Kaohnitic clays

Sadek, O.M. et al.. Adsorption of poly(4-sodium styrene sulfonate) on kaohnite clays, J. Appl. Polym. Sci., 100, 1712, 2006. 

Kandarpa, R, Anamika, J., Nirada, D. 2011. Characterization of an iron-rich kaohnite clay and its application as heterogeneous catalyst for the microwave-mediated dry synthesis of V-containing heterocycles. Research Journal of Chemistry and Environment 15 86-91. 

Particle size days with a high proportion of particles <2 pm have a higher flexural strength than kaohnitic clays. 

Clays composed of attapulgite, montmorillonite, and kaoHnite are used for pesticides in finely pulverized or granular form. Granular formulations are reportedly less expensive, more easily handled, reduce loss caused by wind drift, and produce a more effective coverage. 

Other Clay Uses. Other appHcations for clays include use as a suspending agent, eg, montmorillonite and attapulgite in Hquid fertilizers and dishwasher detergents in pharmaceuticals (qv), eg, kaoHnite and attapulgite for diarrhea control in cosmetics, montmorillonite and attapulgite and in water impedence where bentonite linings are used for reservoirs and waste disposal areas. 

Dioxins are mainly by-products of industrial processes, but can also result from natural processes, such as volcanic eruptions and forest fires. Besides the anthropogenic (man-made) sources of PCDD/F discussed earher, biogenic and geogenic sources for dioxins also have been discovered recently. In natural clays of the kaohnite-type found in German mines in Westerwald, considerable levels of PCDD / F have been detected the same findings were obtained in special ball clays in the Mississippi area of the United States. The pattern (isomeric ratios) of this natural type of dioxins is different from the pattern obtained from incineration plants. 

Hayes M. J. and Boles J. R. (1992) Volumetric relations between dissolved plagioclase and kaohnite in sandstones imphcations for aluminum mass transfer in the San Joaquin Basin, Cahfomia. In Origin, Diagenesis, and Petrophysics of Clay Minerals in Sandstones (eds. D. W. Houseknecht and... 

Weiss, A. (1959). Cation exchange properties of clay minerals III. Cation exchange in kaohnite (in German). Z. Anorg. Allg. Chem., 299, 92—120. 

Farrah, H., Pickering, W.F., 1976a. The sorption of copper species by clays. 1 Kaohnite. Anst. J. Chem. 29, 1167-1176. 

Soil wettability is another important factor besides contamination, which governs water retention and transport processes [97]. Strong interaction of mineral phases with CDs suggests that the properties of the soils may also be seriously affected by CDs, which may have an influence on soil remediation processes. The effect of RM-/9-CD on surface and pore properties of common clay minerals such as bentonite, illite and kaohnite had been studied and it was found that the wettability of the soil decreased at low CD concentration and increased again at the highest load. The increased concentration of CDs reduced the effective radius of the soil bed which improved the average force of interaction among soil particles via water layer, despite the simultaneous decrease of adhesion forces of water to the soil. 

The clay tested in the present work comes from deposits located in the north of Morocco (Nador area). The results corresponding to its textural and mineralogical composition have been published (Harti et al, 2007). The clay was found to be a mixture of phases, namely, opal, montmorillonite, kaohnite, muscovite, topaz, rutile, calcite, dolomite, suggesting a bentonite type clay. Textural studies perfomed with N2 adsorption desorption at 77 K have shown a BET sp>ecific surface area of 79 m g-i, and a negligible micropore volume of 0.002 cm g-i as comp>ared with total pore volume of 0.205 cm g-i. The pore size distribution obtained following BJH method revealed the presence of a wide pore size distribution in the mesopore range with a significant contribution of pores widths between 8 and 50 nm. 

Figure 6.2 Structure of a clay, showing two layers of the stacked sheets of kaohnite [8].

Clausell JV, Bastida J, Serrano FJ, Pardo P, Huertas FJ. A new FESEM procedure for assessment of XRD microstructural data of kaohnites. Appl Clay Sci 2007 37 127-32. 

The optimmn calcination temperature varies in different clay minerals. For sodium and calcium montmorrilonite a calcination temperatuie of 830 °C has been found to be optimal (He et al, 1996). Galal et al. (1990) reported the same optimmn temperatuie range—600-800 °C— for the calcination of kaohnite, montmorrilonite, and mixed type clays. He et al. (1995) found, for a series of different clay minerals, optimum calcination temperatures ranging between 650 and 960 °C (see Table 9.5). 

They constitute 60% of the earth s crust Feldspars have no color of their own and are often nearly white. They may however be colored due to impurities. On decomposition, feldspars yield kaoHnite and clay minerals. 

Aluminium group Clay minerals group Boehmite Diaspore Gibbsite Goethite HaUoysite Hematite Kaohnite Lepidocrocite Trolard Tardy (1987)... 

Figure 17.4 Representation of the structure of kaohnite, a two-layer clay.

Structurally, clays can be classified as either two-layer clays in which oxygen atoms are shared between a tetrahedral sheet and an adjacent octahedral sheet, and three-layer clays in which an octahedral sheet shares ojg gen atoms with tetrahedral sheets on either side. These layers composed of either two or three sheets are called unit layers. A unit layer of a two-layer clay typically is around 0.7 nanometers (nm) thick, whereas that of a three-layer clay exceeds 0.9 nm in thickness. The structure of the two-layer clay kaohnite is represented in Figure 17.4. Some clays, particularly... 

SA Carroll. The dissolution behavior of corundum, kaohnite, and andalusite A surface complex reaction model for the dissolution behavior of aluminosilicate minerals in diage- netic and weathering environs. PhD thesis, Northwestern University, 1989. P Fletcher, G Sposito. Clay Mineral 24 375-391, 1989. 

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