ADSORPTION OF ACID MINE DRAINAGE METALS ON FLY ASH

Abstract

Fly ash (FA), fluidized bed ash (FBA), and hydrated fly ash (HFA) were assessed for their sorptive properties of metals from acid mine drainage (AMD). Metals in sulfuric acid solutions at different pH conditions were equilibrated with fly ash for varied detention time. Preferential adsorption studies were conducted with respect to six major metals that were found in AMD: iron, manganese, zinc, aluminum, magnesium, and calcium. Comparison of the three fly ashes indicated that all had excellent sorptive properties. However, in the case of the most acidic solution (pH=1), no significant adsorption occurred. After the solution had dropped below a certain pH, adsorption decreased dramatically and release of metals into solution began. Among the six metals, iron seemed to be preferentially adsorbed on fly ash; the adsorption of calcium was not observed. Results indicated that pH was a very significant factor for the adsorption of metals on the fly ash surface. Data obtained from the use of real AMD samples for fly ash treatment were in agreement with experimental observations. Comparison of fly ash with two clays for sorptive properties revealed that fly ash was the best alternative for treatment of acid mine drainage. Treatment of AMD with clay resultedmore » in solutions of low pH and high concentrations of cations in solution.« less