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Clays and Clay Minerals
Published in Benny K.G. Theng, Clay Mineral Catalysis of Organic Reactions, 2018
Hectorite with an ideal composition of (M+x.nH2O)(Mg3−xLix)oct(Si4)tetO10(OH)2 may be regarded as the trioctahedral analogue of montmorillonite in that its layer charge largely resides in the octahedral sheet due to partial substitution of Li+ for Mg2+ ions. Many naturally occurring hectorites also have fluoride replacing hydroxyl in the structure. The synthesis of fluorhectorites, showing interesting rheological and shape-selective sorption properties, has been reported by Barrer and Jones (1970, 1971). A synthetic hectorite-like clay mineral, having the composition of Na+0.33(Mg2.67Li0.33)oct(Si4)tetO10(OH)2 (Neumann and Sansom 1970a, 1970b), is marketed under the trade name Laponite by Laporte Absorbents, UK and BYK-Chemie GmbH, Germany. Saponite is another trioctahedral species in the smectite group of phyllosilicates (Table 1.1) but in this case, the layer charge largely arises from isomorphous substitution of Al3+ for Si4+ in tetrahedral sites.
Removal of emerging pollutants by clay and clay-nZVI nanocomposites-A review
Published in Environmental Technology Reviews, 2023
Geetha Gopal, Amitava Mukherjee
Clay minerals and clays with fine particulate sizes and a porous structure with a large surface area can have excellent physical and chemical interactions with dissolved species. Electrostatic repulsion, crystallinity and adsorption, and complex cation exchange are some of the factors that can impact such interactions. The high bonding strength is shown by highly porous surface areas with good attractive force. Clays are hydrous aluminosilicates consisting of mixtures of minerals of fine-grained clay, other mineral crystals, and metal oxides. Kaolinite is the major component; however, it is also made up of a variety of minerals such as quartz, mica, feldspar, illite, and montmorillonite. Bentonite is predominantly made up of montmorillonite, a smectite-group clay mineral with hydrous magnesium–calcium aluminium silicate structure. It is very colloidal and plastic clay made up of very small particles that are created by in situ devitrification of volcanic ashes. Smectite is the mineral name assigned to the group of silicates, including Na, Ca, Mg, Fe, and Li–Al. The most widely used minerals within the smectite group are Na-montmorillonite, Ca-montmorillonite, saponite (Mg), nontronite (Fe), and hectorite (Li). Ball clay, sedimentary clay that is fine-grained and highly porous, consists primarily of kaolinite, mica, and quartz with minimal quantities of organic matter and other minerals.
On shale swelling: the unrecognized role of diffusion osmosis
Published in Geosystem Engineering, 2023
Abdulrahman Sheref, Talal AL-Bazali
Since clay is a major component of shale composition, there is a direct relationship between shale swelling and the amount of clay minerals it contains. Clay minerals are layered minerals classified among phyllosilicates which consist of stacks of negatively charged two-dimensional aluminosilicate layers. This negative charge on clay minerals was gained during a process known as ‘Isomorphic substitution’. Smectite is a type of clay mineral that is considered as highly sensitive clay to water which tends to expand through the adsorption of water between its sheets. Smectite group incorporates a variety of clays including montmorillonite, hectorite, and beidellite. It is considered as a 2:1 (T-O-T) clay which means that its structure consists of one octahedral sheet sandwiched between two tetrahedral sheets. Many studies of clay swelling have focused on 2:1 smectite clays due to their high swelling potential and the frequency they are encountered during drilling operations. Anderson et al. (2010) proposed that the tendency of sodium-saturated smectite to swell is the principal cause of shale instability in oil well drilling operations which can lead to collapse and wellbore failure.