Kaolinitic soils

Schwertmann, U. Kampf, N. (1984) Properties of goethite and hematite in kaolinitic soils of southern and central Brazil. Soil Sci. 139 344-350... 

Acar et al. (1996 1997) showed that ionic migration could be used for injection and transport of anionic and cationic additives. In a bench-scale experimental setup, ammonium hydroxide (NH4OH) was introduced at the anode compartment and sulfuric acid (H2S04) at the cathode compartment. The electric field caused migration of nitrate ion from anode towards the cathode and sulfate ion from cathode towards the anode. The study reported transport rates of 5 to 20 cm/day in fine sand and kaolinite soil specimens and consequent soil saturation of ammonium and sulfate ions. The study concluded that ion migration under dc fields can be used to inject nutrients, electron acceptors/donors to enhance in situ bioremediation. 

Intact soil cores (6.7 cm i.d.) were taken with spilt spoon at depths of 1 to 2 meters from a field test site located approximately 50 km east of Cincinnati, Ohio. The soil in this interval consists mainly of quartz (60%) and clay minerals (35%) with minor amounts of plagioclase and potassium feldspar. The majority of clay is illite and smectite, with minor amount of kaolinite. Soil chemical properties were analyzed prior to, and after, electroosmosis, in order to evaluate the effects of electroosmosis on the distribution of elements within the soil column. Sampled cores were wrapped in aluminum foil and stored at 12°C until the EO cell was assembled. 

Fusi, P, Ristori, G. G., and Calamai, L., Stotzky G. (1989). Adsorption and binding of protein on clean (homoionic) and dirty (coated with Fe oxyhydroxides) montmorillonite, iUite and kaolinite. Soil Biol. Biochem. 21, 911-920. 

Kretzschmar, R., Hesterberg, D., and Sticher, H. (1997). Effects of adsorbed humic acid on surface charge and flocculation of kaolinite. Soil Sci. Soc. Am. I. 61,101-108. 

Scott, H.D. and J.F. Lutz (1971). Release of herbicides from clay minerals as a function of water content I. Kaolinite. Soil Sci. Soc. Am. Proc., 35 374-379. 

C. Surfaces that exhibit pH-dependent electrical potential show various degrees of selectivity for the same cation. For example, kaolinite or kaolinitic soils at high pH (high negative surface electrical potential) shows increasing preference for divalent cations than monovalent cations, while at low pH (low negative electrical potential), kaolinite, or kaolinitic soils show increasing preference for monovalent cations than divalent cations. 

Udo, E. J. 1978. Thermodynamics of potassium-calcium and magnesium-calcium exchange reactions on a kaolinitic soil clay. Soil Sci. Soc. Am. J. 42 556-560. 

FIGURE 4.8 Charge balance test for a kaolinitic soil in LiCl solutions. Electrolyte concentration circles, 0.001 M triangles, 0.005 M and squares, 0.001 M. Error bars are only given for 0.001-M electrolyte. Bars are similar in the other two cases. Data provided by J. Chorover. 

Examples of this behavior were given by Chorover and Sposito29 for kaolinitic soils from Brazil and by Schroth and Sposito34 for two Georgia kaolinites, shown in Figure 4.8. Equation 4.10 is a test for charge balance and consistency. Deviations from the behavior described by the equation reveal data inconsistency and indicate inaccuracy or inappropriateness of any of the methods used to measure the charge components. The equation is also very useful to correct relative aH versus pH curves.29 If astr and Aq are known, at least one pH value, the absolute aH, can be calculated at that pH, and the whole relative aH versus pH curve can be corrected. 

Several sets of experimental data providing proton adsorption and ion adsorption on clays and clay-containing soils are described below and modeled later. The description starts with two monmorillonite samples, continues with illite, and finishes with a kaolinitic soil. 

Financial support for this research was provided by the Fundacion Antorchas, CONICET, SECyT-UNC, and Region Rhone-Alpes (France). We are grateful to J. Chorover for providing the kaolinitic soil experimental data. 

The Cl-, NOT, and SG anions are considered to be nonspecifically adsorbed. Table 9.1 shows typical data for Cl- and SO - adsorption by soils. The capacity of soils to adsorb anions increases with increasing acidity and is much greater for the kaolinitic soil, which has significant pH-dependent charge. At all pH values, the divalent SO - ion is adsorbed to a greater extent than the monovalent Cl- Ion, as would be expected on the basis of electrostatic attraction forces alone. 

Saltzman, S., B. Yaron and U. Mingelgrin. 1976. The surface catalyzed hydrolysis of parathion on kaolinite, Soil Sci. Soc. Amer. Proc., 38 231-234. 

Olsen, H.W. 1969. Simultaneous fluxes of liquid and charge in saturated kaolinite. Soil Science Society of America, Proceedings, 33(3) 338-344. 

Figure 5.10 shows Ca-K exchange isotherms for two horizons in an acidic soil from Guinea, Nigeria (Agbenin and Yakubu 2006). This is mainly a kaolinitic soil, with the oxide fraction being dominated by iron oxides. The dashed lines show the nonpreference isotherms it can be seen that the surface horizon shows a small preference for potassium, whereas the subsurface shows a nearly nonpreferential behavior. 

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