The new applications for carbon nanotubes (CNTs) in various fields and consequently their greater production volume have increased their potential release to the environment. Landfills are one of the major locations where carbon nanotubes are expected to be disposed and it is important to ensure that they can limit the release of CNTs. Diffusion of multiwall carbon nanotubes (MWCNTs) dispersed in an aqueous media through a high-density polyethylene (HDPE) geomembrane (as a part of the landfill barrier system) was examined. Based on the laboratory tests, the permeation coefficient was estimated to be less than 5.1×10−15 m2/s. The potential performance of a HDPE geomembrane and geosynthetic clay liner (GCL) as parts of a composite liner in containing MWCNTs was modelled for six different scenarios. The results suggest that the low value of permeation coefficient of an HDPE geomembrane makes it an effective diffusive barrier for MWCNTs and by keeping the geomembrane defects to minimum during the construction (e.g., number of holes and length of wrinkles) a composite liner commonly used in municipal solid waste landfills will effectively contain MWCNTs.
Partitioning and diffusion experiments performed on bisphenol A (BPA) and high-density polyethylene (HDPE) geomembrane are reported. The tests indicate no measurable partitioning to the geomembrane and an estimated upper bound permeation coefficient is 3 × 10−15 m2/s. This low value of permeation coefficient suggests that an HDPE geomembrane will be a very effective diffusive barrier for BPA for the conditions examined. Partitioning tests on BPA in a mixture with 12 other phenolic compounds did not show any measurable change in partitioning of BPA to the geomembrane due to the presence of the other compounds. The partitioning coefficients for phenolic compounds examined range from 0.61 for 2-methylphenol to 31 for 2,3,4,6-tetrachlorophenol and the diffusion coefficients ranged from 9.3 × 10−15 m2/s for 2,3,4,6-tetrachlorophenol and pentachlorophenol to 9.3 × 10−14 m2/s for 2- methylphenol.
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