EAGER: Mapping the Distribution and Interaction of Multi-Adsorbates at Metal Oxide-Water Interfaces Using EC-STM/STS

本研究的主要目的是建立一种新的方法，利用电化学扫描隧道显微镜(EC-STM)和扫描隧道光谱(STS)对金属氧化物表面的多重吸附进行原位标绘和鉴定。由于磷酸盐和钙在环境和水处理系统中对铁氧化物对砷的吸附有显著影响，因此一个包含砷酸盐、磷酸盐、钙和赤铁矿的多重吸附体系将被用作竞争吸附模型体系。所提出的研究是基于这样的假设：被吸附的阴阳离子在金属氧化物表面可以有不同的分布和相互作用，如斑块和混合分布，对不同表面羟基的优先吸附，表面和三维团簇的形成，被吸附的阴离子之间的静电排斥，阴离子表面物种的阳离子桥联，以及表面诱导的氢键。目前，还没有技术来确定这些基本的表面特征，这限制了我们开发多组分吸附模型来预测污染物在环境中的去向和迁移以及水处理系统中吸附剂的吸附能力的能力。本研究建立的表面分析方法将使科学家和工程师能够在分子水平上研究污染物和共存化合物在矿物和吸附剂表面的竞争吸附，催化剂(如二氧化钛)和纳米材料表面的化学反应，以及由于共存化合物在溶液中的不可逆吸附而导致的催化剂中毒。了解被吸附的多组分物种的分布和相互作用将有助于开发新的吸附模型和发明更有效的吸附剂和催化剂。该项目整合了尖端研究和更广泛的教育，面向研究生、本科生和预科学生，以及代表不足的群体。一名研究生将在皮？S的指导下接受培训，进行拟议的研究。一名本科生将通过史蒂文斯暑期奖学金计划参与一些研究。PI和研究生研究助理将通过现有的推广计划向EN375LA环境工程实验室班级的本科生以及初中生和中学教师演示EC-STM成像过程。该研究所将把研究成果整合到EN 551《土壤和自然表面环境化学》的课程材料中。这些关键发现将发表在科学期刊上，并在科学和非科学会议上报告。

0946543MengThe principal objective of this research is to establish a novel method for in-situ mapping and identification of multi-adsorbates on metal oxide surfaces using electrochemical scanning tunneling microscopy (EC-STM) and scanning tunneling spectroscopy (STS). A multi-adsorbate system containing arsenate, phosphate, calcium, and hematite will be used as a model competitive adsorption system because phosphate and calcium significantly influence the adsorption of arsenic by iron oxides in the environment and in water treatment systems. The proposed research is based on the hypotheses that adsorbed anions and cations can have various distributions and interactions on metal oxide surfaces, such as patch and mixed distributions, preferential adsorption to different surface hydroxyl groups, formation of surface and three dimensional clusters, electrostatic repulsion among adsorbed anions, cation-bridging of anionic surface species, and surface-induced hydrogen bonds. Currently, there are no technologies to determine these fundamental surface features, which limit our ability to develop multi-component adsorption models for prediction of the fate and transport of pollutants in the environment and the adsorption capacity of adsorbents in water treatment systems. The surface analysis methods established in this study will enable scientists and engineers to investigate competitive adsorption of pollutants and co-existing compounds on mineral and adsorbent surfaces, chemical reactions on catalyst (such as titanium dioxides) and nano-material surfaces, and poisoning of catalysts by irreversible adsorption of co-existing compounds in solutions, at molecular levels. Understanding the distribution and interaction of adsorbed multi-component species will lead to the development of new adsorption models and invention of more effective adsorbents and catalysts. This project integrates cutting-edge research and broader education of graduate, undergraduate, and pre-college students, and underrepresented groups. A graduate student will be trained by performing the proposed research under the PI?s supervision. An undergraduate student will participate in some of the research through a Stevens Summer Scholarship program. The PI and graduate research assistant will demonstrate the EC-STM imaging process to undergraduate students in the EN375LA Environmental Engineering Laboratory class and to middle and high school students and school teachers through existing outreach programs. The PI will integrate the research findings into the course materials of EN 551 Environmental Chemistry of Soils and Natural Surfaces. The key findings will be published in scientific journals and reported at scientific and non-scientific meetings.