Optimization of hydrocarbons extraction from contaminated soil using a sophorolipid biosurfactant

In the present study, a sophorolipid biosurfactant produced by Candida catenulata was used to extract hydrocarbons from a polluted soil collected from Naft Shahr oil-field. The critical micelle concentration (CMC) was 250 mg L-1 for the biosurfactant. Biosurfactant was efficient in leaching of hydrocarbons from contaminated soil due to the role of the surfactant in increasing the solubility of hydrocarbon in aquatic media. The effects of concentration of biosurfactant, temperature, and agitation speed were investigated on extraction yield using central composite design at 5 levels for each parameter. Data analysis and mathematical modeling were then performed using surface response methodology (RSM). The results showed agitation speed as the most effective factor followed by temperature and concentration of the biosurfactant. By optimizing the operating conditions of the process, the maximum removal efficiency of petroleum with 95.2% was achieved under the following conditions: concentration of biosurfactant 220mg L-1, temperature 55 °C and agitation speed of 400 rpm.