Repartitioning of co-precipitated Mo(VI) during Fe(II) and S(-II) driven ferrihydrite transformation

Schoepfer, Valerie A.; Lindsay, Matthew B.J.

doi:10.1016/j.chemgeo.2022.121075

Cited by 4 publications

(4 citation statements)

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“…In contrast, in organic-rich surface soils, wetlands, and marine sediments with higher S(-II)/Fe molar ratios, OM significantly inhibits ferrihydrite sulfidation, so prolonged exposure of ferrihydrite–organic coprecipitates to DS(-II) may have a limited effect on the crystallinity and transformation of the mineral phase. Sulfate reduction-induced Fh–OM coprecipitate mineral transformation may affect the mobility of nutrients and trace metals, , promoting the release of organics or their synchronous sequestration with trace metals. , Furthermore, in the current study, simple organic ligands were selected as EPS proxies, which were not expected to interact directly or significantly with DS(-II). ,, However, native EPS is heterogeneous and has a more complex composition capable of oxidizing and binding DS(-II) at a rate comparable to that of DS(-II) reacting with Fe(III)-(hydr)oxide in anoxic environments. Our results suggest that microbiogenic EPS has a more potent inhibitory effect on mineral transformation than EPS proxies.…”

Section: Discussionmentioning

confidence: 99%

“…The interaction between poorly crystalline Fe(III)-(hydr)oxides, such as ferrihydrite (Fh), and dissolved sulfide is a prominent pathway of electron transfer in many anoxic environments, such as in flooded soils and oceans or lake sediments. − Sulfide-induced ferrihydrite mineralogical transformations include the formation of Fe–S secondary minerals, such as mackinawite and finally pyrite, , and Fe(II)-catalyzed recrystallization of Fe(III)-oxides (e.g., lepidocrocite, goethite, and magnetite). Ferrihydrite sulfidation may alter its chemical reactivity and surface morphology, , potentially affecting mineralogical stability, bioavailability, and mobility of nutrients , and the geochemical behavior of many contaminants, such as arsenic, antimony, and uranium. − …”

Section: Introductionmentioning

confidence: 99%

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Transformations of Ferrihydrite–Extracellular Polymeric Substance Coprecipitates Driven by Dissolved Sulfide: Interrelated Effects of Carbon and Sulfur Loadings

Wang

et al. 2023

Environ. Sci. Technol.

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The association of poorly crystalline iron (hydr)oxides with organic matter (OM), such as extracellular polymeric substances (EPS), exerts a profound effect on Fe and C cycles in soils and sediments, and their behaviors under sulfate-reducing conditions involve complicated mineralogical transformations. However, how different loadings and types of EPS and water chemistry conditions affect the sulfidation still lacks quantitative and systematic investigation. We here synthesized a set of ferrihydrite−organic matter (Fh−OM) coprecipitates with various model compounds for plant and microbial exopolysaccharides (polygalacturonic acids, alginic acid, and xanthan gum) and bacteriogenic EPS (extracted from Bacillus subtilis). Combining wet chemical analysis, X-ray diffraction, and X-ray absorption spectroscopic techniques, we systematically studied the impacts of C and S loadings by tracing the temporal evolution of Fe mineralogy and speciation in aqueous and solid phases. Our results showed that the effect of added OM on sulfidation of Fh−OM coprecipitates is interrelated with the amount of loaded sulfide. Under low sulfide loadings (S(-II)/Fe < 0.5), transformation to goethite and lepidocrocite was the main pathway of ferrihydrite sulfidation, which occurs more strongly at pH 6 compared to that at pH 7.5, and it was promoted and inhibited at low and high C/Fe ratios, respectively. While under high sulfide loadings (S(-II)/Fe > 0.5), the formation of secondary Fe−S minerals such as mackinawite and pyrite dominated ferrihydrite sulfidation, and it was inhibited with increasing C/Fe ratios. Furthermore, all three synthetic EPS proxies unanimously inhibited mineral transformation, while the microbiogenic EPS has a more potent inhibitory effect than synthetic EPS proxies compared at equivalent C/Fe loadings. Collectively, our results suggest that the quantity and chemical characteristics of the associated OM have a strong and nonlinear influence on the extent and pathways of mineralogical transformations of Fh−OM sulfidation.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transformations of Ferrihydrite–Extracellular Polymeric Substance Coprecipitates Driven by Dissolved Sulfide: Interrelated Effects of Carbon and Sulfur Loadings

Wang

et al. 2023

Environ. Sci. Technol.

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“…Past studies of charged interfaces in water experiencing adsorption events have commonly relied on empirical studies, supported by various spectroscopic techniques and surface complexation models (SCM), while some recent studies have used more advanced methodologies 7, [14][15][16][17][18][19] . SCM account for surface charge along with solute-surface adsorption complex equilibrium constants to fit a model of surface complexes to batch adsorption experiments data 20,21 .…”

Section: Toc Art Introductionmentioning

confidence: 99%

Probing Atomic-Scale Processes at the Ferrihydrite-Water Interface With Reactive Molecular Dynamics

Hayatifar,

Gravelle,

Moreno

et al. 2024

Preprint

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Interfacial processes involving metal (oxyhydr)oxide phases are important for the mobility and bioavailability of nutrient and contaminant elements in soils, sediments, and water. Consequently, these processes influence ecosystem health and functioning, and have shaped the biological and environmental co-evolution of Earth over geologic time. Here we employ reactive molecular dynamics simulations, supported by synchrotron X-ray spectroscopy to study the molecular-scale interfacial processes that influence surface complexation in ferrihydrite-water systems containing aqueous \ce{MoO_4^{2-}}. We validate the utility of this approach by calculating surface complexation models directly from simulations. The reactive force-field captures the realistic dynamics of surface restructuring, surface charge equilibration, and the evolution of the interfacial water hydrogen bond network in response to adsorption and proton transfer. We find that upon hydration and adsorption, ferrihydrite restructures into a more disordered phase through surface charge equilibration, as revealed by simulations and grazing incident X-ray scattering. We observed how this restructuring leads to a different interfacial hydrogen bond network compared to bulk water by monitoring water dynamics. Using umbrella sampling, we constructed the free energy landscape of aqueous \ce{MoO_4^{2-}} adsorption at various concentrations and the deprotonation of the ferrihydrite surface. The results demonstrate excellent agreement with the values reported by experimental surface complexation models. These findings are important as reactive molecular dynamics opens new avenues to study mineral-water interfaces, enriching and refining surface complexation models beyond their foundational assumptions.

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“…Past studies of charged interfaces in water experiencing adsorption events have commonly relied on empirical studies, supported by various spectroscopic techniques and Surface complexation models (SCM), while some recent studies have used more advanced methodologies [7,14,15,16,17,18,19]. SCM account for surface charge along with solute-surface adsorption complex equilibrium constants to fit a model of surface complexes to batch adsorption experiments data [20,21].…”

Section: Introductionmentioning

confidence: 99%

Probing atomic-scale processes at the ferrihydrite-water interface with reactive molecular dynamics

Hayatifar,

Gravelle,

Moreno

et al. 2024

Preprint

View full text Add to dashboard Cite

Interfacial processes involving metal (oxyhydr)oxide phases often control the mobility and bioavailability of nutrient and contaminant elements in soils, sediments, and water. Consequently, these processes influence ecosystem health and functioning and have shaped the biological and environmental co-evolution of Earth over geologic time. Here we employ reactive molecular dynamics simulations, supported by synchrotron X-ray spectroscopy, to derive accurate surface complexation model constants for ferrihydrite-water systems containing aqueous \ce{MoO_4^{2-}}. This is achieved by employing a force-field that is adept at capturing the realistic dynamics of surface restructuring, surface charge equilibration, and the evolution of the interfacial water hydrogen bond network in response to adsorption processes or proton transfer events. We inform surface complexation models by exploring the free energy landscape of \ce{MoO_4^{2-}} adsorption at the ferrihydrite-water interface at different concentrations. We find how hydration and adsorption induce changes in surface charge, prompting the surface to restructure into more disordered ferrihydrite phases. We observe how the dynamics of adsorbed complexes are concentration-dependent and how surface restructuration, along with adsorption, influence the interfacial hydrogen bond network. By incorporating reactivity, reactive molecular dynamics opens new avenues to study mineral-water interfaces, enriching and refining surface complexation models beyond their foundational assumptions.

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Repartitioning of co-precipitated Mo(VI) during Fe(II) and S(-II) driven ferrihydrite transformation

Cited by 4 publications

References 91 publications

Transformations of Ferrihydrite–Extracellular Polymeric Substance Coprecipitates Driven by Dissolved Sulfide: Interrelated Effects of Carbon and Sulfur Loadings

Transformations of Ferrihydrite–Extracellular Polymeric Substance Coprecipitates Driven by Dissolved Sulfide: Interrelated Effects of Carbon and Sulfur Loadings

Probing Atomic-Scale Processes at the Ferrihydrite-Water Interface With Reactive Molecular Dynamics

Probing atomic-scale processes at the ferrihydrite-water interface with reactive molecular dynamics

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