Water kinetics

The kinetic interpretation of the chemistry of oceanic waters (kinetics of inputs of primary constituents interactions between biologic and mixing cycles) leads to the development of steady state models, in which the relatively constant chemistry of seawater in the recent past (i.e., Phanerozoic cf. Rubey, 1951) represents a condition of kinetic equilibrium among the dominant processes. In a system at... 

Haag, W. R., and J. Hoigne, Ozonation of Bromide-Containing Waters Kinetics of Formation of Hypobromous Acid and Bro-mate, Environ. Sci. Technol., 17, 261-267 (1983). 

Note that water kinetic energy is found to be independent of the methods of computation. 

Haag WR, HoigneJ (1983) Ozonation of bromide-containing waters kinetics of formation of hypobromous acid and bromate, Environmental, Science Technology 17 261-267. 

Sotelo J L, Beltran F J, Benitez F J, Beltran-Heredia J (1987) Ozone Decomposition in Water - Kinetic Study, Industrial Engineering and Chemical Research 26 39-43. 

Also in Bishnoi s laboratory, Dholabhai et al. (1993) studied the effect of electrolytes on methane hydrate formation kinetics. They found that after the equilibrium fugacity (or driving force) is adjusted for the presence of salt, hydrate growth kinetics are quantitatively described by the pure water kinetics model of Englezos. 

Model Conduction Convection Cas Water Kinetics Method... 

Isotope Effects in Supercritical Water Kinetic Studies of Coal Liquefaction... 

Sotelo JL, Beltran FJ, Benitez J, Beltran-Heredia J. Ozone decomposition in water kinetic study. Ind Eng Chem Res 1987 26 39-43. 

Ragaini, V., Selli, E., Bianchi L.C. and Pirola C. (2001) Sono-photocatalytic degradation of 2-chlorophenol in water Kinetic and energetic comparison with other techniques. Ultrason. Sonochem. 8,251-258. 

Solar Energy-Assisted Electrochemical Splitting of Water Kinetic, energetic, and solid-state considerations in the search for suitable electrodes for water splitting elaborated. 61... 

Controls on the H4Si04 Concentration in Sediment Pore Waters Kinetics... 

Salomaa, P., Hakala, R., Vesala, S., and Aalto, T., 1969, Solvent deuterium isotope effects on acid-base reactions. Part III. Relative acidity constants of inorganic oxyacids in light and heavy water. Kinetic applications Acta Chemica Scandinavica, v. 23, p. 2116-2126. 

R. Del Vecchio, N.V. Blough, Photobleaching of chromophoric dissolved organic matter in natural waters Kinetics and modeling. Mar. Chem., submitted. 

Thermodynamic calculations show that chromate is the expected form in oxygenated sea water, while the insoluble Cr(III) species would predominate in very low-oxygen (so called suboxic ) or anoxic waters. However, it is important to note that thermodynamic calculations only predict elemental spe-ciation at equilibrium (when the rates of formation and destruction are balanced), but they do not consider the rates of conversion themselves. For example, Cr(III) should not exist in oxygenated sea water, but its rate of oxidation to Cr(VI) is slow (days to months), meaning that Cr(III) can persist in oxic water ( kinetic stabilization ). In the eastern North Pacific Ocean, Cr(VI) displays a surface concentration of 3 nmol 1 (Figure 2A), but then decreases rapidly to a minimum of 1.7 nmol 1 at 300 m depth and increases below this to levels of 4-5 nmol in the deeper waters. While chromate appears to display a mixture of scavenged and nutrient-like behavior, the Cr(VI) minimum occurs at the same depth as the widespread suboxic zone in the eastern Pacific. 

Water electrolysis has also been used as a method of producing heavy water. Kinetic factors determine that hydrogen is evolved more rapidly than deuterium (by a factor of 2—10) and hence the deuterium concentrates in the electrolyte. 

Izzo, B., Harrell, C.L. and Klein, M.T. (1997) Nitrile reaction in high-temperature water Kinetics and mechanism, AIChE Jourruil 43,2048-2095... 

Another radionuclide that has been commonly used in physiological studies of terrestrial animals is tritium. As stated in Section 8.2.1, water can be labeled as HTO and the compound used to study the water pool in plants. Somewhat similarly, total body water and water turnover in mammals can be studied. Longhurst et aL (1970) utilized HTO to compare water kinetics in winter and summer Columbian black-tailed deer (Odocoileus hemionus columbianus) and domestic sheet (Ovis aries). The animals were injected intravenously with 8 mCi HTO, and blood samples were collected periodically and examined for radioactivity with a liquid scintillation counting system. In a water-turnover study in mule deer (Odocoileus hemionus), Knox et aL (1969) also used HTO and observed that the biological half-life of HTO differed in animals maintained in a 0.9 X 1.5 m metabolism stall from that in the same animals maintained in a 4.6 X 5.8 m room. 

Solubilization as a bulk reaction Molecular dissolution and diffusion of oil into the aqueous phase takes place, with a subsequent uptake of oil molecules by surfactant micelles [156-161]. This mechanism is operative for oils (like benzene, hexane, etc.), which exhibit a sufficiently high solubility in pure water. Theoretical models have been developed and verified against the experiment [157,159-161]. The bulk solubilization includes the following processes. First, oil molecules are dissolved from the surface of an oil drop into water. Kinetically, this process can be characterized by a mass transfer coefficient. Next, by molecnlar diffnsion, the oil molecules penetrate in the water phase, where they react with the micelles. Thus, the concentration of free oil molecules dimmishes with the distance from the oil-water interface. In other words, solubilization takes place in a certain zone around the droplet [159,160]. 

Tratnyek, P. G. and Hoigne, J., Photo-oxidation of 2,4,6-trimethylphenol in aqueous laboratory solutions and natural waters kinetics of reaction with singlet oxygen, /. Photochem. Photobiol. A, 84, 153, 1994. 

The same catalysts and conditions may operate for both reaction directions, that is, either towards the synthesis of methanol or towards its oxidation. Again, CO2 reduction must be able to compete with the electrochemical reduction of water-yielding hydrogen gas. Thermodynamically, the reduction of CO2 to CH3OH is slightly more favourable than the reduction of water. Kinetically, CO2 reduction can be favoured by electrodes, which act as poor catalysts for water reduction, including metallic Mo, Cu, In, Sn and Sb. Using nearly neutral electrolytes, rather than acidic ones, rendered CO2 reduction kinetically more favourable [148]. A detailed mechanism of the mediated electroreduction of carbon dioxide to methanol is addressed in the next section. 

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