NSF Award
2310137
Advanced oxidation processes (AOPs) such as the commercial UV/AOP process are increasingly being utilized as a final treatment barrier to remove organic micropollutants (OMPs) in advanced water reclamation and reuse plants in the United States and worldwide. In a typical UV/AOP process, UV-C light (254 nm in wavelength) is combined with an oxidant (e.g., hydrogen peroxide) to generate OH free radicals that can destroy and mineralize OMPs including personal care products, pharmaceuticals, pesticides, herbicides, etc. Krypton chloride excimer lamps (KrCl* excilamps) are novel and promising mercury-free UV sources that emit radiation with a wavelength of 222 nm. Compared to low-pressure mercury lamps that are utilized in commercial UV/AOPs, only limited research has been devoted to the characterization of the photochemical properties and performance of KrCl* excilamps. In addition, more research is needed to assess and benchmark the performance of KrCl* excilamps against those of low-pressure UV-C lamps used in commercial UV/AOP systems to degrade and mineralize OMPs from contaminated drinking water sources and wastewater. The overarching goal of this project is to address these knowledge gaps. To advance this goal, the Principal Investigators (PIs) propose to carry out a fundamental investigation of the degradation and mineralization of OMPs in aqueous solutions and environmentally relevant water/wastewater samples using UV photolysis and UV/AOP with a KrCl* excilamp that emits UV radiation at 222 nm. The successful completion of this project will benefit society through the generation of the foundational knowledge required to advance the design and implementation of KrCl* exilamp-based UV processes for the removal of OMPs during water treatment and wastewater reclamation. Additional benefits to society will be achieved through student education and training including the mentoring of one graduate student and one undergraduate at Georgia Tech and one graduate student at North Dakota State University.<br/><br/>Krypton chloride excimer lamp (KrCl* excilamp) emitting light at 222 nm is a promising ultraviolet (UV) source for water treatment. Because of the high-energy photons at 222 nm, KrCl* excilamps exhibit effective disinfection performance and have the potential to enhance removal of organic micropollutants (OMPs) in photolysis and UV-based advanced oxidation processes (UV/AOPs). However, limited fundamental knowledge is available on the photolysis and UV/AOP of OMPs under a KrCl* excilamp. To address this critical knowledge gap, the Principal Investigators (PIs) propose to systematically investigate the KrCl* excilamp based photolysis and UV/AOP at 222 nm to degrade OMPs in aqueous solutions with the goal of elucidating the relevant reaction mechanisms and the impact of water matrix composition on performance. The specific objectives of the research are to 1) measure the direct photolysis rate constants, molar extinction coefficients, and quantum yields of KrCl* excilamps at 222 nm for a wide range of structurally-diverse OMPs, and compare the measured properties with those at 254 nm; 2) quantify and model the generation of reactive species in a UV/AOP at 222 nm using hydrogen peroxide, peroxydisulfate, and peracetic acid, and determine the degradation efficiency of selected OMPs using UV/AOP at 222 nm; 3) evaluate the effect of water matrix composition on the photolysis and degradation of OMPs using UV/AOP at 222 nm, with a focus on nitrate which strongly absorbs UV light and is highly reactive at 222 nm; and 4) identify organic micropollutant transformation products and elucidate the mechanisms of photolysis and AOP at 222 nm including the generation of disinfection byproduct precursors. To implement the education and training goals of the project, the PIs propose to leverage existing programs at Georgia Tech and North Dakota State University (NDSU) to recruit and mentor undergraduate students from underrepresented groups to work on the project. In addition, the PIs plan to integrate the research findings into existing environmental engineering graduate/undergraduate courses and outreach activities (e.g., STEM science fairs and summer camps for K-12 students) at Georgia Tech and NDSU.<br/><br/>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.
