Solution equilibria of dissolved mineral species

However, our estimates based on available information on the charge density of silica (40 Clew at pH 11 and ionic strength 10 kmol/m ) suggest that in the present case, the surface pH will not be significantly different from the bulk pH, since 3 x 10 mol/cm of calcium is reported to adsorb at this pH. Thus, it can be seen that the sharp increase in adsorption coincides with the conditions for the surface precipitation of Ca(OH)2. Adsorption of a number of other metallic cations has been analyzed along the lines discussed above and in all such cases the sharp increase in adsorption at a particular pH can be accounted for by the surface precipitation of the hydroxide of the adsorptive. 

Similar phenomena have been observed in numerous other systems such as those of aluminum quartz (Ananthapadmanabhan and Somasundaran, 1985), nickel-quartz (Nagaraj and Somasundaran, 1981), cupric-chrysocolla (Latiner, 1952), manganous-rhodonite (Butler, 1967) and ferrous-chromite. 

When mineral particles are contacted with water, they will undergo dissolution, the extent of which is dependent upon the type and concentration of chemicals in solution. The dissolved mineral species can undergo further reactions such as hydrolysis, complexation, adsorption and even surface or bulk precipitation. The complex equilibria involving all such reactions can be expected to determine the interfacial properties of the particles and their flotation behavior. The concentration of each dissolved mineral species can be calculated from various solution equilibria of the minerals. The calculated results are plotted as log C-pH diagram. The equilibria in selected salt-type mineral systems with special reference to calcite and apatite are examined below. 

Two relevant situations are considered (i) closed system system closed to atmospheric CO2 (ii) open system system open to atmospheric CO2. 

When calcite is brought in contact with water, its dissolution will be followed by pH dependent hydrolysis and complexation of the dissolved species. The following are the equilibria that will control the system (Amankonah, 1985 Somasundaran and Wang, 1984). 

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