Sedimentation kinetics of kaolinitic and illitic clay: Impact of cation valence, ionic concentration, and water content

Abstract

Investigating the sedimentation of clay in saline water was extensively studied because of its wide applications in engineering. This study investigated the impact of cation valence, ionic concentration, and water content on sedimentation behavior of kaolinitic and illitic clays through batch sedimentation tests for the comprehensive understanding of clay particle association and elapsed time for the transition of settling regimes from initial hindered settling to zone settling. The quantitative representation of observed settling curves was achieved using four fitted parameters in batch sedimentation model, which represented the shape of settling curves and the boundary of the initial hindered, zone, and consolidation settling regimes. In addition, the obtained settling velocity from the settling curves provided the fraction of clay particles and the size of clay flocs. The observed settling curves, trends of fitted parameters, and the estimated size of clay flocs shown in this study implied that the type of clay particle association (face-to-face aggregation or edge-to-face flocculation), settling velocity, final interface height, and boundary between initial hindered and zone settling are function of clay mineralogy, water content, cation valence, and ionic concentration.