Lithium is a soft metal which is used for many applications, such as production of high-temperature lubricants or heat-resistant glass. Furthermore, lithium is used in large quantities for battery production. It is obtained from brines and high-grade lithium ores. Depending on the lithium concentration, extraction may or may not be economically viable.

This Application Note demonstrates a method to determine the lithium concentration in brines by potentiometric titration. Lithium and fluoride precipitate in ethanol as insoluble lithium fluoride. Using ammonium fluoride as titrant and a fluoride ion selective electrode (ISE), determination of lithium via potentiometric titration is possible.

This method is more reliable, faster, and less expensive than the determination of lithium in brine by other more sophisticated techniques such as atomic absorption spectroscopy (AAS).

Two samples with ~20% (m/m) and ~40% (m/m) lithium chloride are analyzed. No further sample preparation is required.

905 Titrando with tiamo. Example setup for the analysis of lithium in brine.
Figure 1. 905 Titrando with tiamo. Example setup for the analysis of lithium in brine.

The analysis is carried out with an automated system consisting of tiamoTM in combination with a 905 Titrando. A fluoride ion selective electrode (ISE) in combination with a Long Life ISE reference electrode is used for the indication of the titration.

After transferring an appropriate amount of sample into the titration vessel, enough ethanol is added to cover the diaphragm of the electrode. The titration is carried out using ammonium fluoride until after the first equivalence point is reached.

Calcium will interfere with the analysis and has to be analyzed separately.

For both samples this method gave reliable and reproducible results.

Table 1. Results of the lithium determination in brines.
n = 3 Assay of LiCl brine 1 in % Assay of LiCl in brine 2 in %
Mean 41.3 14.85
SD(abs) 0.7 0.11
SD(rel) 1.6 0.7
Figure 2. Example curve of the lithium determination in brines.

Using ethanol as solvent, ammonium fluoride as titrant, and the fluoride ISE for indication, the determination of lithium in brine can be performed reliably and cost-efficiently.

Therefore, this method provides an inexpensive and simple approach to determine if an extraction of lithium from brine is economically feasible or not.


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