Overburden is the earth material removed during opencast mining, which is typically not contaminated with toxic materials. After mining operations, overburdens are dumped on exhausted mining sites. However, some opencast mines are not properly backfilled, and this causes harmful environmental effects, such as leaching of acid mine drainage. The flyash produced from thermal power plants is also a major waste that must be disposed of environmentally friendly. This study focuses on filling the voids of an abandoned mine with a mixture of 70% overburden + 30% flyash. A considerable improvement in acid mine drainage characteristics was found after either adding overburden or an overburden and flyash mixture. Sustainable management of coal mines should include the careful restoration of exhausted mines, which can be made possible by repurposing relevant industrial waste.

Acid mine drainage (AMD) occurs naturally in abandoned coal mines, and it contains hazardous toxic elements in varying concentrations. In the present research, AMD samples collected from an abandoned mine were treated with fly ash samples from four thermal power plants in Singrauli Coalfield in the proximate area, at optimized concentrations. The AMD samples were analyzed for physicochemical parameters and metal content before and after fly ash treatment. Morphological, geochemical and mineralogical characterization of the fly ash was performed using SEM, XRF and XRD. This laboratory-scale investigation indicated that fly ash had appreciable neutralization potential, increasing AMD pH and decreasing elemental and sulfate concentrations. Therefore, fly ash may be effectively used for AMD neutralization, and its suitability for the management of coalfield AMD pits should be assessed further.