Mechanistic understanding of Curium(III) sorption on natural K-feldspar surfaces

Demnitz, Maximilian; Schymura, Stefan; Neumann, Julia; Schmidt, Moritz; Schäfer, Thorsten; Stumpf, Thorsten; Müller, K.

doi:10.1016/j.scitotenv.2022.156920

Cited by 3 publications

(15 citation statements)

References 62 publications

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“…Consistent with the IS complex observed at 1 and 10 mM Y(III) at pH 7 here, Demnitz et al find a larger contribution of species with <4 remaining hydration water molecules with increasing pH. 38 3.5.3. Comparison to Other Mineral Phases.…”

Section: Y Coveragesupporting

confidence: 83%

“…Additionally, we recently investigated the impact of nanoscale surface roughness on the sorption of Cm(III) on an individual K-feldspar crystal of the (001) orientation using spatially resolved luminescence spectroscopy. 38 We find that the surface reactivity depends upon the topographic variation of the K-feldspar surface. Therefore, models describing adsorption need to take into account types and densities of defects are insufficient for robust environmental transport predictions.…”

Section: Introductionmentioning

confidence: 77%

“…Due to its perfect cleavage plane, the orthoclase (001) surface is well suited for investigations of molecular-scale processes, including mineral dissolution − and ion sorption. , For the latter, spectroscopy and X-ray scattering techniques allow the discrimination of different sorption modes, which are usually divided based on differences in the degree of adsorbate hydration. Inner-sphere (IS) complexes show a partially removed hydration shell, while for outer-sphere (OS) and extended OS sorption complexes, the first or multiple intervening hydration layers are preserved…”

Section: Introductionmentioning

confidence: 99%

“…While studies using mineral powder samples give a solid basis for the determination of thermodynamic parameters for surface complexation reactions, − the development of realistic reactive transport models requires an understanding of facet-specific reactivity, the influence of surface roughness, ,, and solid–liquid ratios more similar to those in natural systems. Orthoclase (KAlSi 3 O 8 ), a common polymorph of K-feldspar, has a monoclinic crystal structure ( a = 8.56 Å, b = 12.99 Å, c = 7.19 Å, α = γ = 90°, and β = 116°) with perfect cleavage planes along the (001) and (010) orientations, which are commonly exposed in natural systems .…”

Section: Introductionmentioning

confidence: 99%

“…Another naturally abundant group of minerals are feldspars, which are composed of a negatively charged 3D framework of oxygen-bridged aluminosilicate tetrahedra, whose charge is compensated by K + , Na + , or Ca 2+ in the structure. Some studies are available on the sorption of trivalent heavy metals on feldspars, − most of which use mineral powder samples. For example, our group has recently studied the sorption of REEs (Eu, La, Lu, Nd, and Y) as well as Am(III) and Cm(III) on K-feldspar powders.…”

Section: Introductionmentioning

confidence: 99%

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Y(III) Sorption at the Orthoclase (001) Surface Measured by X-ray Reflectivity

Neumann

Lessing

Lee

et al. 2022

Environ. Sci. Technol.

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Interactions of heavy metals with charged mineral surfaces control their mobility in the environment. Here, we investigate the adsorption of Y(III) onto the orthoclase (001) basal plane, the former as a representative of rare earth elements and an analogue of trivalent actinides and the latter as a representative of naturally abundant K-feldspar minerals. We apply in situ highresolution X-ray reflectivity to determine the sorption capacity and molecular distribution of adsorbed Y species as a function of the Y 3+ concentration, [Y 3+ ], at pH 7 and 5. With [Y 3+ ] ≥ 1 mM at pH 7, we observe an inner-sphere (IS) sorption complex at a distance of ∼1.5 Å from the surface and an outer-sphere (OS) complex at 3−4 Å. Based on the adsorption height of the IS complex, a bidentate, binuclear binding mode, in which Y 3+ binds to two terminal oxygens, is proposed. In contrast, mostly OS sorption is observed at pH 5. The observed maximum Y coverage is ∼1.3 Y 3+ /A UC (A UC : area of the unit cell = 111.4 Å 2 ) for all the investigated pH values and Y concentrations, which is in the expected range based on the estimated surface charge of orthoclase (001).

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Section: Y Coveragesupporting

confidence: 83%

Section: Introductionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Y(III) Sorption at the Orthoclase (001) Surface Measured by X-ray Reflectivity

Neumann

Lessing

Lee

et al. 2022

Environ. Sci. Technol.

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Variability of Radionuclide Sorption Efficiency on Muscovite Cleavage Planes

Schabernack,

Oliveira,

Heine

et al. 2023

Advcd Theory and Sims

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In deep geological repositories for nuclear waste, the surrounding rock formation serves as an important barrier against radionuclide migration. Multiple potential host rocks contain phyllosilicates, which have shown high efficiency in radionuclide sorption. Recent experimental studies report a heterogeneous distribution of adsorbed radionuclides on nanotopographic mineral surfaces. In this study, the energetic differences of surface sorption sites available at nanotopographic structures such as steps, pits, and terraces are investigated. Eleven important surface sites are selected and the energies of ad‐ and desorption reactions are obtained from density functional theory calculations. The adsorption energies are then used for the parameterization of a kinetic Monte Carlo model simulating the distribution of adsorbed europium on a typical nanotopographic muscovite surface. On muscovite, silicon step sites are favorable for europium sorption and lead to an increased adsorption in regions with high step concentrations. Under identical chemical conditions, sorption on typical nanotopographic surfaces is increased by a factor of three compared to atomically flat surfaces. Desorption occurs preferentially at terrace sites, leading to an overall 2.5 times increased retention at nanotopographic structures. This study provides a mechanistic explanation for heterogeneous sorption on nanotopographic mineral surfaces due to the availability of energetically favorable sorption sites.

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Mechanism of Potassium Release from Feldspar by Mechanical Activation in Presence of Additives at Ordinary Temperatures

Zhang,

He,

Jia

et al. 2023

Materials

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To improve the potassium availability of feldspar at ordinary temperatures, the mechanical grinding and addition of sodium hydroxide/salts were employed to study the effects of mechanical activation and strong alkali addition on particle characteristics, water-soluble potassium, and the available potassium of feldspar. A laser particle size analyzer was utilized for the direct determination of particle size distribution (PSD) using ground samples. The Brunauer–Emmett–Teller (BET) method was employed for specific surface areas. X-ray diffraction (XRD) was employed for structural characterization, scanning electron microscopy (SEM) for morphology exploration, and energy dispersive spectroscopy (EDS) to determine the chemical composition of potassium feldspar powder. The results revealed that the mechanical activation of potassium feldspar could reduce the particle size and produce agglomerated nanoparticles in the later period. The addition of NaOH and sodium salt did not cause agglomeration, and NaOH dissolved the nanoparticles. The water-soluble potassium content of feldspar in each treatment increased during mechanical grinding, from 21.64 mg kg−1 to 1495.81 mg·kg−1, by adding NaOH 5% weight of potassium feldspar powder and to 3044.08 mg·kg−1 by adding NaOH 10% weight with effects different from those of mechanical shaking. By comparison, only 162.93 mg·kg−1 water-soluble potassium was obtained by adding NaOH 5% weight. The dissolved potassium in the former case was significantly higher than in the latter, and the addition of NaOH and sodium salts significantly enhanced the water-soluble potassium contents due to ion exchange. Furthermore, the addition of sodium hydroxide improved the water-soluble potassium due to its mechanochemical action on potassium feldspar. The mechanical energy changed the crystal structure of potassium feldspar, explaining the increase in available potassium. The addition of sodium salts did not promote change in the feldspar’s structure, thereby did not raise the available potassium content. The reason for this was related to the mechanochemical action on sodium hydroxide and feldspar, which could promote the dissolution of fine particles, thereby incrementing the available potassium.

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Mechanistic understanding of Curium(III) sorption on natural K-feldspar surfaces

Cited by 3 publications

References 62 publications

Y(III) Sorption at the Orthoclase (001) Surface Measured by X-ray Reflectivity

Y(III) Sorption at the Orthoclase (001) Surface Measured by X-ray Reflectivity

Variability of Radionuclide Sorption Efficiency on Muscovite Cleavage Planes

Mechanism of Potassium Release from Feldspar by Mechanical Activation in Presence of Additives at Ordinary Temperatures

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