GB/T 3058-2019Determination of arsenic in coal (English PDF)

11723.2016 "Solid mineral fuels - Determination of arsenic and selenium -

Eschka's mixture and hydride generation method". The degree of consistency

with ISO 11723.2016 is nonequivalent.

This standard was proposed by the China Coal Industry Association.

This standard shall be under the jurisdiction of the National Coal

Standardization Technical Committee (SAC/TC 42).

Drafting organization of this standard. Testing Branch of Coal Science and

Technology Research Institute Co., Ltd.

Drafters of this standard. Chen Huizhu, Fu Kun, Yang Guang, Yang Huayu.

This standard replaces the standard previously issued as follows.

- GB/T 3058-1982, GB/T 3058-1996, GB/T 3058-2008.

Determination of arsenic in coal

3.1 Method summary

The coal sample is mixed with Eschka reagent and burned. The burned material

is dissolved with hydrochloric acid and sulfuric acid. A reducing agent is added

to reduce pentavalent arsenic to trivalent arsenic. Add zinc particles to form and

release arsenic hydride gas. Use iodine solution to absorb and oxidize it to

arsenic acid. Add ammonium molybdate-hydrazine sulfate solution to produce

arsenic molybdenum blue. Then use a spectrophotometer to determine it.

3.2 Reagents and materials

Unless otherwise specified, only use reagents and distilled or deionized water

or equivalent purity water confirmed to be analytically pure in the analysis.

3.2.1 Arsenic-free zinc metal. In accordance with GB/T 2304, screen out zinc

particles with a particle size of not less than 3 mm for use.

3.2.2 Eschka reagent (hereinafter referred to as Aldrin). Commercially available,

or 2 parts by mass of light magnesium oxide and 1 part by mass of anhydrous

sodium carbonate are mixed and ground to a particle size of less than 0.2 mm,

then stored in a closed container.

3.2.3 Hydrochloric acid. The relative density is 1.18.

3.2.4 Hydrochloric acid solution. c(HCl) = 6 mol/L. Mix 1 volume of hydrochloric

acid with 1 volume of water evenly.

3.2.5 Sulfuric acid solution. c(1/2 H2SO4) = 6 mol/L. Measure 167 mL of sulfuric

acid with a relative density of 1.84 and slowly add it to an appropriate amount

of water. Stir it while adding. Then use water to dilute it to 1 L.

3.2.6 Sulfuric acid solution. c (1/2 H2SO4) = 5 mol/L. Measure 139 mL of sulfuric

acid with a relative density of 1.84 and slowly add it to an appropriate amount

of water. Stir it while adding. Then use water to dilute it to 1 L.

3.2.7 Potassium iodide solution. 176.5 g/L. Dissolve 3.0 g of potassium iodide

in 17 mL water and prepare it before use.

3.2.8 Stannous chloride hydrochloric acid solution. 666.7 g/L. Dissolve 8.0 g of

stannous chloride in 12 mL of hydrochloric acid (3.2.3) and prepare it before

use.

3.2.9 Iodine solution. 1.5 g/L. After using a small amount of water to dissolve

9.0 g of potassium iodide and 1.5 g of iodine. Dilute it to 1 L.

3.2.10 Ammonium molybdate solution. 10 g/L. Dissolve 10.0 g of ammonium

molybdate in 1 L sulfuric acid solution (3.2.6).

3.2.11 Hydrazine sulfate solution. 1.2 g/L. Dissolve 1.2 g of hydrazine sulfate in

3.2.12 Ammonium molybdate-hydrazine sulfate mixed solution. Mix 1 volume

of ammonium molybdate solution (3.2.10) and 1 volume of hydrazine sulfate

solution (3.2.11) evenly. Prepare it before use.

3.2.17 Lead acetate cotton. It is replaced each time of the experiment. The

absorbent cotton is fully soaked in a lead acetate solution which has a mass

concentration of 400 g/L. Take it out and twist it dry. Dry it at 80 °C ~100 °C.

Store it in a desiccator for later use.

3.2.18 Porcelain crucible. The capacity is 30 mL. The enamel on the inner

surface is intact.

3.3 Instrument and equipment

3.5 Test procedure

3.5.1 Drawing of working curve

3.5.1.1 Respectively use the single marking line pipette to take 0.00 mL, 1.00

mL, 2.00 mL, 3.00 mL, 4.00 mL, 5.00 mL of arsenic standard working solution

(3.2.16). Place it into the round flask of the arsenic determination device. First

add 10 mL of sulfuric acid solution (3.2.5). Then add 20 mL of hydrochloric acid

solution (3.2.4). Use water to dilute it to 50 mL.

3.5.1.2 Add 2 mL of potassium iodide solution (3.2.7), 1 mL of stannous chloride

solution (3.2.8). Shake it uniformly. Place it at room temperature for 15 min.

3.5.1.3 Use a pipette to add 3 mL of iodine solution (3.2.9), 1 mL of sodium

bicarbonate solution (3.2.13), 6 mL of water to the absorber of the arsenic

determination device. Insert the absorber into the absorber casing which

contains lead acetate cotton (3.2.17).

abscissa and the corresponding absorbance as the ordinate. Proceed it

simultaneously with the analysis of the coal sample.

3.5.2 Sample determination

3.5.2.1 Weigh 2 g of aldrin agent in a porcelain crucible (accurate to 0.01 g).

Then weigh 0.99 g ~ 1.01 g (accurate to 0.0002 g) of coal sample for general

analysis test which has a particle size of less than 0.2 mm. Use a glass rod to

stir it uniformly. Then use 1 g (accurate to 0.01 g) of Aldrin to evenly cover the

mixed coal sample (no black coal particles can be seen). When the ash content

in the coal sample is greater than 40%, or the arsenic content is greater than

3.5.2.5 Determine the absorbance of the sample blank solution and the sample

solution according to the method specified in 3.5.1.6.Check the corresponding

arsenic mass [micrograms (µg)] from the drawn working curve (3.5.1.7).

3.6 Calculation and expression of results

3.6.1 Result calculation

4.1 Method summary

The coal sample is mixed with aldrin and burned. The burned material is

dissolved by hydrochloric acid. The pentavalent arsenic is reduced to trivalent

arsenic by potassium iodide.

4.2 Reagents and materials

Unless otherwise specified, only use reagents and distilled or deionized water

or equivalent purity water confirmed to be analytically pure in the analysis.

4.2.1 Aldrin. Same as 3.2.2.

4.2.2 Hydrochloric acid. Same as 3.2.3.

4.2.3 Sodium hydroxide solution. 5 g/L. Weigh 5.0 g of sodium hydroxide and

dissolve it in 1 L of water.

4.2.10 Nitrogen. Purity above 99.9%.

4.2.11 Porcelain crucible. Same as 3.2.18.

4.2.12 Porcelain evaporating dish. The capacity is 100 mL. The enamel on the

inner surface is intact.

4.3 Instrument and equipment

4.3.1 Atomic absorption spectrophotometer. It has the functions of absorption

peak area integration and peak height measurement.

4.3.2 Hydride generator. It can automatically wash and measure liquid, which

has an accuracy of 0.5%.

4.3.3 Light source. Arsenic hollow cathode lamp or arsenic electrodeless

discharge lamp.

4.3.4 Muffle furnace. Same as 3.3.3.

4.3.5 Analytical balance. Same as 3.3.4.

4.3.6 Balance. The division value is 0.01 g.

4.4 Sample

The sample is the same as 3.4.

4.5 Test procedure

4.5.1 Preparation of sample solution

4.5.2 Preparation of blank solution

4.5.4 Hydride generation-atomic absorption determination

4.5.4.1 Instrument preparation

Install the atomizer of the hydride generator on the burner of the atomic

absorption spectrophotometer according to the instrument instructions, so that

the quartz tube is located directly above the burner slit. Adjust the up and down,

front and rear positions and rotation angle of the burner, to make the axis of the

quartz tube coincide with the main optical axis of the atomic absorption

spectrophotometer. Connect the gas path.

4.5.4.2 Selection of working parameters of atomic absorption

spectrophotometer

The parameter selection is as follows.

4.6 Calculation and expression of results

4.6.1 Result calculation

The arsenic content (mass fraction) in the air-dried coal sample is calculated

according to formula (2).