Collaborative Research: Enhanced Photolysis and Advanced Oxidation Processes by Novel KrCl* (222 nm) Irradiation

高级氧化工艺(AOPS)，如商品化的UV/AOP工艺，正越来越多地被用作去除美国和世界各地先进水回收和回用工厂中有机微污染物(OMP)的最终处理屏障。在典型的UV/AOP过程中，UV-C光(波长为254 nm)与氧化剂(如过氧化氢)相结合，生成可破坏和矿化OMP的OH自由基，这些OMP包括个人护理产品、药品、农药、除草剂等。与商用UV/AOPS中使用的低压汞灯相比，仅有有限的研究致力于表征KRCL*激射灯的光化学特性和性能。此外，还需要更多的研究来评估KRCL*激射灯的性能，并将其与商业UV/AOP系统中使用的低压UV-C灯的性能进行比较，以降解和矿化受污染的饮用水水源和废水中的OMP。该项目的首要目标是解决这些知识差距。为推进这一目标，首席调查员建议利用紫外线光解和带有KRCL*激射器的UV/AOP对水溶液和与环境相关的水/废水样本中的OMPS的降解和矿化进行基础研究。该项目的成功完成将使社会受益，因为它将产生所需的基础知识，以推动基于KRCL*exilamp的紫外光工艺的设计和实施，以在水处理和废水回收过程中去除OMPS。还将通过学生教育和培训为社会带来更多好处，包括指导佐治亚理工学院的一名研究生和一名本科生以及北达科他州州立大学的一名研究生。在222纳米处发光的氯化氪准分子灯(KRCL*激光灯)是一种很有前途的水处理紫外线(UV)来源。由于在222 nm处有高能光子，KRCL*激射灯具有有效的消毒性能，并有可能在光解和基于紫外光的高级氧化工艺(UV/AOPS)中增强对有机微污染物(OMP)的去除。然而，关于有机微球在KRCL*准分子激光作用下的光解和UV/AOP的基础知识是有限的。为了解决这一关键的知识差距，首席调查员(PI)建议系统地研究基于KRCL*激发剂的光解和222 nm处的UV/AOP来降解水溶液中的OMP，目的是阐明相关的反应机理和水基质组成对性能的影响。本研究的具体目标是：1)测量各种结构不同的有机微球在222 nm处的直接光解速率常数、摩尔消光系数和量子产率，并与254 nm处的结果进行比较；2)对222 nm处使用过氧化氢、过二硫酸盐和过氧乙酸的UV/AOP中的反应物种的生成进行量化和建模，并利用222 nm处的UV/AOP来确定选定的OMPS的降解效率；3)评价水基质组成对OMPS在222 nm处的UV/AOP光解和降解的影响，重点研究在222 nm处对紫外光有强烈吸收且具有高活性的硝酸盐；4)鉴定有机微污染物的转化产物，阐明222 nm光解和AOP的机理，包括消毒副产物前体的产生。为了实现该项目的教育和培训目标，私人投资机构建议利用佐治亚理工学院和北达科他州立大学(NDSU)的现有计划，从代表性不足的群体中招募和指导本科生参与该项目。此外，PIS计划将研究成果整合到佐治亚理工学院和南加州州立大学现有的环境工程研究生/本科课程和外联活动中(例如，STEM科学博览会和K-12学生的夏令营)。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.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.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.