Research Materials Engineer
US Army Cold Regions Research and Engineering Laboratory
Emily Asenath-Smith is a Research Materials Engineer at the US Army Cold Regions Research and Engineering Laboratory. With expertise in surface and interface chemistry, especially those involving disparate materials classes (e.g., organic-inorganic hybrid materials), she is uniquely suited to take on a wide range of cold regions and environmental challenges. She has made significant contributions to the fields of nanocomposites and bioinspired materials by demonstrating the ability to tune functional properties (e.g., photocatalytic) by controlling interface structures in hierarchical materials.
Surface Modified Photocatalysts for Treatment of Multi-Contaminant Systems
Due to the vast differences in chemical structure, identifying one method for removal of contaminants of emerging concern (CECs), from wastewaters is difficult. Photocatalytic reactions have shown great promise towards the degradation of a variety contaminants from aqueous media, yet most reports to date are focused on single contaminant systems. This research focuses on the photocatalytic degradation of CECs, with an emphasis on multi-contaminant systems and the complete removal of all degradation products.
Key to photocatalytic reactions are the generation of reactive oxygen species (ROS) (e.g., hydroxyl radical, singlet oxygen, and superoxide) that are capable of attacking specific bonds of the target contaminants. Different ROS interact with different locations/types of bonds, thereby introducing a level of selectivity to the photocatalyst. Surface modified photocatalysts have the reported ability to modify both selectivity and degradation rates as well as ROS production, presenting a means to achieve high degradation rates in multi-contaminant systems.
In this research, we investigated surface-modified TiO2 photocatalysts for the degradation of CECs. Three CECs from 3 different contaminant classes were chosen; diclofenac (pharmaceutical), 4-chlorophenol (pesticide), and methyl orange (dye). In particular, we explored the use of amino acid surface functionalities (e.g., arginine, phenylalanine) to control selectivity, ROS type, and thus degradation rates of each of the contaminants. Through the use of scavenging molecules, the types of ROS produced by each photocatalystic material was elucidated. A straightforward liquid chromatography- mass spectroscopy (LC-MS) method (12 mins) was developed to simultaneously monitor by-product generation by these contaminants during photocatalytic degradation.