Kaolinitization

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. 

Fireclay. Fireclays consist mainly of the mineral kaolinite [1318-74-7] 2 3 small amounts of other clay minerals, quart2ite,... 

NaAlSigOs + 2 H+ + 9 H2O Al2Si2 O5 (OH) + 4 H4Si04(aq) + 2Na albite hydrogen water kaolinite silicic acid sodium... 

There are no unequivocal weathering reactions for the siUcate minerals. Depending on the nature of parent rocks and hydrauhc regimes, various secondary minerals like gibbsite, kaolinite, smectites, and iUites are formed as reaction products. Some important dissolution processes of siUcates are given, for example, by the following reactions (19). 

Binders. To create needed physical strength in catalysts, materials called binders are added (51) they bond the catalyst. A common binder material is a clay mineral such as kaolinite. The clay is added to the mixture of microparticles as they are formed into the desired particle shape, for example, by extmsion. Then the support is heated to remove water and possibly burnout material and then subjected to a high temperature, possibly 1500°C, to cause vitrification of the clay this is a conversion of the clay into a glasslike form that spreads over the microparticles of the support and binds them together. 

The least compHcated clay minerals are the 1 1 clay minerals composed of one tetrahedral (T) layer and one octahedral (O) layer (see Fig. 1). These 1 1 clay minerals are also referred to as TO minerals. The TO package has a basal spacing (nominal thickness) of 0.7 nm (7 E) and they are commonly referred to as 7 E minerals. Kaolinite, the dioctahedral 1 1 mineral, has filling two of three octahedral sites, and serpentine [12168-92-2J, (Mg)3Si205(0H)4, the trioctahedral 1 1 mineral has filling all three octahedral sites. The kaolin minerals have limited substitution in the octahedral... 

Kaolinite and dickite are easily distinguished where they occur in recognizable crystals (87). Nacrite is relatively rare. HaUoysite (7 E) is usually exceedingly fine-grained, showing a mean index of refraction of about 1.546. The index of refraction for haHoysite (10 E) varies somewhat with the immersion Hquid used it ranges from 1.540 to 1.552 (83). 

Regularly interstratified (1 1) chlorite and vermiculite has been attributed to the mineral corrensite [12173-14-7] (141). Chlorite mixed layers have been documented with talc, vermicuhte, smectite, iUite, biotite, kaolinite, serpentine, and muscovite. The mixed-layer mineral is named after the components, eg, talc—chlorite. The eadier Hterature, however, has reference to specific minerals such as kulkeite [77113-95-2] (talc—chlorite and tosudite... 

Chlorite is another mineral that is commonly associated with mixed-layered clays. Complete soHd solutions of chlorite mixed-layer minerals have not been identified. In contrast to iUite—smectite mixed-layer minerals, chlorite mixed-layer minerals occur either as nearly equal proportions of end-member minerals (Rl) or dominated by one end member (RO) (142). Mixed-layer chlorite may consist of any of the di—tri combinations of chlorite and chlorite mixed-layering occurs with serpentine, kaolinite, talc, vermicuhte, smectite, and mica. References of specific chlorite mixed-layer minerals of varied chemical compositions are available (142,156). 

Property Kaolinite nhte Hahoysite Montmoril-lonite Attapulgite... 

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