title: Dynamics of polyelectrolyte adsorption and colloidal flocculation upon mixing studied using mono-dispersed polystyrene latex particles.
abstract: The dynamic behavior of polyelectrolytes just after their encounter with the surface of bare colloidal particles is analyzed, using the flocculation properties of mono-dispersed polystyrene latex (PSL) particles. Applying a Standardized Colloid Mixing (SCM) approach, effects of ionic strength and charge density of polymer chain on the rate of flocculation, the electrophoretic mobility of particle coated with polyelectrolyte, and the thickness of adsorbed polymer layer were analyzed, focusing on distinguishing features of two modes of flocculation, namely bridging formation and charge neutralization. In the case of excess polymer dosage, the bridging flocculation clearly highlights the transient behavior of polymer conformation from random-coil-like in bulk solution to increasingly flatten on the surface. The adsorption of polymer chains leads to a stagnant layer of solvent near the solid wall, which is confirmed by electrokinetic data. In the regime near optimum dosage two cases emerge. For high charge density polymer, charge neutralization is dominant and advantageous for the continuous progress of flocculation by heterogeneous double layer interaction. As a function of elapsed time after the onset of mixing, crossover from bridging to charge neutralization is found. In the case of low charge density polymer, bridging flocculation is the mechanism. Fluid mixing is concluded to have an essential role in the formation of bridges.
authors.affiliation: School of Water Conservancy, North China University of Water Resources and Electric Power, No. 36, Beihuan Road, Zhengzhou, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Feng
authors.affiliation: Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6307 HB Wageningen, The Netherlands.
authors.forename: Martien Cohen
authors.initials: MC
authors.lastname: Stuart
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba-shi, Ibaraki 305-8572, Japan. Electronic address: adachi.yasuhisa.gu@u.tsukuba.ac.jp.
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Adachi
keywords: Bridging flocculation; Charge neutralization; Colloidal flocculation; Dynamics of polyelectrolyte adsorption; Proximate stagnant layer