Understanding the merging dynamics of surface nanobubbles and the resulting capillary force between particles from molecular simulations

纳米气泡是液体中充满气体的空洞，直径从几十纳米到几百纳米不等。纳米气泡与普通大气泡的关键区别在于，大气泡迅速上升到液体表面并破裂，而纳米气泡可以悬浮在液体中数小时甚至数天。由于其独特的性质，纳米气泡在泡沫浮选、废水处理、无洗涤剂清洁和脱墨等广泛的技术应用中非常有用。这些应用的关键过程是纳米气泡在颗粒表面的聚并，从而导致液体中颗粒聚集体的形成。该项目的主要目标是利用数值模拟和理论模型来了解纳米气泡的合并动力学以及相邻颗粒之间产生的毛细力。与此项目相关的教育活动将吸引加州中央山谷地区的高中生，特别是那些代表性不足的群体的高中生参加工程项目，培养学生进行气泡动力学研究，并指导学生进行STEM的博士研究项目。本项目将采用分子动力学模拟和基于连续体的理论分析相结合的方法，研究气泡大小、表面张力、接触角和表面拓扑结构对纳米气泡合并动力学的影响，以及纳米气泡包覆颗粒之间产生的毛细力。分子水平的建模将使实验无法获得的微观细节的研究成为可能，并将提供对纳米气泡动力学和纳米气泡之间毛细力的许多关键方面的基本理解和定量预测。此外，这种微观预测不受连续统和理论建模中使用的许多假设和近似的阻碍。建模结果将使从业者能够制定提高细/超细矿物颗粒浮选率的策略，并提高废水处理、表面清洁和纸张回收等过程中污染物的去除率。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nanobubbles are gas-filled cavities in liquids with diameters ranging from tens to hundreds of nanometers. The key difference between nanobubbles and ordinary, larger bubbles is that larger bubbles rise rapidly to the surface of a liquid and burst, while nanobubbles can remain suspended in liquids for hours or even days. Due to their unique properties, nanobubbles are extremely useful in a broad range of technological applications such as froth flotation, wastewater treatment, detergent-free cleaning, and de-inking. The key process in these applications is the coalescence of nanobubbles on the surfaces of particles, which results in the formation of particle aggregates in a liquid. The main objective of this project is to use numerical simulations and theoretical models to understand the merging dynamics of nanobubbles and the resulting capillary force between adjoining particles. The education activities related to this project will attract high school students, especially those in underrepresented groups, in the central valley (California) to the engineering program, train students to conduct research in bubble dynamics, and guide students toward doctoral research programs in STEM.This project will use molecular dynamics simulations coupled with continuum-based theoretical analysis to study the effects of bubble size, surface tension, contact angle, and surface topology on merging dynamics of nanobubbles and the resulting capillary force between particles coated with nanobubbles. The molecular level modeling will enable the study of microscopic details that are inaccessible to experiments and will provide a fundamental understanding and quantitative predictions of many key aspects of nanobubble dynamics and the nanobubble capillary force between particles. Moreover, such microscopic predictions are not hindered by many assumptions and approximations used in continuum and theoretical modeling. The modeling results will enable practitioners to develop strategies for enhancing the flotation rate of fine/ultrafine mineral particles and to improve removal rates of contaminants in processes such as wastewater treatment, surface cleaning, and recycling of paper.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.