Evaluating Inter-Species Interaction in the Differential Settling of Binary Particle Suspensions

This study investigates the differential settling behavior of binary particle suspensions through a combination of theoretical modeling and batch settling experiments. A classical zone-formation differential settling model is adopted, and a comprehensive experimental program is designed to generate data for model evaluation. Batch settling tests conducted using fine copper tailings and coarse silica sands show that distinct settling zones can be identified, and the solids’ concentrations of the particle species are consistent with theoretical predictions. However, the behavior within the sediment region differs from model assumptions, as a range of solids’ concentrations is observed, suggesting the presence of a transition zone rather than a sharp transition from the hindered settling region to a sediment with maximum solids’ concentration. Experimental observations of the sediment boundary also reveal a discrepancy between theoretical predictions and measured propagation velocities. This discrepancy is attributed to inter-species interactions arising from differential settling velocities, which are not accounted for in conventional models. The results highlight the limitations of widely used differential settling models and emphasize the importance of incorporating species–species interactions and transition zone behavior to improve the prediction of settling behavior in multi-species suspensions.