Remediation of a Heavy Metal Contaminated Soil by a Rhamnolipid Foam

Studies were initiated with a rhamnolipid biosurfactant in columns to simulate in situ conditions. The biosurfactant was injected in the form of a foam and liquid solutions. The study was conducted in three steps: evaluation of the foam characteristics, investigation of pressure buildup by foam injection and removal of metals by the foam. Foam quality of the rhamnolipid was shown to vary between 90 and 99% with stabilities from 17 to 41 minutes. Pressure build up was then evaluated with different flow rates, foam quality and biosurfactant solutions. Metal removal was then evaluated from a sandy soil contaminated with 1,710 ppm of Cd and 2,010 ppm of Ni. Maximum removal was obtained by a foam produced by 0.5% rhamnolipid solution after 20 pore volumes. Removal efficiency for the biosurfactant foam was 73.2 % of Cd and 68.1% of Ni. For the biosurfactant liquid solution, 61.7% Cd and 51.0 % were removed. Distilled water removed only 18 % of both Cd and Ni. Liquid solutions with concentrations of 0.5, 1.0 and 1.5% rhamnolipid at pH values of 6.8, 8 and 10 were also evaluated for their ability to remove metals but they did not show any significant beneficial effects. Therefore, rhamnolipid foam may be an effective and non-toxic method of remediating heavy metal contaminated soils. Further efforts will be required to enable its use at field scale.

• INTRODUCTION

• MATERIALS AND METHODS

• RESULTS AND DISCUSSION

• CONCLUSIONS

• ACKNOWLEDGEMENTS

• REFERENCES