Evaluation of Zeolite/Backfill Blend for Acid Mine Drainage Remediation in Coal Mine

Brazilian coal exhibits high ash and sulfur content, making it more susceptible to acid mine drainage (AMD). Furthermore, combustion of this coal generates a significant amount of ash containing amorphous silicon and aluminum oxides, allowing alkaline hydrothermal processing of this waste via zeolites. These versatile compounds have been suggested as an alternative material for AMD remediation. This study aims to evaluate the use of zeolite Na–P1 in backfill blends for application in coal mines. Laboratory scale leaching experiments were performed, and several techniques (major and trace elements, pH, and conductivity) were monitored over time, in order to assess AMD remediation and the mobilization of ions in leachates using different zeolite/tailing blends. The results indicate that the addition of zeolites, obtained from coal ash, promotes the remediation of metal content in water generated by AMD and is therefore a more beneficial process in the removal of metal ions. With regard to the 50:50 backfill/zeolite blend, reductions of 100, 98, 39, 55, 94, and 41% were observed in aluminum, iron, calcium, magnesium, zinc, and manganese content, respectively, after 7 days of leaching. The increase in pH caused by zeolite addition promoted the precipitation of both metal ions and sulfate ions. The addition of 50% or 25% of zeolite in the backfill sample increased pH from 2.36 to 8.38 or 4.66, respectively, over a leaching period of 7 days