High-lithium clay

Flint clays and other related rocks are another potential lithium source. These are high alumina clays that are composed largely of we11-crysta11i2ed kaolinite [1318-74-1] and are used for the manufacture of refractories (qv). The lithium content ranges from <100 to 5000 ppm. Deposits occur in many states, including Missouri, Peimsylvania, and Ohio. Lithium (at ca 1.3%) is present in a chlorite mineral that is similar to cookeite [1302-92-7]. High lithium contents may be the reason why some deposits are unsatisfactory for refractory use. 

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... 

The predominant type of lithium mineral formation is that of high-lithium pegmatites, although a few micas, clays and other minerals have been reported with a comparatively high lithium content. Pegmatites are an exceptionally coarse-grained... 

High-Lithium Clays (Hectorite) Other Rocks... 

In the early days of the lithium industry considerable attention was paid to the recovery of lithium from moderately high-lithium Clay. Lien (1985) noted that in laboratory tests some clays could have as high as an 80% lithium extraction with a simple sulfuric acid leach, but that most required a more complex process. In brief tests a roast at 750°C with two parts of clay and one part limestone, followed by a leach with an excess of 20% hydrochloric acid gave a 70% lithium yield. In a second series of tests five parts of clay, three parts of gypsum and three parts of limestone were roasted at 900°C. A water leach resulted in an 80% recovery of lithium as lithium sulfate. In the later process the raw materials were first groimd together to a -100 mesh size and then formed into 6.5 mm pellets before being roasted. The pellets reduced the dust loss and increased the particles contact with the flue gas. 

Recovery from Ores and Clays. The preferred method of extraction of lithium from spodumene ore is the sulfuric acid process (18), used on ore concentrates of 5—6% Li O, representing 62—74% pure spodumene. Methods suitable for extraction from spodumene also can be used for petaUte, because the latter mineral converts to P-spodumene—Si02 soHd solution on heating to a high temperature. 

Aluminum chlorite, (Al,Fe)4(Si,Al)402Q(0H)g, in which a gibbsitelike interlayer proxies in part for the bmcitelike interlayer, is being discovered in increasing occurrences and abundance (11,141). Chloritelike stmctures have been synthesi2ed by precipitation of Mg and Al between montmorillonite sheets (143). Cookite [1302-92-7], an aluminous chlorite containing lithium, has been found in high alumina refractory clays and bauxite [1318-16-7] (139). 

As an alternative to lithium enolates. silyl enolates or ketene acetals may be used in a complementary route to pentanedioates. The reaction requires Lewis acid catalysis, for example aluminum trifluoromethanesulfonate (modest diastereoselectivity with unsaturated esters)72 74 antimony(V) chloride/tin(II) trifluoromethanesulfonate (predominant formation of anti-adducts with the more reactive a,/5-unsaturated thioesters)75 montmorillonite clay (modest to good yields but poor diastereoselectivity with unsaturated esters)76 or high pressure77. 

In contrast to these transformations, Michael additions of simple enolates to acceptor-substituted dienes often yield mixtures of 1,4- and 1,6-addition products27-30. For example, a 70 30 mixture of 1,4- and 1,6-adducts was isolated from the reaction of the lithium enolate of methyl propionate with methyl sorbate30. This problem can be solved by using the corresponding silyl ketene acetal in the presence of clay montmorillonite as acidic promoter under these conditions, almost exclusive formation of the 1,4-addition product (syn/anti mixture) was observed (equation ll)30. Highly regioselective 1,4-additions... 

All of the experimental evidence shows extraction of Li from hasalt, altered hasalt and sediments even at temperatures <100°C. Lithium was incorporated into clays at temperatures up to 150°C during hasalt alteration (Seyfried et al. 1984 James et al. 2003), with affinity proportional to the fluid/rock ratio, such that Li was simultaneously added to and removed from fluids. Under high temperature, solid-dominated hydrothermal conditions (c. 350°C), Li was universally removed from materials and kept in solution, rather than in alteration minerals. The limited isotopic fractionation at these conditions has been estimated as a 0.994 (= (fl.i/ Li,ecomiMynm imk)/( LiALis tai )) Chan et al. 1993 Seyfried et al. 1998). 

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