Title page for ETD etd-08042011-121649


Type of Document Master's Thesis
Author Herman, David Joel
URN etd-08042011-121649
Title Stabilization of weakly charged microparticles using highly charged nanoparticles
Degree Master of Science
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Walz, John Y. Committee Chair
Davis, Richey M. Committee Member
Ducker, William A. Committee Member
Keywords
  • Colloidal stability
  • Nanoparticle adsorption
  • Colloidal aggregation
  • Patchy adsorption
Date of Defense 2011-08-04
Availability unrestricted
Abstract
An experimental investigation was conducted to evaluate the possible use of highly-charged spherical nanoparticles to stabilize an aqueous dispersion of weakly-charged microspheres. At low pH values, the surface of silica is weakly charged, which leads to flocculation of colloidal suspensions of silica microspheres. Binary solutions of weakly charged silica microspheres and highly charged polystyrene latex nanoparticles result in adsorption of the nanoparticles onto the surface of the silica microspheres. This effectively “recharges” the silica spheres, with effective zeta potentials increased to the range that is unfavorable for flocculation of microspheres in a silica-only solution. However, this does not guarantee stability, and comparisons between positively charged amidine latex nanoparticles and negatively charged sulfate latex nanoparticles indicate that the degree of coverage plays an important role in the restabilization. The sulfate latex nanoparticles do not cover the surface sufficiently, and though they seemingly provide sufficient charge, the weakly charged patches of the exposed silica substrate can lead to flocculation. The amidine latex nanoparticles, on the other hand, cover the surface more completely, and effectively prevent flocculation of the silica microspheres. The mechanisms responsible for this different adsorption and stabilizing behavior are not entirely understood, as both the amidine and sulfate latex nanoparticles are of similar size and the magnitude of the zeta potentials of the different particle types are comparable.
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