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Clays and Clay Minerals
Published in Benny K.G. Theng, Clay Mineral Catalysis of Organic Reactions, 2018
The octahedral vacancy in each kaolinite layer occurs at the same site while successive layers in a particle are displaced by −a/3. Two possible enantiomorphic structures can therefore arise, depending on whether the left-hand or right-hand site is selected to have the vacancy (Brown et al. 1978). By contrast, in a particle of dickite (an ordered polytype of kaolinite), there is a left-right alternation of vacant sites between successive layers while the stacking sequence of layers is similar to that in kaolinite (Newnham 1961; Bailey 1963). On the other hand, nacrite (another ordered polytype) differs from kaolinite in its layer-stacking sequence as well as in the pattern of octahedral vacancies relative to successive ditrigonal cavities (Blount et al. 1969).
Elastomer–Clay Nanocomposites
Published in Anil K. Bhowmick, Current Topics in ELASTOMERS RESEARCH, 2008
Susmita Dey Sadhu, Madhuchhanda Maiti, Anil K. Bhowmick
This group has three members (kaolinite, dickite, and nacrite) and a formula of Al2Si2O5(OH)4 [6]. The different minerals are polymorphs, meaning that they have the same chemistry but different structures. The general structure of the kaolinite group is composed of silicate sheets (Si2O5) bonded to aluminum oxide/hydroxide layers (Al2(OH)4). The silicate (tetrahedral layer, T) and aluminum oxide (octahedral layer, O) layers are tightly bonded together with bonding existing between the T and O paired layers (Figure 2.1) [7]. These are mostly used in ceramics, as filler for paint, rubber, and plastics. The largest use is in the paper industry that uses kaolinite to produce a glossy paper such as that used in most magazines.
Clay and Ceramics as Sustainable and Green Materials to Remove Methylene Blue from Water: A Critical Analysis
Published in Vikram Bali, Rajni Mohana, Ahmed A. Elngar, Sunil Kumar Chawla, Gurpreet Singh, Handbook of Sustainable Development through Green Engineering and Technology, 2022
Priyanka Sharma, Kushal Qanungo
Clays are hydrated aluminosilicates with a variable amount of other ions, such as Mg, Fe, alkali, and alkaline earth metals, with a particle size of less than 2 μm. Kaolinite, montmorillonite-smectite, illite, and chlorite are the major groups of clays. The kaolinite group includes kaolinite, dickite, halloysite, and nacrite minerals. The minerals pyrophyllite, talc, vermiculite, sauconite, saponite, nontronite, and montmorillonite, are present in the smectite group. Clay micas are in illite group (Adeyemo et al., 2017). Clay has several advantages, including high specific surface area, ion-exchange potential, good adsorption power, and nontoxic nature. However, very few reports show ceramics being used as an adsorbent material for MB removal (Njoya et al., 2017).
Mineralogical and geochemical characterisation of kaolin deposit from Debre Tabor area northwestern, Ethiopia
Published in Applied Earth Science, 2021
Alemu Mesele, Teklay Gidey, Tilahun Weldemaryam, Wuletaw Mulualem, Tamrat Mekuria, Yahya Ali, Gizachew Mulugeta, Betelhem Tesfaye, Mulgeta Brihan
Clay minerals are the chemical weathering product of granite and feldspathic rocks (Idenyi and Nwajagu 2003) when rocks are in contact with water, air (Kabeto et al. 2012), and hydrothermal fluid (Okunlola 2008). Mostly they are found in soil, sedimentary rocks, and hydrothermal deposits (Idenyi and Nwajagu 2003; Murray 2007). The polymorphs of clay minerals are kaolinite, halloysite, nacrite, and dickite, which are characterised by the same chemistry but different structures (Baker and Uren 1982). The rate of clay minerals formation is controlled by the composition of pre-existing rock mineralogy, the nature of parent rock, the intensity of weathering, and the length of time (Murray and Kogel 2005; Akinola and Obasi 2014). According to Mosser (1980) and Mosser et al. (1991), clay minerals can preserve the geochemical fingerprint of trace elements from the source rock.