Neutralization of acid mine drainage by Turkish lignitic fly ashes; Role of organic additives in the fixation of toxic elements

Lignitic fly ashes from two power plants in western Turkey were employed to neutralize the Acid Mine Drainage (AMD) effluents originating from a pyritic ore from northern Turkey. The AMD was rich in heavy metals with a pH of about 2. The fly ash samples, on the other hand, showed strong alkalinity when mixed with water. The product was an aggregate with basic reactivity in most cases. The fly ashes were able to neutralize large amounts of AMD. When the aggregate was placed in water, notable leaching of toxic metals into solution was observed. When an organic additive, waste motor oil in this case, was added during the mixing step, the leaching of metals into water from the resulting aggregate was practically zero.