Biosurfactant (Rhamnolipid) Sorption and the Impact on Rhamnolipid-Facilitated Removal of Cadmium from Various Soils under Saturated Flow Conditions

Abstract

The efficiency of biosurfactant-facilitated removal of soil-bound metals is affected by biosurfactant sorption to soil. In this study, batch and column experiments were performed to minimize rhamnolipid biosurfactant sorption and to optimize rhamnolipid application for removal of cadmium from four soils. In batch studies, rhamnolipid sorption to a model coarse loamy soil was found to vary with applied rhamnolipid and K+ concentration of the rhamnolipid matrix. The presence of solution-phase biosurfactant was correlated to the release into solution of a soil-bound metal (cadmium). A series of column experiments was performed to evaluate whether rhamnolipid could remove cadmium from soil under saturated flow conditions. Four different soils were contaminated with cadmium and treated first with an KNO3 electrolyte solution (3.5 or 7 mM K+) and then with a rhamnolipid-containing solution (5 or 10 mM). Results showed that between 15 and 36% of the cadmium was removed by the initial electrolyte treat ment and a...