The Society of Rheology 87th Annual Meeting

October 11-15, 2015 - Baltimore, Maryland


Poster Session

Optimal polyelectrolyte assembly in solution using macro and microscale flows

October 14, 2015 (Wednesday) 6:05

Poster Session / Atrium/Harborview

(Click on name to view author profile)

  1. Wilkinson, Nikolas (University of Minnesota, Chemcial Engineering)
  2. Ruud, Eric (University of Minnesota, Mechanical Engineering)
  3. Dutcher, Cari (University of Minnesota, Mechanical Engineering)

(in printed abstract book)
Nikolas Wilkinson1, Eric Ruud2, and Cari Dutcher2
1Chemcial Engineering, University of Minnesota, Minneapolis, MN 55455; 2Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455

Wilkinson, Nikolas

Water-soluble polymers with ionizable groups, or polyelectrolytes, are used in a number of applications due to the polymers unique ability to form mesoscale structures in solution. There are a number of known potential mechanisms for the mesoscale solute assembly, including charge neutralization, polymer depletion, polymer bridging, polymer adsorption, and patch flocculation, but the impact of time-dependent chemical and hydrodynamic conditions on assembly kinetics and final microstructure still remains largely uncertain. We seek to improve understanding of the dynamics of particle-particle, polymer-polymer, and polymer-particle interactions in complex aqueous solutions, and in complex hydrodynamic flows. Here, we explore assembly dynamics using cationic polyacrylamide, a polymer commonly used in water treatment. Particles used in this study include monodispered PS beads as well as more complex bentonite clays, ranging in size from 0.015 μm to 2 μm. For the inorganic clay systems, we present surprising evidence that the zeta potential of the bentonite clay has no direct effect on flocculation performance. Instead, we find that the solution pH controls flocculation performance indirectly through influencing bentonite particle size and structure prior to polymer injection. Likewise, we show that ionic strength effects optimal polymer dosing concentrations and turbidity reduction, via kinetic trapping of the initial clay morphology and size. Solutions were studied with a pH varying from 3 to 11, with a three-fold change in zeta potential, and over 4 orders of magnitude in ionic strength. This work sheds more light on the complexities of polymer flocculation, towards improving dosing and treatment optimization for more efficient water treatment. For the beads, we use microscopy to explore fundamental particle-particle and particle-polymer assembled structures with negatively charged polystyrene microbeads.