Ultramicroscopic studies of stabilization of mixed FeOOH-ZrO2 dispersions by heteroadagulation

Flow ultramicroscopy was used to study heterocoagulation in a mixed FeOOH-ZrO 2 dispersion under conditions close to the point of zero charge of both components (pH 7). The studies were performed in a wide concentration range of the background electrolyte (NaCl). Time dependences of the degree of particle aggregation in the mixed dispersions were measured at various ratios between the components. The FeOOH dispersion that was initially unstable with respect to aggregation is stabilized due to heteroadagulation of the stable (with respect to aggregation) fine ZrO 2 particles (less than 100 nm in size) on the surface of the larger (300 nm) FeOOH particles. The results are explained by the existence of developed boundary layers of water at the surfaces of ZrO 2 particles.