Iron ore analysis with the ARL OPTIM’X XRF Spectrometer

Importance of the Topic

Iron ore refinement underpins steel production and emerging battery technologies, demanding accurate compositional analysis to ensure material quality and performance. Rapid, reliable quantification of major and minor oxides in ore feedstocks supports process optimization, cost reduction, and compliance with purity requirements in sectors ranging from construction to advanced energy storage.

Objectives and Study Overview

This study demonstrates a wavelength dispersive X-ray fluorescence method for fast, precise analysis of iron ore using the ARL OPTIM’X spectrometer. Key goals include minimizing analysis time, achieving high repeatability on certified reference materials, and evaluating detection limits for major and trace components in a production context.

Methodology

• Sample preparation: Seven iron ore reference materials fused into glass beads at a 1:10 sample-to-flux ratio with ammonium nitrate oxidizer. Fusion eliminates particle size and mineralogical effects on fluorescence.
• Calibration: Constructed using 6–7 certified reference materials per oxide. Concentration ranges spanned trace to major levels for Al₂O₃, CaO, Cr₂O₃, Fe₂O₃, K₂O, MgO, MnO, P₂O₅, SO₃, SiO₂, TiO₂, and V₂O₅. Linear regression yielded R² values above 0.99 for most oxides, with higher errors for Cr₂O₃ and V₂O₅ due to limited concentration range and low intensity.
• Analysis conditions: Measurements at 30 kV and 1.67 mA. Major oxides collected in 36 seconds each, MgO in 60 seconds, for a total of 7.6 minutes per sample on the 50 W unit. A 200 W version can reduce total time to ~3 minutes without compromising accuracy.

Instrumentation

The ARL OPTIM’X spectrometer is a compact WDXRF system equipped with a SmartGonio goniometer covering elements from fluorine to americium. The 50 W tube version delivers ten times better spectral resolution than typical energy‐dispersive systems and requires no water cooling. Its stability and precision support critical element detection, including Na, Mg, and low-Z elements.

Main Results and Discussion

Validation on an iron ore CRM (405) over ten replicates showed excellent agreement with certified values. Major oxides exhibited differences within ±0.04 %, repeatability standard deviations below 0.07 % for Fe₂O₃, and comparable precision for Al₂O₃ and SiO₂. Trace elements (Cr₂O₃, V₂O₅) showed greater variability due to tenfold dilution in fused beads; precision can be improved by longer counting times or pellet preparation.

Benefits and Practical Applications

• High throughput: Analysis time under 8 minutes per sample accelerates quality control in large-scale mining operations.
• Broad elemental coverage: From major oxides to trace metals, enabling comprehensive feedstock characterization.
• Robust repeatability and accuracy: Suitable for process monitoring, specification compliance, and R&D in battery material development.

Future Trends and Potential Applications

Advances in XRF detector technology and automation will further reduce analysis times and improve sensitivity for trace elements. Integration with online process control could enable real-time monitoring of ore beneficiation, while new fusion protocols may expand capabilities for complex mineral matrices. In battery research, rapid screening of iron-based cathode precursors will benefit from enhanced throughput and lower detection limits.

Conclusion

The ARL OPTIM’X spectrometer combined with fused-bead sample preparation provides a fast, precise WDXRF method for iron ore analysis. Major oxides are quantified with high linearity and repeatability, while trace element determination can be optimized through tailored sample preparations. The option of a higher-power tube further accelerates throughput without sacrificing performance.

References

• U.S. Geological Survey, Mineral Commodity Summaries – Iron Ore, January 2022