Simultaneous removal of polycyclic aromatic hydrocarbons and copper from soils using ethyl lactate-amended EDDS solution.

A new approach using aqueous ethyl lactate-modified [S,S]-ethylenediaminedisuccinic acid (EDDS) washing solutions was examined in the laboratory for the simultaneous removal of phenanthrene, pyrene, and Cu from contaminated soils. Ethyl lactate demonstrated greater solubilization efficiency for phenanthrene and pyrene than ethanol. Thus ethyl lactate has a great potential for extracting polycyclic aromatic hydrocarbons (PAHs) from contaminated soils. For soils with varying properties, removal efficiencies were found to be negatively correlated with soil organic carbon contents. Aqueous EDDS solution effectively extracted Cu from soils. The extraction efficiency reached about 36.7% at a EDDS:Cu molar ratio of 5. The addition of ethyl lactate in EDDS solution (EDDS/Cu molar ratio = 2) efficiently enhanced the extraction of the PAHs and also significantly increased the Cu removal from 34.8 to 42.9%. The latter was mainly attributed to the fact that ethyl lactate increases the stability constant for Cu-EDDS complexes, hence shifting the degree of desorption of Cu from soil. Sequential extraction indicated that the EDDS/ethyl lactate solution extracted Cu primarily from the acid extractable fraction, the reducible fraction and the oxidizable fraction. The results suggest that simultaneous removal of PAHs and heavy metals from contaminated soils is feasible by soil washing using an aqueous EDDS solution enhanced with ethyl lactate.