Adsorption of copper, zinc and lead on biosurfactant produced from cassava wastewater

The remediation of soils contaminated by hydrophobic compounds, especially petroleum derivatives, using surfactants has been fairly studied. The use of these compounds in heavy metal contaminated areas is incipient and their mechanism of action has not been totally elucidated yet. The biosurfactants are compounds with surfactant characteristics produced by living organisms and have several environmental advantages, like greater biodegradability and production from renewable sources. The aim of this study was to evaluate the adsorption potential of the metals copper, zinc and lead onto the biosurfactant structure and to relate it to the Langmuir and Freundlich physicochemical models of adsorption. The biosurfactant produced presented an emulsification index (EI) around 60%, which was stable even after 72 h of emulsion formation. The analysis of FTIR and HPLC confirmed that the biosurfactant produced is composed mainly of surfactin, found in concentration of 28%. The biosurfactant was capable of adsorbing the metals in its structure. In the adsorption process of Pb2+, the biosurfactant was considered as an interesting adsorbent, but this behavior did not adjust satisfactorily to Langmuir and Freundlich models. Thus, the biosurfactant has the potential to be utilized in remediation processes of soils and treatment of effluents contaminated by heavy metals.   Key words: Bacillus subtilis, trace elements, heavy metals, remediation of contaminated areas, agro industrial residue, surfactin.