RUI: Adsorption and Surface Mediated Photo-Degradation Rate of Contaminants on Colloidal Natural Organic Matter

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With support from the Environmental Chemical Sciences Program of the Chemistry Division, Dr. Mahamud Subir and his students at Ball State University explore the influence of Natural Organic Matter (NOM) on the transport and fate of emerging contaminants (ECs). ECs, such as pharmaceuticals and endocrine disruptors, are commonly detected in aquatic environments. NOM are particles suspended in environmental waters that consist of carbon-based molecules. NOM plays a role in aquatic pollutant distribution and transformation, but exactly how and to what extent remains unclear. This study focuses on finding the effect of NOM particle size and surface constituents on the uptake and photochemical breakdown of organic contaminants. The projects provide undergraduate students with a unique opportunity to perform hands-on experiments. The study creates information about binding strength of the contaminant molecules and NOM, and the rates of reactions that are mediated by the NOM surfaces. These findings help to explain the impact of ECs on our ecosystem and our health. This study uses both traditional and advanced laser spectroscopic tools in the areas of nano-, surface, and environmental chemistry. Second Harmonic Generation (SHG) and other analysis techniques isolate the surface effect from the bulk solution phase photochemistry of organic pollutants. The project develops model colloidal NOM using humic substances of distinct composition. The binding affinities of various ECs to the model NOM surfaces are measured. The rate of photolysis of both chemi- and physi-sorbed molecules at the NOM-aqueous interface is determined. In addition, the project investigates the influence of NOM size, solution acidity, and presence of reactive hydroxyl radicals on the processes of interest. These results are expected to yield an extensive catalogue of adsorption equilibrium and photo-kinetic parameters. They also provide fundamental insight into the nature of specific EC-NOM surface interactions. This knowledge can potentially assist in developing remediation methodologies.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.