Critical evaluation of the performance of rhamnolipids as surfactants for (phyto)extraction of Cd, Cu, Fe, Pb and Zn from copper smelter-affected soil

The aim was to evaluate the feasibility of rhamnolipid-mediated phytoextraction of several heavy metal ions from soil located in the vicinity of a copper smelter. The following aspects were investigated: i) selectivity of rhamnolipids towards Cu, Zn, Pb, Cd and Fe during soil washing; ii) phytoextraction efficiency of each ion with respect to the effective concentration of rhamnolipids used for treatment; iii) possible phytotoxic effects.

The experiments involved the use of flame atomic absorption spectroscopy (AAS) to evaluate soil washing efficiency, sequential BCR extraction to determine the impact of rhamnolipids on the mobility of metal ions, phytoextraction trials with maize and finally evaluation of phytotoxic effects on the plant based on analysis of dry matter as well as chlorophyll fluorescence and content.