Solubilization kinetics for polycyclic aromatic hydrocarbons transferring from a non-aqueous phase liquid to non-ionic surfactant solutions

Abstract

A modified rotating disk apparatus was used to investigate the mass transfer of two polycyclic aromatic hydrocarbon (PAH) compounds, naphthalene and phenanthrene from a synthesized non-aqueous phase liquid (NAPL) comprised of hexadecane and the 2 PAHs into different non-ionic surfactant solutions. Major factors influencing the rate of solubilization of PAHs from a NAPL in micelles of different non-ionic surfactants were determined. As the surfactant concentration increased, the mass transfer coefficients for both PAHs from the NAPL decreased. The maximum rates of solubilization of the PAHs however increase with surfactant dose. The rate of solubilization was found to be limited by rates of desorption of mixed micelles from the NAPL and their rate of diffusion into the bulk solution phase. The influence of the surfactant molecular structure on the kinetics of the solubilization process was investigated. The results suggested that the length of the alkyl portion of the non-ionic surfactant and the micelle volume influenced the solubilization kinetics. The results of the investigation improve our ability to provide a rational basis for selecting the optimum surfactant and dose to enhance the solubilization of PAHs from NAPLs.