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Formation of Environmentally Persistent Free Radicals on Engineered Nanomaterials During Thermal Treatmen

热处理过程中工程纳米材料上环境持久性自由基的形成

基本信息

批准号：
1834638
负责人：
Eric Vejerano
金额：
$ 38.06万
依托单位：
University of South Carolina at Columbia
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-12-01 至 2023-11-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1834638&HistoricalAwards=false
关键词：
Formation Environmentally Persistent Free Radicals

项目摘要

Environmentally persistent free radicals, a new class of environmental pollutants, are formed during the thermal treatment of wastes and hazardous materials. Environmentally persistent free radicals are present at sufficiently high levels in diverse environments such as atmospheric particulate matter. Unlike previously identified atmospheric free radicals that exhibit lifetimes of less than a second, environmentally persistent free radicals exist for hours to months, lifetimes which are long enough for them to be transported over long distances from their source. Despite pioneering studies on environmentally persistent free radicals that have significantly improved our understanding of their environmental and human health effects, fundamental questions remain unanswered. This project will assess the impact of engineered nanomaterials on the formation of environmentally persistent free radicals during thermal treatment of wastes. Results will: 1) improve understanding of the interaction of engineered nanomaterial in forming environmentally persistent free radicals during thermal treatment of wastes; 2) improve understanding of the behavior, fate, transformation of and human and environmental exposures to engineered nanomaterials and environmentally persistent free radicals; and 3) support the nanotechnology revolution by informing the development of disposal strategies suitable for engineered nanomaterials. Results will assist in mitigating adverse impacts of engineered nanomaterials and environmentally persistent free radicals and will facilitate the development of potentially safer applications of engineered nanomaterials that can lead to enhanced economic opportunities. In addition, underrepresented students will be trained in science and engineering topics through their participation in the research project. The project will also involve the promotion of teaching and learning by integrating project concepts, methods, and results in the development of new curriculumPrevious studies have simulated experimentally the formation of environmentally persistent free radicals on nano-sized transition metal oxides that are supported on surfaces of large micron-sized particles. The prevailing thought on the formation of environmentally persistent free radical assumes that the transition metal is a key component, serving as the electron donor to an organic molecule. This view explains environmentally persistent free radicals that are formed over some transition metal oxides, but it is inconsistent with those formed over a zinc oxide surface in which an electron transfers to the organic molecule instead. Hence, the current mechanism cannot be generalized, and environmentally persistent free radicals may form via other pathways. Answers to these questions hinge on the hypothesis that since band gap energy for engineered nanomaterials exhibits size-dependence and thermally excited electrons may cross this band gap easily, some engineered nanomaterials, depending on size and electronic and chemical properties, may form and stabilize aromatic organic species forming environmentally persistent free radicals. Extending this hypothesis, engineered nanomaterials, other than those composed of transition metals that survive incineration, may form environmentally persistent free radicals. Experimental studies will determine if: (1) engineered nanomaterials and engineered nanomaterials, other than transition metals, can form and stabilize environmentally persistent free radicals; (2) changes in the physicochemical properties of engineered nanomaterials during thermal treatment impact environmentally persistent free radicals formation; or (3) environmentally persistent free radicals can form on engineered nanomaterials at temperatures lower than those that occur during combustion. Experimental methods will use these analytical techniques: electron paramagnetic resonance spectroscopy to measure and characterize environmentally persistent free radicals; mass spectroscopy to determine the nature of chemical species formed when persistent free radicals recombine, and electron microscopy and other surface-sensitive techniques to characterize changes in the nanomaterials. The results of this study are expected to transform the current understanding on environmentally persistent free radicals. First, if environmentally persistent free radicals can form on non-metallic engineered nanomaterials, it will challenge the existing thought that environmentally persistent free radicals form exclusively on transition metal oxide nanoparticles. Second, if environmentally persistent free radicals can form at a lower temperature on engineered nanomaterials, it suggests that environmentally persistent free radicals can form easily and are thus more prevalent.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.

环境持久性自由基是废物和有害物质在热处理过程中形成的一类新的环境污染物。环境持久性自由基在大气颗粒物等多种环境中以足够高的水平存在。与之前发现的大气自由基的寿命不到一秒不同，环境持久性自由基可以存在数小时到数月，寿命足够长，可以从源头长途运输。尽管对环境持久性自由基的开创性研究大大提高了我们对其对环境和人类健康影响的理解，但基本问题仍未得到解答。该项目将评估工程纳米材料对废物热处理过程中环境持久性自由基形成的影响。结果将：1)提高对工程纳米材料在废物热处理过程中形成环境持久性自由基的相互作用的认识；2)提高对人类和环境暴露于工程纳米材料和环境持久性自由基的行为、命运、转变的理解；3)通过为开发适合工程纳米材料的处理策略提供信息，支持纳米技术革命。研究结果将有助于减轻工程纳米材料和环境持久性自由基的不利影响，并将促进工程纳米材料潜在更安全应用的发展，从而增加经济机会。此外，代表性不足的学生将通过参与研究项目获得科学和工程主题的培训。该项目还将通过整合项目概念、方法和新课程开发的结果来促进教学和学习。以前的研究已经通过实验模拟了纳米级过渡金属氧化物上环境持久性自由基的形成，这些氧化物被支持在大微米级颗粒的表面上。关于环境持久性自由基形成的普遍观点认为，过渡金属是一个关键成分，作为有机分子的电子供体。这种观点解释了在一些过渡金属氧化物上形成的环境持久性自由基，但它与在氧化锌表面形成的自由基不一致，因为氧化锌表面的电子转移到了有机分子上。因此，目前的机制不能一概而论，环境持久性自由基可能通过其他途径形成。这些问题的答案取决于这样一个假设：由于工程纳米材料的带隙能量表现出尺寸依赖性，热激发电子可以很容易地穿过这个带隙，一些工程纳米材料，取决于尺寸和电子和化学性质，可能形成并稳定芳香有机物质，形成环境持久性自由基。延伸这一假设，工程纳米材料，除了那些在焚烧中幸存下来的过渡金属组成的材料，可能会形成环境持久性自由基。实验研究将确定：(1)工程纳米材料和工程纳米材料，除了过渡金属，可以形成和稳定环境持久性自由基；(2)热处理过程中工程纳米材料理化性质的变化影响环境持久性自由基的形成；或者(3)环境持久性自由基可以在工程纳米材料上形成，温度低于燃烧时的温度。实验方法将使用以下分析技术：电子顺磁共振波谱法测量和表征环境持久性自由基；质谱法用于确定持久性自由基重组时形成的化学物质的性质，电子显微镜和其他表面敏感技术用于表征纳米材料的变化。这项研究的结果有望改变目前对环境持久性自由基的认识。首先，如果环境持久性自由基可以在非金属工程纳米材料上形成，这将挑战现有的环境持久性自由基只在过渡金属氧化物纳米颗粒上形成的观点。其次，如果环境持久性自由基可以在较低的温度下在工程纳米材料上形成，这表明环境持久性自由基更容易形成，因此更普遍。该奖项反映了美国国家科学基金会的法定使命，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。