CAREER: Adsorption and Transport in Heterogeneous Porous Media

职业：非均质多孔介质中的吸附和传输

• 批准号: 0243300
• 负责人: Christian Lastoskie
• 金额: $ 9.64万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0243300&HistoricalAwards=false
• 关键词: CAREER; Adsorption; Transport; Heterogeneous; Porous

ABSTRACT CTS-9733086 Lastoskie/Michigan State U. Physical and chemical heterogeneities in porous media strongly impact the thermodynamic and transport properties of fluids confined within porous materials. To fully exploit engineering processes which involve porous materials, the effects of heterogeneity on the properties of fluids in porous media must be more completely understood. In this CAREER plan, a set of research activities will be undertaken to develop statistical thermodynamic methods for characterizing fluid properties in heterogeneous porous media. Three thematic areas will be investigated: (1) sorption and diffusion of fluids in porous solids; (2) chemical dilution in heterogeneous media; and (3) enhancement of cellular transport in porous media via chemotaxis. Adsorbed-fluid phase equilibria and diffusive transport in microporous solids will be investigated using density functional theory and molecular dynamics simulation, respectively. These models will be used to interpret sorptometer measurements of gas uptake on microporous adsorbents and soils. A statistical thermodynamic model of mixing, the spatial variability index, will be used to model the dilution of solutes transported through disordered porous media. The predictions of the mixing model will be compared with the results of tracer experiments in packed columns and with field tests at aquifer injection wells. Cellular transport through porous media will be examined using cellular dynamics computer simulation. Validation of the cellular dynamics transport models will be obtained from diffusion gradient chamber visualizations of cell migration through porous media. The three research thrust areas have a strong relevance to environmental concerns regarding the fate, transport and bioremediation of contaminants in soils and groundwater. The educational component of the CAREER plan will thus be directed toward application of chemical engineering thermodynamics to environmental engineering issues, through the d evelopment of an air pollution course and environmental design problems in undergraduate chemical engineering courses. Research experiences for undergraduates will also be provided. The thermodynamic and transport properties of fluids and cells confined within porous media originate from fundamental interactions between fluid-phase species and porous solid surfaces. As such, they are strongly impacted by the heterogeneity of the porous material. Traditional empirical thermodynamic correlations do not provide detailed insight into the relationship between the structure of the porous solid and the properties of the adsorbed fluid. Statistical thermodynamics and molecular simulation, by contrast, are well suited to examining fluid phase equilibria and transport coefficients in confined porous media. Similarly, the migration of bacterial species in the aqueous phase has been studied extensively by both theoretical and experimental means, whereas bacterial migration in disordered porous media is poorly understood. Cellular dynamics simulation provides a direct means of predicting cell transport coefficients in highly heterogeneous environments that are otherwise difficult to analyze experimentally. Molecular modeling methods have gained widespread acceptance in research applications in the core areas of chemical engineering, such as gas separations, supercritical reactions and polymer processing. The benefits of molecular simulation can soon be brought to bear upon environmental process modeling of contaminant transport in natural systems, once the additional heterogeneity present in "natural" porous materials (e.g. soils) is properly accounted for. There is much controversy currently surrounding the fate of groundwater and soil contaminants in natural systems and the processes by which pollutants are retained in the subsurface. The knowledge gained from molecular simulations of contaminant transport in porous media will address these uncertainties. Insufficient mass transfer of inject ed nutrients and inadequate distribution of microbial agents are two of the principal causes of failure in attempts to restore contaminated aquifers via in situ bioremediation. Studies of chemical dilution in porous media will suggest improved design strategies for delivery of injected nutrients at bioremediation sites. Bacterial motility is a major, often the dominant, component of overall cellular transport in porous aquifer media, and there is evidence that this motility can be strongly attenuated by chemotactic response to chemical gradients in acetate and other substances. Cellular dynamics simulations of bacterial transport in porous media will guide the engineering of chemotaxis into bioremediation systems.

摘要CTS-9733086美国密歇根州立大学拉斯托斯基分校多孔介质中的物理和化学非均质性强烈地影响了受限于多孔材料中的流体的热力学和输运性质。为了充分利用涉及多孔材料的工程过程，必须更全面地了解非均质性对多孔介质中流体性质的影响。在这份职业计划中，将开展一系列研究活动，以开发描述非均匀多孔介质中流体性质的统计热力学方法。将研究三个主题领域：(1)流体在多孔固体中的吸附和扩散；(2)非均质介质中的化学稀释；(3)通过趋化作用加强细胞在多孔介质中的传输。分别用密度泛函理论和分子动力学模拟方法研究了微孔固体中的吸附-流体相平衡和扩散输运。这些模型将被用来解释气体在微孔吸附剂和土壤上的吸气量测量结果。混合的统计热力学模型，空间变异性指数，将被用来模拟溶质在无序多孔介质中传输的稀释。混合模型的预测结果将与填充柱中的示踪剂实验结果和含水层注水井的现场实验结果进行比较。将使用细胞动力学计算机模拟来研究细胞在多孔介质中的传输。细胞动力学传输模型的验证将从细胞在多孔介质中迁移的扩散梯度室可视化获得。这三个研究重点领域与土壤和地下水中污染物的去向、迁移和生物修复等环境问题密切相关。因此，职业计划的教育部分将通过开发空气污染课程和本科化学工程课程中的环境设计问题，将化学工程热力学应用于环境工程问题。还将为本科生提供研究经验。流体和细胞在多孔介质中的热力学和输运性质源于流体相物种和多孔固体表面之间的基本相互作用。因此，它们受到多孔性材料的非均质性的强烈影响。传统的经验热力学关联式不能详细了解多孔固体的结构和被吸附流体的性质之间的关系。相比之下，统计热力学和分子模拟非常适合于研究受限多孔介质中的流体相平衡和输运系数。类似地，细菌在水相中的迁移已经通过理论和实验手段得到了广泛的研究，而细菌在无序多孔介质中的迁移却知之甚少。细胞动力学模拟提供了一种直接的方法来预测高度异质环境中的细胞传输系数，否则很难进行实验分析。分子模拟方法在气体分离、超临界反应和聚合物加工等化学工程核心领域的研究应用中得到了广泛的接受。一旦“天然”多孔材料(如土壤)中存在的额外的非均质性得到了适当的解释，分子模拟的好处很快就可以应用于自然系统中污染物迁移的环境过程模拟。目前，围绕地下水和土壤污染物在自然系统中的去向以及污染物在地下保留的过程存在很大争议。从污染物在多孔介质中传输的分子模拟中获得的知识将解决这些不确定性。注入的营养物质传质不足和微生物制剂分布不充分是试图通过就地生物修复恢复受污染含水层失败的两个主要原因。对多孔介质中的化学稀释的研究将为在生物修复部位输送注入的营养物质提出改进的设计策略。细菌的运动性是多孔含水层介质中整个细胞运输的一个主要的，通常是占主导地位的成分，有证据表明，这种运动性可以通过对醋酸盐和其他物质中的化学梯度的趋化反应而强烈减弱。细菌在多孔介质中传输的细胞动力学模拟将指导将趋化性工程应用于生物修复系统。