Removal of Heavy Metals from Contaminated Soils by Washing with Citric Acid and Subsequent Treatment of Soil-Washing Solutions

Soil washing experiments were carried out with citric acid as washing reagent for the remediation of soils highly contaminated with heavy metals, then activated carbon was used in absorption processing for leaching solution. In this study, the effects of the main operating variables for removal of metals from soils were first discussed. The results showed that 36.% Pb, 47.74% Cu and 61.88% Cd were removed from the contaminated soils by optimizing the washing parameters at citric acid concentration 0.2 mol/l, mixing time 2 h, liquid-soil ratio 20 and solution pH=4, respectively. In the adsorption experiments of leachates, the optimum conditions were found as follows: solution pH=7, mixing time of 2 h, standing time of 60 min and activated carbon dosage of 1g/100ml.