Determination of fluorine and chlorine in iron ore using combustion ion chromatography

Importance of the topic

Fluorine and chlorine impurities in iron ore pose significant health, environmental, and industrial challenges. Fluorine released during ore combustion can form gaseous or aerosol products that, when inhaled, lead to fluorine poisoning. Chlorine can generate carcinogenic compounds such as dioxins and corrodes iron-based materials, compromising steel quality. Accurate quantification of these halogens is therefore critical for ore quality control, regulatory compliance, and the safety of workers and end users.

Aims and study overview

This study aimed to develop a robust, automated method for determining fluorine and chlorine levels in iron ore using combustion ion chromatography (CIC). Six representative iron ore samples from Australia were analyzed to evaluate method performance. Key performance metrics included chromatographic separation, linearity, detection limits, and precision.

Methodology

Samples (10–15 mg) were combusted in a quartz tube fitted with a ceramic liner at 1000–1100 °C under controlled argon and oxygen flows. Combustion products were absorbed into deionized water and injected directly into the ion chromatography system. Calibration standards covered 0.025–5 mg/L for fluoride and 0.05–10 mg/L for chloride. Limit of detection (LOD) was established at signal-to-noise of 3, resulting in 0.762 µg/g for fluorine and 0.738 µg/g for chlorine.

Instrumentation Used

• CIC Unit: Mitsubishi Chemical Analytech AQF-2100H comprising automatic boat controller, horizontal furnace, gas absorption unit, and solution selector.
• IC System: Thermo Scientific Dionex Integrion HPIC with Dionex IonPac AS18-Fast-4µm guard and analytical columns, EGC 500 KOH eluent generator, CR-ATC trap column, ADRS 600 suppressor, and conductivity detector.
• Software: Thermo Scientific Chromeleon CDS v7.2.9 and Mitsubishi NSX-2100 v10.2.3.0.

Main results and discussion

High-resolution separation of fluoride, chloride, carbonate, sulfate, bromide, and tungstate was achieved within 15 minutes using the Thermo Scientific Dionex IonPac AS18-Fast-4µm column. Calibration curves displayed excellent linearity (r2≥0.9997). Sample analyses yielded fluorine concentrations from 410 to 2006 µg/g and chlorine from 23.1 to 98.9 µg/g across six ore types. Relative standard deviation (RSD) for triplicate analyses ranged from 0.48% to 2.8%, demonstrating high precision. Tungsten oxide proved essential as a combustion aid to enhance fluorine recovery and protect quartz components.

Benefits and practical applications

• Automated CIC reduces manual handling and potential errors, enhancing laboratory throughput.
• Reagent-free eluent generation simplifies operations and ensures consistent high-purity potassium hydroxide supply.
• High sensitivity and precision support rigorous quality control in mining, metallurgy, and environmental monitoring.

Future trends and applications

Advancements may include integration of real-time data analytics and remote monitoring for in-line ore processing. Miniaturized combustion modules and multi-halogen detection could broaden applicability to other minerals and complex matrices. Coupling CIC with mass spectrometric detection could further improve specificity and trace-level quantification.

Conclusion

The developed CIC method provides a reliable, sensitive, and fully automated approach for quantifying fluorine and chlorine in iron ore. By combining an optimized combustion protocol with high-efficiency ion chromatography, the procedure delivers excellent linearity, low detection limits, and high precision, making it suitable for routine quality assessment in industrial laboratories.

Reference

1. Ando M., Tadano M., Yamamoto S. Health effects of fluoride pollution caused by coal burning. Science of the Total Environment. 2001, 271(1–3):107–116.
2. Liu G.-R., Zheng M.-H., Cai Z.-W., et al. Dioxin analysis in China. Trends in Analytical Chemistry. 2013, 46(6):178.
3. Thermo Scientific Technical Note 72211. Combustion Ion Chromatography with a Dionex Integrion HPIC System. Sunnyvale, CA, 2017.
4. Mitsubishi Chemical Analytech. Operation Manual for NSX-2100 Series Automatic Combustion Unit Model AQF-2100H. Instruction Manual of Absorption Unit GA-210.
5. Thermo Fisher Scientific. IonPac AS18-Fast-4µm Column Manual. Man-065499, EN.
6. ICH. Q2B Validation of Analytical Procedures: Methodology (CPMP/ICH/281/95). Geneva, 1996.