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Abstract Submission Form

Desert Remedial Action Technologies

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**Title:** Bench-Scale and Field-Scale Evaluation of Nanoscale Iron
Transport and Reactivity

**Name of First Author:** Laurie LaPat-Polasko

**Email of Author:** llapat@geomatrix.com **Author Phone Number:**
480-348-1283

**Organization to Which Author(s) belong** Geomatrix Consultants

**Conference Theme Considered Appropriate for Contents of
Presentation:** In situ remediation of Volatile Chlorinated Organics

**Other Authors (name and e-mail):**Peter Bennett;
pbennett@geomatrix.com

**Author Biography:**      

Dr. LaPat-Polasko has more than 20 years of experience as a technical
consultant and project manager for efforts involving groundwater and
soil remediation and wastewater treatment. Combining her knowledge of
microbiology with a background in civil engineering, Dr. LaPat-Polasko
has focused on remediation and natural attenuation of groundwater and
soil impacted by organic and inorganic compounds. She has dealt with
contaminants ranging from fluoride and arsenic to chlorinated solvents
and explosives. Dr. LaPat-Polasko has been actively involved in numerous
Water Quality Assurance Revolving Fund (WQARF) and Superfund (CERCLA)
sites.

Dr. LaPat-Polasko has developed, designed, and implemented remediation
plans for water and soil systems. She has field- and laboratory-tested
aerobic and anaerobic methods for treating contaminated groundwater and
soil and has studied the treatment role of various microbial
communities. She has identified and evaluated a wide variety of
pathogens in surface water and groundwater. She has taught several
graduate courses in water and soil remediation at Arizona State
University. Dr. LaPat-Polasko has extensive experience interacting with
the U.S. Environmental Protection Agency (EPA), the Arizona Department
of Environmental Quality (ADEQ), and various county and city regulatory
agencies in Arizona and California.

**Text of the Abstract:**      

Several bench-scale tests were performed to assess the transport of iron
nanoparticles in soil. The first bench-scale test evaluated the
transportability of the nanoscale iron A through different sand and soil
matrices. Fifteen 24 inch by 1 inch columns were prepared using three
different matrices: silica sand, a silty sand and a sandy clay. The
columns were flushed with three void volumes of water containing \~ 2.5
mg/L of suspended nanoscale iron A into the triplicate columns
containing the three media described above. Duplicate control columns
received the same water without nanoscale iron. The study involved
measuring iron in the column effluent and in the soil matrices. Iron was
not detected in column effluents after five void volumes had passed
through the silica sand columns. Chemical analysis of the top 2" of the
silica sand from each column indicated that all of the nanoscale iron
was present at the influent end of the column. This observation suggests
that transport of the nanoparticles was strongly retarded relative to
water in the silica sand columns.

A second bench-scale was conducted to evaluate the transportability of
four different nanoscale irons through #2-12 silica sand packed in
columns that were 24 inches in length, and 1-inch in diameter. The
results of this study indicated that after 2 pore volumes had been
passed through the columns, two recently developed formulations of
nanoscale iron: had transported through the entire length of the column.
Whereas one of the other two nanoscale iron products was transported
less than 50 percent of the distance through the column, and the fourth
product did not appear to move more than an inch or two.

Field experiments were conducted with the freshly prepared nanoparticles
at a former manufacturing facility, where groundwater was impacted by
chlorinated solvents. To our knowledge, this field testing program
represents the first onsite fabrication and field testing program for
stabilized nanoparticles composed of iron and iron/palladium. Field
production of the nanoparticles was accomplished using a batch reactor
capable of producing 30 to 90 gallon batches of stabilized
nanoparticles. The nanoparticles were prepared within a deoxygenated
aqueous solution of ferrous iron and sodium carboxymethyl cellulose
(CMC- the stabilizing agent to prevent agglomeration). Sodium
borohydride was added to the solution to reduce the ferrous iron to
zerovalent iron (ZVI) nanoparticles (nZVI). A palladium salt was then
added to one of the batches prepared to further increase the reactivity
of the nanoparticles by coating them with a palladium metal catalyst.
Bromide was added to each batch as a conservative tracer prior to
injection of each batch of stabilized nanoparticles. Four single well
push-pull tests were conducted to assess the site-specific
transportability of nZVI in saturated coarse-grained alluvial sediments,
and to assess reactivity of the freshly prepared nanoparticles *in
situ*. The push-pull test results indicated that the in situ destruction
of chlorinated solvents was rapid upon nZVI injection, based on an
increase in ethane and ethene concentrations relative to chlorinated
ethenes. The reactivity and transportability of the nanoparticles
appeared to be somewhat short-lived. Transportability was lost after
several hours perhaps because of CMC consumption by subsurface bacteria.