Dynamics of Silica Colloid Deposition and Release in Packed Beds of Aminosilane-Modified Glass Beads

Abstract

The transport and deposition dynamics of colloidal particles in packed porous media were investigated. The colloids were negatively charged silica particles (0.1 and 0.3 μm in diameter), and the packed-bed columns comprised aminosilane-modified glass beads. The glass beads acquired a positive surface charge by anhydrous chemical reaction with aminoethyl(N-aminopropyl)dimethoxymethylsilane. Maximum attainable surface-coverage (θmax) and excluded-area-parameter (β) values were determined for particle deposition experiments under various physicochemical conditions, namely, solution ionic strength, flow velocity, and particle size. The results demonstrated that excluded-area-parameter values increased with decreasing ionic strength and increasing flow velocity and particle size. Observed excluded-area-parameter values smaller than 1.83, the hard-sphere jamming limit according to random-sequential-adsorption (RSA) mechanics, alluded to the occurrence of multilayer deposition. The release of deposited particles after complete breakthrough was also investigated by reducing the ionic strength of the solution and by reversing the collector surface charge with an anionic surfactant (sodium dodecyl sulfate). Because colloid release was predominantly observed following deposition runs with higher values of surface coverage, which suggested the possible presence of multilayer deposition, it could be inferred that particle−particle repulsion was mainly responsible for the observed colloid release.