An obsolete term for opal-CT.
See opal

See opal.

See opal.

In civil engineering, an organic clay is a clayey soil containing a specific range of organic matter content (ASTM Standard D2487). Organic clay is usually distinguished by determining the change in the liquid limit of a clay that was oven-dried at 105 – 110^oC. If the ratio of the liquid limit of the oven-dried clay to that of the natural (i.e., without oven drying) clay is < 0.75, then the soil is classified as organic clay. Cf., liquid limit, organoclay, organic soil

A phyllosilicate, typically smectite, vermiculite, or kaolin, but also other minerals (e.g., double metal hydroxides) with sorbed organic molecules, such that the properties of the mineral are altered. Commonly, the sorption occurs between the 2:1 or 1:1 layers. The mechanism for sorption may vary depending on the organic molecule and concentration. In alkylammonium organoclays, alkylammonium cations replace inorganic cations, and these organic cations are bonded to the layers via electrostatic (= Coulombic) forces. In organophilic alkylammonium organoclays where large organic cations completely fill the interlayer, van der Waals interactions between the alkyl groups augment the Coulombic forces, which increase both adsorption and organoclay stability. Adsorptive type organoclays have small organic cations that partially fill the interlayer, are stabilized by Coulombic forces, and act as pillared materials where there are accessible areas between the pillars for additional adsorption. These pillars increase surface areas relative to untreated clay or organophilic clays. In grafted compound-type organoclays with organic compounds such as silanes in the interlayer, bonding to the clay layer is covalent. Organoclays with adsorbed neutral polymers are attached to the clay layer by weak multiple dipole-induced dipole type bonds. In organoclays prepared from charged polymers, such as proteins, the polymers are bonded by both electrostatic and dipole-induced dipole bonds. Organoclays can be used as adsorbents, thickening and thixotropic agents, in nanocomposites, and in new materials with catalytic, optical, and electronic properties (Lagaly et al., Ogawa, and Dékány, 2006).
Syn., organo-clay, clay-organic complex;
Cf., organoclay, adsorptive; organoclay, alkylammonium; organoclay, organophilic alkylammonium phyllosilicate; pillared clay; phyllosilicate

Based on organic contaminant adsorption isotherms and sorptive behavior, the adsorptive-type organoclays (generally producing nonlinear and Langmuir-type isotherms) have exchanged organic cations that act as interlayer props to hold the interlayer open. This arrangement facilitates additional organic contaminant adsorption onto the siloxane surfaces, which are relatively hydrophobic except near exchangeable cation sites (Chen, 1976; Jaynes and Boyd, 1991a). These clays are prepared from smectite by replacing inorganic exchangeable cations with small organic cations, such as tetramethylammonium or trimethylphenylammonium. Lower charge clay minerals (i.e., lower charge smectite) with adsorbed small organic cations yield organoclays that more effectively adsorb organic contaminants compared to the unmodified clay. See Boyd and Jaynes (1994).
Cf., organoclay, organophilic; organoclay.

Using organic contaminant adsorption isotherms and sorptive behavior, organophilic-type organoclays (which produce simple, linear isotherms) are defined as having large exchanged organic-cation alkyl groups. These groups seem to act as a solvent phase (e.g. partitioning phase, i.e., solubilized), but are located in the interlayer, to absorb organic contaminants (Jaynes and Boyd, 1991b).

a) Synthetic systems. These clays are prepared from smectite or vermiculite by using large quaternary (> C-10) organic cations, such as hexadecyltrimethylammonium (C-16) or dioctadecyltrimethylammonium (C-18). These higher charge clay minerals (e.g., vermiculite, illite, high-charge smectite) adsorb greater numbers of large organic cations and yield organoclays that are more effective in absorbing organic contaminants compared to the unmodified clay. See also Boyd and Jaynes (1994).
b) Natural systems. Soil organic matter and organic compounds adsorbed to (internal or external) clay- mineral surfaces can act as a solvent phase for organic contaminants dissolved in water. Organic compounds (e.g., benzene, toluene, xylenes in gasoline) are more soluble in soil organic matter or the organic phase derived from organic compounds adsorbed to mineral particles than in water. Nonionic organic compounds may be partitioned (i.e. solubilized) into soil organic matter; see Chiou et al. (1979).
Cf., organoclay, adsorptive; organoclay

A characteristic property of a clay whereby the clay can sorb an organic solvent. These clays are usually surface modified, commonly by sorbing various quaternary ammonium compounds, which allow the clay to swell in organic liquids.
See organoclay.
Cf., organophobic

A characteristic property of a clay whereby the clay repels an organic liquid. Most naturally occurring clays are organophobic and are not wetted by nonpolar organic liquids.
See organoclay
Cf., organophilic

A trioctahedral member of the true mica group. The end-member, ideal formula is KLi₂Ti⁴⁺Si₄O₁₀(O,F), and orlovite occurs as the 1M polytype. Orlovite is from the Darai-Pioz alkaline massif of the Garmskii district, northern Tajikistan. Ti occurs in two positions in what is normally the M1 site in a mica (the M1 site is typically on a center of symmetry, but in orlovite each of the positions is displaced along the m plane away from the center) separated by 0.432 Å, indicating short range order where Ti is occupied in one domain in one of these positions and in the other domain by the other (Sokolova et al., 2018). Charge balance to offset the 4+ charge of the Ti cation occurs by the substitution of an oxygen anion for fluorine.