GB/T 3884.9-2025Methods for chemical analysis of copper concentrates — Part 9: Determination of arsenic, antimony and bismuth contents (English PDF)

4.1 Principle

The test material is decomposed using a mixture of potassium chlorate-nitric acid solution, ammonium hydrogen fluoride, and sulfuric acid. Arsenic, antimony, and bismuth are precipitated from the solution in an ammoniacal medium - utilizing the iron present in the test material and a specific amount of added lanthanum - thereby separating them from copper. The precipitate is dissolved in hot hydrochloric acid. An aliquot of the solution is taken, pre-reduced with ascorbic acid, and residual copper is masked with thiourea. In a hydride generator, arsenic, antimony, and bismuth are reduced to their respective hydrides by potassium borohydride. These hydrides are swept by argon gas into a quartz furnace atomizer, and their fluorescence intensity is measured using an atomic fluorescence spectrometer with a hollow cathode lamp as the light source.

4.2 Reagents

Unless otherwise specified, only confirmed analytically pure reagents are used in the analysis.

4.2.1 Water. complying with GB/T 6682, of Grade II purity or higher.

4.2.2 Hydrochloric acid (rho = 1.19 g/mL). guaranteed reagent.

4.2.3 Aqueous ammonia (rho = 0.90 g/mL). guaranteed reagent grade.

4.2.4 Potassium chlorate-nitric acid solution (80 g/L). weigh 40 g of potassium chlorate

and dissolve it in nitric acid (rho = 1.42 g/mL, guaranteed reagent). Dilute to 500 mL with nitric acid (rho = 1.42 g/mL, guaranteed reagent). Mix well.

4.2.5 Ammonium hydrogen fluoride solution (300 g/L).

4.2.6 Hydrochloric acid (1+24). 4.2.7 Sulfuric acid (1+1).

4.2.8 Ammonia washing solution (5+95).

4.2.9 Thiourea-ascorbic acid mixed solution. weigh 10 g of thiourea and 5 g of ascorbic acid separately, dissolve them in water, dilute to 100 mL, and mix well.

4.2.10 Lanthanum nitrate solution (50 g/L). weigh 5 g of lanthanum nitrate, dissolve in water, dilute to 100 mL, and mix well.

4.2.11 Ferric nitrate solution. weigh 73.40 g of ferric nitrate [Fe(NO3)3-9H2O] into a

250 mL beaker. Add 10 mL of nitric acid (rho = 1.42 g/mL, guaranteed reagent). Add an appropriate amount of water to dissolve the salt. Transfer the solution to a 1000 mL volumetric flask, dilute to the mark with water, and mix well. This solution contains 10 mg of iron per 1 mL.

4.2.12 Potassium borohydride solution (15 g/L). weigh 15 g of potassium borohydride

and dissolve it in 1000 mL of sodium hydroxide solution (2 g/L). Prepare when needed.

4.2.13 Arsenic standard stock solution. weigh 0 1320 g of primary standard arsenic

trioxide (previously dried at 100°C~105°C for 1 h and cooled to room temperature in a desiccator) into a 100 mL PTFE beaker. Add 5 mL of sodium hydroxide solution (200 g/L). Heat gently to dissolve, then allow to cool. Add 50 mL of water and 2 drops of phenolphthalein-ethanol solution (1 g/L). Neutralize with sulfuric acid (4.2.7) until the red color just disappears, then add an excess of 2 mL. Transfer the solution to a 1000 mL volumetric flask, dilute to the mark with water, and mix well. This solution contains 100 µg of arsenic per 1 mL.

4.2.14 Antimony standard stock solution. weigh 0 1000 g of metallic antimony (wSb >=

99.99%) into a 200 mL beaker. Add 50 mL of nitric acid (1+1) and 3 g of tartaric acid.

Heat gently to dissolve. Allow to cool. Transfer to a 1000 mL volumetric flask, dilute to the mark with water, and mix well. This solution contains 100 µg of antimony per 1 mL.

4.2.15 Bismuth standard stock solution. weigh 0 1000 g of bismuth metal (wBi >= 99.99%) into a 250 mL beaker. Add 50 mL of nitric acid (1+1). Cover with a watch glass. Heat gently to dissolve. Boil to expel nitrogen oxides. Allow to cool. Transfer the solution to a 1000 mL volumetric flask using nitric acid (1+24), dilute to the mark with water, and mix well. This solution contains 100 µg of bismuth per 1 mL.

4.2.16 Mixed standard solution. pipette 5.00 mL of arsenic standard stock solution

(4.2.13), 5.00 mL of antimony standard stock solution (4.2.14), and 5.00 mL of bismuth standard stock solution (4.2.15) into a 500 mL volumetric flask. Add 50 mL of hydrochloric acid (4.2.2). Dilute to the mark with water and mix well. 1 mL of this solution contains 1 µg each of arsenic, antimony, and bismuth.

4.2.17 Argon gas (purity >=99.99%).

4.3 Instruments

Atomic fluorescence spectrometer. equipped with a shielded quartz furnace atomizer and specialized hollow cathode lamps (or high-intensity hollow cathode lamps) for arsenic, antimony, and bismuth.

Provided the instrument is operating under optimal conditions, any setup capable of meeting the following specifications may be used.

- Limit of detection. no greater than 9 x 10-10 g/mL;

- Precision. measure the fluorescence intensity 10 times using a 0.1 µg/mL standard solution of arsenic, antimony, or bismuth. The standard deviation shall not exceed 5.0% of the mean fluorescence intensity.

4.4 Sample

4.4.1 The particle size of the sample shall be no greater than 100 µm.

4.4.2 The sample shall be dried at 100°C~105°C for 1 h and then cooled to room temperature in a desiccator.

4.5 Test steps

4.5.1 Test material

Weigh 0.2 g of the sample (4.4), accurate to 0 0001 g.

4.5.2 Parallel test

Perform the test in duplicate and take the average value.

4.5.3 Blank test

Conduct a blank test alongside the test material.

4.5.4 Determination

4.5.4.1 Place the test material (4.5.1) into a 300 mL PTFE beaker. Moisten with a small amount of water. Add approximately 2 mL of ammonium hydrogen fluoride solution (4.2.5). Add 10 mL of potassium chlorate-nitric acid solution (4.2.4). Cover with a watch glass. Once the vigorous reaction has ceased, place on a hot plate and heat to dissolve the sample, reducing the volume to 3 mL~5 mL. Remove from the heat and allow to cool slightly. Add 5 mL of sulfuric acid (4.2.7) and mix well. Heat until dense white fumes appear. Remove from the heat and allow to cool. Rinse the watch glass and the inner walls of the beaker with water, bringing the total volume to approximately 50 mL. Heat to boiling, then remove from the heat and allow to cool slightly.

4.5.4.2 Add 5 mL of lanthanum nitrate solution (4.2.10). Dilute with water to

approximately 150 mL. Place on a hot plate and heat until near boiling. Remove from the heat. While stirring, add ammonia solution (4.2.3) until the resulting copper hydroxide precipitate completely dissolves. Add an additional 20 mL of ammonia solution (4.2.3). Slowly heat to boiling. Move to a lower-temperature area (approximately 60°C) and maintain the temperature for 30 min.

4.5.4.3 Filter while hot using rapid quantitative filter paper. Wash the beaker and the precipitate 4~5 times with hot ammoniacal wash solution (4.2.8). Then, wash the beaker and the precipitate 3~4 times with hot water. Discard the filtrate.

4.5.4.4 Remove the filter paper containing the precipitate from the funnel. Rinse the

precipitate into the original beaker using a small amount of water. Add the appropriate volume of hydrochloric acid (4.2.2) as specified in Table 1.Wash the filter paper with hydrochloric acid (4.2.6) until the yellow color characteristic of trivalent iron is no longer visible. Heat the mixture on an electric hot plate until the soluble salts have dissolved. Allow it to cool, then transfer the solution - using hydrochloric acid (4.2.6) - into a volumetric flask of the volume specified in Table 1.Dilute to the mark with water and mix well.

4.5.4.5 According to Table 1, transfer the test solution (4.5.4.4) and add the

hydrochloric acid (4.2.2) and the thiourea-ascorbic acid mixed solution (4.2.9) into the corresponding volumetric flasks containing 30 mL of water. Dilute to the mark with water and mix well.

Table 1 -- Volume of test solution aliquot and volume of acid added 4.5.4.6 Pipette 2 mL of the test solution (4.5.4.5) into the hydride generator. Following the instrument's operating procedure, add the potassium borohydride solution (4.2.12) at the recommended pump speed. Measure the fluorescence intensity using the atomic fluorescence spectrometer. Subtract the fluorescence intensity of the accompanying reagent blank and determine the corresponding mass concentrations of arsenic, antimony, and bismuth from the calibration curve.

4.5.5 Plotting of working curve

4.5.5.1 Pipette 0 mL, 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL, and 5.00 mL of the mixed standard solution (4.2.16) into a set of 50 mL volumetric flasks. Add 5 mL of hydrochloric acid (4.2.2), 0.25 mL of ferric nitrate solution (4.2.11), 2.5 mL of lanthanum nitrate solution (4.2.10), and 5 mL of the mixed thiourea-ascorbic acid solution (4.2.9). Dilute to the mark with water and mix well.

4.5.5.2 Measure the fluorescence intensity according to the instrument's operating

procedure under the same conditions used for the test material. Subtract the fluorescence intensity of the "zero" concentration standard solution. Plot calibration curves with the mass concentrations of arsenic, antimony, and bismuth on the x-axis and the fluorescence intensity on the y-axis.

between the two results shall not exceed the reproducibility limit (R); instances where the difference exceeds the reproducibility limit (R) shall not exceed 5%. The reproducibility limit (R) is determined using linear interpolation or extrapolation based on the data in Table 3.

Table 3 -- Reproducibility limit (R) of Method 1

5.1 Principle

The test material is decomposed using a mixture of potassium chlorate-nitric acid solution, ammonium hydrogen fluoride, and sulfuric acid. In a 6 mol/L hydrochloric acid medium, with potassium bromide acting as a catalyst, arsenic(V) is reduced to arsenic (III) using hydrazine sulfate, and arsenic trichloride is separated from other elements via distillation. After the arsenic trichloride is absorbed in water, the solution is titrated with a standard potassium bromate solution - using methyl orange as the indicator - until the red color disappears, marking the endpoint.

5.2 Reagents

Unless otherwise specified, only confirmed analytically pure reagents are used in the analysis.

5.2.1 Water. conforming to GB/T 6682, of Grade 3 purity or higher. 5.2.2 Potassium bromide. 5.2.3 Hydrazine sulfate.

5.2.4 Hydrochloric acid (rho = 1.19 g/mL). 5.2.5 Sulfuric acid (1+1).

5.2.6 Hydrochloric acid (1+1).

5.2.7 Ammonium hydrogen fluoride solution (300 g/L).

5.2.8 Potassium chlorate-nitric acid solution (80 g/L). weigh 40 g of potassium chlorate

and dissolve it in 300 mL of nitric acid (rho = 1.42 g/mL). Then, dilute to 500 mL with nitric acid (rho = 1.42 g/mL) and mix well.

5.2.9 Arsenic standard solution. weigh 0 2641 g of primary standard arsenic trioxide

(previously dried at 100°C~105°C for 1 h and cooled to room temperature in a desiccator) and place it in a 250 mL beaker. Add 10 mL of sodium hydroxide solution (200 g/L). Heat gently until completely dissolved. Add 50 mL of water and 2 drops of phenolphthalein-ethanol solution (1 g/L). Neutralize with hydrochloric acid (5.2.4) until the red color just disappears, then add an excess of 2 drops. Transfer the solution to a 1000 mL volumetric flask, dilute to the mark with water, and mix well. 1 mL of this solution contains 0.2 mg of arsenic.

5.2.10 Potassium bromate standard titration solution (c1/6 KBrO3) ~ 0.005 mol/L). Prepare

and standardize according to the following procedure.

a) Preparation. weigh 0.74 g of potassium bromate and 3.7 g of potassium bromide (5.2.2) and place them in a 250 mL beaker. Add a small amount of water, heat to dissolve, and allow to cool slightly. Transfer the solution to a reagent bottle, dilute to 5 L with water, and mix well.

b) Standardization. pipette four 20.00 mL aliquots of the arsenic standard solution (5.2.9) and place them into separate 250 mL beakers. Dilute each with water to 100 mL. Add 15 mL of hydrochloric acid (5.2.4) and heat to 60°C. Add 2 drops of methyl orange indicator (5.2.11). Titrate with the potassium bromate standard titration solution until the red color of the solution disappears (end point).

Conduct a blank test alongside the standardization.

Calculate the actual concentration of the potassium bromate standard titration solution according to formula (2). Where, rho1 - mass concentration of the arsenic standard solution, in grams per milliliter (g/mL);

V6 - volume of the arsenic standard solution taken, in milliliters (mL);

V5 - volume of the potassium bromate standard titration solution consumed to titrate the arsenic standard solution during standardization, in milliliters (mL);

V4 - volume of the potassium bromate standard titration solution consumed to titrate the blank test solution during standardization, in milliliters (mL);

37.46 - molar mass of 1/2 arsenic, in grams per mole (g/mol). ......