Impaction of EDTA on the engineering properties of heavy metal contaminated soil

To provide the reference for secondary utilization of the heavy metals contaminated soil washed by EDTA (Ethylene Diamine Tetraacetic Acid), batch tests are conducted to determine the permeability, water holding characteristics, deformation characteristics, and shear strength of lead contaminated soil after washing remediation by EDTA with different concentrations. And X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) tests are conducted to reveal the mechanism of changes on the engineering characteristics. Results show that pH of the washes soil decreases from 7.94 to 5.12, hydraulic conductivity decreases by more than one order of magnitude, cohesion reduces by more than 50% and void ratio decreases from 0.813 to 0.764 as the concentration of EDTA increased from 0 to 0.15 mol/L, but the internal friction angle and water holding capacity increase. XRD test results show that the mineral content of montmorillonite (from 7.87% to 0.07%), illite, albite decrease and quartz increases by 11.09%. MIP test results show that the total void volume reduces as the concentration increasing, and the amount of intrudes mercury per unit mass decreases from 0.22 ml/g to 0.15 ml/g. Research results indicate that it is imperative not only considering about the removal rate of heavy metals in soil and economic index of the remediation engineering, but also the weaken soil engineering properties brought by the process of washing remediation.