The effects of metal oxides and clays on the transport of zinc oxide nanoparticles (ZnO-NPs) in saturated porous media were investigated under different ionic strength (IS) conditions. We studied the transport and retention behavior of ZnO-NPs for different types of porous media (untreated, acid treated, and acid–salt treated sand). The selected untreated sand was used as a representative sand, coated with both metal oxide and clay. The acid treated and acid–salt-treated sands were used and compared to investigate the effects of clays on the surface of the sand. In addition, the effects of clay particles in bulk solutions on the mobility and retention of ZnO-NPs were observed using bentonite as a representative clay particle. We found that the increased mobility of positively charged ZnO-NPs can be attributed to increasing charge heterogeneity of silica sand with metal oxides (mainly, iron oxide) and clays in untreated sand. No breakthrough of ZnO-NP was observed for acid-treated (presence of clays and absence of metal oxides) and acid–salt-treated sand (absence of both metal oxide and clays). Most of the injected ZnO-NPs were deposited on the surface of the sand near the column inlet. The transport of bentonite-facilitated ZnO-NPs was improved at the lowest IS (0.1 mM) (∼20%), whereas there was no difference in the mobility of ZnO-NPs at high IS solutions (1 mM and 10 mM). In particular, the breakthrough amount improved with increasing bentonite concentration. Classical Derjaguin–Landau–Verwey–Overbeek interactions help explain observed interactions between ZnO-NPs and sand as well as bentonite and sand.

中文翻译：

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带正电的氧化锌纳米粒子在饱和多孔介质中的传输和保留：金属氧化物和粘土的影响


研究了不同离子强度（IS）条件下金属氧化物和粘土对饱和多孔介质中氧化锌纳米粒子（ZnO-NPs）输运的影响。我们研究了不同类型多孔介质（未经处理、酸处理和酸盐处理砂）中 ZnO-NP 的传输和保留行为。所选择的未处理砂被用作代表性砂，其上涂有金属氧化物和粘土。使用酸处理砂和酸盐处理砂进行比较，以研究粘土对砂表面的影响。此外，使用膨润土作为代表性粘土颗粒，观察了本体溶液中粘土颗粒对 ZnO-NPs 迁移率和保留率的影响。我们发现，带正电荷的 ZnO-NP 的流动性增加可归因于未处理砂中硅砂与金属氧化物（主要是氧化铁）和粘土的电荷异质性增加。对于酸处理（存在粘土且不存在金属氧化物）和酸盐处理砂（不存在金属氧化物和粘土），没有观察到 ZnO-NP 的突破。大多数注入的 ZnO-NP 沉积在柱入口附近的沙子表面。膨润土促进的 ZnO-NPs 的传输在最低 IS (0.1 mM) (∼20%) 下得到改善，而在高 IS 溶液（1 mM 和 10 mM）下 ZnO-NPs 的迁移率没有差异。特别是，突破量随着膨润土浓度的增加而提高。经典的 Derjaguin-Landau-Verwey-Overbeek 相互作用有助于解释观察到的 ZnO-NP 与沙子以及膨润土与沙子之间的相互作用。