Abstract: Abstract:Batch experimentation was conducted to investigate the washing effect of a chelating surfactant, sodium N-lauroyl ethylenediamine triacetate (LED3A), on Pb and Zn co-contaminated soils. The influences of washing time, LED3A concentrations and washing temperature on washing efficiency and changes of metal speciation in the soil before and after LED3A elution were investigated. The results showed that LED3A could effectively remove Pb and Zn at 7.0 g/L of LED3A within 7.0 h. The time to reach equilibrium was shortened with the increase of initial LED3A concentrations. The washing processes could be well fitted by the pseudo-second-order kinetic equation. The results of the intra-particle diffusion model implied that the overall rates of Pb and Zn desorption were controlled by pore diffusion, and intra-particle diffusion was not the only rate-limiting step. The isothermal equilibrium washing experiments indicated that high temperature was conducive to the coordination of LED3A with heavy metal, and desorption of Pb and Zn was an endothermic process. By analyzing the data of metal speciation before and after washing, the washed percentages of acid-extractable, reducible, oxidizable and residual fractions of metals were as follow:Pb-79.87%, 31.82%, 18.83%, 2.30%, and Zn-72.51%, 21.81%, 17.60%, 26.22%, respectively. The percentage distributions of Pb and Zn in contaminated soil before and after LED3A washing illustrated that the mobile fractions (acid-extractable fraction) decreased and immobile fractions (reducible fraction, oxidizable fraction and residual fraction) increased. LED3A was an effective chelator for treatment of heavy metal contaminated soil, and a kind of environmentally friendly chelating reagent.