Response of interfacial water to arsenate adsorption on corundum (0 0 1) surfaces: Effects of pH and adsorbate surface coverage

Xu, Tingying; Stubbs, Joanne E.; Eng, Peter J.; Catalano, Jeffrey G.

doi:10.1016/j.gca.2018.07.041

Cited by 16 publications

(20 citation statements)

References 72 publications

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“…In fact, the outer-sphere complexes are more prevalent than the inner-sphere complexes under most conditions. Xu et al [99] used surface-sensitive spectroscopic methods (X-ray scattering) to measure AsO 4…”

Section: Outer-sphere Adsorptionmentioning

confidence: 99%

“…Arsenate adsorbs to most minerals through inner-sphere complexation on surface functional groups. However, on the corundum surface, Xu et al [99] observed that AsO 4…”

Section: Outer-sphere Adsorptionmentioning

confidence: 99%

“…3is the driving force for the outer-sphere adsorption on the corundum (001) surface. Xu et al [99] determined that at high surface coverages, up to 40% of the AsO 4 3adsorption on aluminum oxides occurs as outer-sphere complexes. These molecular-scale observations provide mechanistic evidence that water-molecule dynamics are important factors in adsorption processes.…”

Section: -mentioning

confidence: 99%

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Sorption Mechanisms of Chemicals in Soils

Strawn

2021

Soil Systems

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Sorption of chemicals onto soil particle surfaces is an important process controlling their availability for uptake by organisms and loss from soils to ground and surface waters. The mechanisms of chemical sorption are inner- and outer-sphere adsorption and precipitation onto mineral surfaces. Factors that determine the sorption behavior are properties of soil mineral and organic matter surfaces and properties of the sorbing chemicals (including valence, electron configuration, and hydrophobicity). Because soils are complex heterogeneous mixtures, measuring sorption mechanisms is challenging; however, advancements analytical methods have made direct determination of sorption mechanisms possible. In this review, historical and modern research that supports the mechanistic understanding of sorption mechanisms in soils is discussed. Sorption mechanisms covered include cation exchange, outer-sphere adsorption, inner-sphere adsorption, surface precipitation, and ternary adsorption complexes.

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Section: Outer-sphere Adsorptionmentioning

confidence: 99%

“…Arsenate adsorbs to most minerals through inner-sphere complexation on surface functional groups. However, on the corundum surface, Xu et al [99] observed that AsO 4…”

Section: Outer-sphere Adsorptionmentioning

confidence: 99%

Section: -mentioning

confidence: 99%

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Sorption Mechanisms of Chemicals in Soils

Strawn

2021

Soil Systems

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“…However, our EXAFS fitting results showed the CN Al is much smaller than 2 for both minerals regardless of pH and arsenate surface coverage (Table S3), indicating the presence of an additional type of arsenate surface species such as monodentate inner-sphere or outer-sphere complexes. Our EXAFS model refinements did not reveal monodentate inner-sphere binding configurations in the samples, suggesting the possible co-occurrence of arsenate outer-sphere surface complexes. ,, The EXAFS-derived CN Al on average is lower for gibbsite than that for bayerite, and statistical test ( t -tests) showed that this difference is significant. Thus, the lower CN Al suggests a greater proportion of outer-sphere arsenate complexes in the gibbsite system.…”

Section: Resultsmentioning

confidence: 67%

“…Our EXAFS model refinements did not reveal monodentate inner-sphere binding configurations in the samples, suggesting the possible co-occurrence of arsenate outer-sphere surface complexes. 32,57,58 The EXAFS-derived CN Al on average is lower for gibbsite than that for bayerite, and statistical test (t-tests) 31 showed that this difference is significant. Thus, the lower CN Al suggests a greater proportion of outer-sphere arsenate complexes in the gibbsite system.…”

Section: ■ Results and Discussionmentioning

confidence: 97%

Effects of Phosphate Competition on Arsenate Binding to Aluminum Hydroxide Surfaces

Wang

et al. 2021

ACS Earth Space Chem.

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Aluminum hydroxide plays a substantial role in regulating the environmental fate and transport of arsenate and phosphate. These minerals display multiple types of surface reactive sites with distinct adsorption affinities. As arsenate and phosphate coexist in many natural systems, a detailed understanding of their interactive adsorption behaviors on aluminum hydroxides and the underlying binding mechanisms is thus required to develop predictive models of their fate and mobility. In this study, we explore how phosphate affects arsenate adsorption onto the aluminum hydroxide polymorphs gibbsite and bayerite and develop a unified surface complexation model (SCM) to predict arsenate adsorption under diverse conditions parameterized only from noncompetitive uptake data. Macroscopic studies show that both oxyanions behave similarly in individual adsorption experiments. The addition of phosphate reduces arsenate adsorption on both minerals with a greater effect observed on gibbsite. Extended X-ray absorption fine structure spectroscopy reveals that similar arsenate species occur on both minerals and are unchanged in the presence of phosphate. This indicates that competitive adsorption does not affect arsenate surface speciation. These results demonstrate that arsenate and phosphate primarily interact on aluminum hydroxide surfaces via site competition. Notably, their similar pK a values and adsorption affinities minimize modification of adsorption behavior from surface electrostatic effects. The SCMs demonstrate that multiple arsenate surface species are needed to reproduce the observed competitive uptake data, in apparent conflict with the spectroscopic results that reveal no change in coordination at different surface coverages. This indicates that the molecular-scale drivers of differences in surface complex stability are not only from distinct local coordination, instead other factors, such as hydrogen bonding among the adsorbates, surface oxygens, and interfacial water or different surface complexes coordinating to functional groups with distinct connections to the underlying mineral structure, may also play an important role.

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Interfacial X-Ray Scattering From Small Surfaces: Adapting Mineral-Fluid Structure Methods for Microcrystalline Materials

Stubbs

Wanhala

Eng

2021

Clays and clay miner.

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Crystal truncation rod (CTR) X-ray diffraction is an invaluable tool for measuring mineral surface and adsorbate structures, and has been applied to several environmentally and geochemically important systems. Traditionally, the method has been restricted to single crystals with lateral dimensions >3 mm. Minerals that meet this size criterion represent a minute fraction of those that are relevant to interfacial geochemistry questions, however. Crystal screening, data collection, and CTR measurement methods have been developed for crystals of <0.3 mm in lateral size using the manganese oxide mineral chalcophanite (ZnMn3O7·3H2O) as a case study. This work demonstrates the feasibility of applying the CTR technique to previously inaccessible surfaces, opening up a large suite of candidate substrates for future study.

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Response of interfacial water to arsenate adsorption on corundum (0 0 1) surfaces: Effects of pH and adsorbate surface coverage

Cited by 16 publications

References 72 publications

Sorption Mechanisms of Chemicals in Soils

Sorption Mechanisms of Chemicals in Soils

Effects of Phosphate Competition on Arsenate Binding to Aluminum Hydroxide Surfaces

Interfacial X-Ray Scattering From Small Surfaces: Adapting Mineral-Fluid Structure Methods for Microcrystalline Materials

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Response of interfacial water to arsenate adsorption on corundum (0 0 1) surfaces: Effects of pH and adsorbate surface coverage

Cited by 16 publications

References 72 publications

Sorption Mechanisms of Chemicals in Soils

Sorption Mechanisms of Chemicals in Soils

Effects of Phosphate Competition on Arsenate Binding to Aluminum Hydroxide Surfaces

Interfacial X-Ray Scattering From Small Surfaces: Adapting Mineral-Fluid Structure Methods for Microcrystalline Materials

Contact Info

Product

Resources

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Response of interfacial water to arsenate adsorption on corundum (0 0 1) surfaces: Effects of pH and adsorbate surface coverage