Presented paper

IMWA2019 Students work

Determination of Salt Precipitation and Interferences in Lithium Brine Solutions

Bowell, Rob (1); Declercq, Julien (1); de los Hoyos, Camilo (2)
1: SRK Consulting, United Kingdom; 2: SRK Consulting, Argentina

Lithium brine are one of the main source of lithium in the world and the majority is extracted in the Salars of South America. The composition of these natural hypersaline brines is complex and often the desired commodities within them such as lithium or boron occur in trace concentrations (Evans, 2014). This requires evaporation by solar or mechanical methods to generate a feed solution to a plant that can separate and concentrate the commodity of interest. However, the concentration process concentrates all the elements, not just those of interests. Several elements are known to have a detrimental effect, fouling effect, on lithium extraction process. Typically, Mg is present and this is a challenge for the separation the element of interest and reduce the quality of the final products (Garrett, 2004).An experimental study has been undertaken to assess the interference of competing ions on lithium separation from an idealised natural brine. The effect depends on the interfering cation and is greatest for Mg2+ > Na+ > K+ > Ca2+. In terms of anions, both lithium chloride and lithium sulfate can be carbonated to produce a saleable lithium carbonate product. In parallel a numerical prediction in PHREEQC has also been undertaken to assess speciation of these elements as well as lithium. Numerical predictive calculations support the order of interference, but a major challenge to apply thermodynamic predictive calculations to emulate the processing of hypersaline brines is the limit of thermodynamic data available. Typically, the Pitzer approach will be taken, to minimise the uncertainty due to the ionic strength of these solutions but limited available data limits the application of this approach. By experimentally determining activity coefficients for the relevant salts these predictions can be improved and this provides greater understanding of the main mechanisms that control lithium separation in the brine both naturally and in a process plant.

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Evans, K. (2014). Lithium in: Critical Metals Handbook, Gunn, G (ed). Wiley & Sons Ltd, 230-260

Garrett, D. (2004). Handbook of Lithium and Natural Calcium Chloride, first ed. Elsevier Academic Press