Immobilization of Metal Ions from Acid Mine Drainage by Coal Bottom Ash

The removal of Cu(II), Zn(II), Mn(II), and Fe(II)/Fe(III) from acid mine drainage by using coal bottom ash was investigated at pH 4.2. Metal ion sorption, measured as amount of metal ion sorbed per gram of coal bottom ash (mg/g), was strongly influenced by the L/S (liquid-to-solid ratio), contact time, and equilibrium metal ion concentration. Metal ion sorption increased with increasing contact time as well as the equilibrium metal ion concentration and eventually reached a steady value. Sorption of a particular metal ion from a multi-component solution onto coal bottom ash was always lower as compared to sorption from the single-component solution due to the effect of competing ions. Batch sorption of metal ions onto coal bottom ash followed pseudo-second-order kinetics, while the sorption isotherm followed the Langmuir isotherm model. Removal of metal ions from single- and multi-component metal ion solutions by coal bottom ash followed the sequence: Fe(II)/Fe(III) > Cu(II) > Mn(II) > Zn(II).