High-Carbon Fly Ash as a Reactive Medium in Permeable Sorptive Barriers: Batch and Column Experiments

There is an increasing interest in the reuse of coal combustion byproducts, such as high carbon fly ash, which is generated in large quantities as a result of equipping power plants with low nitrogen oxide burners. In this study, a laboratory investigation was conducted to evaluate the use of high carbon fly ash as a reactive medium for passive groundwater remediation applications via permeable sorptive barriers. Specifically, batch and column sorption-desorption experiments were performed using three fly ashes with a range of carbon contents, and naphthalene and o-xylene as model contaminants. Results from the batch and column tests were consistent in showing adsorption/desorption hysteresis, and a strong positive correlation between the hydrocarbon adsorption capacity and the carbon content of the fly ashes. However, the hydrocarbon adsorption capacity in the column sorption-desorption tests was overpredicted when parameters from batch tests were used in model simulations, possibly because of the limited accessibility of sorption sites in the columns compared with the batch tests. (C) 2014 American Society of Civil Engineers.