ICP-OES Quality Control of Elements in Brines Produced by Direct Lithium Extraction (DLE)

ICP-OES Quality Control of Elements in Lithium Brines from Direct Lithium Extraction (DLE)

Significance of the Topic

Direct Lithium Extraction (DLE) enables faster, water-saving, land-efficient recovery of lithium from brine deposits. Quality control of elemental composition at each process stage ensures the purity of Li concentrates for battery-grade salts and supports sustainable battery supply chains.

Objectives and Study Overview

This study evaluates an automated ICP-OES method for simultaneous measurement of twelve elements in raw, tail, and concentrate brines produced by membrane-based DLE. It aims to demonstrate rapid calibration, matrix management, and long-term stability for routine QC in Li extraction.

Methodology and Instrumentation

An Agilent ICP-OES Automation System was employed, combining:

• 5900 SVDV ICP-OES with vertical plasma torch and 27 MHz SSRF generator
• AVS 7 switching valve for rapid sample introduction and reduced torch fouling
• ADS 2 advanced dilution system for prescriptive (up to 400×) and reactive dilutions
• SPS 4 autosampler for high-throughput sample handling
• ICP Expert Pro software with IntelliQuant Screening for semiquantitative profiling and star-rating wavelength selection

Radial viewing, internal standard correction (Sc, Rb, Te mix), and fitted background correction were used to mitigate matrix interferences from high TDS (up to 31 %).

Key Results and Discussion

• Calibration and Linearity: Automated standards (spanning 0.1–1000 mg/L) yielded correlation coefficients ≥0.99993 for all analytes.
• Detection Limits: MDLs in 1 % NaCl matrix ranged from 0.004 mg/L (Ba) to 1.39 mg/L (K).
• Prescriptive and Reactive Dilution: ADS 2 applied 50× routine dilutions, with additional reactive steps (150–250×) to bring analytes into range, managed without analyst intervention.
• Elemental Profiles: Distinctive composition of raw brine (18 % NaCl, 11 % CaCl2, etc.), Li concentrate (~10 000 mg/L Li), and Li-free tail brine confirmed rapid process monitoring.
• Accuracy and Precision: Spike recoveries between 98 % and 104 %, %RSD <3.1 %. Continuing calibration checks over seven hours remained within 100 ± 5 % recovery for all elements.
• Robustness: No internal standard failures or torch fouling observed during 306 sequential analyses, demonstrating high method stability.

Benefits and Practical Applications

• High throughput and minimal manual preparation support routine QC during DLE operations.
• Automated dilution and calibration reduce contamination risks and human error.
• Comprehensive multi-element profiling accelerates process optimization for battery salt production.

Future Trends and Opportunities

• Integration of real-time ICP-OES data with process control for closed-loop DLE optimization.
• Advancements in AI-driven spectral deconvolution to further improve interference correction.
• Expanded suite of automation accessories (e.g., inline sample preparation) to support higher matrix varieties.
• Application of similar workflows to new critical mineral extraction processes beyond lithium.

Conclusion

The Agilent ICP-OES Automation System enables accurate, precise, and robust elemental analysis of high-TDS Li brines generated by DLE. Automated calibration, dilution, and interference management ensure efficient QC in lithium recovery workflows, supporting sustainable battery material production.

Reference

1. International Lithium Association. Direct Lithium Extraction (DLE): An Introduction. Version 1.0.1, 2024.
2. Agilent Technologies. A Practical Guide to Elemental Analysis of Lithium Ion Battery Materials Using ICP-OES. Publication 5994-5489EN.
3. Gagnon, M-A. Elemental Analysis of Brine Samples Used for Lithium Extraction. Agilent Publication 5994-5149EN.
4. Agilent Technologies. Reduce Costs and Boost Productivity with the Advanced Valve System (AVS) 6 or 7 Port Switching Valve System. Publication 5991-6863EN.
5. Agilent Technologies. Agilent Advanced Dilution System (ADS 2) – Technical Overview. Publication 5994-7211EN.
6. Agilent Technologies. Agilent IntelliQuant Screening: Smarter and Quicker Semiquantitative ICP-OES Analysis. Publication 5994-1518EN.
7. Agilent Technologies. Agilent IntelliQuant Software: For Greater Sample Insight and Simplified Method Development. Publication 5994-1516EN.