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Differential Settling Tendencies of Clay Minerals in Saline Waters
- U. Grant Whitehouse, Lela M. Jeffrey, James D. Debbrecht
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- Journal:
- Clays and clay minerals (National Conference on Clays and Clay Minerals) / Volume 7 / February 1958
- Published online by Cambridge University Press:
- 01 January 2024, pp. 1-79
- Print publication:
- February 1958
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Differential settling velocities of individual clay mineral types and clay mineral mixtures in quiet saline water are reported for ocean water chlorinity range 0–18‰, brackish water ionic strength range 0.0–0.686 moles-(unit charge)2/kg, temperature range 6–26°C, clay mineral concentration range 0.01–3.6 g/1., and pH range 6.5–9.8. The materials employed included natural deposit clay minerals and clay minerals extracted from marine sedimentary matter and from terrestrial soils.
Settling velocities at 26°C for illitic and kaolinitic materials reached values of 15.8 and 11.8 m/day, respectively, at an ocean water chlorinity of 18‰ and exhibited little dependence upon chlorinity above a chlorinity of 2‰. Settling velocities for montmorillonites were found to be functions of chlorinity over the entire chlorinity range 0–18‰ and to increase exponentially to a limit of 1.3 m/day at 26°C. The settling velocities were determined by pipette analysis, Oden balance techniques, Kelley-Wiegner manometer methods, and spectrophotometric methods, using artificial sea-water and filtered Gulf of Mexico water.
In quiet brackish water, variations in ionic ratio composition alter the settling rates of illites and kaolinites less than 15 percent from such rates in ocean water, at constant, brackish water, ionic strength of 14 or greater. In contrast, montmorillonitic settling rates in such water varied by 40 percent or more from ocean water rates, at constant ionic strength unless the magnesium—potassium or magnesiun-strontium ionic ratios of the brackish water were kept constant. These induced variations were not sufficient in magnitude, however, to change the general relative order of settling rates for the clay minerals.
Decreasing temperatures over the range 26°-6°C decreased settling rates (of all clay types) progressively up to about 40 percent in accordance with temperature-induced changes in the viscosity and density of the saline water medium.
The influences of fifty-seven different organic compounds or materials (carbohydrates and proteins dissolved or dispersed in the water) upon the settling velocities are cited. In general, carbohydrates increased the settling rates of montmorillonitic materials as much as 25 percent, and proteins decreased such rates a maximum of 1–5 percent. Kaolinitic materials suffered a 30–40 percent decrease in settling velocity under the influence of some proteins. So-called “humic acids,” derived from quinone and soil fractions, decreased kaolinitic and montmorillonitic settling rates to lesser extent. No significant alterations of illitic settling rates by organic materials were noted.
Chlorite-montmorillonites were found to settle slightly faster than sodium and calcium montmorillonites. Potassium-saturated montmorillonites settled from two to three times as rapidly as the reference montmorillonites. Chlorite settling rates, of magnitude comparable to rates found for kaolinites, and vermiculite settling rates, comparable at higher chlorinities to illite settling rates, are also reported.
The apparent interaction of illite and montmorillonite to form illitic-montmorillonitic settling entities in some clay mineral mixtures was noted. Other mixtures, exposed to artificial sea-water for 3–6 years, exhibited a tendency to transport 5–20 percent kaolinite within a developed illitic-chloritic mix, when reagitated.
Evidence is also presented to support the argument that clay minerals do not settle in single solid particulate units in saline waters. The effective settling unit, after flocculation, is described as a coacervate, i.e. as a thermodynamically reversible assembly of solid clay particles or strands within a settling solid-rich liquid unit phase. Settling rate increases are thereby not a consequence of any irreversible formation of larger solid particles or solid aggregates by coalescence of fresh water particles at or beyond the fresh-water-saline-water interface.
Differential transport of clay minerals by the turbulent flow of saline water in a pipe is quantitatively described. Flow rates of about 6 miles/hr were required to eliminate differential transport of the clay minerals. Clay mineral concentrations over the range 0.01–15.0 g/l. were considered.
Chemical data, electron and x-ray diffraction data, base exchange data, and electron micrographs support the settling velocity information.
Diagenetic Modification of Clay Mineral Types in Artificial sea Water
- U. Grant Whitehouse, Ronald S. McCarter
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- Journal:
- Clays and clay minerals (National Conference on Clays and Clay Minerals) / Volume 5 / February 1956
- Published online by Cambridge University Press:
- 01 January 2024, pp. 81-119
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- February 1956
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Analyses of samples of kaolinitic, illitic, and montmorillonitic clay materials exposed to artificial sea water for periods of six months to five years have yielded some evidence to support the contention that chloritic and illitic clay types may ultimately develop from montmorillonitic material in the marine environment. However, no indications of the initiation or induction of any major lattice alteration of the original kaolinite and illitic type structures have been recognized on the basis of the data collected.
The techniques of electron diffraction, electron microscopy, x-ray diffraction, and chemical analysis were employed to detect and measure the extent of modification of the clay materials at selected time intervals during the five year period.
Actual separations of illitic-like and chloritic-like materials from treated montmorillonitic material were accomplished by gravitational settling methods. Relative weight percents of 18.2 for chloritic clay separates and 4.4 for illitic clay separates were obtained after more than four years of treatment. Chemical analysis and electron microscopy data suggest that lattice alteration preceded the development of forty to seventy percent of the chloritic and illitic material separated.
The chloritic material apparently developed by initial formation of a magnesium-enriched montmorillonite having a hectoritic appearance. Subsequent development of threadlike extensions from the magnesium montmorillonite is shown by electron micrographs. These threads were observed to decrease or equilibrate in apparent amount within the chloritic separates as platelike forms began to appear after three years. The illitic separates were characterized by fine granulai material with increasing occurrence of larger platelike forms as exposure time increased.
The modification of montmorillonitic clay was observed to be more dependent upon the magnesium-potassium ratio in the sea water than upon the total salt concentration levels. The limiting magnesium-potassium ratio was found to be approximately 9.4 with a limiting low potassium concentration of 0.005 moles per liter for montmorillonitic material of less than 0.5 micron settling diameter. The alteration of the montmorillonitic material was noted only for material that was initially settled through the artificial sea water media. As the potassium concentration level of these media dropped by extraction below 0.005 molar, a bulk effect of the settling material became operative and the relative percent of altered material decreased.
Further, the relative amounts of modified material detected were decreased by the introduction of carbohydrate material into the sea water media. The amounts present after a definite time interval were also observed to be dependent upon the distributive tendencies of the source materials and the physical disturbance of the sea water media. Resuspension of the material by reagitation of the system decreased and significantly governed the rate of diagenetic modification.
Special electron micrographs are presented to illustrate relative stages of flocculation of montmorillonitic material as the ionic concentration of sea water increases. It is suggested that these stages govern to an appreciable extent the extent and rate of initiation of any ionic exchange and lattice changes that occur.
Peptization Resistance of Selected Samples of Kaolinitic, Montmorillonitic, and Illitic Clay Materials
- U. Grant Whitehouse, Lela M. Jeffrey
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- Journal:
- Clays and clay minerals (National Conference on Clays and Clay Minerals) / Volume 3 / February 1954
- Published online by Cambridge University Press:
- 01 January 2024, pp. 260-281
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- February 1954
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Variations in the peptization resistance of selected samples of clay mineralogical materials toward alkaline dispersing agents are discussed from a quantitative point of view.
Clay samples, collected from South Carolina, Wyoming, Illinois, New Mexico, South Wales, Great Britain and Cornwall, England were subjected to the action of solutions of Calgon (“sodium hexametaphosphate”), ammonia, sodium hydroxide, sodium carbonate, sodium pyrophosphate, and “sodium lignosulfonate.” The resulting apparent dispersion, in each case, was expressed as a function of the employed concentration and chemical nature of the dispersing agent. Pipette analysis and Oden balance techniques at constant temperature were used to measure the degree of dispersion. All clay samples employed were identified as to type by X-ray diffraction, chemical analysis, thermal analysis, and electron microscopy.
All samples examined exhibited a maximum in apparent dispersion (suspension stability) at a specific concentration of dispersing agent. Such maximum was followed by a sudden decrease in apparent dispersion, i.e., flocculation, at higher concentrations of dispersing agent. Concentrations of dispersing agent were varied in steps of one part per thousand. One hundred and twenty experimental runs were made on each type of material examined. Differences in the degree of apparent dispersion attained by use of different dispersing agents were expressed in terms of a threshold concentration which altered “equivalent diameter” one tenth of a phi unit. Among dispersing agents employed, “sodium lignosulfonate” was found to be least selective of clay mineral type in its peptizing action.
An equation for the calculation of a “peptization resistance factor” is presented. Results obtained by application of this equation indicate that differences in the response of the same clay material to different alkaline dispersing agents may be attributed, in part, to differences in degree of peptization achieved by “threshold mechanisms” of peptization and by “adjustment mechanisms” along the peptization path. Such equation may have future value in the differentiation of marine and terrestrial clay deposits.