On-site analysis of lithium ore leaching solutions using Micro-Discharge Optical Emission Spectroscopy

The fast and accurate on-site analysis of brines and ore leaching solutions is still a challenge. Conventionally used laboratory methods such as ICP-OES or ICP-MS are not suitable for on-site applications due to high plasma gas flow rates and power consumption. On the other hand, portable X-ray spectrometers are not able to analyse light elements such as Li, Na or K with adequate accuracy. Therefore, a fast and precise method combining on-site suitability and quantification of light elements would be preferable.

Here we investigated the potential of the Micro-Discharge Optical Emission Spectroscopy (µDOES) for the on-site and on-line analysis of lithium ore leaching solutions, whose industrial end product is an essential precursor for the battery industry. The technology is based on a micro-plasma, which is directly created inside the liquid sample without any carrier gas by applying high voltage pulses to electrodes enabling optical emission spectroscopy on-site^[1].

After parameter optimisation (conductivity, wavelength selection, discharge energy), on-line measurements of different process steps at a lithium hydroxide pilot plant were carried out. In addition to Li, other elements like Na, K, Ca, Mg or Rb were quantified. The technique demonstrated its capability for the fast and precise on-site analysis of major components and trace elements in saline solutions. Results showed good agreement with established laboratory methods, such as ICP-OES and ion chromatography.

[1] B. Wiggershaus, M. Jeskanen, A. Roos, C. Vogt and T. Laurila, Trace element analysis

in lithium matrices using Micro-Discharge Optical Emission Spectroscopy, J. Anal. At.
     Spectrom., 2024. DOI:10.1039/D4JA00044G.