title: Surfactant induced complex formation and their effects on the interfacial properties of seawater.
abstract: The effect of a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB), on the interfacial properties of seawater has been studied by dynamic and equilibrium surface tension and by dilational rheology essays. Important modifications of the surface tension and dilational rheology response have been observed already at the very low CTAB concentrations, where the effects due to the high ionic strength are negligible. The comparison with the effects of CTAB in different seawater models, or in natural seawater fractions, points out the establishment of strong interactions between the surfactant molecules and the lipophilic fraction of organic material dispersed/dissolved in seawater, affecting the interfacial activity of the molecules. Considering the biochemical richness of seawater, these results can be explained assuming interaction mechanisms and adsorption schemes similar to those speculated for protein and other macromolecules in the presence of surfactants, which in fact show similar features. Thus already at the low concentrations the surfactant molecules form highly surface-active complexes with part of the organic fraction of seawater. At the larger surfactant concentrations these complexes compete for adsorption with an excess of free CTAB molecules which, according to the thermodynamic conditions, are most favoured to occupy the liquid interface. The results of this study underline the important role of the sea organic content in enhancing the surface-activity of surfactants, which is relevant for a deeper understand of the direct and indirect effects of these types of pollutants on the physico-chemical environment in the sea coastal areas and develop mitigation strategies.
authors.affiliation: Istituto per l'Energetica e le Interfasi-U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy. Electronic address: e.guzman@ge.ieni.cnr.it.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Guzmán
authors.affiliation: Istituto per l'Energetica e le Interfasi-U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy. Electronic address: e.santini@ge.ieni.cnr.it.
authors.forename: Eva
authors.initials: E
authors.lastname: Santini
authors.affiliation: Istituto per l'Energetica e le Interfasi-U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Benedetti
authors.affiliation: Istituto per l'Energetica e le Interfasi-U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Ravera
authors.affiliation: Istituto per l'Energetica e le Interfasi-U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Ferrari
authors.affiliation: Istituto per l'Energetica e le Interfasi-U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy.
authors.forename: Libero
authors.initials: L
authors.lastname: Liggieri
mesh_terms: D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry; D012623:Seawater / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D002593:Cetrimonium Compounds; D013501:Surface-Active Agents; D000077286:Cetrimonium
keywords: Adsorption; Contamination; Interfacial properties; Seawater; Surfactant