Aggregation of nanoscale iron oxyhydroxides and corresponding effects on metal uptake, retention, and speciation: I. Ionic-strength and pH

Dale, James G.; Stegemeier, John P.; Kim, C.S.

doi:10.1016/j.gca.2014.08.029

Cited by 27 publications

(25 citation statements)

References 51 publications

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“…Stegemeier et al . 49 , 50 pointed out that the factors that enhance iron oxyhydroxides nanoparticle aggregation generally follow the order of ionic strength ≈ pH < aging < freezing < drying. Accordingly, the interstitial water and pore space between aggregated particles are decreased by these factors and result in greater compaction of the aggregates and smaller specific surface areas in the same order.…”

Section: Resultsmentioning

confidence: 99%

Roles of different types of oxalate surface complexes in dissolution process of ferrihydrite aggregates

Koopal

Tan

2018

Sci Rep

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The dissolution of ferrihydrite induced by low molar mass (LMM) organics is an important process that provides bioavailable iron for organisms. Here, ATR-FTIR analysis was combined with characterization of ferrihydrite nanoparticles and kinetic modeling to investigate the roles of different oxalate surface complex species in the dissolution of ferrihydrite aggregates. ATR-FTIR results revealed that at least four different species were present at or near the ferrihydrite surface in the process of ferrihydrite aggregate dissolution. At a relatively low addition of oxalate (oxalate/Fe < 0.1), oxalate was dominantly present as binuclear bidentate surface complexes and aqueous species. The binuclear bidentate complexes mainly caused electrostatic repulsion between particles, resulting in the disaggregation of large ferrihydrite aggregates into colloidal particles with hydrodynamic diameters of 116–174 nm. Kinetic modeling showed that these colloidal particles were stable at the oxalate/Fe ratio of 0.1. With increasing addition of oxalate (oxalate/Fe ≥ 0.1), mononuclear bidentate oxalate complexes and hydrogen-bonded surface complex replaced the binuclear bidentate complexes and aqueous species. The aggregates or larger colloidal particles were further disaggregated into smaller colloidal particles with hydrodynamic diameters of 35–64 nm. Additionally, the mononuclear bidentate oxalate complexes promoted the dissolution of ferrihydrite colloids into dissolved Fe.

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Section: Resultsmentioning

confidence: 99%

Roles of different types of oxalate surface complexes in dissolution process of ferrihydrite aggregates

Koopal

Tan

2018

Sci Rep

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“…Finally, the formation of open versus closed structures upon nanoparticle aggregation or agglomeration has important implications for ion sorption by nanoscale oxides and merits further investigation. For example, one study showed that Fe oxide aggregates retained copper more strongly than dispersed nanoparticles, 86 even though the adsorption capacity of aggregates was lower than that of dispersed nanoparticles. 34 …”

Section: Implications For Nanoparticle Reactivitymentioning

confidence: 99%

Crystal growth and aggregation in suspensions of δ-MnO₂nanoparticles: implications for surface reactivity

Marafatto

Lanson

Peña

2018

Environ. Sci.: Nano

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a Birnessite (layer-type Mn oxide) is a key reactive phase in soils and sediments and its sorption and oxidative properties render it attractive for use in technical applications. The most widely used synthetic analog of natural and biogenic birnessite in laboratory studies is nanocrystalline δ-MnO 2 . However, a wide range of physicochemical properties have been reported in the literature for δ-MnO 2 . In this study, we produced several batches of δ-MnO 2 and identified the mechanisms leading to significant variations in particle size, as probed by X-ray diffraction (3 to 7 nm), dynamic light scattering (85 to 501 nm) and N 2 Ĳg) BET specific surface area (SSA: 119 to 259 m 2 g −1) measurements. Both the coherent scattering domain (CSD) size in the ab plane and the wet-aggregate size decreased with increasing suspension pH and Na content, which is consistent with base-catalyzed oxidation and nucleation at high pH and growth by oriented attachment at low pH. The increase in the CSD size upon sample acidification but not basification provides further evidence for OA as a crystal growth mechanism. Finally, the sample SSA was not related to the crystallite size, but instead was inversely correlated to the suspension pH and Na : Mn content. The surface charge and counter-cation content of δ-MnO 2 control the aggregate structure, where low pH (low Na : Mn) favored high surface area structures and high pH (high Na : Mn) favored low surface area structures. The reversibility of SSA upon the acidification or basification of parent suspensions and the crystal growth only upon suspension acidification confirmed that the primary crystallite size and the aggregate/agglomerate size are highly sensitive to solution chemistry and surface charge and has direct implications for δ-MnO 2 nanoparticle reactivity towards organic and inorganic contaminants in environmental systems that can encompass a dynamic range of pH values and ionic compositions.

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“…6). Factors that might have contributed to the discrepancy between modeled and measured results are ageing effects such as aggregation and ordering of the ferrihydrite (Dale et al, 2015;Vu et al, 2013), not captured by the oxalate extraction. Another contributing factor could be blocking of reactive sites by humic substances (Gustafsson, 2006), which was not considered in the modeling.…”

Section: Dissolved Concentrations Of Copper and Arsenicmentioning

confidence: 99%

Immobilization of Cu and As in two contaminated soils with zero-valent iron – Long-term performance and mechanisms

Tiberg

Kumpienė

Gustafsson

et al. 2016

Applied Geochemistry

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Immobilization of trace elements in contaminated soils by zero-valent iron (ZVI) is a promising remediation method, but questions about its long-term performance remain unanswered. To quantify immobilization and predict possible contaminant remobilization on long timescales detailed knowledge about immobilization mechanisms is needed. This study aimed at assessing the long-term effect of ZVI amendments on dissolved copper and arsenic in contaminated soils, at exploring the immobilization mechanism(s), and at setting up a geochemical model able to estimate dissolved copper and arsenic under different scenarios.Samples from untreated and ZVI-treated plots in two field experiments where ZVI had been added 6 and 15 years ago were investigated by a combination of batch experiments, geochemical modeling and extended X-ray absorption fine structure (EXAFS) spectroscopy.Dissolved copper and arsenic concentrations were described by a multisurface geochemical model with surface complexation reactions, verified by EXAFS. The ZVI remained "reactive" after 6-15 years, i.e. the dissolved concentrations of copper and arsenic were lower in the ZVI-treated than in the untreated soils. There was a shift in copper speciation from organic matter complexes in the untreated soil to surface complexes with iron (hydr)oxides in the ZVI-treated soil. The pH value was important for copper immobilization and ZVI did not have a stabilizing effect if pH was lower than about 6. Immobilization of arsenic was slightly pH-dependent and sensitive to the competition with phosphate. If phosphate was ignored in the modeling, the dissolution of arsenate was greatly underestimated.

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Aggregation of nanoscale iron oxyhydroxides and corresponding effects on metal uptake, retention, and speciation: I. Ionic-strength and pH

Cited by 27 publications

References 51 publications

Roles of different types of oxalate surface complexes in dissolution process of ferrihydrite aggregates

Roles of different types of oxalate surface complexes in dissolution process of ferrihydrite aggregates

Crystal growth and aggregation in suspensions of δ-MnO₂nanoparticles: implications for surface reactivity

Immobilization of Cu and As in two contaminated soils with zero-valent iron – Long-term performance and mechanisms

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Aggregation of nanoscale iron oxyhydroxides and corresponding effects on metal uptake, retention, and speciation: I. Ionic-strength and pH

Cited by 27 publications

References 51 publications

Roles of different types of oxalate surface complexes in dissolution process of ferrihydrite aggregates

Roles of different types of oxalate surface complexes in dissolution process of ferrihydrite aggregates

Crystal growth and aggregation in suspensions of δ-MnO2nanoparticles: implications for surface reactivity

Immobilization of Cu and As in two contaminated soils with zero-valent iron – Long-term performance and mechanisms

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Crystal growth and aggregation in suspensions of δ-MnO₂nanoparticles: implications for surface reactivity