Lithium Solvent Extraction
Solvent extraction offers a cutting-edge alternative to the evaporation process commonly used for the recovery of lithium. Despite its widespread adoption in other industries, solvent extraction was not utilized for lithium recovery on a commercial scale until recently due to the absence of effective lithium extractants. Working with Tenova Advanced Technologies, Solvay has created a highly effective means for recovering lithium powered by our CYANEX® 936P lithium extractant.
Although the evaporation process for lithium recovery from brines has benefits, including its low operational costs, it is also inefficient, time-consuming, capital-intensive, weather-dependent and inherently unsustainable. Due to climatic conditions and brine composition, many lithium-bearing brine deposits are not amenable to the evaporative processing used in the Salar de Atacama in northern Chile, the most significant source of lithium brine.
Lithium Solvent Extraction: Better, Faster, Greener
Lithium solvent extraction is faster and more economical than competing lithium extraction processes, taking only a matter of hours compared to the 18-month average residence time required by the evaporation and precipitation route.
This alternative extraction process for lithium promotes improved efficiency as less lithium is lost throughout each stage of the recovery and purification process. Lithium solvent extraction is not dependent on weather conditions and has been shown to reduce the environmental footprint of lithium production. Brine be returned to the salar after lithium extraction, and lithium solvent extraction requires a fraction of the surface area that evaporation ponds demand.
Additionally, lithium solvent extraction is a highly versatile process enabling direct production of high-purity lithium hydroxide monohydrate, LiOH.H2O, with no additional costs and without the need for conversion from lithium carbonate, Li2CO3. Where applicable, lithium solvent extraction facilitates the direct production of high-purity lithium carbonate through precipitation with soda ash.
Additional Advantages of Lithium Solvent Extraction
Although various direct lithium extraction processes - such as adsorption and ion exchange - are effective in purifying lithium, only solvent extraction can reach required lithium concentration levels without additional processing steps. While other direct lithium extraction routes concentrate lithium to some extent, solvent extraction can achieve any concentration factor up to the saturation limit.
Lithium solvent extraction is essentially a stand-alone process, whereas adsorption and ion exchange typically require an additional concentration step, either through smaller solar evaporation ponds, forced (artificial) evaporation, or solvent extraction, before the purified solution can be converted to the final product.
Solvay’s Offering for Lithium Solvent Extraction
Solvay and Tenova Advanced Technologies have collaborated to offer producers a high-performing lithium extractant that is reliable, efficient and designed specifically for lithium solvent extraction operations. CYANEX® 936P is a phosphorus-based extractant that is particularly well suited to extract lithium from salar brines. Although this lithium reagent is most commonly applied to brines, it can be used for lithium extraction in spent solutions or mother liquors. CYANEX® 936P may also be suitable for other lithium deposits, including geothermal sources, clay and hard-rock deposits.
CYANEX® 936P offers several unique benefits to help producers streamline the lithium solvent extraction process:
- High efficiency and selectivity for lithium over other minerals, like boron, sodium and potassium
- Recovery rate and lithium salt purity greater than 99%
- High extraction capacity, meaning lithium can be extracted from a typical stream in only a few stages
- Facilitates the use of a fast, continuous, non-weather-dependent process
- Contributes to the use of a lower CAPEX- and OPEX-intensive lithium extraction process than traditional methods
- Facilitates a non-water-intensive process, allowing lithium-depleted brine to be reinjected into the salar
CYANEX® 936P works on any lithium stream that is free of divalent ions, which means Mg2+ and Ca2+ must be pre-removed via filtration or precipitation. The aqueous feed solution, or brine, contains lithium in low concentration along with impurities and is contacted with an organic phase containing CYANEX® 936P. The lithium is selectively extracted from the aqueous feed solution into the organic phase by forming a complex with Solvay’s CYANEX® 936P during the extraction phase. This stage is followed by a scrubbing stage to remove any remaining impurities before the stripping stage, which produces a high-purity solution saturated with lithium.
The lithium-filled solution is directly converted into high-purity lithium hydroxide through electrolysis or lithium carbonate via precipitation with soda ash. CYANEX® 936P enables a continuous lithium production process in a matter of hours, regardless of weather conditions, promoting sustainable, cost-effective lithium extraction.