Chemical Extraction of Heavy Metals from the Ash Using Perchloric Acid
Elementary compositions of municipal solid waste incineration (MSWI) fly ash was analyzed. In addition, influence of perchloric acid concentration and liquid to solid ratio on removal efficiency of the four heavy metals was investigated. It was found that there are 11 major elements in fly ash, with content over 1%, and content of them follows sequence of O > Ca > Si > Cl > Al > Fe > Na > S > C > Mg. These major elements account for around 97.5~98.7% of the ash. Removal ratio of Zn, Pb, Cd and Cu followed the decreasing sequence of Zn > Pb > Cd >Cu for acid extraction using perchloric acid. The optimal extraction conditions are: perchloric acid 3 M, liquid to solid ratio 30 mL liquid / 1 g ash, resulting in an extraction ratio of 89% for Zn, 85% for Pb, 41% for Cd and 32% for Cu.