An Overview of Commercial Lithium Production
Most lithium is commercially produced from either the extraction of lithium-containing salts from underground brine reservoirs or the mining of lithium-containing rock, such as spodumene. Lithium production from clay sources is expected to become commercially viable, though perhaps not until 2022.
Lithium is a metal commonly used in batteries like the rechargeable ones found in laptops, cellphones, and electric cars as well as in ceramics and glass. It is the lightest metal on Earth and is soft enough to be cut with a knife when in its elemental form.
Processing From Brine
Much of the lithium produced today is extracted from brine reservoirs called salars that are located in high-elevation areas of Bolivia, Argentina, and Chile. In order to extract lithium from brines, the salt-rich waters must first be pumped to the surface into a series of large evaporation ponds where solar evaporation occurs over a number of months.
Potassium is often first harvested from early ponds, while later ponds have increasingly high concentrations of lithium. Economical lithium-source brines normally contain anywhere from a few hundred parts per million (ppm) of lithium to upwards of 7,000 ppm.
When the lithium chloride in the evaporation ponds reaches an optimum concentration, the solution is pumped to a recovery plant where extraction and filtering remove any unwanted boron or magnesium. It is then treated with sodium carbonate (soda ash), thereby precipitating lithium carbonate. The lithium carbonate is then filtered and dried. Excess residual brines are pumped back into the salar.
Lithium carbonate is a stable white powder that is a key intermediary in the lithium market because it can be converted into specific industrial salts and chemicals—or processed into pure lithium metal.
Processing From Minerals
In contrast to salar brine sources, extraction of lithium from spodumene, lepidolite, petalite, amblygonite, and eucryptite requires a wide range of processes. Because of the amount of energy consumption and materials required, lithium production from mining is a much more costly process than brine extraction, even though these minerals have a higher lithium content than the saltwater.
Of the five minerals, spodumene is the most commonly used for lithium production. After it is mined, spodumene is heated to 2012 degrees Fahrenheit and then cooled to 149 degrees. It's then crushed and roasted again, this time with concentrated sulfuric acid. Ultimately, sodium carbonate, or soda ash, is added, and the resulting lithium carbonate is crystallized, heated, filtered, and dried.
Processing From Clay
Several companies are exploring the extraction of lithium from clay in Nevada, including American Lithium and Noram Ventures. The companies are testing different production methods, including sulfuric acid leaching.
Turning Lithium Into Metal
Converting lithium into metal is done in an electrolytic cell using lithium chloride. The lithium chloride is mixed with potassium chloride in a ratio of 55% to 45% in order to produce a molten eutectic electrolyte. Potassium chloride is added to increase the conductivity of the lithium while lowering the fusion temperature.
When fused and electrolyzed at about 840 degrees Farhenheit, chlorine gas is liberated while molten lithium rises to the surface, collecting in cast-iron enclosures. The pure lithium produced is wrapped in paraffin wax to prevent oxidization. The conversion ratio of lithium carbonate to lithium metal is about 5.3 to 1.
Global Lithium Production
The top five countries for lithium production in 2018 were Australia, Chile, China, Argentina, and Zimbabwe. Australia produced 51,000 metric tons of lithium that year, the latest for which figures are available. Total global production, excluding the U.S., amounted to 70,000 metric tons.
The companies that produce the most lithium are Albemarle, Sociedad Quimica y Minera de Chile, and FMC.
GrabCAD Blog. "How Does LIthium Mining Work?" Accessed Jan. 24, 2020.