Mechanistic Studies of Water Disinfectants on Iron Interfaces

在化学系环境化学科学项目的支持下，Kathryn Perrine和她的学生将研究氯胺（一种用于水消毒的化合物）与铁、氧化铁和碳酸铁表面之间的基本化学相互作用。消毒剂用于处理供水管道中的病原体，但也会与天然有机物发生反应，产生不需要的副产品，这些副产品可能会进入地下水。（单）氯胺是一种首选的氧化性消毒剂，因为它产生的副产品比其他含氯消毒剂少。铁、氧化铁和碳酸铁表面在环境中无处不在，并以矿物和含铁分布线路的形式存在。氯胺在铁界面上的表面吸附机理和失活机理尚不清楚。本项目将研究氯胺在明确界面上的表面化学反应和分解机理。这些研究有可能促进我们对水系统中影响污染物对水质影响的复杂混合物氧化机制的理解。本科生将体验暑期研究实习和大学前拓展活动。6-12年级的学生将参加以探究为基础的实验室，这将是密歇根理工大学暑期青年项目的一部分。这些活动将集中在水表面化学和腐蚀，pH值对金属溶解的影响，以及液/固界面的表面反应。重点研究氯胺在单晶表面气/固界面铁界面上的吸附和分解机理。水和H2解离对铁表面位点和羟基位点的影响会促进或阻断氯胺的反应和分解途径。氯胺在液/固界面上对铁的吸附将使用PI的新的原位偏振调制红外反射吸收光谱（PM-IRRAS）方法在空气/液/固界面上进行测量，以将原始条件下的表面机理与凝聚相中的实际反应联系起来。该研究利用新型表面分析技术测量气/固和液/固界面的反应，有可能影响水资源及其净化的跨学科领域，并与水源、维护和管理相关的社会影响。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。

With support from the Environmental Chemical Sciences Program in the Division of Chemistry, Kathryn Perrine and her students will study fundamental chemical interactions between chloramine, a compound used for water disinfection, with iron, iron oxide, and iron carbonate surfaces. Disinfectants are used to treat pathogens in distribution water lines, but also react with natural organic matter to produce undesired byproducts that can make their way into ground water. (Mono)chloramine is a preferred oxidizing disinfectant since it produces fewer byproducts than other chlorine-containing disinfectants. Iron, iron oxide, and iron carbonate surfaces are ubiquitous in the environment and present as minerals and iron-containing distribution lines. The surface adsorption mechanism and deactivation of chloramine on iron interfaces is not well understood. This project will investigate the surface chemical reaction and decomposition mechanisms of chloramine on well-defined interfaces. These studies have the potential to advance our understanding of oxidation mechanisms in complex mixtures in aqueous systems that impact the effect of contaminants in water quality. Undergraduate students will experience summer research internships and precollege outreach activities. Students in grades 6-12 will participate in inquiry-based labs that will be developed as part of Michigan Tech’s summer youth programs. These activities will focus on aqueous surface chemistry and corrosion, effects of pH on metal dissolution, and surface reactions at the liquid/solid interface.The key objectives will be addressed on the kinetic adsorption and decomposition mechanism of chloramine on iron interfaces at the gas/solid interface on well-defined single crystal surfaces. The influence of the iron surface sites and hydroxyl sites from water and H2 dissociation will promote or block the chloramine reaction and decomposition pathways. The adsorption of chloramine on iron at the liquid/solid interface will be measured using the PI’s new in situ polarized modulated infrared reflection absorption spectroscopy (PM-IRRAS) method at the air/liquid/solid interface to connect the surface mechanism under pristine conditions with realistic reactions in the condensed phase. Using novel surface analysis techniques that measure reactions at the gas/solid and liquid/solid interface, the research being conducted under this award, has the potential to impact areas across disciplines focusing on water resources and their purification, with societal implications associated with water sourcing, maintenance and management.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.