Dispersion of Weathered Biodiesel, Diesel, and Light Crude Oil in the Presence of Sophorolipid Biosurfactant in Seawater

Abstract

Sophorolipid biosurfactants have shown promise in remediation of oil-contaminated environments. This study investigated the potential application of sophorolipid biosurfactants for enhanced dispersion of weathered biodiesel, diesel, and light crude oil–contaminated water under salinities (, 1, 2, and 3 ppt), temperatures (8, 22, and 35°C), and pH (6–8) using bench-scale experiments. Solutions of oil-artificial seawater-sophorolipid were prepared, shaken, solvent extracted, and analyzed. Sophorolipid biosurfactants reduced the surface tension of seawater (3 ppt) to 34 mN/m with a critical micelle concentration of 38 mg/L. Results of dispersion experiments showed that oil dispersion significantly increased as the sophorolipid concentrations increased so that the biodiesel, diesel, and light crude oil dispersion in seawater was enhanced 27, 16, and 12%, respectively, by 8 mg/L of sophorolipid. Salinity, mixing, and temperature influenced the oil dispersion, but pH had the least effect on the oil dispersion. Oil dispersion was because of the decreases in the surface and interfacial tensions and encapsulation of oil droplets in micelles. This study suggests that sophorolipid has the properties to enhance oil dispersion in seawater under the examined laboratory conditions.