it is not applicable to the determination of the total rare earth content in single and mixed rare earth metals and their compounds mainly based on erbium, thulium, ytterbium, and lutetium or the individual content of thorium and lead is greater than 0.1%. Method-2 is applicable to the determination of the total rare earth content in the single rare earth metals and mixed rare earth metals and their compounds mainly based on heavy rare earth holmium, erbium, thulium, ytterbium, and lutetium; the determination range is shown in Table 2; it is not applicable to the determination of the total rare earth content in the single rare earth with relative purity less than 99.5%, as well as in a single rare earth metal and its compounds with other impurity elements greater than 0.5%; it is also not applicable to the determination of the total rare earth content in materials with individual content of thorium, scandium, and zinc greater than 0.1%.
GB/T 14635-2020
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.120.99
H 14
GB 14635-2020
Replacing GB/T 14635-2008
Rare Earth Metals and Their Compounds
- Determination of Total Rare Earth Content
ISSUED ON: NOVEMBER 19, 2020
IMPLEMENTED ON: OCTOBER 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Method-1: Oxalate Gravimetric Method ... 7
3 Method-2: EDTA Titration Method ... 14
4 Quality Assurance and Control ... 21
Rare Earth Metals and Their Compounds
- Determination of Total Rare Earth Content
1 Scope
This Standard specifies the determination method of total rare earth content in the rare earth metals and their compounds.
This Standard is applicable to the determination of the total rare earth content in rare earth metals and their compounds. This Standard contains two methods: Method-1 is oxalate gravimetric method, and Method-2 is EDTA titration method. Method-1 is applicable to the determination of the total rare earth content in single and mixed rare earth metals and their compounds; the determination range is shown in Table 1; it is not applicable to the determination of the total rare earth content in single and mixed rare earth metals and their compounds mainly based on erbium, thulium, ytterbium, and lutetium or the individual content of thorium and lead is greater than 0.1%. Method- 2 is applicable to the determination of the total rare earth content in the single rare earth metals and mixed rare earth metals and their compounds mainly based on heavy rare earth holmium, erbium, thulium, ytterbium, and lutetium; the determination range is shown in Table 2; it is not applicable to the determination of the total rare earth content in the single rare earth with relative purity less than 99.5%, as well as in a single rare earth metal and its compounds with other impurity elements greater than 0.5%; it is also not applicable to the determination of the total rare earth content in materials with individual content of thorium, scandium, and zinc greater than 0.1%. Table 1 ?€? Determination Range in Method-1
ammonium chloride and 2mL of ammonia water (2.2.5).
2.2.8 Oxalic acid lotion (2g/L).
2.2.9 Hydrochloric acid lotion: 100mL of water contains 2mL of hydrochloric acid (2.2.3). 2.2.10 Accurate range pH test paper (0.5~5.0).
2.2.11 Cresol red solution (2g/L), 50% ethanol solution.
2.3 Apparatus
2.3.1 Analytical balance, the division is no greater than 0.1mg.
2.3.2 High-temperature furnace, the upper limit of temperature is no less than 1000??C. 2.3.3 Oven.
2.3.4 Crucible (platinum crucible or porcelain crucible).
2.4 Specimen
2.4.1 The oxide layer on the surface shall be removed from the metal specimen and weigh immediately after sampling.
2.4.2 There are many types of rare earth compounds, and their chemical properties are different. The basic state of using the different compound specimens to determine the total rare earth content is different. The basic state of measurement of each different compound is shown in Table 3. There are usually 3 ways:
a) Determine the total rare earth content by the original sample: directly weigh the sample.
b) Determine the total rare earth content after drying: the sample is dried in an oven at 105??C for 1h; cool to room temperature in a desiccator; and weigh immediately. c) Determine the total rare earth content after burning: the sample is burned in a muffle furnace at 950??C for 1h; cool to room temperature in a desiccator; and weigh immediately.
(2.2.3) [dissolve testing materials with high cerium content, use nitric acid (2.2.4) to dissolve] and 1mL of hydrogen peroxide (2.2.2); heat at low temperature to dissolve completely; and evaporate to about 1mL. Add 20mL of water and heat to dissolve the salts until clear. Transfer to a 100mL volumetric flask [if there is insoluble matter, filter, receive the filtrate in a 100mL volumetric flask; wash the beaker and filter paper for 5~6 times by hydrochloric acid lotion (2.2.9); discard the filter paper]; dilute with water to scale and mix well. Pipette 50mL of test solution into a 300mL beaker. 2.5.3.1.4 Dissolution of rare earth fluoride testing materials: place the testing materials (2.5.1) in a 200 mL PTFE beaker; add 10 mL of nitric acid (2.2.4), 1 mL of hydrogen peroxide (2.2.2), and 3mL of perchloric acid (2.2.1); heated at low temperature to emit perchloric acid fumes. Slightly cold, wash the vessel wall by water. Add 2mL of perchloric acid (2.2.1); heat at low temperature to emit perchloric acid fumes; when the testing materials are completely dissolved (if the dissolution is incomplete, repeat it again); evaporate to about 1mL. Add 20mL of water and heat to dissolve the salts until clear. After filtering, the filtrate is received in a 300mL beaker; and the beaker and filter paper are washed by hydrochloric acid lotion (2.2.9) for 5~6 times; and the filter paper is discarded.
2.5.3.1.5 Dissolution of mixed rare earth oxide of ion-type rare earth ore: place the testing materials (2.5.1) in a 200mL beaker; add 5mL of water, 4mL of hydrochloric acid (2.2.3), 1mL of hydrogen peroxide (2.2.2), and 3mL of perchloric acid (2.2.1) [the rare earth samples containing high cerium shall be dissolved by adding 10mL of nitric acid (2.2.4)]; after decomposition, add 3mL of perchloric acid (2.2.1); and heat until the dissolution is complete. Continue to heat until white smoke of perchloric acid is emitted and evaporated to about 1mL. Take it off and cool it slightly; add 20 mL of hydrochloric acid (2.2.3); wash the vessel wall by hot water; add 10 mL of water; and heat to dissolve the salts until clear. Filter by quantitative slow-speed filter paper. Receive the filtrate in a 300mL beaker. Wash the beaker and filter paper for 5~6 times by hydrochloric acid lotion (2.2.9); then wash with hot water for 2 times, and discard the filter paper. 2.5.3.1.6 Dissolution of rare earth chloride, rare earth nitrate, and rare earth carbonate testing materials: place the testing materials (2.5.1) in a 300 mL beaker; add 20 mL of water, 20 mL of hydrochloric acid (2.2.3) and 1 mL of hydrogen peroxide (2.2.2); heat at low temperature to dissolve completely; and evaporate to about 5mL [when dissolving insoluble samples, use 20mL of nitric acid (2.2.4) and 3mL of perchloric acid (2.2.1) to dissolve]. Add 50mL of water and heat to dissolve the salts until clear. After filtering, the filtrate is received in a 200mL volumetric flask; and the beaker and filter paper are washed for 5~6 times by hydrochloric acid lotion (2.2.9); and the filter paper is discarded. Dilute the filtrate to the mark by water and mix well. Pipette 10mL of test solution into a 300mL beaker.
2.5.3.1.7 Dissolution of rare earth sulfide testing materials: place the testing materials (2.5.1) in a 200 mL beaker; add 20 mL of water, 10 mL of hydrochloric acid (2.2.3); heat at low temperature, and evaporate to about 5mL. Take it off and cool. Add 5mL of perchloric acid (2.2.1); heat at low temperature to emit white smoke of perchloric acid; and evaporate to 1mL~2mL; take it off. After cooling slightly, add 5mL of nitric acid (2.2.4); heat at low temperature and add hydrogen peroxide (2.2.2) dropwise to complete dissolution. Take if off and cool, filter by slow-speed filter paper; receive the filtrate in a 300mL beaker; wash the beaker and filter paper by hydrochloric acid lotion (2.2.9) for 5~6 times; discard the filter paper.
2.5.3.2 Separation of precipitation
2.5.3.2.1 Dilute the test solution (2.5.3.1) by water to about 100mL; heat it to near boiling; titrate ammonia water (2.2.5) until precipitation just appears; add 0.1mL of hydrogen peroxide (2.2.2), 30mL of ammonia water (2.2.5); and boil. Take it off, and filter by medium-speed quantitative filter paper. Wash the beaker for 2~3 times by ammonium chloride-ammonia water lotion (2.2.7); precipitate for 6~7 times; and discard the filtrate.
2.5.3.2.2 Put the precipitate and filter paper in the original beaker; add 10 mL of hydrochloric acid (2.2.3); mash the filter paper. Add 100mL of water and boil. Add 50mL of oxalic acid solution (2.2.6) near boiling; adjust the pH to 2.0 by ammonia water (2.2.5), hydrochloric acid (2.2.3) and accurate range pH test paper (2.2.10); or add 4~6 drops of cresol red solution (2.2.11); adjust by ammonia water (2.2.5) to make the solution orange-yellow (pH 1.8~2.0). Heat to boil; or keep at 80??C~90??C for 40min; cool to room temperature; and place for 2h.
2.5.3.2.3 Filter by a slow-speed quantitative filter paper; wash the beaker by oxalic acid lotion (2.2.8) for 2~3 times; wipe the beaker by a small piece of filter paper; transfer all the precipitate to the filter paper; and wash the precipitate for 8~10 times. Put the precipitate together with the filter paper into a crucible burnt to a constant mass at 950??C; and heat at low temperature to ash the precipitate and filter paper. 2.5.3.2.4 Burn the crucible (2.5.3.2.3) in a high temperature furnace at 950??C for 1h. Place the crucible and the burnt rare earth oxide in a desiccator; cool to room temperature; and weigh its mass.
2.5.3.2.5 Repeat operation in 2.5.3.2.4 until the mass of the crucible together with the burnt material is constant.
2.6 Calculation of analysis results
2.6.1 Calculation and expression of the total rare earth content in rare earth metal testing materials
The total rare earth content is calculated by the mass fraction w (RE) of rare earth metals (RE); and calculated as per Formula (1):
add 5mL of hydrochloric acid (3.2.5); dilute to the mark by water, and mix well. 3.2.13 Ethylenediaminetetraacetic acid disodium salt (EDTA) standard titration solution (c???0.01mol/L):
a) Preparation: take about 7.5g of ethylenediaminetetraacetic acid disodium salt (3.2.13) in a 250mL beaker; add a small amount of water to dissolve; transfer the solution to a 2L volumetric flask; dilute to the mark by water, and mix well. b) Calibration: pipette 25.00mL of zinc standard solution (3.2.12) in a 250mL triangular flask; add 50mL of water, 1 drop of methyl orange (3.2.9) or p- nitrophenol (3.2.10) indicator. Use ammonia water (3.2.6) and hydrochloric acid (3.2.5) to adjust the solution to just turn yellow; add 5mL of
hexamethylenetetramine buffer solution (3.2.11), 2 drops of xylenol orange (3.2.8); use the EDTA standard titration solution (3.2.13) to titrate the solution till it turns from red (when the acidity is adjusted by methyl orange) or purple (when the acidity is adjusted by p-nitrophenol) just to yellow, which is the end point. Calibrate 3 portions in parallel; and the range of the volume of the consumed EDTA standard titration solution (3.2.13) shall not exceed 0.10 mL; take the average value.
The concentration c of the EDTA standard titration solution is calculated in mol/L, which is calculated as per Formula (3):
Where:
?? ?€? mass concentration of zinc standard solution, in g/L;
V5 ?€?volume of the separately-pipetted zinc standard solution, in mL;
V6 ?€? volume of EDTA standard titration solution consumed by titration of zinc, in mL; M1 ?€? molar mass of the zinc, in g/mol.
3.3 Specimen
3.3.1 The surface oxide layer shall be removed from the metal specimen; and weigh immediately after sampling.
3.3.2 There are many types of rare earth compounds and their chemical properties are different. The basic state of the different compound specimen to determine the total rare earth content is difference. The basic state of measurement for each different compound is shown in Table 8. There are usually 3 ways:
3.4.3.1.2 Dissolution of rare earth oxide and rare earth hydroxide (except cerium oxide, terbium oxide and cerium hydroxide): place the testing materials (3.4.1) in a 150mL beaker; and add 10mL of hydrochloric acid (3.2.5); cover with a watch glass; heat at low temperature to dissolve completely; take it off and cool to room temperature. Transfer the solution into a 200mL volumetric flask; dilute to the mark with water, and mix well.
3.4.3.1.3 Dissolution of cerium oxide, terbium oxide and cerium hydroxide: place the testing materials (3.4.1) in a 150mL beaker; add 10mL of nitric acid (3.2.4), 1mL of hydrogen peroxide (3.2.3); cover with a watch glass; heat at low temperature to dissolve completely and steam until there are no small bubbles (volume is about 1mL~2mL); take if off and cool. Add 2mL of hydrochloric acid (3.2.5); wash the vessel wall and tableware by water; dissolve the salts at low temperature; take it off and cool to room temperature. Transfer the solution into a 200mL volumetric flask; dilute to the mark with water, and mix well.
3.4.3.1.4 Dissolution of rare earth fluoride: place the testing materials (3.4.1) in a 150mL beaker; add 5mL of perchloric acid (3.2.2), 5mL of nitric acid (3.2.4); and heat at low temperature until it emits the white smoke of perchloric acid. Take it off and cool slightly; add 2mL of perchloric acid (3.2.2); cover with watch glass; heat at low temperature to dissolve till it emits the white smoke of perchloric acid (if the dissolution is incomplete, repeat again); and steam to about 1mL; take it off, and cool. Add 2mL of hydrochloric acid (3.2.5); wash the vessel wall and watch glass by water; dissolve the salts at low temperature; take it off and cool to room temperature. Transfer the solution into a 200 mL volumetric flask; dilute to the mark with water, and mix well. 3.4.3.1.5 Dissolution of rare earth chloride: place the testing materials (3.4.1) in a 200mL beaker; add 20mL of water, 10mL of hydrochloric acid (3.2.5); cover with a watch glass; and take it off and cool to the room temperature after heating at low temperature to dissolve completely. Transfer the solution into a 200 mL volumetric flask; dilute to the mark with water, and mix well.
3.4.3.1.6 Dissolution of rare earth sulfide: place the testing materials (3.4.1) in a 150mL beaker; add 20mL of water, 10mL of hydrochloric acid (3.2.5); heat to about 5mL at low temperature; take it off and cool. Add 5mL of perchloric acid (3.2.2); heat at low temperature to emit white smoke of perchloric acid; and evaporate to 1mL~2mL; and take it off. After cooling slightly, add 5mL of nitric acid (3.2.4); heat at low temperature and titrate hydrogen peroxide (3.2.3) until the sample is completely dissolved. Take it off and cool; wash the vessel wall and watch glass by water; dissolve the salt at low temperature; and cool to room temperature. Transfer the solution into a 200mL volumetric flask; dilute to the mark with water, and mix well.
3.4.3.2 Titration
Pipette the test solution (3.4.3.1) into a 250mL triangular flask according to Table 9;

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