Nano-remediation is a promising in situ remediation technology. It consists in injecting reactive nanoparticles (NPs) into the subsurface for the displacement or the degradation of contaminants. However, due to the poor mobility control of the reactive nanoparticle suspension, the application of nano-remediation has some major challenges, such as high mobility of the particles, which may favor override of the contamination, and particle aggregation, which can lead to a limited distance of influence. Previous experimental studies show the potential of combining nano-remediation with foam flooding to overcome these issues. However, in order to design and optimize the process, a model which couples nanoparticle and foam transport is necessary. In this paper, a mechanistic model to describe the transport of NPs with and by a foam is presented. The model considers the delivery of nanoscale zero-valent iron (nZVI) and accounts for the processes of aggregation, attachment/detachment, and generation/destruction. Simulations show that when NPs are dispersed in the liquid phase, even in the presence of a foam, they may travel much slower than the NPs carried by the foam bubbles. This is because the nanoparticles in suspension are affected by the attachment onto the rock walls and straining at the pore throats. When the nanoparticle surface is, instead, modified in order to favor their adsorption onto the gas bubbles, NPs are carried by the foam without retardation, except for the small fraction suspended in the liquid phase. Moreover, very stable high-quality foam ( $$f_\mathrm{g}$$ f g ), i.e., 80–90 vol% of gas, can be attained using properly surface-modified nZVI (i.e., a nanoparticle-stabilized foam), allowing a significant reduction of water for the operation, while increasing the efficiency of nZVI delivery, even in a low-permeability medium within the shallow subsurface.

中文翻译：

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在泡沫存在的情况下模拟多孔介质中的纳米粒子传输

纳米修复是一种很有前景的原位修复技术。它包括将反应性纳米颗粒 (NP) 注入地下以置换或降解污染物。然而，由于反应性纳米颗粒悬浮液的流动性控制较差，纳米修复的应用存在一些重大挑战，例如颗粒的高流动性，这可能有利于污染的覆盖，以及颗粒聚集，这可能导致影响距离有限。以前的实验研究表明，将纳米修复与泡沫驱油相结合可以克服这些问题。然而，为了设计和优化该过程，需要一个耦合纳米颗粒和泡沫传输的模型。在本文中，提出了一种描述 NPs 与泡沫传输的机械模型。该模型考虑了纳米级零价铁 (nZVI) 的传递，并考虑了聚集、附着/分离和生成/破坏的过程。模拟表明，当 NPs 分散在液相中时，即使存在泡沫，它们的移动速度也可能比泡沫气泡携带的 NPs 慢得多。这是因为悬浮的纳米粒子会受到附着在岩壁上和在孔喉处应变的影响。相反，当纳米颗粒表面被改性以有利于它们吸附到气泡上时，除了悬浮在液相中的小部分外，纳米颗粒被泡沫无阻地携带。此外，使用适当的表面改性的 nZVI 可以获得非常稳定的高质量泡沫（$$f_\mathrm{g}$$fg），即 80-90 vol% 的气体（即，