Impact of dissolved organic matter on phenolic contaminant oxidation by manganese oxides

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Manganese (Mn) oxides are naturally occurring minerals found in soil that have shown great promise to transform toxic waterborne contaminants less hazardous byproducts. However, natural dissolved organic matter (DOM) may dramatically limit this transformation capacity. Given that DOM is present in natural waters, the impacts of DOM must be understood to further develop Mn oxides as a treatment technology. This research project will address this issue through detailed analysis of contaminant transformation in the presence of DOM using state-of-the-science chemical analysis. Successful completion of this research will allow assessing the feasibility of Mn oxide-based remediation of contaminated water and guide efforts to increase the efficiency of the process. Additional benefits to society will come from supporting women and underrepresented minorities in the research, thus broadening the diversity of the Nation’s STEM workforce. Additional educational outreach to K-12 students will increase understanding of environmental pollution and increase the Nation’s scientific literacy. Manganese (Mn) oxides are ubiquitous, strong oxidants capable of reacting with inorganic and organic contaminants. The use of natural or synthetic Mn oxides in engineered systems and for in situ treatment of contaminated waters is currently being explored. However, a fundamental understanding of how organic contaminants interact with Mn oxides is in its infancy. The ubiquitous nature of dissolved organic matter (DOM) in natural environments adds to the complexity of determining the rates and mechanisms of organic contaminant degradation by Mn oxides. Not only does DOM sorb and react with Mn oxides, it also may stabilize dissolved organic and inorganic reaction products. Previous work indicates that DOM may therefore increase, decrease, or have no effect on phenolic contaminant degradation by Mn oxides. A better understanding of these interactions is needed to apply Mn oxides for water treatment. Thus, the overall goal of the proposed project is to identify the key mechanisms that govern the interactions of DOM, Mn oxides, and phenolic contaminants in engineered systems designed to oxidize contaminants. This goal will be achieved through the following research objectives to: 1) characterize the interactions of DOM with Mn oxides using six model DOM isolates and three whole waters that cover a wide range of DOM composition; and 2) assess the impact of DOM on organic contaminant transformation by Mn oxides using six phenolic contaminants that have different rate-limiting steps. Together, this novel approach combining surface and aqueous chemistry will facilitate understanding the mechanisms by which DOM alters contaminant transformation rates and the interactions between DOM, Mn oxides, and phenolic contaminants.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.