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Clay Mineralogy[edit]
Structures of Clay Minerals in Soil[edit]
Clay minerals are layer silicates formed as products of chemical weathering of silicate minerals at the Earth's surface are form an important group of the phyllosilicates (sheet silicate) family of minerals distinguished by layered structures composed of sheets of silica tetrahedral linked to octrahedral sheets [1].The octrahedral sheet is comprised of oxygens and hydroxyls with aluminum, iron, and magnesium atoms arranged in an octahedral formation[2]. The tetrahedral sheet is comprised of silica atoms equidistant from four oxygens (or hydroxyls) arranged to form a tetrahedron with silicon atom in the center. The tetrahedra are arranged in a hexagonal network repeated, to form the tetrahedral sheet[2]. Tetrahedral sheets and octahedral sheets are joined through sharing of oxygens/hydroxyls to form 1:1 clay mineral layer or 2:1 clay mineral layer[3]. The geochemical importance of clay minerals is related to their cosmopolitan presence in soils and sediments, high specific surface area, and ion exchange capacities[1].
Classification of clay minerals[edit]
Common clay minerals are classified according to layer type, magnitude of net layer charge, type of interlayer material, character of the octahedral sheet, and the composition or structure of the individual species[1].
- Allophane
- Kaolinite
- Smectite
- Vermiculite
- Illite
- Chlorite
- Palygorskite and sepiolite
- Mixed-layer clay minerals
Properties of clay minerals in soils[edit]
The small size and unique crystalline structures give clay minerals special properties including: cation exchange capabilities, plastic behavior when wet, catalytic abilities, swelling behavior, and low permeability[4].
Clay minerals can act as electron acceptors and/or donors in organic reactions[5] and are important in understanding cation and ion exchange in soils, due to interlayer water cations and layer charge[6]. Clay has absorptive capacity through physical absorption, ion exchange absorption, and zeolitic absoprtion [7]. The permeability of clay minerals can be explained by the type and distribution of clay minerals within the pore system[4].
- ^ a b c SHOJI, SADAO; ONO, TSUYOSHI (1978-11-XX). "PHYSICAL AND CHEMICAL PROPERTIES AND CLAY MINERALOGY OF ANDOSOLS FROM KITAKAMI, JAPAN". Soil Science. 126 (5): 297–312. doi:10.1097/00010694-197811000-00007. ISSN 0038-075X.
{{cite journal}}: Check date values in:|date=(help) - ^ a b Brigatti, M.F.; Galan, E.; Theng, B.K.G. (2006), "Chapter 2 Structures and Mineralogy of Clay Minerals", Developments in Clay Science, vol. 1, Elsevier, pp. 19–86, doi:10.1016/s1572-4352(05)01002-0, ISBN 978-0-08-044183-2, retrieved 2021-04-28
- ^ "Chapter 1 General Introduction: Clays, Clay Minerals, and Clay Science". Developments in Clay Science. 1: 1–18. 2006-01-01. doi:10.1016/S1572-4352(05)01001-9. ISSN 1572-4352.
- ^ a b Aboudi Mana, Suzanne Christine; Hanafiah, Marlia Mohd; Chowdhury, Ahmed Jalal Khan (2017-07-03). "Environmental characteristics of clay and clay-based minerals". Geology, Ecology, and Landscapes. 1 (3): 155–161. doi:10.1080/24749508.2017.1361128. ISSN 2474-9508.
- ^ Solomon, D. H. (1968). "Clay Minerals as Electron Acceptors and/or Electron Donors in Organic Reactions". Clays and Clay Minerals. 16 (1): 31–39. doi:10.1346/CCMN.1968.0160105. ISSN 0009-8604.
- ^ Gillott, J. E., "CLAY, ENGINEERING GEOLOGYClay, engineering geology", Encyclopedia of Earth Sciences Series, Dordrecht: Kluwer Academic Publishers, pp. 45–59, ISBN 0-442-22537-7, retrieved 2021-04-30
- ^ Giese, Rossman F.; van Oss, Carel J. (2002-06-21). Colloid And Surface Properties Of Clays And Related Minerals. CRC Press. ISBN 978-0-203-91065-8.