EPA Nanotechnology and the Environment ... - Mechatronics

Nanotechnology and the Environment: Applications and Implications STAR Progress Review Workshop
Nanoscale Bimetallic Particles for In Situ Remediation
Wei-xian Zhang
Lehigh University, Bethlehem, PA
Abstract
Nanoscale bimetallic (Fe/Pd, 99.9% Fe) particles are
among the vanguard of a new generation of remediation
technologies that could provide cost-effective remedial
solutions to some of the most difficult sites. Nanoparticles
feature large surface areas and extremely high surface
reactivity. Equally important, they provide enormous flexibility
for in situ remedial applications. The primary goal
of this research is to continue the research and development
of the nanoscale bimetallic particle technology for
in situ remediation.
Several key technical issues of the nanoscale bimetallic
particle technology will be investigated—the most
important being the optimization and scaleup of the synthesis
processes. A system will be built with the capacity
to synthesize 500 to 1,000 grams of nanoparticles per
day. The major experimental tasks include: (1) synthesis
of various nanoscale particles (Fe/Pd, Fe/Ag, Fe/Ni, Fe/
Co, Fe/Cu, etc.); (2) feasibility studies (batch and column)
of treatment of perchlorate (ClO 4-
) and chromium
(Cr(VI)) with various nanoparticles; (3) batch and column
studies of treatment of mixed wastes, including
organic solvents and heavy metals; and (4) modeling
and column studies of injection, transport, and reactions
of nanoparticles in porous media.
The complete reduction of aqueous perchlorate to
chloride by nanoscale iron particles over a wide concentration
range (1-200 mg/L) has been observed. The reaction
is temperature sensitive as evidenced by progressively
increasing rate constant values of 0.013, 0.10,
and 1.52 mg perchlorate per g iron per hour, respectively,
at temperatures of 25 ºC, 40 ºC, and 75 ºC. The
large activation energy of 79.02 ± 7.75 kJ/mole partially
explains the stability of perchlorate in water. Iron
nanoparticles may represent a feasible remediation alternative
for perchlorate-contaminated groundwaters, an
environmental concern of growing importance. In a more
general sense, the results illustrate the profound impact
of particle size in surface mediated reactions.
The results of this research will provide insight and
information that are essential for: (1) cost-effective production
of the nanoparticles in large quantity; (2) potential
applications of the nanoparticles for in situ remediation;
and (3) education of students in environmental nanotechnologies.
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The Office of Research and Development’s National Center for Environmental Research