Factors affecting the association of fatty acids with mineral particles in sea water

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Certain factors influencing the incorporation, transport and release of fatty acids by clay minerals, calcite and marine sediments have been investigated. Salinity was found to be an important factor. The adsorption of heptadecanoic acid by bentonite clay at 4%. was nearly triple that at 0%.. However, from 4%. to 35%., only a minor adsorption increase occurred. This behavior is believed to be related to flocculation of the clay at the lower salinity range. The pH over the range of 6.0-8.5 has a small influence on fatty acid-clay association, depressing it somewhat as the basicity increases. When the temperature of the fatty acid solution was increased from 0°C to 50°C, a decrease in adsorption on to clay was found. This effect may be due to increased water solubility of the acid at higher temperatures, since solubility is very important in controlling the degree of fatty acid-mineral interaction. Furthermore, apparent solubilization of fatty acids by indigenous dissolved organic matter in sea water reduces adsorption on to clay minerals. Based upon the heat of adsorption of -14.6 kcal/mole, fatty acids are physically bound to clay minerals by weak van der Waals forces and hydrogen bonds. Bentonite and kaolinite were found to be the most adsorptive minerals investigated, followed in order by illite, montmorillonite and calcite. Sediments from Narragansett Bay were found to lie between illite and montmorillonite in adsorptive capacity after indigenous sediment organic matter had been removed. Sediment organic matter reduced fatty acid uptake by a factor of 1.6. © 1973.

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Geochimica et Cosmochimica Acta