Irreversibility of sulfate sorption on goethite and hematite

Turner, Laurie J.; Kramer, James R.

doi:10.1007/bf00475619

Cited by 30 publications

(11 citation statements)

References 25 publications

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“…Trends observed in adsorption and desorption behavior align well with the observed isotherm characteristics for our experimental conditions (Figure S5 and Table S4). Overall, these isotherms represent strong association of SO 4 2– with hematite under all conditions studied, in agreement with previous studies, demonstrating high affinity binding between hematite and SO 4 2– . , For both ionic strengths used, the identity of background cations present does not seem to influence adsorption affinity, with similar affinities observed for isotherms in KCl and CaCl 2 backgrounds at respective ionic strengths. Ionic strength, on the other hand, has a notable influence on sulfate adsorption affinity, with ionic strength reducing binding constants by more than an order of magnitude.…”

Section: Resultssupporting

confidence: 91%

Spectroscopic Quantification of Inner- and Outer-Sphere Oxyanion Complexation Kinetics: Ionic Strength and Background Cation Effect on Sulfate Adsorption to Hematite

Schmidt

Siciliano

Peak

2020

ACS Earth Space Chem.

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Sulfate adsorbs on Fe-oxide minerals by both inner-and outer-sphere modes; however, the time dependence of coexisting surface species is not clear. Using in situ attenuated total reflectance−Fourier transform infrared spectroscopy, peak fitting, and multivariate curve resolution analyses, we quantify adsorption and desorption kinetics of inner-and outer-sphere sulfate species on hematite at two ionic strengths (I = 0.01 and 0.10 M) and background cations (K + and Ca 2+ ) at pH 4.5. We experimentally observed inner-sphere, bidentate bridging and outer-sphere species kinetics congruent with the stepwise Eigen−Werner−Wilkins mechanism, in which a rapid formation of outer-sphere association precedes a slower conversion of outersphere to inner-sphere sulfate complexes. The rate limitation imposed by inner-sphere complex formation is likely linked to the displacement of protonated surface hydroxyl groups on the oxide surface by the adsorbing oxyanion. Outer-sphere complexes are responsible for rapid adsorption and desorption at I = 0.10 M seen in total sulfate, whereas inner-sphere species desorb more slowly. At I = 0.01 M, outer-sphere complexes similarly adsorb rapidly relative to inner-sphere complexes but desorb more slowly than inner-sphere complexes, possibly because of ionic strength effects on surface charge density. This work presents a novel, direct spectroscopic quantification of mixed surface species adsorption kinetics on a model mineral surface, which may be used to confirm proposed molecular mechanisms for other oxyanion adsorption to mineral surfaces. Our results enhance molecular-level understanding of oxyanion adsorption on soils and help predict their behavior in soils.

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Section: Resultssupporting

confidence: 91%

Spectroscopic Quantification of Inner- and Outer-Sphere Oxyanion Complexation Kinetics: Ionic Strength and Background Cation Effect on Sulfate Adsorption to Hematite

Schmidt

Siciliano

Peak

2020

ACS Earth Space Chem.

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“…For example, the distribution coefficient (Kd) for the linear parts of AQDS/AH2DS sorption isotherms was calculated (Kd ) ST/b) to be 18-20 L/kg at pH 4.5 and 4-10 L/kg at pH 6.9. The calculated Kd values for the linear parts of SO4 2sorption isotherms were 680 and 160 L/kg at pH 3 and 7, respectively (16). The weak AQDS/AH2DS sorption was expected because sulfonate (17,18) and quinone groups (19) react with mineral surfaces through outer sphere complexation.…”

Section: Resultsmentioning

confidence: 96%

Kinetics of Reductive Dissolution of Hematite by Bioreduced Anthraquinone-2,6-disulfonate

Liu

Zachara

Foster

et al. 2007

Environ. Sci. Technol.

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The reductive dissolution of hematite (alpha-Fe2O3) was investigated in a flow-through system using AH2DS, a reduced form of anthraquinone-2,6-disulfonate (AQDS), which is often used as a model electron shuttling compound in studies of dissimilatory microbial reduction of iron oxides. Influent flow rate, pH, and Fe(II) and phosphate concentrations were varied to investigate the redox kinetics in a flow-through reactor. The hematite reduction rates decreased with increasing pH from 4.5 to 7.6 and decreased with decreasing flow rate. The rates also decreased with increasing influent concentration of Fe(II) or phosphate that formed surface complexes at the experimental pH. Mineral surface properties, Fe(II) complexation reactions, and ADDS sorption on hematite surfaces were independently investigated for interpreting hematite reduction kinetics. AH2DS sorption to hematite was inferred from the parallel measurements of AQDS and AH2DS sorption to alpha-Al2O3, a redox stable analog of alpha-Fe2O3. Decreasing Fe(ll) and increasing AH2DS sorption by controlling flow rate, influent pH, and Fe(II) and phosphate concentrations increased the rates of reductive dissolution. The rates were also affected by the redox reaction free energy when reductive dissolution approached equilibrium. This study demonstrated the importance of the geochemical variables for the reductive dissolution kinetics of iron oxides.

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“…They also found that sulfate retained from desorption results were significantly different in comparison with results based on adsorption data. Such behavior is commonly referred to as hysteresis and may be a result of irreversible reactions as suggested by Hodges and Johnson (1987) Lack of irreversible retention of sulfate has been observed by Gobran et al (1998b) This observation has also been noted in soils by Harrison et al (1989) and on oxide mineral surfaces by Turner and Kramer (1992) It should also be noted that deviations between sorption and desorption could be related to kinetic retention behavior (Gobran et al, 1998a, 1998b). Irreversible sorption–desorption and the extent of kinetic reactions has also been quantified using the pressure‐jump relaxation method on goethite by Zhang and Sparks (1990) They found that sulfate adsorption occurs rapidly at initial reaction stages whereas desorption is slower and may be considered as a limiting step.…”

mentioning

confidence: 86%

Mobility of Sulfate in Forest Soils: Kinetic Modeling

Selim

Gobran²,

Guan³

et al. 2004

J of Env Quality

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Understanding sulfate transport and retention dynamics in forest soils is a prerequisite in predicting SO4 concentration in the soil solution and in lake and stream waters. In this study forest soil samples from the Gårdsjön catchments, Sweden, were used to study SO4 transport in soil columns from the upper three soil horizons (E, Bs, and BC). The columns were leached using a sequential leaching technique. The input solutions were CaSO4 equilibrated with forest floor material. Leaching behavior of SO4 and concentration in the effluent were measured from columns from individual horizons. Sulfate was always retained in the Bs and BC horizons, while the pattern for the E horizon varied. Attempts were also made to model SO4 breakthrough results based on miscible displacement approaches and solute convection-dispersion equation (CDE) in porous media. Several retention mechanisms were incorporated into the CDE to account for possible reversible and irreversible SO4 reactions in individual soil layers. Our modeling efforts were inadequate in describing the mobility of SO4 in the top (E) horizon. Moreover, a linear equilibrium approach was generally inadequate for describing SO4 sorption during transport in the Bs and BC horizons. In contrast, we found that the model provided good descriptions of all breakthrough results when SO4 reactivity was accounted for based on nonlinear equilibrium or first-order kinetic processes. Moreover, based on model parameter estimates, the reactivity or retention of SO4 during transport is concentration dependent. We conclude that sulfate retention during transport in this forest soil is most likely controlled by kinetic reactivity of SO4 of the reversible and irreversible mechanisms.

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Irreversibility of sulfate sorption on goethite and hematite

Cited by 30 publications

References 25 publications

Spectroscopic Quantification of Inner- and Outer-Sphere Oxyanion Complexation Kinetics: Ionic Strength and Background Cation Effect on Sulfate Adsorption to Hematite

Spectroscopic Quantification of Inner- and Outer-Sphere Oxyanion Complexation Kinetics: Ionic Strength and Background Cation Effect on Sulfate Adsorption to Hematite

Kinetics of Reductive Dissolution of Hematite by Bioreduced Anthraquinone-2,6-disulfonate

Mobility of Sulfate in Forest Soils: Kinetic Modeling

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