State Water Resources Research Institute Program

Project ID: 2008ND165B
Title: Selected Pesticide Remediation with Iron Nanoparticles: Modeling and Barrier Applications
Project Type: Research
Start Date: 3/01/2008
End Date: 2/28/2009
Congressional District: 1
Focus Categories: Methods, Groundwater, Water Quality
Keywords: Iron nanoparticles, Treatment, Herbicides, Groundwater remediation
Principal Investigator: Bezbaruah, Achintya Nayan (North Dakota State University)
Federal Funds: $ 5,000
Non-Federal Matching Funds: $ 10,000
Abstract: Iron metal has been used for the remediation of contaminated groundwater for about two decades. The most common mode of contaminant degradation by iron is reductive dehalogenation. Typically, iron for remediation is in the form of filings or microscale powder. In this manner, iron has been used in the field and laboratory to remediate water contaminated with chlorinated ethanes, chlorinated methanes, arsenic, and pesticides. The advantages of iron metal for remediation include its non-toxicity, economy, and faster reaction rates than biological processes. The above reaction has been shown to be surface area dependant. Because of the relatively low surface area of iron filings and powder, reactions may be slow or incomplete, resulting in possibly toxic degradation by-products. With the development of nanoscale zero-valent iron (nZVI) for environmental remediation, many of the problems associated with iron filings were resolved. Iron nanoparticles are typically 1-100 nm in diameter. This results in specific surface areas in the order of 20-30 m2/g compared to about 0.05 and 5 m2/g for iron filings and lab-grade iron micropowder, respectively. Research has shown that nZVI can successfully degrade chlorinated ethenes , chlorinated methanes, PCBs, arsenic , and other metals in anoxic environments. Additionally, a recent study has shown that some pesticides can be treated by nZVI in oxic conditions. Advantages of nZVI over microparticles include improved economics of direct injection into the aquifer, very fast reaction rates and more complete reactions. Pesticides, including herbicides, insecticides and fungicides, are among the many contaminants successfully treated by conventional iron powder or iron filings. Numerous studies have demonstrated success on the bench scale and field scale. Research has shown that pesticides, when applied and handled properly, will not accumulate to high levels in groundwater. However, accidents and spills can and do happen, often resulting in very high pesticide concentrations. Iron nanoparticles have shown potential to remediate such spills. While the proposed nZVI/pesticide trials have been largely successful in the laboratory (see "Research Progress Made"), the final goal of the work is a small-scale pesticide spill remediation technology. To achieve this, a delivery vehicle is needed. Polymeric delivery vehicles have been developed that both disperse nZVI and protect it from non-target species. Unfortunately, these polymeric coatings are synthetic and thus, may not be desirable in the subsurface. While this may be an acceptable trade-off for highly toxic and recalcitrant chlorinated solvent sites, this is an unsuitable approach for smaller, less toxic pesticide spills. For the proposed application, the delivery vehicle must be biodegradable, economic and relatively simple to use. Calcium alginate is an ideal candidate for this application. This work aims to entrap and encapsulate (two distinct technologies) nZVI in calcium alginate with the end goal being a product that can be easily emplaced in a trench or bore hole for site remediation. Alginate entrapment/encapsulation is a process where nZVI is captured in an alginate matrix (entrapment) or encapsulated in a thin-walled alginate capsule (encapsulation). Although the entrapped/encapsulated nZVI (E/E nZVI) will lack many of the specialized properties of more advanced polymeric vehicles, it will be biodegradable, inexpensive, and simple to emplace.

Progress/Completion Report, PDF

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