Lithium ion batteries power everything from cell phones and laptops to electric vehicles (EVs) and backup systems for power grids. The lithium used in these batteries comes from two sources: hard rock mining of the mineral spodumene in Canada, Australia, and China, or from solar evaporation of brines extracted from aquifers below salt flats or Salars. The brines contain about 58 percent of the world’s lithium sources and are located primarily in North and South America and Asia.
Now, a company called Lilac Solutions—a startup from Northwestern University—has devised a third way of producing lithium. The company, which was formed in 2016, has developed ion-exchange materials that can be used to extract lithium directly from brines. This process promises to save huge amounts of processing time and may prove to be more environmentally friendly.
Lilac Solutions’ new process for lithium extraction from brines promises a dramatic decrease in both time and cost. (Image source: Lilac Solutions)
Salt brine deposits tend to form in arid areas. They are created in a closed basin containing a salt lake or salt flat. The climate must be dry enough so that surface waters can flow into the basin, but do not flow out. The inflow brings dissolved calcium, magnesium, potassium, sodium, and lithium from the surrounding area into the basin. If the lake dries out completely, it can leave a salt flat covered by evaporated minerals—rock salt being the best known of these.
As the water evaporates, lithium acts differently than the other dissolved minerals. Because it is more soluble, lithium remains in solution. It becomes concentrated as it sinks into the underlying aquifer brine, which can be up to several hundred meters below the salt surface.
To extract lithium with the traditional method, the brine is pumped to the surface and placed in shallow evaporation ponds. It can take two to three years of pumping the brine from one evaporation pond to another to the point where the lithium is enriched to as high as 5,000 ppm (about 0.5%). When it reaches this concentration, it is pumped to a chemical plant, where lithium carbonate and lithium hydroxide are produced.
Processing the brine has three major problems. Only about 50% of the lithium available is extracted during the processing of the concentrate salt solution. Time is also a factor. Two to three years is a long time to wait and the pricing of lithium is quite volatile, making it difficult to predict future profits. Lastly, the variability of the weather can greatly influence the ability of the solar ponds to evaporate the brine solution. Such was recently the case with an Argentinian lithium producer that reported lower lithium production than expected because the local weather interfered with the evaporation of its brine ponds.