CONICET | Buscador de Institutos y Recursos Humanos

evaluation of new amphiphilic systems with possible applications in remediation of polluted soilsThe contamination of soil and water by hydrophobic organic compounds has become an environmental problem nowadays. Surfactants with different structures and properties can be used for different purposes of decontamination. The use of surfactants is an alternative for the remediation of contaminated soils.Polycyclic aromatic hydrocarbons (PAHs) are some of the most common hydrophobic organic contaminants that can be found in contaminated sites. They represent a risk to human health through their bio-accumulation and their effects on food chain.The objective of this work was to propose the use of certain amphiphilic systems as builders of the methodologies applied in the remediation of contaminated soils.At first we carried out the physicochemical characterization of mixtures of a non-ionic surfactant, Tween 80, and a gemini lipoamino acid one, named 3,3′-disulfanediyl bis 2-decamido propanoic acid (SDDC), synthesized in our laboratory. The mixed systems were studied by surface tension measurements, fluorescence quenching DLS and SAXS determinations. Both surfactants formed mixed micelles in different relationships and the properties of the mixtures were more similar to those of their major component. SAXS analysis showed that the micelles were triaxial ellipsoids, type core shell. The mixtures exhibited non-ideal behaviour, was as indicated by critical micelle concentrations (CMC) lower than those of the individual surfactants, and negative interaction parameters, β, which indicates attractive interaction.The capability of the different solutions of pure, non-ionic (Tween 80 (T80)), and anionic (SDDC)surfactants was determinated for the solubilization of naphthalene, phenanthrene and pyrene. The solubility of organic contaminants increases linearly whit the increase of the surfactant concentration due to the partitioning of the compounds in the micelles. Synergistic effect was observed with the mixtures: T80-SDDC for the solubilization of naphthalene and phenanthrene, quantified in terms of the molar solubilization ratio and the micelle water partition coefficient.Although the T80-SDDC mixture was effective for water solubilization of naphthalene and phenanthrene, this is not certainty of a similar effect for desorption of contaminants from solid matrices. Because of this, the ability of the mixture to extract contaminants from solid matrices was evaluated. Two types of solid matrices were used: silica gel and sandy soil, hoping to find favorable conditions for the desorption of contaminants from them, which could then be tested in real soil. Synergistic effect was found in the desorption of phenanthrene and naphthalene from silica gel and sandy soil when T80-SDDC mixture was used. This may be due to the formation of mixed micelles that produce a combination of beneficial effects to desorb contaminants from solid matrices, decreasing the adsorption of T80 in the matrices on one side, and decreasing the precipitation of SDDC in contact with solids on the other side.Finally, the effect of surfactants, Tween 80, gémini SDDC and the mixture of both surfactants, on the availability of contaminants (naphthalene and phenanthrene) to specific microorganisms, that was analyzed can use these contaminants as a source of carbon for their growth The strain Halomonas titanicae KHS3 was used as a PAH specific microorganism. The biodegradation of naphthalene and phenanthrene by the microorganism was studied using two methodologies, by turbidity, determining the optical density at 600 nm and by viability, quantifying the growth of the strain. Colonies developed at 24 h were expressed as the logarithm of Colony Forming Units per milliliter (Log CFU/mL). Similar microbial growth values were obtained when naphthalene or phenanthrene were used, finding that SDDC and its mixtures with T80 are toxic for the microorganism. However, in certainity conditions T80 alone results efficient to provide naphthalene solubilized to the microorganism, promoving its growthing.The results obtained suggest that this mixed micellar system can be a good alternative to be applied in soil remediation