FIRST-ORDER AND SECOND-ORDER KINETICS APPROACHES FOR MODELING THE TRANSPORT OF COLLOIDAL PARTICLES IN POROUS-MEDIA

We present results from experiments on the migration of inorganic colloids through laboratory columns containing clean quartz sand. Particle retention on the quartz collectors was found to be substantially less in experiments using negatively charged silica (SiO2) colloids than in experiments using positively charged anatase (TiO2) or boehmite (AlOOH) colloids. Analysis of these data with respect to two different advection-dispersion models indicates that deposition of colloidal silica follows a first-order, reversible kinetics process, while deposition of both anatase and boehmite is more closely depicted by second-order kinetics. Fitted values of the rate constant used to describe particle attachment vary consistently with the mean grain size of the sand and, for anatase and boehmite, are within a factor of 2 of the values predicted on the basis of colloid filtration theory.