Electrophoretic mobility of poly(acrylic acid)-coated alumina particles

The effect of poly (acrylic acid) (PAA) adsorption on the electrokinetic behavior of alumina dispersions under high pH conditions was investigated as a function of polymer concentration and molecular weight as well as the presence, concentration and ion type of background electrolyte. Systems of this type are relevant to nuclear waste treatment, in which PAA is known to be an effective rheology modifier. The presence of all but the lowest molecular weight PAA studied (1800) led to decreases in dynamic electrophoretic mobility at low polymer concentrations, attributable to bridging flocculation, as verified by measurements of particle size distribution. Bridging effects increased with polymer molecular weight, and decreased with polymer concentration. Increases in background electrolyte concentration enhanced dynamic electrophoretic mobility as the polymer layers were compressed and bridging was reduced. Such enhancements were reduced as the cation was changed from K+ to Na+ to Cs+.

Change in electrophoretic mobility of poly(acrylic acid)-coated and bare alumina particles with electrolyte concentration.Figure optionsDownload high-quality image (80 K)Download as PowerPoint slideResearch highlights
► Dynamic and steady state (dc) electrophoretic mobility of PAA coated colloidal alumina.
► Variables: PAA molecular weight (MW) and concentration; salt concentration and type.
► All but lowest MW reduces dynamic electrophoretic mobility due to bridging.
► Same enhancement in surface charge independent of PAA MW.
► Bridging influenced by cation type (Na+, K+, Cs+) at high ionic strengths.