Analysis of rare earth elements in clay using XRF and XRD

Significance of the Topic

Rare earth elements (REEs) are essential to modern technologies such as permanent magnets, electric vehicles and wind turbines. Precise identification and quantification of REE-bearing clays are critical for exploration, guiding resource evaluation and optimizing extraction strategies.

Objectives and Study Overview

This study evaluates benchtop X-ray diffraction (XRD) and wavelength dispersive X-ray fluorescence (WDXRF) techniques for characterizing a certified REE ore analogue (NCS DC 86311). The goal is to demonstrate rapid phase analysis and standardless oxide quantification to support geochemical workflows in mining and exploration.

Methodology and Instrumentation

The reference clay was pressed into cups for XRD and pellets for WDXRF. XRD measurements used Cu Kα radiation in θ/θ Bragg–Brentano geometry with sample spinning for 20 minutes, followed by Rietveld refinement in Profex. WDXRF analysis employed a 2500 W Rh X-ray tube, nine analyzing crystals and UniQuant software for 20 s counting time per line, enabling standardless oxide determinations.

Used Instrumentation

• Thermo Scientific ARL X’TRA Companion X-ray Diffractometer with solid-state pixel detector and SolstiX Pronto software for single-click Rietveld quantification.
• Thermo Scientific ARL PERFORM’X WDXRF Spectrometer with wavelength dispersive optics, multi-crystal setup and UniQuant standardless analysis software.

Main Results and Discussion

• XRD phase analysis revealed quartz (~50 wt %), microcline (~31 wt %), smectite (~10 wt %), kaolinite (~4 wt %) and minor feldspars and oxides, consistent with ion-adsorption clay profiles.
• WDXRF oxide concentrations (e.g., SiO₂ 74.5 %, Al₂O₃ 14.7 %, K₂O 4.96 %) matched certified values within ±0.5 %, while trace REE oxides were quantified accurately against reference standards.

Benefits and Practical Applications

The combined XRD and WDXRF approach delivers fast, reliable mineralogical and geochemical data without extensive calibration, enabling exploration teams to identify REE-rich clay zones and make informed sampling decisions.

Future Trends and Opportunities

Emerging detector technologies, machine learning-driven phase recognition and integration with geospatial data platforms will enhance throughput and decision support, driving more efficient REE discovery and assessment.

Conclusion

The integrated benchtop XRD and WDXRF workflow offers a robust solution for the rapid characterization of REE-bearing clays, supporting more effective exploration and resource evaluation in high-technology and green energy applications.