S.W. Song, L. Wang, X.X. Wang, G.C. Qi, L. Yu, J. Liu
A chemical extraction procedure for removing extractable heavy metals Zn, Cu, Cd using organic acid as extractant has been applied to wastewater sediments collected from wastewater treatment plant. The Tessier’s five-stage sequential extraction procedure for extractable heavy metals determination is applied to sludge samples. The results show that the extractable content of tested heavy metals exhibits a positive correlation with increasing acid concentration, reaction temperature and time. After the extraction process, citric acid is more efficient in removing Zn, oxalic acid exhibits higher extractability in removing Cu but inefficient in Zn and Cd. Zn removed by citric acid is mainly in stable form, resulting in a relative increase of its unstable and exchangeable form in sludge. Though the removal rate of Cu and Cd are lower, their exchangeable form has still increased after the action of tested organic acid.