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GB/T 8151.1-2012 PDF in English


GB/T 8151.1-2012 (GB/T8151.1-2012, GBT 8151.1-2012, GBT8151.1-2012)
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GB/T 8151.1-2012English170 Add to Cart 0-9 seconds. Auto-delivery. Methods for chemical analysis of zinc concentrates -- Part 1: Determination of zinc content -- Precipitate separation-Na2EDTA titrimetric method and extractive separation -- Na2EDTA titrimetric method Valid


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GB/T 8151.1-2012: PDF in English (GBT 8151.1-2012)

GB/T 8151.1-2012
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.120.60
H 13
Replacing GB/T 8151.1-2000
Methods for Chemical Analysis of Zinc Concentrates –
Part 1: Determination of Zinc Content – Precipitate
Separation-Na2EDTA Titrimetric Method and Extractive
Separation-Na2EDTA Titrimetric Method
(ISO 13291:2006 (E), Zinc Sulfide Concentrates – Determination of Zinc –
Solvent Extraction and EDTA Titrimetric Method, NEQ)
ISSUED ON: DECEMBER 31, 2012
IMPLEMENTED ON: OCTOBER 01, 2013
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Method 1 -- Precipitate Separation-Na2EDTA Titrimetric Method ... 6
3 Method 2 -- Extractive Separation-Na2EDTA Titrimetric Method ... 11
Appendix A (Informative) Influence of Potential Interference Elements ... 17
Methods for Chemical Analysis of Zinc Concentrates –
Part 1: Determination of Zinc Content – Precipitate
Separation-Na2EDTA Titrimetric Method and Extractive
Separation-Na2EDTA Titrimetric Method
1 Scope
This Part of GB/T 8151 specifies the determination of zinc content in zinc concentrates.
This Part is applicable to the determination of zinc content in zinc concentrates. The
Method-1 determination range: 30.00% ~ 60.00%; while the Method-2 determination
range: 11.00%~62.00%.
2 Method 1 -- Precipitate Separation-Na2EDTA
Titrimetric Method
2.1 Method summary
The testing material was dissolved by hydrochloric acid, nitric acid and sulfuric acid,
and precipitated and separated coexisting elements such as iron, manganese and lead.
A masking agent is added to the filtrate to mask small amounts of interfering elements.
In the acetic acid-sodium acetate buffer solution with pH 5~6, using xylenol orange as
an indicator, titrate with Na2EDTA standard titration solution. The measured result is
the total content of zinc and cadmium; and the content of cadmium is deducted, which
remains the content of zinc.
2.2 Reagents
Unless otherwise specified, only use reagents and distilled water or deionized water
or equivalent purity water confirmed to be analytically pure in the analysis.
2.2.1 Metal zinc (wZn ≥ 99.99%) has no oxidation on the surface before use. Zinc is
washed by hydrochloric acid (1+9) for 1 min; then rinsed by water and acetone; and
dried in an oven at 50°C.
2.2.2 Ammonium chloride.
2.4.3 Blank test
Do the blank test with the testing material.
2.4.4 Determination
2.4.4.1 Place the testing material (2.4.1) in a 400mL beaker; add a small amount of
water for wetting (if the sample contains a high content of silica, 1g of ammonium
fluoride shall be added); add 10mL of hydrochloric acid (2.2.5); cover the watch glass,
dissolve at a low temperature to expel the hydrogen sulfide for 5min ~ 10min. Add 5mL
of nitric acid (2.2.6) to complete decomposition of the testing material; take off the
watch glass.
2.4.4.2 When the lead content is less than 4%, add 5 mL of sulfuric acid (2.2.12); and
continue to heat until it is wet and salty [if the testing material contains high content of
carbon, it may be taken off when it is steamed to emit white smoke and left to cool.
Add 1mL~2mL of perchloric acid (2.2.8) and continue heating until it is wet and salty],
take off and let cool. Add 20mL of sulfuric acid (2.2.13); cover the watch glass; heat to
dissolve the salt; cool slightly; rinse the watch glass and the wall of the beaker with
water; and dilute the volume to about 60 mL [if the iron content in the solution is low,
add iron sulfate stock solution (2.2.21) makes the solution contain about 20mg of iron].
2.4.4.3 When the lead content is greater than 4%, add 5mL of sulfuric acid (2.2.7) to
heat it up to thick white smoke appears; and steam to a volume of about 2mL; take off
it, and cool. Rinse the watch glass and the wall of the beaker with water; and dilute the
volume to about 50mL; heat it to boil for 10min; cool to room temperature; and stand
for 1h. Filter with slow quantitative filter paper; take the filtrate with a beaker; wash the
beaker and precipitate for 5 times by sulfuric acid (2.2.14), respectively; wash the
beaker and precipitate for 1 time by water, respectively; retain the filtrate.
2.4.4.4 Add 3g~5g of ammonium chloride (2.2.2) and 5mL of ammonium persulfate
solution (2.2.17) to 2.4.4.2 or 2.4.4.3; neutralize with ammonia water (2.2.9) until
precipitation is complete, and then excess 10mL. Heat to boil slightly for 1min~2min;
filter with fast qualitative filter paper while it is hot; wash the beaker and the precipitate
with hot washing liquid for 2 ~ 3 times, respectively; and retain the filtrate.
2.4.4.5 Wash the precipitate by hot washing solution into the beaker of the original
precipitate; add hydrochloric acid (2.2.11) to dissolve the precipitate; add 5 mL of
ammonium persulfate solution (2.2.17); and neutralize it with ammonia (2.2.9) till the
precipitate is complete; and then excess 10 mL. Heat to boil slightly for 1min~2min;
take off; filter through the original filter paper in the beaker of the retentate; wash the
beaker and the precipitate with hot washing liquid for 3 ~ 4 times, respectively.
2.4.4.6 Boil the filtrate (2.4.4.5) and concentrate to a volume of about 100mL; and
completely destroy the excessive ammonium persulfate; take off it and let it cool.
use iodide ion to mask cadmium; and titrate zinc with Na2EDTA solution at pH 5.5.
3.2 Reagents
During the analysis, use the analytical reagents and Class-II water specified in GB/T
6682.
3.2.1 Metal zinc (wZn≥99.99%) has no oxidation on the surface before use. Zinc is
cleaned by hydrochloric acid (3.2.2) (1+9) for 1 min; then rinsed by water and acetone;
and dried in an oven at 50°C.
3.2.2 Hydrochloric acid (ρ201.16g/mL~1.19g/mL).
3.2.3 Liquid bromine.
3.2.4 Nitric acid (ρ201.42g/mL).
3.2.5 Hydrofluoric acid (ρ201.13g/mL~1.15g/mL).
3.2.6 Hydrochloric acid (1+4).
3.2.7 Sulfuric acid (1+1).
3.2.8 Ammonia (ρ200.89g/mL).
3.2.9 Methyl isobutyl ketone (4-methyl-2-pentanone).
3.2.10 Anhydrous ethanol.
3.2.11 Masking agent: dissolve 60g of thiourea, 100g of diammonium hydrogen citrate,
200g of ammonium thiocyanate in water and dilute to 1L; and filter if necessary.
3.2.12 Sodium fluoride solution (20g/L).
3.2.13 Thiourea solution (100g/L).
3.2.14 Potassium iodide solution (1000g/L), prepared on the same day.
3.2.15 Buffer solution: dissolve 250g of hexamethylenetetramine (methenamine) in
water; add 60mL of acetic acid (ρ201.05g/mL); and then dilute to 1L.
3.2.16 Iron stock solution (45g/L): dissolve 45g of iron nitrate [Fe(NO3)3·9H2O] in water
and dilute to 1L.
3.2.17 Xylenol orange: evenly mix 1g of xylenol orange and 99g of potassium nitrate
crystals, and grind it in a ceramic vessel with a pestle. When the color is consistent, it
is considered that the mixture is uniform.
3.2.18 Disodium ethylenediaminetetraacetic acid (Na2EDTA) standard titration solution
Take 2.50g of specimen, accurate to 0.0001g.
3.4.2 The number of determinations
Perform 2 determinations independently and take the average value.
3.4.3 Blank test
Do a blank test with the testing material (add 5mL of iron stock solution to help turbidity
analysis).
3.4.4 Determination
3.4.4.1 Put the testing material (3.4.1) into a 300mL conical beaker; moisten it with
20mL of water. Add 2mL~3mL of liquid bromine (3.2.3); react at room temperature for
15min and shake occasionally. Add 15mL nitric acid (3.2.4); stand for 15min; put the
conical flask on the electric stove to heat; boil to expel the bromine vapor; add 100mL
of water after cooling; heat to boil, and cool.
3.4.4.2 If the testing material is completely dissolved, transfer the test solution into a
500mL volumetric flask and dilute to the mark with water; otherwise, filter the solution
into a 500mL volumetric flask by medium-speed filter paper; wash the insoluble residue
on the filter paper by water; and put the filtered insoluble residue and filter paper in a
25mL platinum crucible; put into a muffle furnace at 800°C for ashing; add 2mL of
sulfuric acid (3.2.7), 2mL of nitric acid (3.2.4) and 2mL of hydrofluoric acid (3.2.5); and
evaporate the solution to nearly dry and cool. Add a small amount of water to dissolve
the soluble salt; filter the solution by medium-speed filter paper; combine the filtrate
and the cleaning solution into the same volumetric flask mentioned above; and dilute
to the mark with water.
If the testing material contains lead, the platinum crucible may be damaged. In this
case, the insoluble residue should be treated as follows:
Rinse the insoluble residue into a large polytetrafluoroethylene beaker with thin
running water. Then put the filter paper in a ceramic crucible; put it in a muffle furnace
at 600°C ~ 700°C for ashing; and cool the crucible to room temperature.
Use a small amount of water to clean the material in the crucible to the large beaker of
polytetrafluoroethylene used above; and then add 2mL of sulfuric acid (3.2.7), 2mL of
nitric acid (3.2.4), and 2mL of hydrofluoric acid (3.2.5); then evaporate the solution to
near dryness; take off it and cool. Add a small amount of water to dissolve the soluble
salt; filter the solution with medium-speed filter paper; combine the filtrate and the
cleaning solution into the same volumetric flask mentioned above; and dilute to the
mark with water.
If it is determined that the filter paper does not contain zinc, the ashing process can be
omitted.
Appendix A
(Informative)
Influence of Potential Interference Elements
A.1 Cadmium
While extracting zinc, cadmium is extracted in large quantities. Before the final titration,
cadmium must be masked with potassium iodide.
A.2 Cobalt
When the organic phase turns blue, it indicates that most of the cobalt in the specimen
is extracted along with the zinc. If the cobalt content is no more than 0.05%, its
influence may be ignored. Otherwise, it shall be determined by atomic absorption
spectrometry after EDTA titration; and then subtract the content of cobalt from the zinc
value obtained from the analysis.
A.3 Lead
When the lead content is greater than 7%, there shall be interference. In the dissolution
stage, it shall precipitate in the form of lead sulfate, which may be separated by filtration.
A.4 Manganese
When the manganese content is greater than 2%, there shall be interference, which
reduces the analysis result. However, zinc concentrates in international trade rarely
have this content of manganese.
A.5 Magnesium
When the magnesium content is greater than 5%, there shall be interference, which
reduces the analysis results. However, the maximum magnesium content of zinc
concentrate reported in international trade is 0.8%.
A.6 Titanium and vanadium
When the titanium and vanadium content is greater than 0.2%, there shall be
interference. However, there is no such content in zinc concentrates in international
trade.
A.7 Other elements
Other elements no more than the following content do not interfere with Method-2:
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.