Cement-Based Solidification/Stabilization of Soil Contaminated by Polycyclic Aromatic Hydrocarbons Using Organophilic Clay

Abstract

The solidification/stabilization (S/S) method is the most widely used to remediate all types of inorganic pollutants, which has not been developed for organic matters. In this research, the application of cement and organophilic clay (OC) was investigated for the S/S of contaminated soil by polycyclic aromatic hydrocarbons (PAHs). Pyrene, Acenaphthene, Benzo[a]Pyrene, and Benz[a]Anthracene were spiked in a soil specimen. X-ray diffraction analysis (XRD) indicated that OC has a considerable ability to absorb PAHs in its inter-laminar molecular spaces, unlike ordinary bentonite. Toxicity characteristic leaching procedure (TCLP) results showed that application of OC increased PAHs' removal efficiency from contaminated soil up to 80% on average compared to the use of cement only. Samples containing 30% cement and 30% OC with a 14-day curing time had the best removal efficiency. Also, the removal efficiency of heavier PAHs was lower than the lighter ones. Additionally, unconfined compressive strength (UCS) showed a linear descending by increasing OC's proportion. Scanning electron microscopy (SEM) analysis indicated that two reasons have effectively increased the PAHs' removal efficiency of solid samples: a) increasing the amount of OC that increases the PAHs absorption capacity, b) reducing the size of pores in the matrix reduces the pollutant leaching.