ION-EXCHANGE ON MUSCOVITE MICA WITH ULTRAHIGH SPECIFIC SURFACE-AREA

Ion exchange in aqueous solutions on a novel, colloidal ultra-high specific surface area muscovite mica was studied with organic ions. N -dodecylpyridinium chloride (NDP), 2,2′-azobisisobutyramidine hydrochloride (AIBA), and methylene blue in addition to potassium chloride were the salts employed. The extent of ion exchange was determined by UV and ion chromatographic analysis of the supernatant solutions. The results were analyzed in terms of an ion exchange equilibrium model which was fitted to the data. The density of ion exchange sites found with AIBA, NDP, and potassium were all similar (in the range 3.8-4.3 μeq/m2) and in agreement with that expected from the muscovite crystal structure (3.5 μeq/m2). The density of ion exchange sites found with methylene blue was significantly less (2.5 μeq/m2) and this is attributed to incomplete ion exchange because of the large size of the methylene blue ion. The results have implications for the determination of mineral specific surface areas by ion adsorption methods. © 1993 Academic Press, Inc.