SURFACE AND BULK CHARACTERISTICS OF BINARY OXIDE SUSPENSIONS

Coprecipitation, sequential precipitation, and agglomeration are expected events in many aquatic systems, but the properties of the mixed solids that result are not well-known. The bulk and surface characteristics of these mixed solids are fundamental parameters in determining the distribution of a variety of nutrients and pollutants in the environment. The purpose of this study was to describe the bulk and surface characteristics of binary oxide suspensions of aluminum, iron, and silicon and determine how they differ from their component parts. An array of complementary techniques was used, including particle size distribution, determination of the pH of zero charge, X-ray photoelectron spectroscopy, and measurements of the specific surface area. Batch adsorption experiments were also used to contrast the adsorption behavior of Ag, Cd, PO4, SeO3, and Zn. The results indicated that the properties of binary oxide suspensions can be different from their component parts even in a physical mixture. Particle interactions caused changes in particle size distribution, surface, charge, and the adsorption characteristics of the mixed oxides. In all of the binary mixtures that contained Al(OH)3 the surfaces were Alenriched, suggesting the aluminum oxides play an important role in determining surface characteristics in aquatic environments. © 1990, American Chemical Society. All rights reserved.