SOME PHYSICOCHEMICAL PROPERTIES OF THE CHROMIUM(III) HYDROUS OXIDE AQUEOUS-SOLUTION INTERFACE

The surface properties of polydispersed chromium(III) hydrous oxides prepared from chrome alum (CrK(SO4)(2).12H(2)O) and NaOH solutions were studied in aqueous solutions using acid-base potentiometric titrations and stability measurements. The effects of sulfate ions on the acid-base and coagulation behavior was also investigated. The studied materials show high ion and water absorption capacity. The specific interaction of sulfate ions present in the electrolyte (KNO3 or NaClO4) solution decreases both the intersection point of the titration curves performed at different electrolyte concentration and the stability of dispersions in acidic media. On the other hand, sulfate ions located in the particles' bulk coordinating Cr(III) centers also diminish the intersection point but do not change the stability-pH behavior of the samples. The properties of the polydispersed materials resemble those of monodispersed polymeric Cr(OH)(3) samples. (C) 1995 Academic Press, Inc.