The cooperative effect between cyclic naphthenic acids and surfactant enhances the separation efficiency

Abstract Naphthenic Acids (NAs) are responsible for corrosion, produced water pollution, and are toxic to marine life. Therefore, more efficient NAs extraction techniques, such Micellar-Enhanced Ultrafiltration (MEUF), have been developed. In this work, Molecular Dynamics simulations were employed to deepen the comprehension of the behavior and properties of NA in interfacial systems and micellar systems. The calculated distribution coefficient (log D) in different water/oil interfaces demonstrated the greater affinity between NA and cyclic structures, showing a more negative free energy in the systems with toluene. Furthermore, simulations with different NAs and surfactant showed that micelle is effective in NAs carriage by two different interaction conformations, both by intercalation and adsorption of NAs on micelle surfaces, guiding to a micelle increase of about 5%. Radial distribution, hydrogen-bond, and non-bonded analysis indicated that NAs affect interactions between surfactant molecules' by diminishing the Lennard-Jones contribution. Moreover, the incorporated alicyclic molecules are responsible for facilitating the absorption of more NAs by the micelle. So, to enhance NAs separation from oil or produced water, cyclic molecular systems may be employed.