When particles should not stick: Understanding the causes for unfavorable particle deposition

[09:33605] drazer对固液界面颗粒沉积的研究是许多技术应用的核心，如过滤、石油回收、油漆和水处理等。DLVO理论最初是为了解释胶体分散体中的聚集现象而提出的，事实证明，在条件有利的情况下，DLVO理论在描述颗粒沉积方面非常成功和可靠。另一方面，在不利的化学条件下，即静电斥力对颗粒沉积形成屏障时，胶体颗粒的沉积在理论和实验之间存在明显的分歧。在大多数情况下，观察到的沉积比理论模型（如经典的胶体过滤理论（CFT））所期望的要大。尽管已经提出了几种解释来解决这一差异，但我们的理解仍然是支离破碎的，并且没有统一的描述来成功地解释不利条件下的沉积。此外，大多数实验测量的是污水浓度或其他与沉积仅间接相关的量。为了确定为什么不利条件下的沉积会严重偏离经典的颗粒沉积处理，将进行一系列简单的实验，这些实验不仅提供平均结果，还提供颗粒水平上单个沉积事件及其统计分布的详细信息。此外，拟议的实验将在简单和控制良好的几何和流动条件下进行，以便进一步与理论预测进行直接比较，并在需要时对理论提出修正建议。知识价值：建议的工作将有助于解决一个长期存在的问题，即为什么不利的沉积首先存在。此外，了解颗粒沉积和再夹带将影响广泛的学科，如采油策略和微流体装置。因此，了解不利条件下颗粒沉积的根本原因具有重要的工程原理。表面电荷的不均匀性或收集器表面电位的不确定是观察到的差异的根源尚不清楚。设计简单而通用的实验来解决这些问题，将为从实验和理论角度研究颗粒沉积的基础提供一个理想的平台。此外，所提出的粒子跟踪实验将提供单个粒子水平上沉积现象的详细信息，可以直接与布朗动力学模拟进行比较。此外，在这个项目中开发的工具将允许在未来研究更复杂的胶体的沉积，如细菌、病毒或各种形状和表面电荷分布的矿物质。广泛影响：这项工作的广泛影响在于教育和推广活动，以及其技术支持能力。培训将提供给研究生，本科生和高中学生在一个跨学科的环境中，包括强烈接触材料和界面科学领域以及运输现象。它还将提供广泛的实验，建模和模拟工具和方法的经验。PIs的教育理念旨在培养学生对科学的真正热情，让他们有机会积极地生产科学材料，而不是被动地充当消费者。在实验室里，本科生和高中生被鼓励在小组内外展示他们的发现，包括在同行评审的科学出版物上发表论文。从科学和技术的角度来看，了解颗粒沉积将影响几个学科，如采油策略。事实上，石油生产中的一个主要问题是，在注入过程中，粘土和其他矿物以细颗粒的形式释放出来，导致储层岩石的渗透率急剧降低。另一个将受益于当前工作的领域是微流体装置和芯片实验室系统。大量涉及悬浮物运输的微流体装置正在被研究，以用于从医学到爆炸物探测等领域的潜在应用。在许多情况下，胶体沉积和流体通道堵塞是一个重要问题。

0933605DrazerThe study of particle deposition at solid liquid interfaces is central to a number of technological applications, such as filtration, oil recovery, paints, and water treatment, just to name a few. Originally proposed to explain aggregation phenomena in colloidal dispersions DLVO theory has proven extremely successful and robust to describe particle deposition when the conditions are favorable. On the other hand, there is a clear disagreement between the theory and experiment for the deposition of colloidal particles under unfavorable chemical conditions, that is, when electrostatic repulsion creates a barrier to particle deposition. In most cases, the observed deposition is larger than that expected from theoretical models, such as the classical colloidal filtration theory (CFT). Although several explanations have been proposed to address this discrepancy our understanding remains fragmented and there is no unified description that successfully explains deposition under unfavorable conditions. In addition, most experiments measure effluent concentrations or other quantities that are only indirectly related to deposition. In order to determine why deposition under unfavorable conditions deviates strongly from the classical treatment of particle deposition, a series of simple experiments that provide not only average results but also detailed information on individual deposition events at the particle level and their statistical distributions will be performed. In addition, the proposed experiments will be performed under simple and well controlled geometry and flow conditions, to further enable a direct comparison with theoretical predictions and to suggest corrections to the theory where needed.Intellectual Merit:The proposed work will help resolve a long standing issue as to why unfavorable deposition exists in the first place. In addition, understanding particle deposition and reentrainment will impact a wide range of disciplines, such as oil recovery strategies and microfluidic devices. Therefore, there is an important engineering rationale in understanding the underlying causes for particle deposition under unfavorable conditions. Whether surface charge heterogeneities or poor determination of the surface potential of the collector is at the root of the observed discrepancies is unclear. The design of simple and versatile experiments to address these issues will lead to an ideal platform to study the fundamentals of particle deposition from both an experimental and theoretical perspective. Moreover, the proposed particle tracking experiments will provide detailed information on the deposition phenomena at the level of individual particles that can be directly compared with Brownian dynamic simulations. In addition, the tools that will be developed in this project will allow, in the future, studying the deposition of more complex colloids, such as bacteria, viruses, or minerals of various shapes and surface charge distribution.Broad Impacts:The broader impact of this work lies in both education and outreach activities, as well as on its technologically enabling capabilities. Training will be provided to graduate, undergraduates, and high school students in an interdisciplinary environment that includes a strong exposure to the fields of materials and interfacial science as well as transport phenomena. It will also provide experience in a broad range of experimental, modeling and simulations tools and methods. The PIs educational philosophy is designed to foster a true passion for science in students by giving them opportunities to actively produce scientific material, rather than acting as passive consumers. In the lab, undergraduates and high school students are encouraged to present their findings within the group and externally, including authorship in peer reviewed scientific publications. From a scientific and technological perspective understanding particle deposition will impact several disciplines, such as oil recovery strategies. In fact, one of the major problems in oil production is the drastic reduction in permeability of reservoir rocks due to clays and other minerals released in the form of fine particles during injection. Another area that would benefit from the present work is that of microfluidic devices and lab-on-a-chip systems. A large number of microfluidic devices involving the transport of suspended species are being investigated for potential applications in areas that range from medicine, to the detection of explosives. In many cases, colloidal deposition and clogging of fluidic channels is an important problem.