Clay minerals electrokinetics

Collins, Y.E. and Stotzky, G., Heavy metals alter the electrokinetic properties of bacteria, yeasts, and clay minerals, Appl Environ Microbiol, 58 (5), 1592-1600, 1992. 

The use of centrifugation to separate the liquid from solid phases in traditional batch or tube techniques has several disadvantages. Centrifugation could create electrokinetic effects close to soil constituent surfaces that would alter the ion distribution (van Olphen, 1977). Additionally, unless filtration is used, centrifugation may require up to 5 min to separate the solid from the liquid phases. Many reactions on soil constituents are complete by this time or less (Harter and Lehmann, 1983 Jardine and Sparks, 1984 Sparks, 1985). For example, many ion exchange reactions on organic matter and clay minerals are complete after a few minutes, or even seconds (Sparks, 1986). Moreover, some reactions involving metal adsorption on oxides are too rapid to be observed with any batch or, for that matter, flow technique. For these reactions, one must employ one of the rapid kinetic techniques discussed in Chapter 4. 

Sondi, I., Biscan, J., and Pravdic, V., Electrokinetics of pure clay minerals revisited, J. Colloid Interface Sci., 178, 514, 1996. 

Results of electrokinetic studies of different materials, chiefly silica and clay minerals which produced only positive or only negative potentials (no lEP) are shown in Table 3.9. A few sets of electrokinetic data with both negative and positive... 

Kosmulski, M. and Dahlsten, P, High ionic strength electrokinetics of clay minerals. Colloids Sutf. A, 291, 212, 2006. 

Galassi, C.. Gosta, A.L., and Pozzi, P., Influence of ionic environment and pH on the electrokinetic properties of ball clays. Clays Clay Miner., 49, 263, 2001. 

Barany S, Meszaros R et al (2011) Effect of polyelectrolyte mixtures on the electrokinetic potential and kinetics of flocculation of clay mineral particles. Colloids Surf A 383 48... 

Colloid and Surface Properties of Clays and Related Minerals, Rossman F. Giese and Carei J. van Oss Interfacial Electrokinetics and Electrophoresis, edited by Angei V. Deigado... 

Giese, R. F., Wu, W., and van Oss, C. J. (1996) Surface and electrokinetic properties of clays and other mineral particles, untreated and treated with organic or inorganic cations J. Disp. Science and Tech., 17, 527-547. 

While the electrokinetic surface, or -potentials, originate from the surface or interfacial properties of solid materials, they are actually situated about 0.3 to 0.5 nm outside a material s surface and have to be extrapolated inward to the (i/>o) potential at the actual surface, using Eq. 5.54. The electrostatic free energy of interaction, AG, between two surfaces, 1, reaches a value of about -M.O mJ/m at V o 75 mV, in an aqueous medium with a 100 mM salt content of a mono-mono-salt see Table 5.1. Now various clay and other mineral particles can have V o-potentials that are between 50 and 90 mV, in which case AG, while not dominant, is no longer negligible. For instance for a contact between two platey clay particle surfaces over about 100 nm (= 10 ° cm ) an attraction of 1 mJ/m still corresponds to w 2,500 kT. Thus, it is always wise to measure -potentials, from which the actual surface, or V o-potential can be derived. 

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