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

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