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Upscaling dissolution and remobilization of NAPL in surfactant-enhanced aquifer remediation from microscopic scale simulations
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  • Mehdi Ramezanzadeh,
  • Morteza Aminnaji,
  • Mohammad Hossein Ghazanfari,
  • Masoud Babaei
Mehdi Ramezanzadeh
Sharif University of Technology
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Morteza Aminnaji
University of Manchester
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Mohammad Hossein Ghazanfari
Sharif University of Technology, Tehran 11365-9465, Iran
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Masoud Babaei
University of Manchester

Corresponding Author:masoud.babaei@manchester.ac.uk

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The dissolution and mobilization of non-aqueous phase liquids (NAPL) blobs in Surfactant-Enhanced Aquifer Remediation (SEAR) processes are upscaled using dynamic pore network modelling of three-dimensional and unstructured networks. We considered corner flow and micro-flow mechanisms including snap-off and piston-like movement for two-phase flow. Moreover, NAPL entrapment and remobilization were evaluated using force analysis to develop capillary desaturation curve (CDC) and predict the onset of remobilization and complete removal of entrapped NAPL blobs. The corner diffusion mechanism was also applied in the modeling of interphase mass transfer to represent NAPL dissolution as the dominant mass transfer process. Our model showed that although surfactants enhance NAPL recovery during two-phase flow, surfactant-enhanced remediation of residual NAPL through dissolution is highly dependent on surfactant type. When sodium dodecyl sulfate (SDS), as a surfactant with high critical micelle concentration (CMC) and low micelle partition coefficient ( ) was injected into a NAPL contaminated site, reduction in mass transfer rate coefficient (due to considerable changes in interface chemical potentials) significantly reduced NAPL recovery after the end of two-phase flow. However, Triton X-100 (with low CMC and high ) improved NAPL recovery. This is because by enhancing solubility at surfactant concentrations greater than CMC, Triton X-100 overcompensates the interphase mass transfer reduction.