The Finnish company Sensmet has developed a technology called Micro-Discharge Optical Emission Spectroscopy (µDOES), which can measure multiple metals, including lithium and their impurities, in real time. The technology is based on atomic emission spectroscopy and creates a micro-discharge or electric spark directly inside an aqueous sample, causing a microscopic volume of the fluid surrounding the spark to be flash-heated to 10,000 °C. This causes molecular species in the micro-discharge to dissociate into atoms that release light at their characteristic wavelengths, which is then measured by the µDOES system to derive a quantitative analysis of the metals contained in the sample.
Keliber, a Finnish subsidiary of Sibanye-Stillwater, tested the technology in a pilot-scale programme in 2022. The programme ran continuously at a demonstration plant for 400 hours and achieved a total lithium recovery rate of more than 88%. Eighty samples were drawn from the process and analysed in parallel using the µDOES analyser and a laboratory ICP-OES, resulting in a correlation between the methods.
Why it matters
This technology is important for the lithium production industry as it allows for accurate dosing of precipitation chemicals. Inaccurate dosing of chemicals can result in loss of revenue through waste of unreacted lithium and also increases the cost and delay incurred by retreatment. It is also important for lithium hydrometallurgical processes, where direct measurements of dissolved metal concentrations are essential and traditional methods have major limitations. The implementation of strict online monitoring and control using µDOES technology can help to reduce impurity levels, optimise yield and quality, and minimise cost, which can improve the overall efficiency of lithium production. The µDOES technology is also suited for “black mass” recycling of battery metals
“One of the greatest challenges facing the global steel industry today is the control and management of the precise dosage of components used in real-time processes.
In the iron and steel industry, this is already being used in the formation of charge materials for the smelting of specific steel grades. The situation is different in non-ferrous metallurgy: whereas in pyrometallurgy, modern technology enables very fast data collection and analysis, it is not available for hydrometallurgy. The use of micro-discharge optical emission spectroscopy, on the other hand, makes it possible to simplify data acquisition and post-processing and to avoid over- or under-consumption of chemicals, thereby optimising costs” – Expert comment. 
