The effectiveness and longevity of permeable reactive barriers (PRBs) depend on the performance of the reactive materials and the subsurface environment. The relationship of the groundwater velocity on performance of coal waste for the heavy metal removal was reported in our previous study. In this study, we investigated the performance and longevity of coal waste as a PRB material for the removal of Cd considering subsurface environmental conditions such as contamination level and groundwater velocity. The artificial groundwater contaminated by Cd were prepared with various concentrations ranging from 10 to 100 mg L-1. Lab-scale column experiments were conducted using coal waste filled columns by injecting the artificial groundwater. The breakthrough curves were analyzed advection dispersion equation coupled with equilibrium sorption model to determine the retardation factor. The Cd breakthrough curves exhibited different retardation with respect to the contamination levels. The Cd transport was more retarded as the contamination level lowered. The relationship between the retardation factor and the contamination levels could be explained with empirical equations based on non-linear sorption isotherms. By adopting the velocity dependency of sorbent performance in our previous study, transport of Cd within coal waste was simulated under various subsurface environmental conditions to construct the longevity function. The function could be used for the longevity prediction of coal waste as a PRB material considering groundwater velocity and contamination level in subsurface environment.
Keywords: Cadmium; Coal waste; Contamination level; Longevity; Permeable reactive barrier; Pore water velocity.
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