Effects of Different Cations on the Flocculation and Sedimentation of Static Fine-Grained Sediments

Natural water bodies mostly contain cations, and the type and content of these cations are the main factors affecting the flocculation of fine-grained cohesive sediments and the floc sedimentation rate at the interface between clear and turbid water. From the microscopic aspect, this study examined the changing patterns of porosity and the fractal dimension of the flocs of fine-grained cohesive sediments. Sedimentation experiments under different sediment contents and electrolyte conditions were conducted, and microscopic images of the flocs were analysed using Image-Pro Plus (IPP) and MATLAB based on the fractal theory. From the macroscopic aspect, this study experimentally investigated the flocculation and sedimentation of fine-grained cohesive sediments and proposed a sedimentation rate equation by introducing an ion concentration-related parameter into an existing sedimentation rate equation (stagnation zone) based on the adsorption isotherm equation. The equation proposed in this study was validated with measured data. The calculated values were in good agreement with the measured values, with a relative error of 16%. The findings of this study provide a reference for further research on the flocculation and sedimentation of fine-grained cohesive sediments in different water bodies.