Studies on acid production potential of mine tailings and bioremediation of acid mine water from an abandoned indian copper mine

Abstract

Acid Mine Drainage (AMD) is a perennial problem particularly in abandoned mines, occurring due to the oxidation of sulphidic mine wastes. AMD is usually characterized by high concentration of dissolved metal ions, sulphate and low pH. The acid production potential of a typical copper mine tailings has been determined. The efficacies of substrates such as the bark of Eucalyptus tereticornis (Sm.) and red mud are assessed for the removal of metal ions such as iron, zinc and copper from acid mine water obtained from an abandoned copper mine. With respect to tree bark as an adsorbent, about 96% of Fe, 75% of Zn and 92% of Cu could be removed from the acid mine water with an attendant increase in the pH value by two units. Almost complete removal of Fe2+ (98%), Fe3+ (99%) and Cu2+ (97%) and a significant removal of Zn2+ (84%) was achieved from acid mine water at pH 2.3 using red mud. A noteworthy feature was the concomitant increase in pH from 2.3 to 7.6 with the increase in red mud loading under appropriate conditions. The free energy of adsorption of the metal ions onto tree bark and red mud is found to be negative in both the cases, while the adsorption process is exothermic for tree bark and endothermic in nature for red mud. The adsorption process is found to adhere to the Lagergren pseudo-first order rate equation. The filtrate obtained after treatment of red mud with synthetic acid mine water supplemented with carbon and nitrogen sources served as a successful growth medium for the sulphate reducing bacteria namely Desulfotomaculum nigrificans (Dsm. nigrificans) and facilitated sulphate reduction. The possible mechanisms of metal ion and sulphate removal from acid mine water using tree bark and red mud are discussed.