NER: Mesogeochemistry ù Geochemical Reactions and Mass Transfers in Nano-scale Pore Space Confinement

该提案是根据纳米尺度科学与工程计划NSF 01-157 （NER类别）收到的，由GEO理事会共同资助。纳米技术的出现使得在纳米尺度上操纵材料结构成为可能，并极大地促进了我们对这些纳米尺度结构如何产生在块状材料中未见的新物理和化学性质的理解。纳米级孔隙结构，也称为介孔结构，在地质和工程材料中普遍存在。我们的初步实验和理论研究表明，由于纳米尺度的限制，介孔中的化学反应可以在热力学和动力学上得到显着的改变。本研究的目的是：(1)阐明化学物质在纳米尺度孔空间约束下的吸附行为，与在体溶液中的吸附行为相比，并验证中孔表面的金属吸附可以通过约束效应大大增强的假设；(2)测定水在纳米尺度通道中的扩散速率，以验证这些通道在化学反应中可以为质量传递提供通道的假设。为了分离纳米级孔空间限制的影响，我们将在非介孔材料上进行平行吸附实验，并比较介孔和非介孔材料的吸附能力。本文将特别关注介孔中双电层（EDL）重叠对离子吸附和扩散的可能影响。在实验数据的基础上，提出了一种新的表面络合模型，明确地考虑了EDL重叠的影响。本建议要解决的问题是根本性的，所提出的工作将对地球化学研究的许多方面产生重大影响。该研究将为高性能功能材料的开发奠定理论基础，以解决我们今天面临的具有挑战性的环境问题。

Xu & WangNER-0210820This proposal was received in response to the Nanoscale Science and Engineering initiative NSF 01-157, category NER, and is co-funded by the GEO Directorate.The emergence of nanotechnology has made it possible to manipulate material structures at nanometer scales and has greatly advanced our understanding of how these nano-scale structures give rise to novel physical and chemical properties not seen in bulk materials. Nano-scale pore structures, also called mesoporous structures, are ubiquitous in geologic and engineered materials. Our preliminary studies, both experimentally and theoretically, indicate that chemical reactions in mesopores can be significantly modified, both thermodynamically and kinetically, due to the nano-scale confinement. The objective of this proposal is to (1) clarify the sorption behavior of chemical species in a nano-scale pore space confinement as compared to that in bulk solutions and test the hypothesis that metal sorption on mesopore surface can be greatly enhanced by the confinement effect; and (2) to determine the rates of aqueous species diffusion in nano-scale channels to test the assumption that these channels can provide passages for mass transport during chemical reactions.To isolate the effect of nano-scale pore space confinement, we will conduct parallel sorption experiments on non-mesoporous materials, and the measured sorption capabilities will be compared between mesoporous vs. non-mesoporous materials. Particular attention will be paid to the possible effect of electric double layer (EDL) overlap in mesopores on ion sorption and diffusion. Based on the experimental data, a new surface complexation model will be proposed to explicitly include the effect of EDL overlap. The issues to be addressed in this proposal are fundamental, and the proposed work will highly impact many aspects of geochemical research. The proposed research will establish a theoretical foundation for the development of high-performance functional materials for solving challenging environmental issues we are facing today.