Kaolinite solubility studies

Solubility Studies of Kaolinite. There have been numerous attempts to determine the free energy of formation of kaolinite from solubility studies (Table II). Polzer and Hem ( 3) reacted an API standard kaolinite from Lewistown, Mont., for 2 years with an acidic solution approaching equilibrium from undersaturation. The sample appears to have been very near to equilibrium, and these authors report a AG 293 3 5 -903 kcal/mol. 

Most kaolinites contain appreciable amounts of MgO (range 0.01—1.0% modal value between 0.2—0.3%). Bundy et al. (1965) found that MgO as well as total iron and soluble iron were directly related to the C.E.C. and suggested that the Mg and Fe were present in montmorillonite which they believe is commonly present, in amounts less than 5%, in kaolinites. This may be true in part, but electron probe studies (Weaver,1968) indicate that some of the MgO is related to the Ti02-Fe203 material and some is present in biotite. 

Reference [137] reports the absence of significant dissolution of illite. In contrast, [138] reports considerable release of Si and Al from illite. Dissolution of illite, that is, Al, Si, Ca, and Mg concentrations at pH 3-9, was studied in [139]. Dissolution of kaolinite at acidic pH was studied in [140]. Reference [141] reports the release of Si, Fe, Al, and Mg from montmorillonite as a function of pH. Concentrations of Si and Al in solution during titration of smectite are reported in [142]. Solubility of laponite is discussed in [143] and references therein. 

Using a small finger-prong mixer (7.2 cm. wide X 10 cm. long X 10 cm. deep), Michaels and Puzinauskas studied the effect of water content and volume of solids on mixer performance. Their work involved mixing a water soluble powder (dextrose), with a clay (kaolinite), and water. The material consistency varied from a dry powder to a liquid. 

Numerous studies are reported on the electrokinetic removal of heavy metals from soils (Chapter 4). Many of these studies used ideal soils, often kaolinite, as a representative low-permeabiUty soil, which were spiked with a selected single cationic metal (such as lead and cadmium) in predetermined concentration. The spiked soil is loaded in a small-scale electrokinetic test setup and electric potential is applied. The transport and removal of the metal after specified test duration are determined. It is shown that cationic metals exist in soluble ionic form due to reduced pH near the anode regions and they are transported toward the cathode. However, when they reach near the cathode, they get sorbed or precipitated due to increased pH resulting from OH transport from the cathode. The actual removal from the soil is often negligible. 

Nickel sorption on pyrophyllite, kaolinite, gibbsite, and montmorillonite at pH 7.5 results in formation of Ni-nucleation products from solutions which are undersaturated with respect to the thermodynamic solubility product of Ni(OH)2(s). An important finding of the study of Scheidegger et al. (16) is that the structural environment of Ni in all Ni sorption samples is similar. There is also an obvious similarity among the spectra of the Ni sorption samples and the spectrum of takovite, suggesting the presence of Ni phases of similar structure (Table II). 

Anionic Surfactant onto Kaolinite. The adsorption of a petroleum sulfonate surfactant, TRS 10-80, onto Na-kaolinite was conducted in batch experiments at low-to-medium salinity and under conditions in which liquid-crystal suspensions formed in alcohol-containing brines [60]. TRS 10-80 was described as not being very brine-soluble. The adsorption studies were conducted at 30 °C with pH values ranging from 7 to 13. The alcohol used was 2-butanol and its concentration was held constant at 30 g/1. 

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