Rate limited diffusion and dissolution of multi-component non-aqueous phase liquids (NAPLs) in groundwater

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dc.contributor.advisor Tick, Geoffrey R.
dc.contributor.author Burke, William Randolph
dc.date.accessioned 2017-03-01T16:25:46Z
dc.date.available 2017-03-01T16:25:46Z
dc.date.issued 2011
dc.identifier.other u0015_0000001_0000892
dc.identifier.other Burke_alatus_0004M_10967
dc.identifier.uri https://ir.ua.edu/handle/123456789/1389
dc.description Electronic Thesis or Dissertation
dc.description.abstract Contamination of soil and groundwater by nonaqueous phase liquids (NAPLs) poses serious risks to human health and the environment and presents major challenges for cleanup. The presence of complex NAPL mixtures in the subsurface further complicates remediation efforts, transport predictions, and the development of accurate risk assessments. A comprehensive laboratory-scale study was conducted to elucidate the factors affecting dissolution and removal of NAPL including 1) the distribution of NAPL (uniform vs. non-uniform), 2) NAPL-water interfacial area (constant vs. changing), 3) multi-component NAPL systems (composition dependence), and 4) intra-NAPL diffusion. A series of column and time sequential batch experiments were conducted to assess the factors controlling dissolution processes under dynamic flow and equilibrium conditions. For comparison purposes, two independent NAPL systems were established for the series of experiments including single-component trichloroethene (TCE) whereby the NAPL interfacial area decreases as dissolution proceeds, and two-component TCE-hexadecane (HEX) in which the bulk NAPL (comprised primarily of insoluble HEX) interfacial remains constant. The results of this study show that significant dissolution rate and removal limitations during water-flushing exist for systems containing non-uniform NAPL (TCE) distributions, due to less available NAPL-water interfacial area. Effective TCE removal was 2 times longer for the non-uniform NAPL distribution experiment. TCE dissolution in the two-component NAPL systems (TCE and HEX) experienced significantly less rate limitation (absence of concentration tailing) than the single-component TCE systems due to the presence of a constant interfacial area for mass-transfer to occur during flushing. Each column experiment resulted in differing effectiveness with respect to mass removal. The multi-component TCE:HEX system experienced the fastest mass removal time, but was not considered the most efficient. The batch experiments demonstrated that as mole fraction of a particular component of a NAPL (TCE) mixture decreases, greater dissolution nonideality occurs, resulting in greater observed concentrations than those predicted by equilibrium dissolution (i.e. Raoult's Law). Dissolution nonideality, quantified by the NAPL-activity coefficient, increased for the lower TCE mole fraction systems from 1.7 to 6.1 for TCE:HEX mole fractions of 0.2:0.8 to 0.003:0.997, respectively. The results of the batch experiments also indicate that dissolution mass-transfer rates were nearly identical for both the single-component TCE systems and the TCE:HEX systems. This suggests that intra-NAPL diffusion is not a rate-limited process under the conditions of these experiments. Mass flux reduction analyses showed that the two-component (TCE:HEX) NAPL experiment resulted in less efficient removal behavior than the single-component TCE flushing experiments, likely due to the significantly lower TCE mass within the mixed NAPL system. The results from this study improved the understanding of NAPL dissolution and removal processes; most notably for NAPL mixture systems where NAPL-water interfacial area may be maintained during flushing and where significant dissolution nonideality may result from decreasing mole fractions of target contaminants in NAPL.
dc.format.extent 108 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Geology
dc.subject.other Geochemistry
dc.title Rate limited diffusion and dissolution of multi-component non-aqueous phase liquids (NAPLs) in groundwater
dc.type thesis
dc.type text
etdms.degree.department University of Alabama. Dept. of Geological Sciences
etdms.degree.discipline Geology
etdms.degree.grantor The University of Alabama
etdms.degree.level master's
etdms.degree.name M.S.

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