Mineral-solution equilibria

At present, there are serious limitations to the use of geochemical codes to study clay mineral solution-equilibria. These include the sparse and often dubious clay mineral stabilities given in program data bases and the fact that water analyses rarely include reliable data for both dissolved Si and Al. Also, dissolved Al is usually below detection above pH 5 to 6. When reported at higher pH s, aluminum is mostly present in suspended form, as suggested by Example 9.3. For such reasons, many researchers still prefer using graphic methods to depict the stabilities and behavior of clay minerals. 

Chatham, J. R., R. B. Wanty, and D. Langmuir. 1981. Groundwater prospecting for sandstone-type uranium deposits The merits of mineral-solution equilibria versus single element tracer methods. U.S. Dept, of Energy, Report GJO79-360-E. 197. 

Miller, W. R., R. B. Wanty, and J. B. McHugh. 1984. Application of mineral-solution equilibria to geochemical exploration for sandstone-hosted uranium deposits in two basins in west-central Utah. Econ. Geol. 79(2) 266 83. 

Mineral-solution equilibria. Mineral-solution equilibria describe the dissolution of minerals, and exert a critical role in relevant phenomena such as hydration of dissolved mineral species, formation of precipitates and their electrokinetic behavior. Important parameters like concentration of various dissolved mineral species/pH/onset of precipitation and point of zero charge can be calculated from mineral-solution equilibria. All these factors are helpful for determining optimum conditions for flotation. 

The technique presented in this paper to estimate the pressure dependence of ionization constants is simple to use and requires minimal data. Excellent agreement is observed between the calculated and measured values of ionization constants of several aqueous complexes at higher pressures, at least up to 200°C. The discussion presented above shows that the effect of pressure on ionization constants must be considered in geochemical calculations of mineral-solution equilibria at low and high temperatures. 

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