Remediation of a clay soil contaminated with phenanthrene by using MgO and forced carbonation

Abstract

[EN] BACKGROUND The Stabilization and Solidification (S/S) technique is one of the most cost-effective, low-risk, and efficient remedial technologies for contaminated soils. In this research, the effect of MgO (Magnesium Oxide) on the remediation of a clay soil contaminated with phenanthrene with and without forced carbonation was studied by the S/S method. The effects of various parameters in reducing the mobility and leaching of phenanthrene were considered, including the percentage of MgO and curing time with and without forced carbonation, as well as the duration of carbonation. RESULTS The results of the leaching tests showed that by using 5% MgO, the initial concentration of phenanthrene (32.7 mg kg(-1)) is changed to 9.16, 5.77, and 5.1 mg kg(-1) for curing times of 7, 14, and 28 days. In addition, for the mixture of contaminated soil with 0.25% MgO and by using forced carbonation, the initial concentration is changed to 7.9, 4.3, and 3.73 mg kg(-1) after 4, 8, and 24 h of injection of CO2. The S/S mechanisms for the removal of phenanthrene from soil include immobilization, adsorption, and encapsulation mechanisms. These stages are dependent on the hydration products of MgO. CONCLUSION A comparison of the results of the leaching tests without and with forced carbonation showed that forced carbonation can reduce the concentration of phenanthrene in a few hours with a small percent of MgO compared to the case without forced carbonation. Therefore, forced carbonation provides a cost-effective method for the remediation of contaminated soil.