Like the solid-water interface (SWI), air-water and oil-water interfaces (AWI and OWI) also act as collectors for nano-sized particles in porous media. The attachment of hydrophobic nanoparticles, which is often favorable and irreversible, is of particular interest because the transport and retention of such particles is closely linked to the fate of nanoplastics in unsaturated subsurface environments and the success of nanoremediation practices. Here, we show how a pore-network model (PNM) can be used to upscale the kinetics and extent of irreversible nanoparticle attachment at a single fluid-fluid interface under conditions of advection and dispersion in a sphere packing. By focusing on a trapped (immobile) non-wetting phase, we highlight a fundamental difference between the single-collector contact efficiency of AWI/OWI and SWI. Namely, AWI/OWI collectors, which are largely by-passed by the flowing aqueous phase, are exposed to a hydrodynamic environment dominated by diffusion. This difference has profound implications for the modelling of nanoparticle transport in porous media at the continuum (Darcy) scale. This study reveals the potential of pore network modelling as an essential complement to continuum models for upscaling the behavior of nanocolloids in porous media.

中文翻译：

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纳米颗粒在部分饱和多孔介质中的传输：附着在流体界面处


与固-水界面 （SWI） 一样，空气-水和油-水界面（AWI 和 OWI）也充当多孔介质中纳米级颗粒的收集剂。疏水性纳米颗粒的附着通常是有利且不可逆的，因此特别令人感兴趣，因为此类颗粒的运输和保留与纳米塑料在不饱和地下环境中的命运和纳米修复实践的成功密切相关。在这里，我们展示了在球体堆积中的平流和分散条件下，如何使用孔隙网络模型 （PNM） 来放大单个流体-流体界面处不可逆纳米粒子附着的动力学和程度。通过关注被困（不动）的非润湿相，我们强调了 AWI/OWI 和 SWI 的单集电极接触效率之间的根本差异。也就是说，AWI/OWI 捕收剂在很大程度上被流动的水相绕过，暴露在以扩散为主的流体动力学环境中。这种差异对于在连续体 （Darcy） 尺度上模拟多孔介质中纳米颗粒传输具有深远的影响。这项研究揭示了孔隙网络建模作为连续体模型的重要补充的潜力，以扩大多孔介质中纳米胶体的行为。