Mathematical model for formation decontamination by pumping with well bore mixing
Resource
Applied Mathematical Modelling, vol.30, pp446-457.
Journal
Applied Mathematical Modelling
Journal Volume
vol.30
Pages
446-457
Date Issued
2005-05-25
Date
2005-05-25
Author(s)
DOI
246246/2006111501244111
Abstract
The decline of trichloroethylene (TCE) in a metallic iron–water system results from the combination of reduction
reaction and sorption onto iron surfaces. Sorption, particularly by highly impure iron, accelerates the removal of TCE
from the aqueous phase, but delays the prevalence of steady-state conditions. In this case, an overly high value of
reaction rate constant in the design of a treatment system would be used. In this work, the effects of an iron surface with
8.0% C, 6.1% O and 0.8% Si separately following HCl-washing and H2-reducing pretreatment on sorption and
reduction rates were examined. The amounts of both aqueous and sorbed TCE were measured using a modified solventextraction
method. TCE sorption onto an iron surface, as quantified by the Langmuir sorption maximum, followed the
trend H2-reduced Fe04HCl-washed Fe04untreated Fe0 (0.887, 0.365 and 0.311 mg/g, respectively). Measurements of
the concentration of sorbed TCE revealed that about 34–37% of the initial mass of TCE in the aqueous phase was
removed by sorption by H2-reduced Fe0, 16–19% was removed by HCl-washed Fe0 and 13–16% was removed by
untreated Fe0. A combination of new and previously reported data on cast iron’s capacity to sorb TCE revealed a linear
relationship between this capacity and the C fraction in the surface of the iron, with the coefficient of determination (r2)
exceeding 0.99. The first-order observed rate constants (kobs) of the reduction of TCE in contact with Fe0 were obtained
from the slope of a plot of total TCE loss rate (dCT=dt) versus the amount of TCE in the aqueous phase (Cw) using
linear least-squares analysis. The kobs values were 0.080, 0.148 and 0.191 h1 for untreated, HCl-washed and H2-
reduced Fe0, respectively. Normalized to iron surface area concentration, the specific rate constants (kSA) were
2.37 103 , 2.31 103 and 5.62 103 h1m2 L, respectively. The results indicated that HCl-washing
approximately doubled kobs, primarily because of the increase in the surface area of the iron, and it slightly decreased
kSA due to rapid corrosion during the rinsing process. Both the number of reactive sites and the sorption capacity per
unit iron surface area through the H2-reducing pretreatment were increased due to the reduction of iron oxide layer and
the carbonization of carbon-containing subjects on the iron’s surface. Hence, the H2 reduction of cast iron promotes the
removalof TCE from contaminated water by the concurrent sorption and reduction.
r 2005 Elsevier Ltd. All rights reserved.
Subjects
Well bore mixing
Formation
Decontamination
Pumping
Publisher
Taipei:National Taiwan University Dept Comp Sci Informat Engn
Type
journal article
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