Abstract
This study presents an experimental investigations undertaken to evaluate the effect of two
extractant solutions (EDTA- Na2 and/or citric acid) and different conditions (pH, extractant
concentration, and contact time) on the removal efficiency. Iraqi silty soil are studied, the soil was
artificially contaminated with lead (Pb), copper (Cu) and zinc (Zn) to achieve higher levels of
contamination.
A series of batch experiments were conducted to determine the removal efficiency of lead, copper,
and zinc using EDTA- Na2 and/or citric acid. The influence of solution pH, extraction time, and
extractant concentration were studied in order to evaluate the optimum condition for soil washing
process.
The feasibility of soil washing method for decontamination of soil was evaluated in laboratoryscale
batch experiments. Soil samples containing 500 mg/kg of Pb, Cu, or Zn were subjected to
ethelenediaminetetraacitic acid disodium salt (EDTA- Na2) and/or citric acid (CA) treatment. Soil
washing experiments performed on 2.0 g portions of the spiked soil using (0.001, 0.005, 0.01, 0.05,
and 0.1M) chelating agents at a solid:liquid ratio of 1:10 showed that extraction efficiency of
EDTA-Na2 was much higher than that of citric acid, and higher concentrations of complexing agent
lead to better extraction. Results show that EDTA-Na2 was better in releasing soil-bound metals
from the soil compared to citric acid where 67.13% of lead was extracted using 0.1M of EDTA-Na2
while only 36.5% was extracted using the same concentration of CA. Up to 51.48% of copper was
extracted using EDTA-Na2 while only 24.86% was extracted using CA. similar results appear for
zinc, where 44.2% was extracted using EDTA-Na2 and 16.73% was extracted using CA.
The highest extraction values of lead can be observed at pH values from 4 to 5 , copper at pH= 8
and zinc at pH = 9.
