Use of nanoscale zero-valent iron to improve the shear strength parameters of gas oil contaminated clay

Abstract

In recent years, the nanoscale zero-valent iron (NZVI) particles have been used successfully for the degradation of hydrocarbon<br />compounds and remediation of other pollutants. Nevertheless, as far as we know, there is no specific study on the improvement of the<br />geotechnical properties of contaminated soils with hydrocarbon compounds by NZVI. This study used NZVI particles to remove gas<br />oil in a clayey soil and determined the effects of NZVI on Atterberg limits, compaction properties, and shear strength parameters of the<br />soil. In order to determine the optimal reaction time and NZVI dosage, the total organic carbon (TOC) of a contaminated soil with 9%<br />of gas oil was measured. The experimental data showed that the optimum reaction time and NZVI dosage were 24 days and 5%,<br />respectively. Then, the contaminated samples were prepared by mixing the soil with gas oil in the amount of 0, 3, 6, and 9% by dry<br />weight. The results showed a decrease in the friction angle (φ) and an increase in the cohesion (C). Maximum dry density and optimum<br />moisture content of the soil decreased due to the contamination. In addition, an increase in liquid limit (LL) and plastic limit (PL) were<br />observed. Finally, all contaminated specimens were mixed with 5% of NZVI. After 24 days, an increase was seen in the friction angle,<br />cohesion, maximum dry density, and optimum water content. LL and PL of the soil decreased after the treatment