Trapping of oil molecules in clathrates: Oil trapping mechanism, soil composition and thermal studies

Abstract

In the present study, oil spiked soil samples were cleaned up using clathrates, by proposing an innovative mechanism, formed by different combinations of salts like sodium chloride, urea, thiourea and hydroquinone. The clathrates formed act as trap for the oil molecules present in the contaminated soil. The effects of various parameters viz.; medium pH, rpm, salt amount and contact time were studied in the batch mode. For the batch studies, Langmuir isotherm model was applied and provided best fit to the equilibrium data obtained with R2 = 0.99. The maximum oil removal efficiency 87% was obtained using combination B (2.0 g each of sodium chloride, Urea, Thiourea and hydroquinone) at pH 9.0, 180 rpm within 60 min in batch mode. Column studies were also carried out using different salts combination at different flow rates (1.0, 2.0, 3.0 mL min−1). The maximum oil removal efficiency 84% was obtained using combination B at flow rate of 1.0 mL min−1. Further, the FTIR and TGA studies confirmed the formation of clathrates and their application as cages for oil removal from oil spiked soil samples. The outcomes from this study assured that the oil trapping by clathrates is a newly developed and quite effective technique which could be used for treating oil contaminated soils at large scale.