title: Particulate hematite diffusion in sodium polyacrylate solutions. The effect of ionic strength.
abstract: The diffusion coefficients of hematite particles in polyelectrolyte solution have been investigated using dynamic light scattering. Two apparent diffusion coefficients, a fast and a slow diffusional mode, are observed for the hematite particles in high-molecular-weight sodium polyacrylate solution at pH 10.5. The slow diffusion coefficient (Dslow) shows a decrease with increase in polyelectrolyte concentration. The fast diffusion coefficient (Dfast) shows an increase to a maximum with increasing polyelectrolyte concentration and then a rapid decrease as the polyelectrolyte concentration increases further. With an increase in ionic strength from 10(-4) to 0.1 M NaNO3, the maximum value of Dfast increased in magnitude, while the polyacrylate concentration at which the maximum occurs is seen to increase. The dependence of Dfast on the measurement angle indicates that it is coupled to the fluctuations of the chains. The observed behavior is attributed to the hematite probe particle sensing both macroscopic (viscous) and elastic fluctuations associated with the polyelectrolyte motion.
authors.affiliation: CRC for Bioproducts and Particulate Fluids Processing Center, Department of Chemical Engineering, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors.forename: Kristen E
authors.initials: KE
authors.lastname: Bremmell
authors.forename: David E
authors.initials: DE
authors.lastname: Dunstan
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Scales
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Healy
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D004058:Diffusion; D005290:Ferric Compounds / Q000737:chemistry*; D005427:Flocculation; D009994:Osmolar Concentration
chemical_list: D000180:Acrylic Resins; D005290:Ferric Compounds; C000499:ferric oxide; C006903:carbopol 940