Collaborative Research: Overlooked Oxidation of Aqueous Alcohols: Kinetics, Mechanism, and Relevance to Water Reuse

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With support from the Environmental Chemical Sciences Program in the Division of Chemistry, Emily Marron at the University of Utah and Daniel McCurry at the University of Southern California and their students will study chemical processes occurring in wastewater treatment, specifically, when chlorine is added to water to remove harmful bacteria and viruses. However, the addition of chlorine to wastewater also results in the production of unintended chemical byproducts that may be toxic. This project will characterize the reaction of chlorine with alcohols, such as methanol (wood alcohol) and ethanol, which are present in wastewater, to produce aldehydes, such as formaldehyde and acetaldehyde, reactive compounds that can have deleterious biological properties, particularly in adducting biomolecules, including nucleic acids and proteins. Understanding the chemistry of aldehyde production from alcohols and chlorine is important to minimize the formation of these chemicals during wastewater treatment. In the face of climate change and drought, communities across the United States lack reliable sources of drinking water. Re-using wastewater (sewage) is an option to increase water supply in areas facing water stress. Wastewater reuse involves many treatment steps to ensure the water is safe to drink. Undergraduate researchers from both institutions will contribute to the work and inform the scientific community about the project findings through social media.During wastewater reuse, oxidation with ozone or chlorine to inactivate pathogens and transform chemical contaminants can form toxic low molecular weight compounds including aldehydes. While aldehyde generation from ozonation of wastewater is well understood, the kinetics, mechanism of formation, and potential precursors during chlorination are largely unknown. This project will investigate the formation of aldehydes from the chlorination of an overlooked group of precursors: alcohols. Preliminary experiments have demonstrated that methanol can be oxidized to formaldehyde by chlorine under conditions relevant to water treatment. Alcohols such as methanol and ethanol are frequently used as a supplemental carbon source during conventional wastewater treatment, and are likely present in water reuse operations. Additionally, alcohols are routinely used in environmental chemical research for stock solution preparation under the assumption that they are inert with respect to chlorine. The goals of this project include determining the kinetics, products, and mechanism of aqueous alcohol oxidation by chlorine, the development of a new method for quantifying trace alcohols in complex aqueous matrices, and its application to quantify alcohols in wastewater effluent and their contribution to observed aldehyde formation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.