GB/T 6730.13-2025Iron ores — Determination of calcium and magnesium content — EGTA-CyDTA titrimetric method (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents". Drafting.

This document is Part 13 of GB/T 6730.The previously published parts of GB/T 6730 are listed in Appendix A.

This document supersedes GB/T 6730.13-2007 "Determination of Calcium and Magnesium Content in Iron Ore - EGTA-CyDTA Titration Method", and is consistent with...

Compared with GB/T 6730.13-2007, apart from structural adjustments and editorial changes, the main technical changes are as follows.

a) Added "3 Terms and Definitions" (see Chapter 3);

b) Some reagents and preparation methods have been changed (see Chapter 5, Chapter 4 of the 2007 edition);

c) Added requirements for burettes, platinum crucibles, PTFE beakers, high-temperature furnaces, and analytical balances (see Chapter 6, 2007 edition). Chapter 5);

d) The preparation of samples from ores with high levels of bound water or easily oxidizable substances has been expanded (see 7.2.1);

e) The specific requirements for blank tests, validation tests, and assays have been changed (see Chapter 8, Chapter 7 of the 2007 edition);

f) Change the permissible difference of the test results to precision (see Chapter 9, Chapter 8 of the 2007 edition).

Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.

This document was proposed by the China Iron and Steel Association.

This document is under the jurisdiction of the National Technical Committee on Standardization of Iron Ore and Direct Reduced Iron (SAC/TC317).

This document was drafted by: China Steel Group Maanshan Mining Research Institute Co., Ltd., and China Certification & Inspection Group Hebei Co., Ltd.

North China University of Technology, Baowu Resources Co., Ltd., Yangchun New Steel Co., Ltd., Metallurgical Industry Standards and Information Research Institute, Panzhihua Iron and Steel Group Research Institute Technology Center of Institute Co., Ltd. and Tongling Nonferrous Metals Group Holding Co., Ltd.

The main drafters of this document are: Xu Xiuping, Hua Shaoguang, Liao Fei, Li Xiangmei, Zuo Yuhao, Yang Qian, Zhang Weiguo, Li Bo, Li Peiliang, and Zhang Xinxin.

Wang Yang, Zhou Weiping, Jiang Xue, Xia Xiangwei, Liu Lingang, Ma Linlin, Dang Yong, Liu Qian, Cheng Huan, Wan Lili, Wang Yan, Zhang Wenjuan, Liu Liwei, Zhang Chen Gao Chunqing and Yuan Qidong.

This document was first published in 2007, and this is its first revision.

Introduction

Iron ore is the main raw material for the steel industry. Within the steel industry's standard system, the standard system for determining the chemical composition of iron ore is its core component.

This series of method standards is a very important part of iron ore production and plays a vital role in ensuring the quality of iron ore products. It serves the production process of iron ore.

Production, trade, and application provide technical support for the high-quality development of China's steel industry.

GB/T 6730 includes a series of standards for the determination of chemical composition of iron ore, which describe the determination of moisture, total iron, and metal content in iron ore products.

Iron, ferrous iron, silicon, aluminum, calcium, magnesium, sulfur, phosphorus, manganese, titanium, total rare earth elements, barium, chromium, vanadium, tin, copper, cobalt, nickel, zinc, niobium, bismuth, potassium, sodium, carbon, lead, arsenic.

Methods for determining chemical components such as mercury, fluorine, chlorine, loss on ignition, and combined water.

In 1986, GB/T 6730 was the first national standard to release 51 methods for the determination of chemical composition of iron ore. This standard reflects the advancements in analytical techniques in the iron ore field.

Based on technological development and actual production needs, and through years of continuous revision and development, a relatively complete standard system has been formed.

For details of the constituent documents of GB/T 6730, please refer to Appendix A.

Determination of calcium and magnesium content in iron ore EGTA-CyDTA titration method Warning---Personnel using this document should have practical experience working in a formal laboratory. This document does not address all possible safety issues.

Users are responsible for taking appropriate safety and health measures and ensuring compliance with relevant national regulations.

1 Scope

This document describes a method for determining the calcium and magnesium content in iron ore using EGTA-CyDTA titration.

This document applies to the determination of calcium and magnesium content in natural iron ore, iron concentrate, sinter, and pellets; determination range (mass fraction). calcium Content 1.50%~15.00%, magnesium content >=1.00%.

2 Normative references

GB/T 601

GB/T 6682

GB/T 6730.1

GB/T 8170

GB/T 10322.1

GB/T 12805

GB/T 12806

GB/T 12808

3 Terms and Definitions

This document does not contain any terms or definitions that need to be defined.

4 Principles

The sample was decomposed with hydrochloric acid and nitric acid, and then filtered. The residue was treated with hydrofluoric acid to remove silicon (except for fluorine-containing samples), then fused with potassium pyrosulfate, and finally treated with ammonia and hydroxide.

Potassium chloride precipitates iron, aluminum, titanium, etc., as hydroxides, while manganese is oxidized to hydrated manganese dioxide by ammonium persulfate, which is then removed by filtration along with the hydroxides.

At this point, phosphorus is simultaneously separated in the form of iron phosphate.

When the pH is greater than 12, add a calcium indicator and titrate the calcium with a standard ethylene glycol diethyl ether diaminetetraacetic acid (EGTA) solution.

When the value is equal to 10, after chelating calcium with EGTA, add Black T indicator and titrate magnesium with cyclohexanediaminetetraacetic acid (CyDTA) standard titration solution.

5 Reagents

Unless otherwise specified, reagents of analytical grade (or higher) and water conforming to grade III or higher as specified in GB/T 6682 should be used in the analysis. Or water of similar purity.

5.1 Potassium pyrosulfate, fine powder.

5.2 Ammonium persulfate, solid.

5.3 Hydrochloric acid, rho~1.19g/mL.

5.4 Hydrochloric acid solution, 1 1.

The hydrochloric acid solution is prepared in a 1.1 ratio (by volume).

5.5% hydrochloric acid solution, 5.95%.

The hydrochloric acid solution ratio is 5.95 (volume ratio).

5.6 Sulfuric acid solution, 1 1.

The sulfuric acid solution is prepared in a 1.1 ratio (by volume).

5.7 Nitric acid, rho~1.42g/mL.

5.8 Hydrofluoric acid, rho~1.15g/mL.

5.9 Potassium hydroxide solution,.200 g/L, stored in a plastic bottle.

5.10 Potassium hydroxide solution, 300 g/L, stored in a plastic bottle.

5.11 Ammonia water, rho~0.90g/mL. 5.12 Ammonia solution, 1 1.

The ammonia solution ratio is 1.1 (volume ratio). 5.13 Ammonia solution, 1 3.

The ammonia solution ratio is 1.3 (volume ratio).

5.14 Triethanolamine solution, 1 3.

The triethanolamine solution ratio is 1.3 (volume ratio).

5.15 Magnesium sulfate solution, 300 g/L.

5.16 Perchloric acid, rho~1.67g/mL.

5.17 Ammonium chloride, solid.

5.18 Potassium chloride, solid.

5.19 Dextrin solution, 50 g/L.

Mix 5g of dextrin with an appropriate amount of water to form a paste, pour it into 100mL of boiling water, boil, remove from heat, and cool to room temperature.

5.20 Ammonia-ammonium chloride buffer solution.

Weigh 67.5g of ammonium chloride (5.17g) and place it in a 1000mL beaker. Add 250mL of water to dissolve it, then add 570mL of ammonia solution.

(5.11) Mix well, transfer to a 1000mL volumetric flask, dilute with water to the mark, mix well, and then transfer to a reagent bottle for storage. 5.21 Calcium indicator.

Mix 0.1g of calcium indicator [2-hydroxy-1-(2-hydroxy-4-sulfonic-1-naphthezo)-3-naphthoic acid] with 10g of preheated solution at 105°C~110°C.

The dried potassium chloride (5.18) was finely ground and mixed, and then stored in a ground glass bottle.

5.22 Chrome Black T Indicator.

Grind 0.1g of Chrome Black T with 10g of potassium chloride (5.18) that has been dried at 105°C~110°C into a fine powder and mix well. Store the mixture in a ground glass bottle.

5.23 Calcium standard solution, 0.35 mg/mL.

Weigh 0 4370 g of calcium carbonate primary standard material that has been dried to constant weight at 105°C~110°C, place it in a 300 mL beaker, and add...

Add 100 mL of water, cover with a watch glass, and pour 10 mL of hydrochloric acid (5.4) along the spout. Heat to boiling to remove carbon dioxide. Remove from heat and let cool. Transfer to...

Dilute with water to the mark in a 500mL volumetric flask and mix well.

5.24 Magnesium standard solution, 0.30 mg/mL.

Weigh 0 2487 g of magnesium oxide primary standard material that has been ignited to constant weight at 900°C~1000°C, place it in a 300 mL beaker, and add...

Add 100 mL of water, cover with a watch glass, and pour 10 mL of hydrochloric acid (5.4) along the spout. Heat to dissolve. Remove from heat and allow to cool. Transfer to a 500 mL volumetric flask.

Add water to dilute to the mark and mix well.