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

高级氧化工艺（AOP）如商业UV/AOP工艺越来越多地被用作最终处理屏障，以在美国和世界范围内的高级水回收和再利用工厂中去除有机微污染物（OMP）。在典型的UV/AOP工艺中，将UV-C光（波长为254 nm）与氧化剂（例如，过氧化氢）以产生OH自由基，OH自由基可以破坏和矿化OMP，包括个人护理产品、药物、杀虫剂、除草剂等。氯化氪准分子灯（KrCl* excilamps）是新颖且有前途的无汞UV源，其发射波长为222 nm的辐射。与商业UV/AOP中使用的低压汞灯相比，只有有限的研究致力于表征KrCl* excilamps的光化学性质和性能。此外，还需要进行更多的研究，以评估和基准测试KrCl* excilamps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。为了推进这一目标，首席研究员（PI）建议使用UV光解和UV/AOP对水溶液和环境相关水/废水样品中OMP的降解和矿化进行基础研究，其中KrCl* excilamp发射222 nm的UV辐射。该项目的成功完成将有利于社会通过生成所需的基础知识，以推进设计和实施的KrCl* exilamp为基础的紫外线工艺，用于在水处理和废水回收过程中去除OMP。通过学生教育和培训，包括指导格鲁吉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，将为社会带来额外的好处。发射222 nm光的氯化氪准分子灯（KrCl* excilamp）是一种很有前途的水处理紫外线（UV）源。由于222 nm处的高能光子，KrCl* excilamps表现出有效的消毒性能，并有可能在光解和基于UV的高级氧化过程（UV/AOPs）中增强有机微污染物（OMP）的去除。然而，有限的基本知识是可利用的光解和UV/AOP的OMP下的KrCl* exilamp。 为了解决这一关键的知识差距，主要研究人员（PI）建议系统地研究KrCl* excilamp的光解和222 nm的UV/AOP降解水溶液中的OMP，目的是阐明相关的反应机制和水基质组成对性能的影响。本研究的具体目标是：1）测量了KrCl* excilamps在222 nm处的直接光解速率常数、摩尔消光系数和量子产率，并将测量的性质与254 nm处的性质进行了比较; 2）使用过氧化氢、过二硫酸盐和过乙酸，在222 nm下的UV/AOP中对反应性物质的产生进行量化和建模，3）使用UV/AOP在222 nm下评估水基质组成对OMP的光解和降解的影响，重点是强烈吸收UV光并且在222 nm下具有高反应性的硝酸盐;（4）确定了有机微污染物的转化产物，并阐明了222 nm处的光解和AOP机制，包括消毒副产物前体物的产生。为了实现该项目的教育和培训目标，PI建议利用格鲁吉亚理工学院和北达科他州州立大学（NDSU）的现有项目，从代表性不足的群体中招募和指导本科生从事该项目。此外，研究所计划将研究结果纳入现有的环境工程研究生/本科生课程和外展活动（例如，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.