MODIFICATION OF FILTRATION THEORY FOR TRANSPORT AND DEPOSITION OF KAOLINITE IN POROUS MEDIA

One-dimensional column experiments were performed to develop a modified filtration theory for predicting travel distance of kaolinite particles with non-uniform diameter and non-spherical shape in packed glass beads or quartz sand. Kaolinite particles were eluted actually in the column experiments, however, particles were estimated not to reach the column end according to calculation by existing filtration theory (Rajagopalan et al., 1976) assuming average diameter and spherical body of kaolinite particles. Therefore, collector efficiency in the filtration theory was redefined to reflect non-uniformity of particle diameter by dividing kaolinite diameter into several grades and considering frequencies of each fraction. Furthermore, shape factors of colloidal particles and collector were also introduced to reflect irregular shape of kaolinite and quartz sand. For kaolinite, shape factor was determined by the ratio of major axis to minor axis of particles measured by SEM images of 280 kaolinite particles. Dynamic shape factor was used as shape factor of kaolinite. For quartz sand, ratio of the average actual projected area to the projected area assuming spherical body with average diameter was defined as shape factor for quartz sand. Then, theoretical collector efficiencies from modified and existing filtration theory were compared with the experimental collector efficiencies. Results showed that there was significant difference between experimental collector efficiency and theoretical collector efficiency calculated from existing filtration theory. While, modified collector efficiency had considerably good agreement with experimental data. This meant that modified filtration theory can be used to estimate the deposition rate constant in kaolinite transport model from the characteristics of particle and medium material.