The Lithium Research Center (LRC) is located in Tempe, Arizona. The facility is designed around world class laboratory equipment to produce trusted and reliable data for process design and operations. Lithium for use in batteries has very stringent quality parameter’s, and as such, that means that flow sheets for lithium mines must be built upon high quality reliable lab data, this is the focus of the LRC. The LRC also provides ample space to test various flow sheet technologies in pilot plant operations for our project’s, and others.
DIRECT LITHIUM EXTRACTION
Direct Lithium Extraction (DLE) is the process of selectively removing lithium from a solution. DLE has been traditionally been proposed for unconventional brine projects such as oil field brine, geothermal brine and high impurity salars. Given the nature of DLE, it can be performed in four main ways:
Arizona is working on developing its own internal DLE technology, while also utilizing external DLE technologies. This is done to ensure that DLE technology is deployed as efficiently as possible.
Four technologies are emerging as the leading processes for Direct Lithium Extraction:
Ion exchange is a well-known process which is now being investigated to process lithium from subsurface brines. A number of companies are developing lithium selective ion exchange materials to access low-concentration lithium brine resources around the globe.
Basically, the ion-exchange material acts as an ion-sieve with an adjusted atomic porosity suitable just for passage of lithium and hydrogen ions. Consequently, during “Sorption”, the lithium ions of brine pass through the sieve and replace the hydrogen ions whereas during the “Desorption”, the ion-sieve is contacted with an acidic solution promoting the replacement of lithium ions with hydrogen ions.
The main advantages of ion exchange are the high selectivity for lithium and reduced risk of impurity contamination in the product stream.
Adsorption is the most developed DLE technology globally. There are commercial operations that have deployed adsorption technology in some capacity, but not as a full lithium extraction process that doesn’t require evaporation ponds. In adsorption, LiCl molecules from the brine infiltrate within the atomic layers of adsorbent. Once LiCl filled the interstitial layers of adsorbent, it is eluted with a strip solution, typically hot water. Adsorption processes do not require reagents like ion exchange or solvent extraction, but this ease of operation is compromised by lower lithium uptake and carry-over of more impurities into he product.
Solvent-extraction uses an organic solution (containing solvent and extractant) to extract lithium through ion exchange. A challenge for selective solvent-extraction of Lithium is the concentration of impurities in the brine, hence requiring pre-treatment of brine. However, there is potential to use solvent extraction as a post-DLE step to polish the product stream and produce concentrated lithium solutions with high purity.
The last technology being explored for direct lithium extraction and in the earliest stages of development are membranes. These technologies pass only lithium ions through a sieve using differential pressure or temperature. Membranes are advantageous as they require no contact with an extractant like other DLE technologies, but due to high solid content of brines, they are prone to fouling and require pre-treatment prior to use.