Measuring lanthanide concentrations in molten salt using laser-induced breakdown spectroscopy (LIBS)

Area of Science:

• Analytical Chemistry
• Materials Science
• Spectroscopy

Background:

• High-temperature molten salts are crucial in various industrial processes.
• Accurate elemental analysis of these salts is challenging due to extreme conditions.
• Lanthanide elements, such as europium and praseodymium, are important in nuclear fuel reprocessing.

Purpose of the Study:

• To demonstrate the capability of Laser-Induced Breakdown Spectroscopy (LIBS) for analyzing molten salts at high temperatures.
• To quantify the concentrations of europium (Eu) and praseodymium (Pr) in molten LiCl-KCl salt at 500 °C.
• To validate the accuracy and precision of the LIBS method for these specific analytes and conditions.

Main Methods:

• Utilized a laboratory furnace to maintain molten eutectic lithium chloride-potassium chloride (LiCl-KCl) salt at 500 °C under an argon atmosphere.
• Applied laser pulses (1064 nm, 7 ns, 120 mJ/pulse) to the molten salt surface, generating plasma for LIBS analysis.
• Employed a broadband Echelle-type spectrometer to collect emission spectra and Partial Least Squares (PLS) regression with leave-one-sample-out cross-validation for quantification.

Main Results:

• Achieved accurate quantification of europium (Eu) and praseodymium (Pr) concentrations in the molten LiCl-KCl salt.
• Reported a Root Mean Square Error of Prediction (RMSEP) of 0.13% (absolute) for Eu over a 0-3.01% concentration range.
• Reported a Root Mean Square Error of Prediction (RMSEP) of 0.13% (absolute) for Pr over a 0-1.04% concentration range.

Conclusions:

• Laser-Induced Breakdown Spectroscopy (LIBS) is a versatile and accurate analytical technique for high-temperature molten salt applications.
• The developed LIBS method demonstrates excellent performance for quantifying lanthanide elements in challenging molten salt environments.
• This technique holds significant potential for in-situ monitoring and process control in high-temperature chemical systems.