GB/T 18882.2-2017Chemical analysis methods for mixed rare earth oxide of ion-adsorption type rare earth ore - Part 2: Determination of the aluminium oxide content (English PDF)

2.2.4 Nitric acid (rho =

2.2.5 Hydrogen peroxide (30%).

2.2.6 Nitric acid (1+1).

2.3.1 Inductively coupled plasma atomic emission spectrometer, resolution <

0.006 nm (at 200 nm).

2.3.2 Light source: argon plasma light source.

2.4 Test sample

2.4.1 The particle size of the test sample is less than

0.074 mm.

2.4.2 Pre-dry the sample at 105 °C ~ 110 °C for 2 h; then, place it in a desiccator to cool to room temperature.

2.5 Procedure

2.5.1 Test material Weigh 0.1g of test sample (2.4), accurate to 0.000 1 g.

2.5.2 Number of determinations Independently perform two determinations; take the average value.

2.5.3 Blank test Carry out a blank test together with the test material (2.5.1).

2.5.4 Preparation of analytical solution Place the test materials (2.5.1) in a 150 mL polytetrafluoroethylene beaker; add a small amount of water; add 2 mL of nitric acid (2.2.6); heat to decompose for 3 min ~ 5 min; add 2 mL of hydrofluoric acid (2.2.2) and continue to decompose for 3 min ~ 5 min; add 3 mL of perchloric acid (2.2.3) to smoke and evaporate to nearly dry; remove and cool slightly; add 10 mL of hydrochloric acid (2.2.7) and add 3 ~ 5 drops of hydrogen peroxide (2.2.5); heat to dissolve until clear; transfer the test solution into a 100 mL volumetric flask; use water to dilute to the mark; mix well; test.

2.5.5 Series standard configuration According to Table 2, transfer the standard stock solution into six 100 mL volumetric flasks; use water to dilute to the mark; mix well; test. Unless otherwise specified, all reagents used in this Part are analytical reagents that meet national or industry standards, and the water used is grade-II water.

3.2.2 Hydrofluoric acid (rho =

3.2.3 Hydrogen peroxide (30%).

3.2.5 Nitric acid (rho =

3.2.6 Oxalic acid solution (100 g/L).

3.2.7 Sodium hydroxide solution (200 g/L).

3.2.8 Hydrochloric acid (1+1).

3.2.9 Hydrochloric acid (1+4).

3.2.10 Ammonia water (1+1).

3.2.11 EDTA (Ethylene Diamine Tetraacetic Acid) solution (about

0.05 mol/L): Weigh 20 g of EDTA and dissolve it in a small amount of water; transfer it into a 1 000 mL volumetric flask; use water to fix the volume; mix well.

3.2.12 Cresol red indicator (2 g/L): Weigh

0.2 g of cresol red and dissolve it in 100 mL of ethanol solution (1+1).

3.2.13 Phenolphthalein ethanol solution (10 g/L).

3.2.14 Acetic acid-sodium acetate buffer solution (pH 5.5): Weigh 200 g of sodium acetate and dissolve it in a small amount of water; transfer it into a 1 000 mL volumetric flask; add 10 mL of glacial acetic acid (w >= 99.5%); use water to fix the volume; mix well.

3.2.15 Xylenol orange indicator (4 g/L): Weigh

0.4 g of xylenol orange and 20 g of potassium nitrate; dissolve in a small amount of water; transfer to a 100 mL volumetric flask; use water to fix the volume; mix well. Store in a brown bottle.

3.2.16 Sodium fluoride solution (40 g/L).

3.2.17 Aluminum standard solution: Weigh 1.000 0 g of metallic aluminum (spectrally pure, remove all surface oxides before use) into a 500 mL beaker; add 50 mL of water; then, add 40 mL of hydrochloric acid (3.2.1); dissolve at low temperature until clear (add hydrochloric acid and water in between); cool. Transfer to a 1 000 mL volumetric flask; use hydrochloric acid (5+95) to dilute to the mark; mix well. This standard solution contains 1 mg of aluminum in 1 mL.

3.2.18 Zinc sulfate solution (about

0.1 mol/L): Weigh 30 g of zinc sulfate (ZnSO4·7H2O) and dissolve it in an appropriate amount of water; transfer it into a 1 000 mL volumetric flask; use water to fix the volume; mix well.

3.2.19 Zinc sulfate standard solution.

3.2.19.1 Preparation: Weigh

2.4 g of zinc sulfate (ZnSO4·7H2O) and dissolve it in a small amount of water; transfer it into a 1 000 mL volumetric flask; use water to fix the volume; mix well.

3.2.19.2 Calibration: Pipette

10.00 mL of aluminum standard solution (3.2.17) into a 250 mL conical flask; add 20 mL of LEDTA solution (3.2.11); add 1 ~ 2 drops of phenolphthalein ethanol solution (3.2.13); use sodium hydroxide solution (3.2.7) to neutralize until red appears. Use hydrochloric acid (3.2.9) to neutralize until colorless and add 1 drop in excess; add 20 mL of acetic acid-sodium acetate buffer solution (3.2.14); boil slightly at low temperature for 1 min ~ 2 min; remove and cool. Perform the following operations according to the analytical steps (3.4.4). Calculate the concentration of zinc sulfate standard solution according to Formula (2): Where: c - concentration of zinc sulfate, in moles per liter (mol/L); rho0 - mass concentration of aluminum standard solution, in milligrams per milliliter (mg/mL); V1 - volume of aluminum solution pipetted, in milliliters (mL); M - molar mass of aluminum, in grams per mole (g/mol); V2 - volume of zinc sulfate standard solution consumed, in milliliters (mL).

3.3 Test sample

3.3.1 The particle size of the test sample is less than

0.074 mm.

3.3.2 Pre-dry the sample at 105 °C ~ 110 °C for 2 h; then, place it in a desiccator to cool to room temperature.

3.4 Procedure

3.4.1 Test material Weigh 0.25g of test sample (3.3), accurate to 0.000 1 g.

3.4.2 Time of determinations Independently perform two determinations; take the average value.

3.4.3 Blank test Carry out a blank test together with the test material (3.4.1).

3.4.4 Preparation of analytical solution

3.4.4.1 Place the test material (3.4.1) in a 150 mL polytetrafluoroethylene beaker; add 5 mL of hydrochloric acid (3.2.8) and 1 mL of hydrogen peroxide (3.2.3); heat at low temperature to decompose for 3 min; add 5 mL of hydrofluoric acid (3.2.2) and continue to decompose for 5 min; add 8 mL of perchloric acid (3.2.4) until fuming and evaporate to dryness; remove and cool slightly; add 5 mL of hydrochloric acid (3.2.8) to decompose clearly; transfer to a 200 mL beaker; add 10 mL of hot oxalic acid solution (3.2.6); shake well; add 3 ~ 5 drops of cresol red indicator (3.2.12); use hydrochloric acid (3.2.9) and ammonia water (3.2.10) to adjust to orange-red (pH 1.5 ~ 2.0); keep warm at 40 °C for 30 min; cool; transfer the test solution to a 100 mL volumetric flask; dilute to the mark; mix well.

3.4.4.2 Use medium-speed quantitative filter paper to dry-filter the test solution (3.4.4.1) into a 100 mL beaker; transfer

50.00 mL of the solution into a 250 mL conical flask; add 10 mL of nitric acid (3.2.5) and 5 mL of perchloric acid (3.2.4); evaporate at low temperature until all white smoke is emitted; remove and cool; add 5 mL of hydrochloric acid (3.2.8); rinse with a small amount of water; heat slightly until boiling for a few moments to dissolve all the salts.

3.4.4.3 Remove the test solution (3.4.4.2); add 20 mL of EDTA solution (3.2.11); add 1 ~ 2 drops of phenolphthalein ethanol solution (3.2.13); use sodium hydroxide solution (3.2.7) to neutralize until red appears. Use hydrochloric acid (3.2.9) to neutralize until colorless appears and add 1 drop in excess; add 20 mL of acetic acid-sodium acetate buffer solution (3.2.14); boil slightly for 1 min ~ 2 min; remove and cool.

3.4.4.4 Add 2 drops of xylenol orange indicator (3.2.15) to the test solution (3.4.4.3); use zinc sulfate solution (3.2.18) to titrate until it is close to red; then, continue to titrate with zinc sulfate standard solution (3.2.19) until pure red appears (ignore the reading). Add 15 mL of sodium fluoride solution (3.2.16); boil slightly for 1 min ~ 2 min; remove and cool; use zinc sulfate standard solution (3.2.19) to titrate until pure red is the end point. Record the volume of zinc sulfate standard solution (3.2.19) consumed.

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