Modelling colloid adsorption in porous media

Abstract

Accurate knowledge of the processes that control the transport and deposition of colloids in subsurface environments is needed to protect water resources from a wide variety of contaminants. Applied hydrodynamics can play a significant role in colloid retention but is not yet fully understood. In this thesis, the effect of pore shape and velocity on colloid attachment and detachment is researched by performing single pore simulations in MATLAB. The model is based on the geometry of a parabolic constricted tube and simulates a fluid flow through this pore. Firstly, the model was run with only two changed parameters: the constriction radius and the velocity through the chokepoint (μ). The speed is changed from low (0.3e-6 m/s) to average (1.5e-6 m/s) to high (3e-6 m/s). Each speed is run with three constriction radii: small (0.02e-3 m), average (0.15e-3 m) and straight (0.3e-3 m). The results from the 9 (3x3) model runs are grouped and plotted together for colloid attachment vs constriction radius and colloid attachment vs velocity. Secondly, a comparison is made between increasing velocities (3e-6 m/s, 6e-6 m/s, 12e-6 m, 30e-6 m/s, 60e-6m/s and 120e-6 m/s) and colloid retention. I conclude that colloid attachment and detachment is indeed affected by pore shape geometry and applied hydrodynamics. The effects are strongest at the extremes: no adsorption in straight pores and high adsorption in narrow pores. During average constriction radii the effect is the lowest. Further research (based on the model and conclusions of this study) increases our understanding and have a potentially substantial impact on a wide spectrum of subjects, from medicine to water treatment.