Description
and Abstracts
of REU Projects for Summer 2006
TITLE:
Iron-Oxide-Coated Sand For Fluoride Removal In Developing
Countries
Abstract: Excess fluoride in drinking water is a
main health concern in countries throughout the developing
world. Small amounts of fluoride (0.5-1.5 mg/L) promote
dental health; in excess of these amounts, fluoride
in drinking water causes dental and skeletal fluorosis.
Dental and skeletal health problems caused by excess
fluoride intake are irreversible, and can be crippling.
The World Health Organization (WHO) reports that
fluorosis of varying severity affects millions of
people worldwide, and is most prevalent in arid regions
of developing countries because of their geologic
and socioeconomic attributes. Highly affected areas
include India, northern China, Kenya and Tanzania,
northern Africa, central Argentina, and northern Mexico.
To prevent fluorosis in areas of developing countries
where an alternative source of low-fluoride water
is not readily available, WHO has encouraged the defluoridation
of groundwater used for drinking and cooking. Currently,
common defluoridation methods, which have been utilized
with varying degrees of success, include adsorption,
coagulation/flocculation, filtration, reverse osmosis,
and ion exchange. However, costs and risks associated
with commonly used defluoridation techniques have
led to the investigation of simple and sustainable
methods of effective fluoride removal which are appropriate
for remote areas in developing countries. Previous
studies have shown successful removal using readily
available local materials such as bone char, crushed
clay pot chips and plant seeds.
This study will compare the fluoride removal efficiencies
of simple technologies, such as iron oxide coated
sand (IOCS) and bone char, with commonly used adsorbents
such as activated alumina and activated carbon. In
addition, the fluoride removal effectiveness of IOCS
in the presence of competing ions such as arsenic
and sulphate, as well as the potential of co-removal
of fluoride and arsenic ions by IOCS, will be investigated.
Thus, the purpose of this study is to evaluate the
potential of IOCS and bone char iltration as simple
and economically viable methods for fluoride removal
from drinking water sources in developing regions.
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TITLE: Biodegradation of Xylene
Isomers Through Addition of Fumarate
Abstract: Anaerobic
bacteria activate and degrade fuel components (or
hydrocarbons) by an important mechanism called fumarate
addition. In this project, a computational chemistry
software program, Gaussian 03 is used to determine
the thermodynamics of the fumarate addition reaction
with three xylene isomers. The calculations will provide
estimated values of free energy associated with each
molecule in the reaction mechanism. Using these numbers,
a reaction coordinate will be developed for the isomers
to evaluate the thermodynamics possibility of the
reaction.
These numbers are useful as theoretical tools to
explore the energetics of the benzyl succinic synthase
catalyzed fumarate addition reaction to the xylene
isomers to form benzylsuccinic acid. The transition
state structure between each step of the reaction
energy values will also be predicted by these values;
this will assist in developing a better understanding
the thermodynamics of the mechanism.
To validate the numerical findings of the program,
experimental rate data will be compared to each reaction
coordinate to determine if the trend predicted by
the thermodynamics calculations are consistent with
laboratory data. The results are expected to show
that fumarate addition to xylenes is thermodynamically
reasonable. Additionally, comparisons of the three
reaction coordinates is expected to show that fumarate
addition to meta-xylene is the most thermodynamically
favorable reaction then para-xylene and ortho-xylene.
TITLE: The Effectiveness of
Two Different Types of Natural Wetlands on the Immobilization
of Metals
Abstract: The purpose of the experiment was to determine
the effect of soil organic matter accumulation on
fractionation of metals present in the wetland. The
experiment also examined the effect the amount of
metal loading had on fractionation and organic mater
accumulation. Samples were tested for metal compounds
that were water soluble, ion exchangeable, carbonate
bound, bound to Fe or Mn oxides, and organic matter
bound. Total metal content was also examined for each
sample. At the time of this report only the Fe Mn
oxide bound metals were examined. The isolated sites
had more zinc and lead in the flooded zone vs. the
saturated zone. Also the amount of cadmium was greater
in the saturated zones of the isolated sites than
the discharge sites. This was not what was expected
as the amount of metal oxides were assumed to be higher
in saturated areas due to more oxygen and higher in
the discharge areas due to more metal loading.
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TITLE: Metal Contamination
in Volunteer Wetlands
Abstract: Little is known about the effects metal
contamination has on plants living in volunteer wetlands.
The aim of this study was to lay the ground work so
that in the future we could assess the extent to which
settled organic matter and dead macrophytes affected
metal accumulation in volunteer wetlands. We set out
to determine the consequences hydrology and water
saturation may have on our samples. We found that
the organic matter in all three types of wetlands
we sampled were similar. In addition, we found that
organic matter collected in both flooded and saturated
zones of these wetlands were also comparable.
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TITLE:
Abstract:
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TITLE: Effects of Aeration
and Ferric Oxyhydroxide Particulate Seeding on Iron
and Heavy Metals Removal in Net Alkaline Mine Drainage
Abstract: The following research project was conducted
on polluted water at the Tar Creek Superfund Site
in northeastern Oklahoma. Lead and zinc were mined
in the area intermittently between 1891 and 1971.
Water exiting the ground through a natural seep has
elevated levels of iron and other heavy metals. The
open underground cavities created from mining exposed
sulfide minerals such as pyrite, sphalerite, and galena
to oxygen and water. The weathering process formed
sulfate, soluble iron, and acidity. When the water
exits the ground and comes in contact with oxygen,
the dissolved ferrous iron is rapidly oxidizes to
ferric iron (Eq 1). The ferric iron then hydrolyses
to form iron oxyhydroxide precipitate (Eq 2). Although
this reaction releases protons, the water remains
at a circum-neutral pH because the protons are consumed
in a reaction with bicarbonate, which is present in
the water from the dolomitic chert geology (Eq 3).
When the mine water exits the ground, it leaves a
closed system and enters into an open system. The
carbonic acid, which is also present due to the geology,
dissociates into gaseous carbon dioxide and water
(Eq 4).
Fe+2 + 0.25O2 + H+ ? Fe+3 + 0.5H2O (1)
Fe+3 + 2H2O ? FeOOH(s) + 3H+ (2)
H+ + HCO3- ? H2O + CO2 (3)
HCO3- + H+ ? H2CO3* ? CO2(g) + H2O (4)
The rate of iron removal from solution is dependent
on pH. Therefore, it is hypothesized that degassing
carbon dioxide will increase the pH and positively
influence iron removal. Research by Dempsey et al.
(2001) and Nairn et al. (2002) has shown that the
presence of oxyhydroxide solids will increase iron
removal rates through heterogeneous oxidation. The
ferric oxyhydroxide solids in solution act as a catylist
for the oxidation of iron shown in Equation 1. The
effect of heterogeneous oxidation was evaluated in
this experiment. It is predicted that precipitated
iron solids will retain heavy metals through absorption,
a phenomenon which has been observed in other treatment
systems (Davis and Leckie 1978; Webster et al. 1998,
Trivedi and Axe 2000).
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TITLE: Aid of Epoxy Injection
in Repair of RC Bridge Girders
Abstract: This report will look at the performance
of epoxy injection as an additive when attempting
three different repair options on pre-stressed reinforced
concrete bridge girders. We brought three large scale
models of AASHTO concrete bridge girders into the
lab to perform our tests on. The first test performed
on each beam end looked for the load required to achieve
a predetermined deformation (0.3”). Next we
failed each end in shear and recorded loads and deflection
until failure and unloading. Then we performed the
repairs of the girders. Each beam had one end injected
with a crack filling epoxy and then both ends of each
beam were given similar repair but different from
the other beams. One beam used steel stirrups while
the other two will be repair with fiber reinforced
polymer u-wraps, one carbon-fiber and the other fiber
glass. Once the repairs were complete we performed
the deflection and shear failure tests again, and
then did comparison with our data to determine if
injecting epoxy has a positive effect on both stiffness
and strength returns. From our data we were able to
determine that injecting epoxy as crack filler provided
a degree of help by improving stiffness and stability
in end region repairs.
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TITLE: Application and Analysis
of Geosynthetics on Dry and Wet Embankments
Abstract: The research project was to design and
create a computer-generated model using FLAC that
simulated dry and watered earth dams both with and
without geosynthetic reinforcements. The goal was
to compare the performance of earth dam models before
and after retrofitting with geosynthetics which included
their lateral displacements and crest settlements
in addition to their factors of safety against failure.
The influence of reinforcement vertical spacing on
the retrofitting effectiveness (evaluated by the reduction
in dam response and increased factor of safety) was
investigated. Analyzed data revealed that reinforcement
successfully strengthened the dry and wet embankments,
and that placing reinforcement layers at 0.5-meter
spacing significantly enhanced the performance and
structural stability of the model dams compared to
both models with 1.0-meter reinforcement spacing and
unreinforced models. The economic viability of additional
reinforcement viz. the required structural strength
of the resulting model is an important design consideration
that warrants further research. The dry program succeeded
in having an accurately solved model that reflected
conditions dependent on reinforcement and its spacing.
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TITLE: Long-Term Interactions
of PRODAN with Dissolved Humic Materials
Abstract: Aqueous phase interaction of the fluorescent
probe 6-propionyl-2-dimethylaminonaphthalene (PRODAN)
with two dissolved humic acids: Suwannee River humic
acid (SRHA) and Leonardite humic acid (LHA), was studied
as a function of pH, concentration, and time. The
emission spectrum of PRODAN is sensitive to the solvent
polarity, and due to its large dipole moment PRODAN
responds to local polarity change in the form of fluorescence
emission spectra shift. However, the absence of fluorescence
blue shift in aqueous phase when in the presence of
humic acids indicates that PRODAN is associating with
humic material via weak interactions rather than partitioning
into hypothesized pseudo-micelles formed by the cluster
of humic acid molecules. Fluorescence quenching has
identified that the interaction of PRODAN with two
humic acids is influenced by the type of humic acid,
concentration of humic acid, and pH of the sample.
In aqueous phase, at either of the studied concentrations
and pHs of humic acid, the interaction of PRODAN with
SRHA did not reach equilibrium during the studied
time. During the course of the experiment we found
that the interactions of PRODAN with SRHA actually
increased with time. In the case of LHA however, the
interaction of PRODAN at pH 4 reached equilibrium
within 1 hour and at pH 10 the interaction kept increasing
with time until it reached an equilibrium at about
day 8. On the other hand, in 50% DMSO the interaction
of PRODAN with both humic acids decreased as compared
to that in aqueous phase and reached equilibrium with
in 1 hour. We propose that the in aqueous phase, humic
materials undergo conformational changes due to solvophobic
effects over time and provide new sites for PRODAN
to interact with.
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TITLE: Nanomaterial Transport
Through Unsaturated Sand
Abstract: Nanomaterials are impressive do to their
unique physical and chemical properties, yet, consequently
also pose a potential health risk. Studies have linked
nanomaterial to DNA damage, skin irritation, and inflammation
lung tissue [1,2]. The field of nanotechnology is
rapidly expanding, however, the fate of nanomaterial
is not fully understood. The goal of this project
is to determine transport behavior of titanium oxide
(TiO2) and zinc oxide (ZnO) nanopowders through unsaturated
porous media in the vadose zone.
In order to resemble the vadose zone, a 2.5m column
was assembled and filled with sand (SiO2). The column
had to be transparent so that the flow of solution
through the sand could be observed. Furthermore, the
column was designed with holes for core samples every
25cm, so that the transport of the nanopowders could
be more accurately recorded.
Nanopowder solutions were pumped through the unsaturated
sand to resemble the rise and fall of a water table.
Core samples were taken and analyzed using an UV/visible-spectrophotometer.
Fines from the sand interfered with the analysis of
nanopowder concentrations present in the core samples,
preventing any quantitative data to be produced.
Before there can be any conclusion of the behavior
TiO2 or ZnO nanopowder transport through unsaturated
porous media, better means of detecting them must
be used, such as Atomic Absorption Spectroscopy (the
EPA standard method of TiO2 detection [3]) or X-ray
Spectroscopy.
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TITLE: Timber
Joints with Dynamic Loading
Abstract: Observe the joint behavior in timber single-degree-of-freedom
models to study nonlinearity, to increase the database
for nonlinear timber joint response. Find which joint
produces the best response under dynamic loading.
Study joints that are fast, easy, and cheap to use:
nails, L-plates, and mending plates. Also, model a
truss using OpenSees, subject it to similar cyclic
loading, and compare hysteretic response of the joints
from OpenSees and from the experimental SDOF models
in order to show that small models can be representative
of larger structures.
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TITLE: Repair
Methods for End Damage on AASHTO Girders
Abstract: Concrete is a cheap durable material and
therefore is widely used in our nation’s highway
system. The use of deicing salts and other factors
has caused concrete bridge girders to crack and fail.
We have taken scaled model American Association of
State Highway and Transportation (AASHTO) girders,
failed, repaired, and retested them. Six ends of three
beams we tested for stiffness then loaded to failure
in shear. Repairs include carbon fiber reinforced
polymer (CFRP), fiber-glass reinforced polymer (FRP),
and steel rods for strength in shear. They were again
tested for stiffness and failed in shear to compare
results. CFRP performs best for overall stiffness
but FRP has the greatest shear strength recovery.
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