Treatment of Acid-Mine Water with Calcite and Quartz Sand

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Abstract
This study investigates interactions between a typical acid-mine water and a solid mixture of calcite and quartz. In this solid mixture, calcite provides a source of alkalinity whereas quartz surfaces become preferable place for precipitation of produced oxides. The results indicate that neutralization by calcite dissolution is critical for extensive immobilization of metals from these waters. As pH increases, ferrihydrite, amorphous Al(OH)3, Cu(OH)2, and possibly Zn(OH)2 precipitate that decreases the aqueous concentrations of Fe, Al, Cu, and Zn. These precipitates also provide more adsorption sites for metal ions. Under the experimental conditions used in this study, Pb sorption was stronger than either Cd or Zn. The presence of ferrihydrite increased Pb and Cd adsorption significantly. Cd was most mobile with respect to the other metal ions studied. Besides metal ions, SO42− is also adsorbed onto oxide surfaces to some extent. An unknown sulfate mineral was present when the mine water lacked dissolved Fe or was not neutralized by calcite. The mineral is likely a Cu and/or Zn sulfate with structural H2O. Key words: Acid mine; treatment; quartz; calcite