Utilization of Coal Fly Ash for Remediation of Metal Contaminated Soil in Mining Sites

By using a hydrothermal treatment process, coal fly ash was transferred to a series of synthesized zeolites and characterized XRD and SEM observations. The synthesized zeolites exhibited more enhanced adsorption capacities for metals compared to the raw material as the increased CEC of the synthesized zeolites apparently provides a better adsorptive ability for metals. For the three synthesized zeolite amendments, ZFA I shows the best adsorption capacity for metals, followed by ZFA II and ZFA III. Soil amendment with coal fly ash and the synthesized zeolites from the fly ash reduced the leaching of Cu, Zn, Ni, Cd, Cr, and Pb effectively from contaminated soil in laboratory batch experiments. During the column experiment, the leaching amount of all the studied metals kept under a lower level below the TCLP limiting values, and remained constant, indicating that the synthesized zeolites can significantly reduce the leaching of metal pollutants from contaminated soil into groundwater even under the acid rain condition. Coal fly ash was proved a promising agent for in situ remediation of metal contaminated soil.