Kaolin clay

In the rubber industry, silicate layer minerals represent the largest volume of filler, second to carbon black. The silicate mineral used is primarily Kaolin clay. Kaolin occurs naturally. Kaolin clays are mined, and they are subsequently pulverized and refined by air and water 

Clay minerals are classified into kaolinite, illite, smectite (montmorillonite), and palygorskite groups. The most important commercial clay minerals are kaolinite and montmorillonite. Kaolin or kaolinite, known as China clay , has the basic chemical formula Si2Al205(0H)4, and montmorillonite is AlSi205(0H) x H2O. Kaolinite was formed by various hydrothermal alterations or weathering of feldspars and other silicate minerals. 

Comparing the structure of kaolin and montmorillonite, kaolin has 1 1 layer lattice and montmorillonite has 2 1 lattice structure. Kaolin consists of successive layers of alumina and silica mineral (silica-alumina), whereas montmorillonite has two layers of silica with a layer of alumina sandwiched between them (silica-alumina-silica). 

Silica (Tetrahedral layer)-Alumina (Octahedral layer)-Interlayer Space - 

Kaolinite [Sl4Al40 o(OH)g] Rgure 1.15 Crystal structure of kaolinite clay 

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Very finely divided minerals may be difficult to purify by flotation since the particles may a ere to larger, undesired minerals—or vice versa, the fines may be an impurity to be removed. The latter is the case with Ii02 (anatase) impurity in kaolin clay [87]. In carrier flotation, a coarser, separable mineral is added that will selectively pick up the fines [88,89]. The added mineral may be in the form of a floe (ferric hydroxide), and the process is called adsorbing colloid flotation [90]. The fines may be aggregated to reduce their loss, as in the addition of oil to agglomerate coal fines [91]. 

A process has been developed by J. M. Huber Co. to treat kaolin clay pigments using a hydrothermal process (see Clays) (25). The products, called synthetic alkah metal aluminosihcates (SAMS), have superior pigmentary quahties for paper (qv) coating. 

Organofunctional silanes are used to promote polymer-to-filler bonding with clay or siHca fillers. Vinyl silanes are used in peroxide-cured wire insulation to promote stronger bonding with calcined clay fillers. Mercapto silanes are used to treat kaolin clay in sulfur-cured compounds. 

In kaolin (clay) processing, sulfur dioxide reduces colored impurities, eg, iron compounds. In the bromine industry, sulfur dioxide is used as an antioxidant in spent brine to be reinjected underground. In agriculture, especially in California, sulfur dioxide is used to increase water penetration and the avadabiHty of soil nutrients by virtue of its abiHty to acidulate saline—alkaH soils (327). It is also usefiil for cleaning ferric and manganese oxide deposits from tile drains (328). 

High alumina clays refer ia the ceramic iadustries to nodular clays, budey-flint clay, budey and diaspore, gibbsitic or bauxitic kaolins (clays), abrasive clays, and others. Siace the depletion of diaspore varieties ia Missouri and Pennsylvania, most bauxitic kaolin and clay is produced ia Alabama and Arkansas. 

Frequently kaolin clay is used for a raw material. In one of the older processes kaolin is treated with sulfuric acid at elevated temperature and subsequently washed to remove Hberated alumina and alkaUes. Kaolin can also serve as a raw material for preparing a number of synthetic zeofltes (21). 

The filler is a clay incorporated into the catalyst to dilute its activity. Kaoline [A. 2(OH)2, Si205] is the most common clay used in the FCC catalyst. One FCC catalyst manufacturer uses kaoline clay as a skeleton to grow the zeolite in situ. 

Many powdered raw materials, e.g. china clay, talc and calcium carbonate are natural products, coming from the soil and often contaminated with appreciable numbers of bacterial and fungal spores. Products heated to high temperatures during preparation, e.g. calcined kaolin clay used as a titanium dioxide extender, will generally be free from such contaminants. 

Kaolin clay Surround Apple maggot, leafhopper, pear psylla, plum curculio Various fruits and vegetables Insecticide, insect growth regulator... 

A major advantage of the simple model described in this paper lies in its potential applicability to the direct evaluation of experimental data. Unfortunately, it is clear from the form of the typical isotherms, especially those for high polymers (large n) that, even with a simple model, this presents considerable difficulty. The problems can be seen clearly by consideration of some typical polymer adsorption data. Experimental isotherms for the adsorption of commercial polymer flocculants on a kaolin clay are shown in Figure 4. These data were obtained, in the usual way, by determination of residual polymer concentrations after equilibration with the solid. In general, such methods are limited at both extremes of the concentration scale. Serious errors arise at low concentration due to loss in precision of the analytical technique and at high concentration because the amount adsorbed is determined by the difference between two large numbers. 

Figure 4. Data of Bensley (14) for the adsorption of commercial flocculants on a kaolin clay (BET surface area 15 m /g).

The nature section of the BBC Website describes several examples of animals eating kaolin clay to immobilize toxins by adsorption on the clay s surface. For example, see the first entry on the page http //www.bbc.co.uk/nature/weird/az/mo.shtml. Alternatively, read The Life of Mammals by Sir David Attenborough, BBC Books, 2002, p. 170. 

Kaolin, 2 345t. See also Kaolins in dental ceramics, 8 275 powder used in cosmetics, 7 841t uses, 6 688t Kaolin clay, 11 388 as filler, 11 312... 

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