Impact of Interactions between Metal Oxides to Redox Reactivity of Iron and Manganese Oxides

1236517张了解环境中新出现的污染物的命运对于评估它们对生态系统的潜在风险至关重要。然而，复杂环境系统中污染物去向的定量估计不能通过简单的模型系统的实验和建模来准确地获得。为此，该项目将研究包含二元氧化物混合物的复杂模型系统，以模拟土壤-水环境：铁(Fe)或锰(Mn)氧化物作为氧化还原活性氧化物，铝、硅或其他铁氧化物作为第二氧化物。主要目的是确定第二金属氧化物的存在如何影响铁/锰氧化物的氧化还原活性。具体地说，将考察两个模型系统对八种有机污染物的氧化还原反应活性：以二氧化锰或针铁矿为主要氧化剂的氧化环境和以针铁矿为主要还原剂的含有可溶性亚铁离子的还原环境。为研究上述体系中目标污染物的反应动力学，将开展实验和模拟工作。潜在的粒子相互作用将基于表面络合、表面沉淀、异相聚集和竞争吸附来评估。这项研究首次研究了两种不同类型的金属氧化物之间的相互作用如何影响铁和锰氧化物的氧化还原活性。这项研究将产生对预测氧化还原活性土壤-水环境中新出现的污染物的命运至关重要的知识。这个项目的学术价值基于：1)对二元氧化物混合物中相互作用的性质以及这些相互作用如何受到溶液化学(包括pH、氧化物组成和离子强度)的影响的基本理解；2)对第二金属氧化物在氧气和缺氧条件下如何影响铁/锰氧化物的氧化还原行为的机理的理解；3)定量模拟各种金属氧化物之间的相互作用对第二种金属氧化物对铁/锰氧化物氧化还原活性的整体抑制作用的相对贡献。这项研究将为从事金属氧化物研究的水生化学家、环境工程师、地球化学家和微生物学家创造一种新的知识体系，无论是从土壤-水环境的活性还是从污染物去除的角度。通过开发复杂的模型系统，该项目的结果可以实现更准确的风险分析，最终可供公共卫生和环境机构用于污染物监管和环境清理。该项目还将有助于研究生、本科生和高中生的培训、指导和全面发展。其他计划的外联活动包括：代表人数不足的少数族裔学生和女性学生(特别是女工程师协会的学生)参加，为女高中生举办的为期一周的暑期讲习班，在NSF水和环境技术(WET)中心的年度工业咨询委员会会议上向30多个行业合作伙伴广泛宣传，融入坦普尔大学的环境课程，以及在坦普尔研讨会上发表演讲，该研讨会为来自费城地区的1000名坦普尔成员和3000名在职专业人员提供服务。

1236517ZhangUnderstanding the fate of emerging contaminants in the environment is critical for assessing their potential risks to ecological systems. Yet, quantitative estimates of contaminant fate in complex environmental systems cannot be accurately obtained through experimentation and modeling with simple model systems. For this reason, this project will investigate complex model systems containing binary oxide mixtures to resemble soil-water environments: iron (Fe) or manganese (Mn) oxides as the redox active oxides and aluminum, silicon or other iron oxides as the second oxides. The main objective is to determine how the presence of a second metal oxide affects the redox activity of Fe/Mn oxides. Specifically, two model systems will be examined for their redox reactivity with respect to eight organic contaminants: an oxidizing environment containing either manganese dioxide or goethite as the dominant oxidant and a reducing environment containing soluble ferrous ions in the presence of goethite as the dominant reductant. Experimental and modeling work will be carried out to study the reaction kinetics of the target contaminants in the above systems. Potential particle interactions will be evaluated based on surface complexation, surface precipitation, heteroaggregation, and competitive adsorption. This study is the first to examine how the interactions between two different types of metal oxides affect the redox activity of iron and manganese oxides. This research will generate knowledge that is critical for predicting the fate of emerging contaminants in redox active soil-water environments. The intellectual merit of this project is based on: 1) a fundamental understanding of the nature of interactions within binary oxide mixtures and how these interactions are affected by solution chemistry including pH, oxide composition, and ionic strength; 2) a mechanistic understanding of how a second metal oxide affects the redox behavior of Fe/Mn oxides under oxic and anoxic conditions; and 3) quantitative modeling of the relative contribution of each type of interaction between metal oxides to the overall inhibitory effect of a second metal oxide on the redox activity of Fe/Mn oxides.This study will create a new body of knowledge available to aquatic chemists, environmental engineers, geochemists and microbiologists working with metal oxides in terms of either the activity of soil-water environments or contaminant removal. By developing complex model systems, results of this project can enable a more accurate risk analysis which could eventually be used by public health and environmental agencies for contaminant regulation and environmental clean-up. This project will also contribute to training, mentoring and overall development of graduate, undergraduate and high school students. Other planned outreach activities include participation of underrepresented minority and female students (particularly from the Society of Women Engineers), one-week summer workshops for female high school students, broad dissemination to over 30 industrial partners at the annual industrial advisory board meetings for the NSF Water and Environmental Technology (WET) Center, integration into the environmental curriculum at the Temple University, and presentation at Temple seminars that serve 1000+ Temple members and 3000+ working professionals from the great Philadelphia area.