Characterization of different synthetic and natural surfactants for applications in contaminated aquifers remediation using SEAR (Surfactant Enhanced Aquifer Remediation) technology

The research activity is fully integrated in the scientific-technological field of environmental protection. The thesis aims to study and optimize remediation technologies for the treatment and restoration of environmental matrices, polluted by hydrophobic organic compounds. The main objective is the development of effective strategies to attack persistent and slow-release sources of contamination, whose depletion with traditional approaches results extremely critical. In this operational context, the research deeply focuses on theoretical, scientific, and technical aspects of SEAR (Surfactant-Enhanced Aquifer Remediation) technology, based on the use of surfactants in solution to mobilize and solubilize hydrophobic organic compounds, such as NAPLs (non-aqueous liquid phases), which are the most found pollutants in contamination scenarios. In this regard, a wide range of different surfactants was considered, both non-ionic and anionic, both synthetic and biosurfactant, belonging to various families: synthetic alkyl-polyglycosides (APGs) and alkyl-sulphosuccinates (ASSs), sophorolipids (SLs) and rhamnolipids (RLs) of 100% natural origin. The ability of these surfactants to ensure the removal of NAPls was evaluated through a series of experiments conducted in both batch and continuous column configurations, on polluted matrices, both synthetics (specifically created in the laboratory) and real matrices (from real polluted sites) and also considering different forms in which the pollutants may be present in a secondary source of contamination. Specifically, three different studies were conducted. We started with preliminary studies on the enhanced solubilization of strongly adsorbed reference pollutants on a synthetic contaminated matrix. Afterward, the ability of surfactants to mobilize a complex mixture of organic contaminants from a historically contaminated real matrix, characterized by the most residual, persistent, and recalcitrant fraction, was evaluated. Finally, the mobilization of the pure organic phase trapped in the porosities was evaluated by exploring the ability of two surfactants to form stable microemulsions with the organic phase and enhance its displacement and mobilization from the saturated porous medium.