Naslov
Electrokinetics of Natural and Mechanically Modified Ripidolite and Beidellite Clays

Autori
Sondi, Ivan ; Pravdić, Velimir

Izvornik
Journal of Colloid and Interface Science (0021-9797) 181 (1996), 2; 463-469

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
beidellite ; clay minerals ; electrokinetic potential ; fulvic acid ; milling ; modification of surfaces ; ripidolite

Sažetak
Particles of clay minerals were studied due to their importance in geochemical processes in natural waters, such as adsorption and transfer of ionic contaminants, stabilization by organics, and flocculation and sedimentation phenomena. Information on the behavior of clays was sought by experiments with model systems. Measurements of electrophoretic mobilities in relation to pH, at varying concentrations of well-characterized fulvic acid (FA) were performed on two structurally well defined, representative clay minerals prepared with clean surfaces: ripidolite (a well-known trioctahedral nonswelling chlorite) and beidellite (a typical dioctahedral smectite). Natural ripidolite and beidellite show high negative electrokinetic potentials in range pH 2 (-10 and -20 mV, respectively) to pH 10 (-60 and -50 mV, respectively). Experiments utilizing mechanical particle disintegration (dry milling), mimicking natural wear and physical weathering, resulted in increases of specific surface area (12.3 and 1.5 times, respectively) and of cation exchange capacity (3.2 and 1.2 times, respectively). Such small-sized particles, show by SEM figures, retain their crystal structure (X ray) and the nature of their structural bonds (FTIR), exhibiting an IEP ( at pH 6.0 and 3.0, respectively). This was interpreted to be the creation of positively, charged edge surfaces. Exposed to fulvic acid in solutions of 10"-3" NaCl at pH=6.5, these new surfaces showed an increase in negative zeta-potential for ripidolite, and, to a smaller extent, for beidellite. In the interaction of clay mineral particles with aqueous medium, it is concluded that the degree of mechanical wear is more decisive than the type of the mineral.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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