Clay hydration, high concentration

Although other clay minerals can also be acid leached and improved somewhat by this treatment, they do not match activity levels attained by calcium montmorillonite. It has been hypothesized that calcium montmorillonite is superior in this regard because it simultaneously develops a high concentration of strong acid sites, and extensive porosity in 50-200-A diameter pores after acid-activation (85). In any case, only those clays that achieve high hydrated silica values upon acid leaching are found to be good candidates for the acid-activation process. 

Of particular interest for chemical transport into a predominantly smectite medium is the shrink-swell property of the clay material. The swelling properties of smectites are explained by two concepts. The first one, developed by Sposito (1973), shows that smectite swelling is caused by the hydration and mobility of the cations, which in turn balance the negative charge of the layer silicates. The second concept, presented by Low (1981), emphasizes the direct interaction of water molecules with the silicate surface. Both viewpoints fit the common observation that smectite swells in a high-hydration environment and at low electrolyte concentrations and shrinks when water is lost and salt is added to the bulk solution. 

On the other hand, a classification of a sorption process on the basis of kinetics data must be conditioned by other chemical properties of the phosphate-soil mixture. For example, if the soil solution is supersaturated initially with respect to some phosphate solid, precipitation is likely to influence the sorption reaction from the beginning. If the soil minerals have a low degree of crystallinity and/or a high degree of hydration, precipitation may be the dominant sorption mechanism even in the rapid stage.In general, low phosphate concentrations and well-crystallized, relatively unhydrated soil minerals tend to favor adsorption as the phosphate reaction mechanism. Other chemical properties, such as the pH value of the soil solution and the kinds of metals in soil clay minerals, exert a quantitative influence on the rapid stage of phosphate sorption, as do such physical properties as temperature. ... 

For salt aqueous solutions in the absence of any other chemical additives, the hydrate suppression temperature (i.e., dissociation temperature shift) can be determined by measuring the electrical conductivity (Mohammadi, et al, 2007) [16], To characterize liquid mixtures for industrial processes, an acoustic multi-sensor system was developed to measure the concentrations of the chemicals such as MeOH and MEG in the solutions without salts (Henning, et al, 2000) [10]. However, these methods may not be applicable to most hydrocarbon transport pipelines where salts and at least one inhibitor often coexist in the aqueous phase. (Sandengen and Kaasa, 2006) [18] developed an empirical correlation that determined the MEG and NaCl concentrations by measuring the density and electrical conductivity of water samples under examination. However, the critical weakness of this method is that it requires high accuracy of the density measurement, which prevents it from application to real produced water samples that usually contain solid particles (sands and clays) and oil droplets. 

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