Adsorption of Some Unsaturated Fatty Acid Salts on Fluorite Mineral — Effect of Temperature

Abstract

The adsorption of some fatty acid salts on fluorite mineral was investigated as a function of temperature. These fatty acids differed in their hydrocarbon chain configuration. The adsorption isotherms were characterized by three distinct regions: region I which occurred at lower equilibrium concentration (< 100 mg/l) where the adsorption density increased at elevated temperature as the number of double bonds increased in the fatty acid; region II where the adsorption density increased sharply due to the surface precipitation of calcium carboxylate; and region III where a decrease in adsorption density was exhibited as the equilibrium concentration reached the CMC of the soaps. The oxidative effect of temperature on the double bond appeared to be the reason for the polymerization of the soap species on the mineral surface which led to the increase in adsorption in region I. The effect of temperature on adsorption in region II could be related to the relative solubility of the precipitated calcium salt of each soap and micelle formation in region III was also affected by temperature which caused a decrease in CMC formation at elevated temperatures.