Enhanced solubilization and desorption of pyrene from soils by saline anionic–nonionic surfactant systems

• Saline surfactant shows lower CMC values than fresh surfactant.
• The lower β values of saline surfactants, the higher pyrene solubilization.
• STPP reduces surfactant sorption onto soil and enhances pyrene desorption.

This study investigates the influence of salinity on micellar behavior, enhanced solubilization and desorption of pyrene within single and mixed saline anionic–nonionic surfactants. Various interaction parameters linked to the micellarization and solubilization process have been correlated through theoretical treatments to quantify micellar characteristics and solubilization capabilities of the systems. Results show that the experimental critical micelle concentration (CMC) values of the saline system were lower than that of non-saline system, indicating more attractive interactions of individual surfactants and higher stability of mixed micelles in the presence of salts. Pyrene solubility in saline surfactant solutions exceeded that in a non-saline solution. Less electrostatic repulsion of saline mixed micelles may be responsible for the reduced CMC of the mixed micelles, the increase of molar solubilization ratio (MSR) and micelle–water partition coefficient (Km). The saline micelles enhanced desorption of pyrene from kaolin-rich soil, and the pyrene desorption increased with the increase of salinity. Furthermore, the presence of salinity reduced the sorption of surfactant onto kaolin-rich soil; e.g. from 15.34 to 11.07 mg of surfactant/g of soil at a mass ratio of 5:5 mixture of anionic and nonionic surfactants. The results of this study provide new insights for estimating the utility of mixed surfactants treatments for soil remediation.

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