Annual Report Year 2004 - Civil and Environmental Engineering

Vikesland winsCAREER awardStudy of corrosion mayimprove remediationFACULTY NEWSPeter Vikesland hopes that by studying the unheraldedrole of a byproduct of groundwater remediation,he not only improves the process, but alsodevelops a powerful new tool to study corrosion.Corrosion causes the loss of up to 20 percent of thenation’s drinking water and creates hazards in chemical plantsand fuel transportation.In support of his effort, the National Science Foundationhas awarded him a $400,000 Early Career DevelopmentProgram (CAREER) grant. The awards are the NSF’s most prestigiousawards for new faculty members.Vikesland is focusing on a promising new method toremove hazardous chlorinated solvents, such as the dry cleaningfluid perchloroethylene, which are major groundwatercontaminants. The remediation scheme is based on aserendipitous discovery in Canada about 10 years ago thatchlorinated solvents react with corroding iron and are renderedharmless.Since then, about 80 systems have been installed based onthis discovery, according to Vikesland. The remediationinvolves intercepting groundwater with a permeable treatmentwall containing corroding iron filings. “It’s a beautifullysimple system,” he said. “Basically, we dig a well situatedtrench and fill it with iron. The hydraulics are planned so thatas the water flows through the wall, the solvents react withthe corroding iron and are removed.”He explained that the systems are designed to last 30years, but the oldest one is only eight years old. “How longthey will actually last is up for debate,” he said. “The laboratorystudies use pure iron, but in the field, we are filling thewalls with scrap iron that contains many impurities other thaniron. Much of the supply of iron filings is recycled from carsand other sources of waste iron,” he said.“Maybe the impurities affect the reactivity,” he conjectured.“We really don’t know. We do know that the reactionis slower when the iron is less pure, but there could be manyreasons for this.”Nanoparticles may hold keyVikesland suggests that a byproduct of the iron corrosion—nanoscale particles of magnetite (iron oxide Fe 3 O 4 )—mayend up being the true workhorse of the process. As the ironfilings corrode in groundwater they break down to form particlesof the iron oxide magnetite that measure less than 50nanometers in diameter. “We have learned in the past decadethat as particles get smaller, their reactivity changes.”Vikesland contends that the magnetite nanoparticles arereacting in addition to the larger iron filings. “They might bereacting more slowly, but since we are designing these systemsto operate for decades, a slower time scale may be very12Peter Vikesland hopes to combine Raman spectroscopy(background) and atomic force microscopy to develop a newtool to study corrosion.appropriate,” he said. Once he has determined the role ofmagnetite, he will investigate the characteristics and propertiesthat affect that role.Part of Vikesland’s project involves studying the manufactureof synthetic magnetite. Magnetite particles are used inapplications including medical imaging and synthetic particlesare used so that geometry and composition can be preciselycontrolled. “We can make synthetic particles with no impuritiesand with well-defined shapes. Preliminary studies conductedby Erik Makus in my laboratory suggest that particlereactivity towards chlorinated solvents increases with adecrease in particle size,” Vikesland said.Once the role of magnetites is understood, systems can bedesigned to intentionally harness their activity, he said. “Wemight build a wall of magnetite particles with high confidencein their long-lasting ability...or we can design systems withquick-reacting particles that can be injected into hot zones.”New tool could aid corrosion studiesVikesland is developing a new tool to capture in-situ informationon the role of magnetite in iron corrosion. His experimentaldesign uses the fluid cell of an atomic force microscope(AFM) to obtain both AFM data and information fromRaman spectroscopy. Raman spectroscopy measures a spectrumthat is created when laser photons are used to vibratemolecules in a sample. Because different compounds generatedifferent spectra, Raman spectroscopy can identify chemicalchanges in a sample.“At its simplest, AFM rasters over the top of a surface providingan X-Y map with topography in the z-dimension” hesaid. “We can then visualize a surface and see where a corrosionsite is developing.” By combining a topographical viewwith chemical change information, obtained by Raman spectroscopy,Vikesland hopes to correlate the growth of a corrosionhole with the rate of chemical reaction. “To our knowledge,the marriage of these two techniques has never previouslybeen attempted to study corrosion,” Vikesland said. “Ifwe are successful, we will have developed a powerful tool tostudy corrosion in any material.”