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Open AccessArticle

Characteristics of Aggregate Size Distribution of Nanoscale Zero-Valent Iron in Aqueous Suspensions and Its Effect on Transport Process in Porous Media

by Ruiqi Duan 1,2,3, Yanhui Dong 1,2,3,* and Qian Zhang 1,2,3
1
Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
2
Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029, China
3
College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
*
Author to whom correspondence should be addressed.
Water 2018, 10(6), 670; https://doi.org/10.3390/w10060670
Received: 18 April 2018 / Revised: 8 May 2018 / Accepted: 15 May 2018 / Published: 23 May 2018
(This article belongs to the Section Hydrology)
Bare nanoscale zero-valent iron (NZVI) particles in aqueous suspensions aggregate into micron to submicron sizes. The transport process of enlarged aggregates or multi-sized aggregates is different from that of nanoparticles. In this work, we performed aggregate size distribution analysis of NZVI suspension using a laser grain size analyzer and conducted a series of continuous injection column experiments with different injected NZVI concentrations. The results show that aggregates in NZVI suspensions range from submicron to submillimeter size and are mainly distributed around 5–9 μm and 50–100 μm. Quantitative calculation of iron transport and retention showed that the retained iron linearly correlates with injected concentration. The cross-section images revealed that clogging weakened from inlet to outlet. Furthermore, larger aggregates (>40 μm) appeared more often in the rising-declining stages of breakthrough curves, whereas small aggregates (<30 μm) dominated the steady stage. Indeed, relatively preferential flow facilitated the transport and discharge of both large and small iron aggregates. Straining of glass beads especially for the large iron aggregates resulted in a decline in breakthrough. Moreover, the blocking of attached and plugged iron prevented later retention of iron, resulting in a certain concentration of iron in the effluents. Our study provides greater insight into the transport of NZVI. View Full-Text
Keywords: NZVI; aggregate size distribution; multi-sized; transport NZVI; aggregate size distribution; multi-sized; transport
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Duan, R.; Dong, Y.; Zhang, Q. Characteristics of Aggregate Size Distribution of Nanoscale Zero-Valent Iron in Aqueous Suspensions and Its Effect on Transport Process in Porous Media. Water 2018, 10, 670.

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