Sr Diffusion and Reaction within Fe Oxides: Evaluation of the Rate-Limiting Mechanism for Sorption

Axe, Lisa; Anderson, Paul

doi:10.1006/jcis.1995.1441

Cited by 63 publications

(105 citation statements)

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“…For amorphous oxides like that of Fe as well as Al and Mn, where porosity, micropores, and adsorption of metal ions are significant, intraparticle surface diffusion has been studied experimentally and theoretically (12)(13)(14)(15)(16). Surface diffusivities of metal ions have been found to range between 10 −16 and 10 −9 cm 2 s −1 .…”

Section: Introductionmentioning

confidence: 97%

“…These aggregates have been observed to possess significant microporosity (12,14). Studies with hydrous ferric, aluminum (HAO), and manganese (HMO) oxides have revealed that internal surfaces constitute as much as 40%, 50%, and 90%, respectively, of the total sites (14).…”

Section: Introductionmentioning

confidence: 98%

“…Amorphous oxides precipitate as water-swelled nanometersized particles that stabilize in water as micron-sized aggregates (12,23). These aggregates have been observed to possess significant microporosity (12,14).…”

Section: Introductionmentioning

confidence: 98%

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Ni and Zn Sorption to Amorphous versus Crystalline Iron Oxides: Macroscopic Studies

Trivedi

Axe

2001

Journal of Colloid and Interface Science

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103

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%

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Ni and Zn Sorption to Amorphous versus Crystalline Iron Oxides: Macroscopic Studies

Trivedi

Axe

2001

Journal of Colloid and Interface Science

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103

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“…The objective of our study was to investigate the external and internal specific surface area, porosity, and pore structure of dense HFO aggregates formed by freezing and thawing. A detailed understanding of the pore structure of such aggregates is a prerequisite for interpreting and modeling the frequently observed slow sorption kinetics of cations and anions to HFO aggregates, which may be limited by pore diffusion [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Characterization of the pores in hydrous ferric oxide aggregates formed by freezing and thawing

Hofmann¹,

Pelletier

Michot

et al. 2004

Journal of Colloid and Interface Science

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Hydrous ferric oxides (HFO) are efficient sorbents for inorganic and organic pollutants and therefore have great potentials in environmental science and engineering applications. Freezing and thawing of HFO suspensions leads to the formation of dense HFO aggregates. It facilitates the handling and increases the drying rate of HFO. In this study, we used a combination of pycnometry, gas adsorption (N 2 gas, water vapor), and small-angle neutron scattering (SANS) to characterize the porosity and pore size distribution of dense HFO aggregates formed by freezing dialyzed HFO suspensions at −25 • C and thawing them at room temperature. The crystallinity of the HFO, which was a 2-line ferrihydrite, was not affected by this treatment. Wet sieving and laser diffraction analysis showed that the dense HFO aggregates had a unimodal size distribution with an average diameter of 235 ± 35 µm. Increasing the freezing rate by cooling with liquid N 2 (−196 • C) resulted in much smaller aggregates with an average diameter of 20 µm. Adding NaNO 3 electrolyte to the HFO suspensions prior to freezing also resulted in the formation of smaller aggregates. The dense HFO aggregates formed at −25 • C had a porosity of 0.73 ± 0.02 l l −1 . SANS revealed a unimodal size distribution of pores, with an average pore diameter of 2.0 nm. The diameter of the HFO crystallites was estimated by transmission electron microscopy to be 1.9 ± 0.5 nm. Geometrical considerations taking into account the unit particle and average pore size suggest that the crystallites retain 1-2 layers of hydration water during the coagulation induced by freezing. Analysis by N 2 gas adsorption showed that drying the dense HFO aggregates induced a reduction in porosity by about 25% and shifted the pore size distribution to smaller diameters. Rewetting during water vapor adsorption did not induce significant changes of the aggregate structure. The specific surface area of the dry HFO aggregates was between 320 and 380 m 2 g −1 .

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“…Sorption experiments using a wide variety of substrates at room temperature have shown that Sr is removed from solution under certain conditions (Malati 1966;Schindler and Gamsjager 1969;Tadros and Lyklema 1969;Fordham 1973;Huang and Stumm 1973;Kinniburgh et al 1975;Fuerstenau et a1. 1981;Yanagi et al 1989;Park et al 1992;Liang et al 1993;Adeleye et al 1994;Axe and Anderson 1995;Gorturk et al 1995). Additionally, strontianite (SrCO 3 ) may precipitate at low Sr concentrations in the pH range of waters in contact with basaltic rocks, which varies between pH 8 and 10.…”

Section: Introductionmentioning

confidence: 99%

Experimental determination of contaminant metal mobility as a function of temperature, time and solution chemistry. 1997 annual progress report

Carroll¹,

Bruton²,

O’Day³

et al. 1997

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Sr Diffusion and Reaction within Fe Oxides: Evaluation of the Rate-Limiting Mechanism for Sorption

Cited by 63 publications

References 0 publications

Ni and Zn Sorption to Amorphous versus Crystalline Iron Oxides: Macroscopic Studies

Ni and Zn Sorption to Amorphous versus Crystalline Iron Oxides: Macroscopic Studies

Characterization of the pores in hydrous ferric oxide aggregates formed by freezing and thawing

Experimental determination of contaminant metal mobility as a function of temperature, time and solution chemistry. 1997 annual progress report

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