Effectiveness of alkaline amendments in acid mine drainage remediation

• Effectiveness of alkalinization for acid mine drainage neutralization.
• Calcium carbonate, calcium oxides and hydroxides is attractive in the remediation of acid mine tailing.
• Effective long term alkalization of acid mine drainage.
• Alkalinization as a promising agent for environmental protection.

Acid mine drainage (AMD) generated from pyrite oxidation in sulfide mine tailings is a major geoenvironmental problem. This AMD is characterized by pH<3.5 and high concentration of trace elements. Thus, liming is a prerequisite for sustainable stabilization and neutralization of acid-producing sulfide mine tailings. The use of agri-food waste and industrial by-products rich calcium carbonate or calcium oxides and hydroxides becomes attractive as an alternative limestone in the remediation of acid mine tailing impoundments. Addition effect of five different types of alkaline amendments into sulfide mine tailing (SMT) was studied. Two series of laboratory experiments were conducted on SMT to evaluate the use of chicken eggshell residue (CES) alone or in combination with neutralizing agents to neutralize acidity and prevent mobilization of trace elements in SMT. This study showed that tailing samples amended with cement or magnesium oxide are more highly buffered and resistant against anthropogenic re-acidification than tailing samples amended with CES, CAL or DOL. Materials rich in oxides, hydroxides and carbonates mixed with eggshells may confer to SMT long-term protection against acid atmospheric deposition or re-acidification of limed SMT. These results may have practical implications in tailing management for the reduction of acid generation and trace metal mobility in sulfide mine drainage system and of water contamination risk.