Screening of biosurfactants for crude oil contaminated soil washing

This study reports experimental measurements on the ability of aqueous biosurfactant solutions (aescin, lecithin, rhamnolipid, saponin, and tannin) at removing Ekofisk crude oil from a laboratory contaminated soil under varying washing conditions. The oil removal performance of the biosurfactants was evaluated against a synthetic anionic surfactant (sodium dodecyl sulphate, SDS) using distilled water as a base case. The washing parameters and ranges tested were temperature, time, shaking speed, volume/mass ratio, and surfactant concentrations. Results indicated that washing temperature was the most influential parameter on the oil removal whilst washing time was the least. It was possible to obtain more than 80% oil removal at 50 °C for all the surfactant solutions, except lecithin, which yielded less than 15% removal. However, saponin, lecithin, aescin, and tannin removed less than 50% crude oil when tested at a temperature of 20 °C and other parameters. Soil washing was found to have considerable potential in removing crude oil from the contaminated soil therefore, we suggest further testing be performed with weathered contaminated soils. Key words: soil washing, biosurfactants, crude oil, contaminated soil, oil removal, oil spill treatment.