Influence of Acid Rain on the Release Characteristics of the Heavy Metals in Coal Ash

The release characteristics of Cd, Pb, Mn, Cu and Zn from coal-ash are investigated by the simulated acid rain. The soaking and leaching experiments were performed to test the heavy metals sensitivity to acidity and the releasing potential in different pH and time conditions. The heavy metals release content was measured by atomic fluorescence spectroscopy (AFS). The release ratio was calculated and the release mechanism was analyzed further. The results show the most release ratio of the heavy metals is increased with pH value decreasing. Its order is Cd>Cu>Zn>Mn>Pb. With the time increasing the release can reach peak value, and the time to reaching peak value is shorten when the acidity is increased; The heavy metals sensitivity to acidity is different, the order is Pb> Cd>Cu>Mn>Zn. It should be given a concern for the heavy metals release from the coal ash in acid rain severity region.