Elucidating Adsorption and Competition of Mixed Oxoanion Pollutants in Porous Materials under Aqueous Conditions

An oxoanion is a negatively charged ion composed of one or more oxygen atoms along with another element. In groundwater, oxoanions are pollutants and are a threat to human health. This project will create better methods for removing such pollutants from water. Specifically, it will provide insight about pollution removal methods that work effectively even when multiple oxoanions are present in water simultaneously. The investigators will study the behavior of several oxoanions in water and show why some materials can remove them better than others. This understanding will enable the design of new materials and improved methods for water treatment. Additional benefits will come from training new scientists, and from hands-on activities at local science museums to educate the general public about water pollution. In situ infrared spectroscopy (IR) will be coupled with ab initio modeling to elucidate the behavior of oxoanions adsorbed onto porous surfaces in contact with water. This project will study the adsorption and competition of different oxoanion pollutants within porous materials, focusing on metal-organic frameworks (MOFs) as the porous materials. MOFs are selected due to their structural diversity and functional flexibility. Adsorption will be studied by infrared spectroscopy, a sensitive tool for discriminating chemical bonds and detecting a wide range of adsorbent/host interactions ranging from weak van der Waals forces to hydrogen and covalent bonds. Several basic processes involved in the adsorption of oxoanions will be examined in detail, including their diffusion, binding, competition, and molecular exchange. The key objectives are to decouple and analyze two processes involved in oxoanion adsorption: diffusion through the porous channels and binding to local sites. The project will identify the competition of different oxoanions during their diffusion through pores, and also their competition for occupying local binding sites. The findings obtained through studying MOFs will translate to other types of nanoporous materials and will provide the scientific foundations necessary for developing novel adsorption-based technologies for water purification. Education and outreach activities in this project will include summer camps, workshops and field trips to local museums to improve the public’s scientific literacy about water the cycle and pollutants. 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.