LAUSR

The remediation of nonaqueous phase liquids (NAPLs) enhanced by surfactant and nanoparticles (NP) has been investigated in numerous studies. However, the role of NP-assisted surfactants in the dissolution process is still not well discussed. Besides, there is a lack of empirical dissolution models considering the effects of initial residual saturation S trap , NAPL distribution, and surfactant concentration in NAPL-aqueous phase systems. In this work, micromodel experiments are conducted to quantify mass transfer coefficients for different injected aqueous phases including deionized water, SDS surfactant solutions, and NP-assisted solutions with different levels of concentrations and flow rates. Observations reveal that silica nanoparticles (SNP) can significantly enhance interphase mass transfer, while SDS surfactant reduces the mass transfer coefficient. In addition, S trap and intrinsic interfacial area a i , as an indicator of dense nonaqueous phase liquids (DNAPL) distribution, influence the interphase mass transfer. The a i is also independent of DNAPL saturation S NAPL except for S NAPL  < 7% when ganglia breakup occurs. Based on these observations, new empirical dissolution models are proposed in the presence and the absence of SDS surfactant and SNP in which a i , S trap , and surfactant concentrations are introduced as new parameters. The evaluated mass transfer rate coefficients using the proposed models show a significant improvement compared to available empirical models. The finding of this study might be attractive for application in field-scale simulations of surfactant-enhanced aquifer remediation (SEAR) and NP-assisted methods.