Water thermal

Direct, One-Step Thermal Water Splitting. The water decomposition reaction has a very positive free energy change, and therefore the equihbrium for the reaction is highly unfavorable for hydrogen production. 

There are significant problems for one-step thermal water spHtting. In future nuclear and solar facihties, about 927°C is considered the upper temperature range, which is not sufficient for this reaction. Even if high temperature heat sources were available, materials of constmction would present difficulties. There would also be separation problems (155). 

Fig. 2.13. (A) Temperature dependence of pH in Japanese thermal waters. Lines indicate the temperature dependence of pH when pH is buffered by the K-feldspar-K-mica-quartz (or chalcedony at less than 200°C) assemblage at a Na + K concentration of 0.1 and 0.01 mol/kg H2O. Symbols are as in Fig. 2.11. (B) Temperature dependence of pH of Icelandic thermal waters. Large circles indicate well discharges. Small dots represent hot spring waters (Chiba, 1991).

Nakamura, H. and Maeda, K. (1961) Thermal waters and hydrothermal activities in Arima hot spring area, Hyogo Prefecture (Japan). Japan Geol Surv. Bull, 12, AKl-VJl. 

Sakai, H. and Matsubaya, O. (1974) Isotopic geochemistry of the thermal waters of Japan and its bearing on Kuroko ore solutions. Econ. Geol, 69, 974-991. 

Joarmon S, Pin C (2001) Ultra-trace determination of Ra in thermal waters by high sensitivity quadrapole ICP-mass spectrometry following selective extraction and concentration using radium-specific membrane disks. J Anal At Spectrom 16 32-37... 

Figure 14. Plot of Li isotopic composition vs. concentration of thermal waters from the continents and the oceans (see text for references). Differences between the isotopic range of marine versus non-marine fluids emphasizes the variability in 5 Li of continental rocks compared to oceanic basalt. The dilution of the continental fluids goes along with their lower temperatures vent fluids are the only truly geothermal samples here, with temperatures in excess of 300°C.

Minerals derived from evaporation of saline solutions have not been extensively examined. Evaporitic salts from the western U.S. Great Basin concentrated Li (5 Li = +31.8 to +32.6 Tomascak et al. 2003). Evaporation of thermal waters from Yellowstone yielded travertine with extremely low 5 Li (-4.8 Sturchio and Chan 2003), offset from its coexisting fluid by -ll.l%o. Such evaporites, where preserved in the sedimentary record, could afford an opportunity to examine variations in spring water compositions and hence information on hydrothermal processes over time. 

Bullen TD, Kharaka YK (1992) Isotopic composition of Sr, Nd, and Li in thermal waters from the Norris-Mammoth corridor, Yellowstone National Park and surrounding region. Itr. Water-Rock Interaction, Proceedings of the Seventh International Symposium on Water-Rock Interaction. Kharaka YK, Maest AS (eds) Balkema Publishers, Rotterdam p 897-901... 

Biscardi D, Castaldo A, Gualillo O et al (2002) The occurrence of cytotoxic Aeromonas hydrophila strains in Italian mineral and thermal waters. Sci Total Environ 292(3) 255-263... 

Fig. 3.10 Isotopic composition of thermal waters and associated local groundwaters. Lines connect corresponsing thermal waters to local groundwaters (Giggenbach, 1992)...

The limitation of solvent evaporation could be avoided by working at high temperature with water vapor in the presence of a solid electrolyte (steam electrolysis). Nominally, at about 4000°C, at which AG = 0, electroless thermal water splitting would be realized. In practice, problems of material stability, necessary... 

Perkins C, Weimer AW (2004) Likely near-term solar-thermal water splitting technologies. Int J Hydrogen Energy 29 1587-1599... 

Rybach, L. 1995. Thermal waters in deep Alpine tunnels. Geothermics, 24, 631 -637. 

Thermal water ICP-QMS + USN (PlasmaQuad PQ2) extraction, ion exchange 226 Ra 2 fgml 1 Joannon and Pin49... 

The Bustcn, Bath, and Bristol thermal waters, como under the same category. Annexed is an analysis of the Buxton water just completed by the Editor it differs matarially from the one made by his friend Playfair some time ago, except in the amount of gases — ... 

Sulphur dioxide and sulphurous gases attack basic rocks and glasses superficially at high temperatures (900° C.) with the formation of water-soluble sulphates, chiefly sodium sulphate.3 It is probable that such reaction and the solution of the products in hot springs during the early post-volcanic period explain the origin of alkaline sulphated thermal waters. 

Fig. I. Energy level diagram lor the hypothetical catalytic and thermal water gas shift reaction. The overall heal of reaction is given by iH iKi, the acuvalion harriers in the forward and backward direction by and...

Thermal Waters of Georgia. Georgian Geothermal Association. Tbilisi, 1998... 

Aiuppa, A., Avino, R., Brusca, L. et al. (2006) Mineral control of arsenic content in thermal waters from volcano-hosted hydrothermal systems Insights from island of Ischia and Phlegrean fields (Campanian volcanic province, Italy). Chemical Geology, 229(4), 313-30. 

Koski, A. and Wood, S. (2003) Aqueous geochemistry of thermal waters in the Alvord Basin, Oregon. Abstracts with Programs. The Geological Society of America, 35(6), 407. 

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