NSF-BSF: UV Advanced Oxidation of Industrial Groundwater Contaminants: The Key Role of Nitrate as *OH Sensitizer and Scavenger

地下水是国家最重要的淡水来源之一。然而，许多地下蓄水层受到工业和农业化学品污染的威胁。由于水资源日益短缺，市政当局可能需要使用受污染的水源，这些水源在使用前需要进行水净化。不幸的是，许多最常见的水处理技术是昂贵的，能源密集型的，并且可能无法完全去除污染物。这可能导致废弃受污染的威尔斯井和宝贵的水的损失，除非我们能够开发更有效和可持续的处理过程。为了应对这一挑战，本研究将利用和评估基于紫外线（UV）的氧化作为受污染地下水的处理解决方案。虽然我们知道这项技术可以降解有机污染物，但我们的知识存在差距，需要解决可持续和有效的处理问题。最重要的是，地下水的复杂性质，含有盐和其他化合物，以未知的方式影响紫外线氧化处理。这项研究通过与美国和以色列的研究人员的国际合作，对这些化学相互作用进行了全面的调查，可以有效地处理地下水。研究结果将广泛分发，并转交给水资源专业人员和其他相关利益攸关方，以帮助建设新的地下水处理设施，改善地下水质量，增加淡水供应。1，4-二氧六环和氯化烃等化学品经常用作工业溶剂。这些化合物释放到环境中导致在美国许多地方的地下水中检测到它们。去除这些污染物的处理方法通常包括空气汽提和/或活性炭吸附。然而，这些技术只是将污染物转移到另一个阶段，残留物仍然需要处理。此外，污染物如1，4-二氧六环的低吸附潜力和低挥发性使得它们不能通过这些技术去除。在这些情况下，高级氧化工艺（AOP），如使用UV/H2 O2被认为是有吸引力的处理替代方案。影响UV-AOP处理地下水的一个关键因素是硝酸盐（NO3-）的存在。NO3-在全球地下水含水层中经常被检测到，主要是由于农业活动。硝酸盐吸收紫外线，并在此过程中产生OH自由基（·OH）和亚硝酸盐（NO2-）。虽然·OH的产生是理想的，因为自由基负责污染物的氧化，但NO2-是一种强自由基清除剂，并导致氧化电位降低。本次合作研究的重点是UV-NO3-光化学，以阐明NO3-对UV-AOP处理过程中·OH生成和卤代有机污染物氧化效率的影响。这将通过一项国际合作来实现，该合作利用美国和以色列研究人员的互补专业知识来确定硝酸盐和碳酸盐诱导的自由基对污染物氧化的贡献，以阐明潜在的反应机制。这项研究的成功完成将导致处理优化和更可持续的地下水污染和补救方法的发展。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。

Groundwater is one of the Nation’s most important sources of freshwater. However, many groundwater aquifers are threatened by contamination from industrial and agricultural chemicals. Due to increased water scarcity, municipalities may need to utilize contaminated water sources that require water purification before use. Unfortunately, many of the most common water treatment techniques are expensive, energy intensive, and may not completely remove the contaminants. This can lead the abandonment of contaminated wells and the loss of valuable water unless we can develop more effective and sustainable treatment processes. To address this challenge, this study will utilize and evaluate ultraviolet (UV) light – based oxidation as a treatment solution for contaminated groundwater. While we know this technology can degrade organic contaminants, there are gaps in our knowledge that need to be addressed for sustainable and effective treatment. Most importantly, the complex nature of groundwater that contains salts and other compounds that impact UV oxidation treatment in unknown ways. This study provides a comprehensive investigation of these chemical interactions through an international collaboration with researchers from the United States and Israel that can lead to efficient groundwater treatment. The findings will be broadly distributed and transferred to water professionals and other relevant stakeholders to help build new groundwater treatment facilities, improve groundwater quality, and increase freshwater supply.Chemicals such as 1,4-dioxane and chlorinated hydrocarbons are frequently used as industrial solvents. Release of these compounds to the environment has resulted in them being detected in groundwater at many locations in the USA. Treatment approaches for the removal of these contaminants typically include air stripping and/or adsorption on activated carbon. However, these techniques merely transfer contaminants to another phase, and the residuals still need to be treated. Furthermore, the low sorption potential and low volatility of contaminants such as 1,4-dioxane render them unable to be removed by these technologies. In these cases, advanced oxidation processes (AOPs) such as the use of UV/H2O2 are considered to be attractive treatment alternatives. A key factor affecting UV-based AOP treatment of groundwater is the presence of nitrate (NO3-). NO3- is frequently detected in groundwater aquifers globally, mainly as a result of agricultural activity. Nitrate absorbs UV light, and in the process produces OH radicals (•OH) and nitrite (NO2-). While the production of •OH is desirable as the radicals are responsible for the oxidation of the contaminant, NO2- is a strong radical scavenger and results in reduction in oxidation potential. The collaborative research in this proposal focuses on UV- NO3- photochemistry to elucidate the impact of NO3- on the generation of •OH and halogenated organic contaminant oxidation efficiency during UV-based AOP treatment. This will be achieved by an international collaboration that leverages the complementary expertise of researchers in the United States and Israel to identify the contribution of nitrate and carbonate induced radicals to pollutant oxidation to elucidate the underlying reaction mechanisms. Successful completion of this research will lead to treatment optimization and the development of more sustainable approaches for groundwater contamination and remediation. These results will be broadly applicable to other fields such as water treatment and wastewater treatment.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.