Leaching of Metals from Fly Ash–Amended Permeable Reactive Barriers

Abstract

One potential beneficial reuse of high-carbon-content (HCC) fly ashes is in reactive barrier applications for remediation of contaminated groundwater. However, leaching of metals from coal fly ashes into the environment is of concern. A series of column leach tests (CLTs) and batch water leach tests (WLTs) were performed to investigate the potential leaching of metals from HCC fly ashes during reactive barrier applications. Fly ash content and pH were two key factors affecting the amount leached in WLTs. Leaching of metals in CLTs exhibited a first flush, followed by a tailing elution pattern, for all fly ashes. Attempts to correlate the WLT and CLT data indicated that scale-up of the WLT results to the column experimental setup provided a better prediction of the leachable amount in CLTs compared with a direct comparison of concentrations. Nevertheless, caution should be exercised when building correlations because of the different testing conditions in the two test setups.