Lithium brine

Recovery from Brines. Natural lithium brines are predominately chloride brines varying widely in composition. The economical recovery of lithium from such sources depends not only on the lithium content but on the concentration of interfering ions, especially calcium and magnesium. If the magnesium content is low, its removal by lime precipitation is feasible. Location and avadabiHty of solar evaporation (qv) are also important factors. 

Lithium brines with commercial potential are found in the Altiplano of BoHvia and Argentina, in salt beds of Chile, and in several salt beds in central and western China. 

Coming back to the activation overpotential for hydrogen evolution It is quite clear that if it is diminished, an explosive chlo-rine/hydrogen mixture will be produced. This will be the case immediately, if ions of heavy metals or other metals are precipitated at the mercury surface. So the brine must be thoroughly purified, as described in Sect. 5.2.3.4.1. This holds especially if potassium- or lithium-brine is used as a feed, because the reversible potentials of these species are more negative. 

The biggest lithium reserves are located in the so-called lithium triangle on the continent of South America where Chile, Argentina tind Bolivia border on each other. Another big occurrence of lithium brines is in China. Considerable lithium mineral reserves can be foimd in Australia, Canada, the USA and China. The other lithium-producing countries such as Portugal and Zimbabwe have few lithium reserves. 

The high-lithium brines usually have obtained most of their lithium from geothermal waters, with perhaps some of the lithium coming from surface leaching of volcanic ash, clays or other rocks. However, lithium is very difficult to leach from the lattice structure of all rocks and minerals, so little is dissolved imless the water is very hot. Experimental studies have shown that at ambient temperatures, only 55-170 ppb dissolves from extended contact with granitic rocks, but at 275-600°C 0.25-2.4 ppm Li can be extracted in the same agitated, long contact-period (Dibble and Dickson, 1976). Analyses of cores into deep-ocean rift or subduction zones... 

Figure 1.5 The salt structure in three basins containing high-lithium brine (Kunasz, 1980 reprinted with permission of the Northern Ohio Geological Society).

There are other potential high-hthium brine sources that were initially medium-lithium brines extensively evaporated to recover other minerals (such as at the Great Salt Lake, Bonneville Salt Hats, the Dead Sea and the Qinghai playa noted above). The Sua Pan in Botswana (Fig. 1.24), for example contains brine with about 20 ppm Li (Table 1.9), and it is evaporated in solar ponds to produce soda ash. The end-liquors should contain from 200 to 400 ppm Li, and could be further concentrated as... 

Parti Lithium Brine Processing Solar Ponds... 

A possible commercial use of similar alumina technology is with FMC s hydrated alumina-lithium chloride granules suggested to be used in countercurrent adsorbent beds for Salar de Hombre Muerto brine, as discussed above. Here the lithium brine to be processed would be maintained saturated with salt as it contacts the alumina-LiCl granules, and the lithium fairly selectively adsorbed. Then the adsorbed lithium would be removed (eluted) from the granules in a second step with low-lithium water in a similar countercurrent manner. The dilute, fairly pure lithium eluate could finally be concentrated in solar ponds, and the resulting strong lithium chloride solution purified and made into the desired products (Bauman and Burba, 1997, 1995). 

Precipitating lithium from low-lithium brines with sodium phosphate has also been tested, after the model of licons being precipitated from Searles Lake brine. Tandy and Canfy (1993) smdied the precipitation of lithium phosphate from Dead Sea potash pond end-liquor, and found that perhaps a 70% Li recovery could be obtained. By adding over a 30-fold molar excess of disodium phosphate to the lithium in the brine, adjusting the pH to 6-7, heating to 80°C, and with a 20-30 min residence time about 76% of the lithium would be precipitated along with dicalcium phosphate and the excess disodium phosphate. The precipitate contained about 0.3% Li, and could be leached with water to recover over 90% of the Li, with the remainder being in the residual phosphate precipitate. The filtrate contained about 1440 ppm Li in a sodium phosphate-chloride solution (Table 1.34). 

Davis, J. R., and Vine, J. D. (1979). Stratigraphic and Tectonic Setting of the Lithium Brine Field, Clayton Valley, Nevada. Basin and Range Symp., pp. 421-430. Rocky Mt. Assoc. Geol.. 

Anon. (1984b). Argentine Project Demonstrates Reserves for Lithium Brines. Mining Eng., 660 (July). Archambault, M., and OUvier, C. (1963). Lithium Carbonate Production. U.S. Patent 3,112,171, 7 pp. (Nov. 26). 

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