Evaluation of waste materials for acid mine drainage remediation

Laboratory scale tests were conducted to assess the efficiency of two different types of waste materials to remediate acid mine drainage (AMD). The waste materials used in the current study were recycled concrete aggregates (RCAs), and fly ashes. Four different RCA materials and three different fly ash materials were evaluated. Column leach tests (CLTs) were conducted to determine the effects of the remediation materials on pH, electrical conductivity, alkalinity, oxidation reduction potential (Eh), and concentrations of sulfate (SO42−), chromium (Cr), iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in AMD. Results of the CLTs suggest RCAs and one of the highly alkaline fly ash can effectively raise pH of the AMD and reduce concentrations of Cr, Cu, Fe, Mn, and Zn in AMD. In addition, sulfate concentrations of AMD decreased significantly after being treated by RCAs while sulfate concentrations of the AMD increased when it was remediated by fly ashes. It is speculated that leaching of sulfate from fly ash samples during treatment may decrease the metal sorption capacity of fly ashes. X-ray fluorescence spectroscopy quantified the impact of CaO and loos on ignition (LOI) in the remediation materials on sorption capacity of metals from the AMD. Sorption capacity for Cr, Cu, Fe, and Zn was found to be greater in materials with high CaO and LOI content, and low unburned carbon.