Reaction of carbon nanotubes with free chlorine and monochloramine disinfectants: Byproduct formation and implications for nanotube environmental fate and toxicity

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Abstract#1233727Valentine, Richard L.Nanotubes may enter drinking water either through their use in novel treatment technologies or by release from nanomaterials. This project addresses their chemical processing by free chlorine and chloramine disinfectants. Intellectual Merit: Converging lines of evidence suggest that chlorine-based oxidants will react with CNTs via an electron transfer reaction that may also result in chlorine addition (i.e., C-Cl bond formation) to the CNT surface as well as other reactions with surface functional groups. However, these processes have not been investigated at environmentally relevant conditions, and soluble products of this reaction, especially disinfectant by-products remain unknown. Changes in CNT behavior resulting from chlorination have not previously been considered. Studies will focus on the identification of material properties of a variety of functionalized CNTs that promote reactivity toward chlorine-based disinfectants. Changes in surface properties and the potential formation of known disinfection by-products will be characterized. The investigators will also assess the impact of these disinfectants on the aqueous stability and cytotoxicity of CNTs. Broader Outcomes: Collectively, results of this work will improve the ability of engineers and scientists to predict the fate and effects of CNTs in the environment. Cytotoxicity data for chlorinated CNTs, in combination with established toxicities of identified disinfectant by-products should help regulators develop sound policy that limits the human and ecological health risks posed by CNTs during their life cycle. The project outcomes will help catalyze the responsible design and application of CNTs, providing manufacturers with guidelines about CNT properties that should be avoided so as to minimize adverse environmental impacts. In addition to moving society toward more sustainable development and applications of nanotechnology, broader impacts of this work will address the need for nanotechnology education at the undergraduate, graduate and professional level in environmental engineering. As the signature outreach effort for this project, the investigators will work with several agencies and organizations in Iowa that are responsible for drinking water supply, treatment, distribution, regulation, and finance to provide this target audience with important information about the future roles that nanotechnology may play in the delivery of safe and acceptable drinking water as well as potential regulatory implications.