Abstract: In this paper, batch experiments were made to examine the effects of different EDTA concentrations, pH, and washing duration of EDTA on the removal of heavy metals from contamina-ted soil. An empirical model was employed to describe the kinetics of heavy metals dissolution and desorption, and the form changes of test heavy metals were determined before and after EDTA wash-ing. The results showed that EDTA was effective to the removal of heavy metals from contaminated soil. At 0.1 mol·L^-1 and pH 7 of EDTA and within 24 h, the removal rate of test heavy metals was the maximum, being 89.14% for Cd, 34.78% for Pb, 14.96% for Cu, and 45.14% for Zn. The mass transfer coefficient was in the order of Cd>Zn>Pb>Cu. Sequential fractionations of treated and untreated soil samples showed that EDTA was effective in removing the exchangeable, carbonate and oxide forms of Cd, Pb, Zn and Cu, but ineffective for the organic and residual forms of test heavy metals.

Key words: Amomum villosum, Tropical forest, Secondary forest