DESORPTION OF LEAD, COPPER AND ZINC FROM IRAQI SILTY CONTAMINATED SOIL

Abstract

This study presents an experimental investigations undertaken to evaluate the effect of twoextractant solutions (EDTA- Na2 and/or citric acid) and different conditions (pH, extractantconcentration, and contact time) on the removal efficiency. Iraqi silty soil are studied, the soil wasartificially contaminated with lead (Pb), copper (Cu) and zinc (Zn) to achieve higher levels ofcontamination.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, andextractant concentration were studied in order to evaluate the optimum condition for soil washingprocess.The feasibility of soil washing method for decontamination of soil was evaluated in laboratoryscalebatch experiments. Soil samples containing 500 mg/kg of Pb, Cu, or Zn were subjected toethelenediaminetetraacitic acid disodium salt (EDTA- Na2) and/or citric acid (CA) treatment. Soilwashing 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 ofEDTA-Na2 was much higher than that of citric acid, and higher concentrations of complexing agentlead to better extraction. Results show that EDTA-Na2 was better in releasing soil-bound metalsfrom the soil compared to citric acid where 67.13% of lead was extracted using 0.1M of EDTA-Na2while only 36.5% was extracted using the same concentration of CA. Up to 51.48% of copper wasextracted using EDTA-Na2 while only 24.86% was extracted using CA. similar results appear forzinc, 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= 8and zinc at pH = 9.