Application of biosurfactant surfactin for the removal of heavy metals from contaminated water and soil via a micellar-enhanced ultrafiltration process

The presence of toxic metals in natural environments presents a potential health hazard for humans, and the removal of toxic metals remains a major challenge. In this study, biosurfactant surfactin was used to remove heavy metals from contaminated soil via a micellar-enhanced ultrafiltration (MEUF) process. Results demonstrate that anionic surfactin with two -COO- groups can bind heavy metals through electrostatic interactions at a pH above its pKa value and then be rejected by the ultrafiltration membranes, resulting in efficient removal of heavy metal ions. By optimizing the operation parameters, over 98% of metals can be removed by adding surfactin at a surfactin/metals ratio of 3:1. Moreover, membrane fouling was characterized and eliminated by an optimized cleaning strategy. Membrane flux recovery can be obtained at 94% without losing separation efficiency. Finally, the validity of the present process was confirmed on real contaminated water and soil, and over 99.2% of metals were removed. Hence, MEUF with surfactin is a reliable and efficient approach for removing heavy metals from contaminated water and soil.