Application of echo-friendly additives as the adsorbents of Petroleum contaminants and their effect on the shear strength of contaminated sand

Petroleum products and their derivatives cause severe soil pollution through transportation, leaks in pipelines or improper storage. These contaminants may affect the physical or chemical parameters of the soil. Nowadays, due to the increase in construction projects and consequently the need for suitable lands, the construction of structures on lands with contaminated soils is necessary. To determine the optimal methods for rehabilitation of contaminated soils, it is necessary to recognize the contaminated soil behavior and characteristics. There are several methods for stabilization of contaminated soils depending on the type of soils and their pollution. In selecting the appropriate method and materials, various aspects such as environmental issues, availability and cost-effectiveness of the method should be considered. In this study, the effect of oil pollutants on the geomechanical parameters of the sandy soil has been investigated and on the other hand, the performance of different environmentally friendly materials as adsorbents of pollutants and also their effect on the contaminated soil behavior was studied.  The studied soil is poorly graded sand that has been sampled from Qazvin district. The petroleum pollutants studied in this study are kerosene and gasoil. Three different materials incuding zeolite, perlite, and produced magnesite were used as sorbent in this study. In this study, the carbon dioxide emissions from industry were utilized to produce magnesium carbonate minerals. In the first step, the percentage of pollutant absorption for studied materials including the sand and sorbents was investigated. The results showed that the magnesite had the highest capability to absorb petroleum contaminants.  The percentage of pollutant absorption in magnesite was about 91% for gasoil and 85% for kerosene, while in studied sand it was 26% and 21% for gasoil and kerosene, respectively. The other sorbents including perlite and zeolite also showed high percentages of pollutant absorption. In order to investigate the effect of petroleum pollutants in the shear strength of sand, the direct shear tests was conducted on pure and polluted sample. The soil specimens with dimension of 10x10x3 cm and dry density of 18.35 kN/m3 were prepared by dry air pluviation method. After installing the sample in the device and before performing the test, the sample was saturated with contaminant. The specimens were sheared under different vertical stresses of 50, 100 and 200 kPa. The results showed a decrease in shear strength and more than 10 degrees decrease in internal friction angle of contaminated samples with respect to pure sand. The direct shear tests were conducted on the contaminated samples, treated by different sorbents. The results demonstrated an increase in shear strength for samples treated with perlite, but a loss in shear strength for samples treated with zeolite. The difference in shear strength between the magnesite-treated samples and the untreated samples was not significant. The study confirmed that perlite, zeolite, and magnesite have a capability to absorb petroleum contaminants in soils.  Carbon dioxide is one of the most influential factors in global warming in the coming decades, so the magnesite produced by capturing CO2 and its application as a pollutant absorbent can be an encouraging finding of this study.