Clay transformation

The concentrations of alkali metals, in the absence of evaporites, are strongly affected by temperature-dependent reactions with clays (transformation of smectite to mixed layer... 

The formation and survival of unstable or metastable micas and clays in sediments and soils at low temperatures reflects kinetic as well as thermodynamic factors. First, the rates of reactions involving solid-aqueous and especially solid-solid transformations in dilute solutions are very slow at low temperatures (most natural waters are dilute )- The slow kinetics of clay transformations reflects small differences in free energy between stable and metastable clays. Also, the occurrence of specific clays is related to the chemistry and crystal structure of source minerals. Thus, illite often results from the weathering of muscovite, and vermiculite results from the weathering of biotite (cf. Drever 1988), consistent with the similar chemistries and structures of these pairs of T 0 T minerals. 

Calibration of the thermal model is possible using present-day bottom-hole temperatures from exploration wells (Deming Chapman 1989) and by the comparison of modelled and measured vitrinite reflectance (see Section 5.7.3), an example of which is shown in Fig. 5.50. There are other measurements that can provide time-temperature constraints, such as fission-track analysis (Naeser 1993 Gleadow Brown 1999), homogenization temperatures of fluid inclusions (Roedder 1984) and clay transformations (Hoffman Hower 1979). 

Fig. 2.11. Flow chart of clay transformation in late diagenesis in sandstones (Triassic Province)...

This process may be an important supplier of siUca to pore solutions. The free silica released by this mechanism is estimated as 2.2 g of quartz or chert per 100 g of clay transformed, producing 1.3% of quartz or chert in an ideal case (Towe 1962). 

Clay transformations in soil genesis during the quaternary. Soil Sci. 99 15-22. 

Addition of a salt can transform the shale by cation exchange to a less sensitive form of clay, or reduce the osmotic swelling effect by reducing the water activity in the mud below that which occurs in the shale. These effects depend on the salt concentration and the nature of the cation. Salts containing sodium, potassium, calcium, magnesium, and ammonium ions ate used to varying degrees. 

Chemical, or abiotic, transformations are an important fate of many pesticides. Such transformations are ubiquitous, occurring in either aqueous solution or sorbed to surfaces. Rates can vary dramatically depending on the reaction mechanism, chemical stmcture, and relative concentrations of such catalysts as protons, hydroxyl ions, transition metals, and clay particles. Chemical transformations can be genetically classified as hydrolytic, photolytic, or redox reactions (transfer of electrons). 

The theoretical energy requirement for the burning of Portiand cement clinker can be calculated from the heat requirements and energy recovery from the various stages of the process. Knowledge of the specific heats of the various phases, and the heats of decomposition, transformation, and reaction then permits calculation of the net theoretical energy requirement of 1760 kj (420 kcal) for 1 kg of clinker from 1.55 kg of dry CaCO and kaolin (see Clays) (8). 

Electromagnetic (EM) Conductivity Measures the electrical conductivity of materials in microohms over a range of depths determined by the spacing and orientation of the transmitter and receiver coils, and the nature of the earth materials. Delineates areas of soil and groundwater contamination and the depth to bedrock or buried objects. Surveys to depths of SO to 100 ft are possible. Power lines, underground cables, transformers and other electrical sources severely distort the measurements. Low resistivities of surficial materials makes interpretation difficult. The top layers act as a shunt to the introduction of energy info lower layers. Capabilities for defining the variation of resistivity with depth are limited. In cases where the desired result is to map a contaminated plume in a sand layer beneath a surficial clayey soil in an area of cultural interference, or where chemicals have been spilled on the surface, or where clay soils are present it is probably not worth the effort to conduct the survey. 

He became intimately familiar with a wide range of catalytic materials—including aluminum oxide, silica, and clay, as well as nickel, platinum, zinc, and copper—and their role individually and as mixtures 111 effecting chemical transformation. One of Ipatieffs most important lines of research was his breakthrough work on the nature and mechanisms of catalytic promoters on organic reactions. 

Movement of raw and transformed materials can take place within the soil and results in zones of accumulation, depletion, or mixing. Formation, migration, and accumulation of different elements, clays, oxides, and organic matter can occur in different parts of the soil. These different zones or layers in soil that are approximately parallel to the surface are called soil horizons. Depleted or enriched soil horizons result in different depths in the soil having different chemical and physical properties. Translocations are caused by a combination of physical, chemical, and biological processes. 

Tomita, K. and Sudo, T. (1981) Transformation of sericite into an interstratified mineral. Clays Clay Minerals,... 

Since lignins are polymers of phenolics and are major plant constituents with resistance to microbial decomposition, they are the primary source of phenolic units for humic acid synthesis (178, 179). Once transformed, these humic acids become further resistant to microbial attack and can become bound to soils (180) form interactions with other high molecular weight phenolic compounds (ex. lignins, fulvic acids) and with clays (181) and influence the biodegradation of other organic substrates in soils (182, 183). 

The kinetics of transformation of Mn and Fe among soil fractions is related to the redox potential (Eh changes) as well as the content of reductants or oxidants in the soil. Generally, a drop in Eh is observed within a few days of the waterlogging of a soil. In a coastal saline silty-clay soil, Eh was reduced to 210 mV after four days of submergence (Bandyopadhyay and Bandyopadhyay, 1984). The decrease in Eh mobilized Mn, and the maximal soluble Mn concentration was found after 14 days of submergence in a sandy-loam soil (Sadana and Takkar, 1988). 

Glycals can be transformed into 1,6-anhydro sugar derivatives by intramolecular cyclization in the presence of Lewis and Brpnsted acids, a reaction that has been termed the intramolecular Ferrier glycosylation.168 Sharma el al.169 showed that a montmorillonite clay-supported silver reagent can be an efficient catalyst for this transformation. The 1,6-anhydro-2,3-dehydro sugars obtained were then selectively dihydroxylated to furnish 1,6-anhydro saccharides. 

Scheme 6.49 Transformation of arylaldehydes to nitriles by hydroxylamine hydrochloride-clay.

Metal oxides have a significant role in influencing physical, chemical, and biological properties of soils. They may exist as ciystalline minerals, as short-range ordered (SRO) mineral colloids, or as surface coatings on clay minerals and organic matter. Organic compounds influence the formation, transformation, and surface properties of these metal oxides. The SRO A1... 

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