ADSORPTION OF IONIC AND IONOGENIC COMPOUNDS BY CARBONACEOUS SUBSTANCES: pKa SHIFTS AND NOVEL INTERACTIONS AT THE SURFACE

1235459色素吸附在土壤、沉积物和大气气溶胶中的有机污染物的流动性、生物有效性和反应性方面起着关键作用，通常构成修复技术的战略基础。 最强的环境吸附剂是有机材料热解或不完全燃烧后剩余的含碳物质，称为黑碳。在结构上与黑碳密切相关的是一些人造物质，如生物炭、活性炭和碳纳米管，用于提高土壤肥力，或协助检测或去除水中的污染物，并稳定受污染的土壤和沉积物。许多新出现的污染物是离子的，或者在自然界或处理系统中通常遇到的条件下变成离子。然而，离子和可离子化的化合物吸附到黑碳上的分子机制却知之甚少。该项目涉及离子和可电离化合物的吸附，这些化合物选自药物、个人护理产品、农药、工业溶剂和内分泌干扰化合物。它将探索与聚芳族表面的新型键合相互作用，这是环境和制造碳的特征。第一种类型的相互作用适用于弱有机酸，其被假定与表面羧基和苯氧基形成异常强的H-键，称为负电荷辅助氢键（CAHB）。第二种类型的相互作用适用于带正电荷的芳族胺和杂芳族胺。因为这些芳香族阳离子是贫电子的，所以它们能够在阳离子-π相互作用的辅助下与炭黑的富电子聚芳族表面进行π-π电子供体-受体相互作用，该键被称为π +-π EDA。为了能够形成CAHB或pi+-pi EDA，假设化合物将与水进行质子交换，将氢氧根离子释放到溶液中，并导致其表面上的pKa相对于其在溶液中的pKa的正位移。一些热力学和光谱实验将进行测试这些假设，确定反应范围，并提供参数化有用的结构-性质的吸附自由能关系。对污染物分子吸附到环境颗粒表面的分子水平的深入理解是预测污染物在环境中的命运和移动的关键，有助于公共卫生法规的知识基础，也是技术控制的先决条件。该项目将研究带正电荷和负电荷的新兴污染物与环境炭黑和相关商业产品表面的新型键合相互作用，这些产品通过其预期用途接触污染物。迄今为止，环境科学家很少注意到这种相互作用。它将导致科学进步的理论和实践的重要性，为科学家感兴趣的命运和风险，这些化合物。将从该项目取得的进展中受益的其他选区包括监管机构和补救，水净化和农业行业及其利益相关者。该项目将顺利与其他项目正在进行的研究人员？的实验室，并将促进与其他机构的合作。该项目将帮助培训研究生、博士后研究人员和访问学者，并将影响高中、大学和研究生一级的教育推广课程。研究结果将在公共和科学论坛上传播。

1235459PignatelloAdsorption plays a critical role in the mobility, biological availability and reactivity of organic pollutants in soil, sediment and atmospheric aerosols, and often forms the strategic basis for remediation technologies. Among the strongest of environmental adsorbents is the carbonaceous substance remaining after pyrolysis or incomplete burning of organic material known as black carbon. Closely related structurally to black carbon are a number of manufactured substances, such as biochar, activated carbon and carbon nanotubes prescribed to improve soil fertility or to assist in the sensing or removal of pollutants in water and stabilization of contaminated soil and sediment. Many contaminants of emerging concern are ionic or become ionic under conditions normally encountered in nature or in treatment systems. The molecular mechanisms by which ionic and ionizable compounds adsorb to black carbon are poorly understood, however. This project addresses adsorption of ionic and ionizable compounds selected among pharmaceuticals, personal care products, pesticides, industrial solvents and endocrine-disrupting compounds. It will explore novel bonding interactions with the polyaromatic surface, which is characteristic of environmental and manufactured carbons. The first type of interaction applies to weak organic acids which are postulated to form exceptionally strong H-bonds, known as negative charge-assisted hydrogen bonds (CAHB), with surface carboxyl and phenoxyl groups. The second type of interaction applies to positively-charged aromatic amines and heteroaromatic amines. Because these aromatic cations are electron-poor they are capable of undergoing pi-pi electron donor-acceptor interactions, assisted by cation-pi interactions, with the electron-rich polyaromatic surface of black carbon, a bond known as pi+-pi EDA. To enable formation of a CAHB or pi+-pi EDA it is postulated that a compound will undergo proton exchange with water, releasing hydroxide ion into solution, and resulting in a positive shift of its pKa on the surface relative to its pKa in solution. A number of thermodynamic and spectroscopic experiments will be carried out to test these hypotheses, determine reaction scope, and provide parameterization useful in constructing structure-property free energy relationships of adsorption. A deep, molecular-level understanding of adsorption of pollutant molecules to the surfaces of environmental particles is a key to predicting the fate and movement of pollutants in the environment, contributes to the knowledge base underlying public health regulations, and is a prerequisite to technological control. This project will investigate novel bonding interactions of positively and negatively charged emerging contaminants with the surfaces of environmental black carbon and related commercial products that contact pollutants through their intended use. Such interactions have so far received little attention by environmental scientists. It will lead to scientific advances of both theoretical and practical importance for scientists interested in the fate and risk of such compounds. Other constituencies that will benefit from advances made in this project include regulatory agencies and the remediation, water purification, and agricultural industries and their stakeholders. The project will link smoothly with other projects now underway in the researcher?s laboratory and will foster collaboration with other institutions. The project will help train graduate students, postdoctoral researchers and visiting scholars, and will influence the course of high school, college and graduate-level educational outreach. The results will be disseminated in both public and scientific forums.