Kaolinite and Lead in Saturated Porous Media: Facilitated and Impeded Transport

Laboratory experiments and mathematical modeling were used to explore the dynamics of kaolinite and Pb in water-saturated porous media. Batch adsorption experiments were used to obtain the adsorption isotherms of Pb onto kaolinite and quartz sand. Both kaolinite and sand adsorbed Pb from water, but the adsorption capacity of kaolinite was about 30 times higher than that of sand. Saturated sand columns were used to examine the transport behaviors of Pb and kaolinite. The presence of kaolinite in the saturated porous media enhanced the mobility of Pb. The presence of Pb on kaolinite and grain surfaces, however, reduced the transport of kaolinite. Additionally, an experiment in which clean kaolinite was passed through sand contaminated with Pb indicated that mobile kaolinite could scavenge the absorbed Pb from the sand surface to facilitate Pb transport. Simulations from the Langmuir model and an advective-dispersive transport model matched well with the experimental data collected from the batch adsorption and column breakthrough studies.