A Unified Model to Predict Electrophoresis in Porous Media and Free Electrolytes

Abstract Current theories of electrophoresis have focused on a free concentrated or dilute electrolyte in the absence of porous media, or porous media saturated with a dilute electrolyte. A predictive model for electrophoresis in porous media saturated with a concentrated electrolyte is lacking. Here, a mathematical model is developed to compute the electrophoretic mobility of a charged colloid in porous media saturated with a concentrated electrolyte. The model is unified in that it can also predict electrophoresis in porous media saturated with a dilute electrolyte, as well as electrophoresis in a free concentrated or dilute electrolyte. Three novel key findings are reported. First, without fitting parameters, the present model captures the electrophoretic mobility sign reversal in a free monovalent electrolyte reported in recent experiments. Second, the present model captures the electrophoretic mobility from experiments with porous media saturated with a concentrated or dilute electrolyte. Third, the present model predicts a novel electrophoretic mobility sign reversal in porous media saturated with an electrolyte. The present model can be used to understand and predict electrophoresis in a wide range of applications, including gel electrophoresis, nanoparticle drug delivery, and soil remediation.