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Extraction
Lithium and its compounds were historically isolated and extracted from hard rock but by the 1990s mineral springs, brine pools, and brine deposits had become the dominant source. Most of these were in Chile, Argentina and Bolivia. Large lithium-clay deposits under development in the McDermitt caldera (Nevada, United States) require concentrated sulfuric acid to leach lithium from the clay ore.

By early 2021, much of the lithium mined globally comes from either "spodumene, the mineral contained in hard rocks found in places such as Australia and North Carolina" or from the salty brine pumped directly out of the ground, as it is in locations in Chile. In Chile's Salar de Atacama, the lithium concentration in the brine is raised by solar evaporation in a system of ponds. The enrichment by evaporation process may require up to one-and-a-half years, when the brine reaches a lithium content of 6%. The final processing in this example is done near the city of Antofagasta on the coast where pure lithium carbonate, lithium hydroxide, and lithium chloride are produced from the brine.

Low-cobalt cathodes for lithium batteries are expected to require lithium hydroxide rather than lithium carbonate as a feedstock, and this trend favors rock as a source.

The use of electrodialysis and electrochemical intercalation has been proposed to extract lithium compounds from seawater (which contains lithium at 0.2 parts per million), but it is not yet commercially viable.

Developing Extraction Methods
As demand for lithium increases, alternative methods for extraction are gaining popularity. Methods that are gaining traction are both geothermal brine water extraction, and seawater lithium extraction.

Geothermal Lithium

Geothermal plants produce energy by pumping high-temperature groundwater up to the surface where the steam drives a turbine. The brine water from this process is then recycled back down into the ground to be reheated and reprocessed. A developing method for lithium extraction, as well as other valuable minerals, is to process geothermal brine water through an electrolytic cell, located within a membrane, to recover valuable minerals. This environmentally sustainable process yields high concentrations of lithium that are also located in convenient locations for transport to processing plants. This can result in a highly profitable and economical process for the extraction of lithium.

Seawater Lithium

If it becomes economically viable, ocean seawater offers a fast amount of lithium. A developing method is using organic ion-selective cells within a membrane that is able to collect lithium either by use of electric field or a concentration difference. The challenge for this method, like desalinization, is producing enough lithium at a high enough rate to prove it economical. Another issue with this method is that the lithium is still dissolved within water and must undergo further treatment to extract metallic or solid lithium.

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