Electrokinetics of natural and mechanically modified ripidolite and beidellite clays
- Rudjer Boskovic Inst., Zagreb (Croatia). Center for Marine Research
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 the range pH 2 ({minus}10 and {minus}20 mV, respectively) to pH 10 ({minus}60 and {minus}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, shown 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{sup {minus}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.
- OSTI ID:
- 367904
- Journal Information:
- Journal of Colloid and Interface Science, Vol. 181, Issue 2; Other Information: PBD: 10 Aug 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
Electrokinetics of pure clay minerals revisited
Molecular dynamics modeling of clay minerals. 1. Gibbsite, kaolinite, pyrophyllite, and beidellite
Related Subjects
CLAYS
SURFACE PROPERTIES
CHLORITE MINERALS
SMECTITE
AQUATIC ECOSYSTEMS
ELECTROPHORESIS
FULVIC ACIDS
ADSORPTION
ION EXCHANGE
SCANNING ELECTRON MICROSCOPY
X-RAY DIFFRACTION
ABSORPTION SPECTROSCOPY
INFRARED RADIATION
SURFACE POTENTIAL
ENVIRONMENTAL TRANSPORT
METALS
ORGANIC COMPOUNDS