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Lithium which will power our battery needs is the 33rd most common mineral of the earth’s crust and it is plentiful in nature as hard rock ore and as brine. Cost efficient methods are being explored for best extraction of this extraordinary mineral. Brine extraction has become the preferred method of lithium extraction.

Lithium carbonate is produced commercially from one of three sources:

  • Extraction from mineral sources such as spodumene
  • Lithium containing brines – commercially available lithium brines in the United States are found in Silver Peak, Nevada and Searles Lake, California.
  • Sea water extraction

The first process used was obtaining pure lithium carbonate from spodumene, or lithium aluminum silicate ore (LiAlSi2O6). The ore is usually recovered from open pit mines, and this process was exploited commercially because of its relatively high lithium content and ease of processing. To manufacture lithium chloride of high purity the lithium carbonate is first transformed into lithium hydroxide before chlorination to give battery grade lithium chloride. This process is both time consuming and is costly in large scale application.

Lithium brine is dried in a series of solar evaporation ponds, and then removed by precipitation using soda ash, which then is transformed to lithium carbonate. Current technology transforms impure lithium carbonate into lithium hydroxide and the precipitation of calcium carbonate by treatment with soda ash. The key to obtaining high grade lithium is to use purified lithium chloride and carrying out electrolysis in the virtual absence of air and humidity to minimize lithium’s rapid reactions. Impurities must be removed, which may include sodium, calcium, magnesium, as well as carbonate, sulfate and borate. The process concentrates brines, either natural or otherwise, containing lithium and other alkali and alkaline metal halides to 2-7% of lithium content. Most of the alkali or alkaline earth compounds are removed by precipitation at a pH between 10.5 and 11.5. The pH is modified with recycled lithium hydroxide, with removal of remaining magnesium and by lithium carbonate and/or carbon dioxide which produces calcium carbonate as a precipitate.

The concentration of lithium in seawater is only 0.2 parts per million, making the extraction of lithium from seawater impractical. Rather, geothermal sources of lithium extraction are proving much more practical. The only efficient method for precipitating lithium from geothermal salts is through the use of aluminum salts. Of greatest interest is that the highest recovery of lithium occurs at a pH greater than 11. No product other than activated alumina is able to perform consistently at this high pH. In the presence of activated alumina the pure lithium salts get bound through adsorption, and are then released with greater than 99% purity.

Given the current interest in the use of lithium to power electric vehicles, the implication is that battery powered vehicles appear here to stay. There is going to be a requirement for superior methods to purify high grade lithium from geothermal and brine sources, and activated alumina by working at pH levels in excess of 11 appear to best fit the bill.

Lithium and the Implications from the Commercial Introduction of Electric Vehicles