Editing Lithium carbonate (section)

===From underground brine reservoirs===
In the [[Salar de Atacama]] in the [[Atacama Desert]] of Northern Chile, lithium carbonate and hydroxide are produced from brine.<ref name="SQM-SUS">{{cite web |title=Sustainability of lithium production in Chile |url=https://www.sqm.com/wp-content/uploads/2020/09/SQM_-_Sustainable_Lithium_-_English.pdf |website=SQM |access-date=1 December 2020 |archive-date=5 November 2020 |archive-url=https://web.archive.org/web/20201105191714/https://www.sqm.com/wp-content/uploads/2020/09/SQM_-_Sustainable_Lithium_-_English.pdf |url-status=live }}</ref><ref>{{cite conference |last1=Telsnig |first1=Thomas |last2=Potz |first2=Christian |last3=Haas |first3=Jannik |last4=Eltrop |first4=Ludger |last5=Palma-Behnke |first5=Rodrigo |title=Opportunities to integrate solar technologies into the Chilean lithium mining industry – reducing process related GHG emissions of a strategic storage resource |conference=Solarpaces 2016: International Conference on Concentrating Solar Power and Chemical Energy Systems |series=AIP Conference Proceedings |date=2017 |volume=1850 |issue=1 |page=110017 |doi=10.1063/1.4984491|bibcode=2017AIPC.1850k0017T |doi-access=free }}</ref>

The process pumps lithium rich brine from below ground into shallow pans for evaporation. The brine contains many different dissolved ions, and as their concentration increases, salts precipitate out of solution and sink.  The remaining [[supernatant]] liquid is used for the next step. The sequence of pans may vary depending on the concentration of ions in a particular source of brine.

In the first pan, [[halite]] (sodium chloride or common salt) crystallises.  This has little economic value and is discarded.  The supernatant, with ever increasing concentration of dissolved solids, is transferred successively to the [[sylvinite]] (sodium potassium chloride) pan, the [[carnalite]] (potassium magnesium chloride) pan and finally a pan designed to maximise the concentration of lithium chloride. The process takes about 15 months.  The concentrate (30-35% lithium chloride solution) is trucked to Salar del Carmen. There, [[boron]] and magnesium are removed (typically residual boron is removed by solvent extraction and/or [[ion exchange]] and magnesium by raising the [[pH]] above 10 with [[sodium hydroxide]])<ref>{{cite web 
|last1=Dry 
|first1=Mike 
|title=Extraction of Lithium from Brine – Old and New Chemistry 
|url=http://downloads.aqsim.com/Extraction%20of%20Lithium%20from%20Brine%20%2013%20Old%20and%20New%20Chemistry.pdf 
|website=Critical Materials Symposium, EXTRACTION 2018, Ottawa, August 26–29 
|access-date=1 December 2020 
|archive-date=6 October 2021 
|archive-url=https://web.archive.org/web/20211006135312/http://downloads.aqsim.com/Extraction%20of%20Lithium%20from%20Brine%20%2013%20Old%20and%20New%20Chemistry.pdf 
|url-status=dead 
}}</ref> then in the final step, by addition of [[sodium carbonate]], the desired lithium carbonate is precipitated out, separated, and processed.

Some of the by-products from the evaporation process may also have economic value.

There is considerable attention to the use of water in this water poor region. [[Sociedad Química y Minera de Chile|SQM]] commissioned a [[life-cycle analysis]] (LCA) which concluded that water consumption for SQM's lithium hydroxide and carbonate is significantly lower than the average consumption by production from the main ore-based process, using [[spodumene]]. A more general LCA suggests the opposite for extraction from reservoirs.<ref name="BBC" >{{cite web |last1=Early |first1=Catherine |title=The new 'gold rush' for green lithium |url=https://www.bbc.com/future/article/20201124-how-geothermal-lithium-could-revolutionise-green-energy |website=Future Planet |publisher=BBC |access-date=2 December 2020 |date=25 Nov 2020 |archive-date=13 February 2024 |archive-url=https://web.archive.org/web/20240213053623/https://www.bbc.com/future/article/20201124-how-geothermal-lithium-could-revolutionise-green-energy |url-status=live }}</ref>

The majority of brine based production is in the "[[lithium triangle]]" in South America.