The role of intra-NAPL diffusion on mass transfer from MGP residuals

摘要

An experimental and computational study was performed to investigate the role of multi-component intra-NAPL diffusion on NAPL-water mass transfer. Molecular weight and the NAPL component concentrations were determined to be the most important parameters affecting intra-NAPL diffusion coefficients. Four NAPLs with different viscosities but the same quantified mass were simulated. For a spherical NAPL body, a combination of NAPL properties and interphase mass transfer rate can result in internal diffusion limitations. When the main intra-NAPL diffusion coefficients are in the range of self-diffusion coefficients (10(-5) to 10(-6) cm(2)/s), dissolution is not limited by internal diffusion except for high mass transfer rate coefficients ( 180 cm/day). For a complex and relatively high viscous NAPL ( 50g/(cm s)), smaller intra-NAPL diffusion coefficients ( 10(-8)) are expected and even low mass transfer rate coefficients (similar to 6 cm/day) can result in diffusion-limited dissolution.