Hydrothermal environments

A freshly manufactured zeolite has a relatively high UCS in the range of 24.50°A to 24.75°A. The thermal and hydrothermal environment of the regenerator extracts alumina from the zeolite structure and, therefore, reduces its UCS. The final UCS level depends on the rare earth and sodium level of the zeolite. The lower the sodium and rare earth content of the fresh zeolite, the lower UCS of the equilibrium catalyst (E-cat). 

Materials formed by acid-base reactions between calcium aluminate compounds and phosphate-containing solutions yield high-strength, low-permeability, C02-resistant cements when cured in hydrothermal environments. The addition of hollow aluminosilicate microspheres to the uncured matrix constituents yields slurries with densities as low as approximately 1200 kg/m, which cure to produce materials with properties meeting the criteria for well cementing. These formulations also exhibit low rates of carbona-tion. The cementing formulations are pumpable at temperatures up to 150° C. 

Fig. 3.39 5D and values for kaolonites and related minerals from weathering and hydrothermal environments. The Meteoric Water Line, kaohnite weathering and su-pergene/hypogene (S/H) lines are given for reference (after Sheppard and Gilg 1995)... 

The additive mnst have a high degree of physical integrity so that it is able to withstand the severe hydrothermal environment of the FCCU. Factors such as attrition resistance, apparent bulk density, and particle size distribution are critical in retaining the additive in the unit. 

Hobbs B.E. (1984) Point defect chemistry of minerals under hydrothermal environment. /. Geophys. Res. 89, 4026-4038. 

Tsukahara, H., Imai, E. I., Honda, H., Hatori, K., and Matsuno, K. (2002). Probiotic oligomerization on or inside lipid vesicles in hydrothermal environments. Orig. Life Evol. Biosph., 32, 13-21. 

McCollom T. M. Seewald J. S. Abiotic synthesis of organic compounds in deep-sea hydrothermal environments. Chem. Rev. 2007, 107, 382-401. 

Thermal and hydrothermal exposures can change the ix>re size and its distribution, porosity and tortuosity of a porous membrane which in turn influence the separation properties of the membrane such as permeability and permselectivity. Several ceramic membranes have been investigated for their responses to thermal and hydrothermal environments. 

Emergence of life (seeded from Mars ) primary origin or refuge in deep hydrothermal environments ... 

While all necessary thermodynamic properties for calculating g/AgCl are available, no reliable high-temperature internal reference electrode has been developed for a temperature range above 300 °C, apparently because of a chemical degradation process of the Ag/AgCl electrochemical couple in a hydrothermal environment. Therefore, no reliable studies have been carried out to find a suitable internal reference electrode that can be employed in high-temperature subcritical and supercritical aqueous solutions. 

Yokoyama, S., Koyama, A.Nemoto, A. et al. (2003). Amplification of diverse catalytic properties of evolving molecules in a simulated hydrothermal environment. Origins of Life and Evolution of Biospheres (formerly Origins of Life and Evolution of the Biosphere). 33, 589-95. 

Figure 10. a) Conceptual sketch of hydrothermal systems, b) P-T diagram illustrating potentially explosive processes for the HfD-NaCl in an hydrothermal environment (see text). Thick solid lines the saturation curve for pure water (Sat) and the three-phase halite-liquid-vapour curve (HLG). Dotted line the critical curve (CC). Thin solid lines the spinodal curves forxj uCl 0.01 (3.2 wt% NaCl), 0.05 (14.6 wt % NaCl) and O.l (26.5 wt % NaCl) with their corresponding critical points (filled circles). The gray zones along liquid spinodal curves Sp(L) indicate the onset of the instability field of superheated NaCl... 

The massive output of microbial biomass that characterises the early stages of event plumes potentially affects, and is affected by, hydrothermal constituents like H2S, Mn2+, Fe2+, H2, CH4. These reducing substances represent important energy sources as in other hydrothermal environments. 

NH4-rich phyllosilicates with K > NH4 and with (001) spacing values intermediate between illite and tobelite are referred to as NBU-rich illite. They occur in hydrothermal environments (Sterne et al. 1982 Higashi 1982 Von Damm et al. 1985 Wilson et al. 1992 Bobos and Ghergari 1999) in black-shales (Sterne et al. 1984) in regionally metamorphosed carbonaceous pelites (Juster et al. 1987 Daniels et al. 1996 Liu et al. 

However, it has been suggested [26] that natural epitaxial coarsening of diamonds could proceed in colloidal pneumatolytic-hydrothermal environments in near-superficial earth zones, because equilibrium data for material trapped as inclusions in diamond indicated closing temperatures of 600-800 C and pressures below 10 MPa [15] and fit to early theories of diamond formation [27]. Based on the petrologic circumstances mentioned in [26], an area of probable diamond hydrogenesis and hydrosynthesis was sketched (Fig. 1). 

For systems with chromophores such as Cr(VI), UV-vis spectroscopy may be used to study chemical equilibria directly without a pH indicator. Cr(VI) is of interest in hydrothermal oxidation because it is soluble and may be separated from high level nuclear wastes by hydrothermal oxidation of insoluble Cr(III)[44]. Also, oxidation of Cr203 is a reason why some stainless steels (e.g. SS 316) lose their corrosion resistance in oxidative hydrothermal environments. The existing literature data on the acid-base equilibria of Cr(VI) are limited to temperatures not exceeding 175 C[45], i.e., much lower than those typical for hydrothermal oxidation processes. 

Illite occurs as fibrous material filling up sandstone pores, with or without smectite. It often replaees kaolinite pseudomorphously. The process of sericitization produces illite from feldspar at lower part of weathering zones. Illitization also takes place in hydrothermal environments around ore deposits. 

Clay s environment can be described in terms of temperature, pressure, chemical composition and reaction time. These variables are condensed into three geological situations based on the idea of Esquevin (1958) and Millot (1970) (i) the weathering environment, (ii) the sedimentary environment and (iii) the diagenetie-hydrothermal environment. 

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