Effects of microwave radiation on extraction of heavy metals from sludge by organic acids leaching

The effects of radiation time, power and energy on microwave-assisted extraction of heavy metals from sewage sludge by using HEDTA and oxalic acid were investigated. The heavy metal fractions in raw and extracted sewage sludge samples were analyzed by the application of tessier´s sequential extraction procedure. The results showed the concentration of extractable fraction of Cu, Ni and Cr in sludge were increased by the increasing of microwave time, power intensity and energy density and the extractable fraction of Zn has no obvious improvement. After the microwave-assisted chemical extraction procedure, the contents of organic fraction of Cu, Cr and Ni were decreased. However, the contents of exchangeable and carbonate fractions were slightly increased; the speciation of Zn in sludge was hardly changed.