The adsorption of gold sols on asbestos surface charge sites

Abstract

The adsorption of gold sols on the surface of amosite and chrysotile asbestos has been investigated under a series of different conditions. The gold sols had diameters near 300 Å and their negative charge was measured by an electrophoresis technique. Asbestos fibres were added to sol solutions with pH from 5.0 to 6.8 and the location and density of the deposited sols were determined by electron microscopy. Per cent surface area coverage by sols ranged from 11 to 4% for amosite and 27 to 3% for chrysotile. The surface coverages were interpreted to give the amount and location of the surface charges for the asbestos fibres as a function of solution pH. The results were also correlated with the surface ion impurities as measured for the asbestos samples (reported here) and the zeta potentials for similar asbestos (as reported elsewhere). In general, it is concluded that for chrysotile, which has a positive zeta potential, the negative sols are attracted to Mg 2+ or impurity cation sites on the brucite surface layer. On the other hand, since amosite and the sols both have negative zeta potentials, a specific adsorption mechanism possibly involving Fe 3+ ions on the amosite surface is required. These results were compared with predictions of a current calculation of charged surface interactions in an electrolytic solution [1].