Competitive adsorption geometries for the arsenate As(V) and phosphate P(V) oxyanions on magnetite surfaces: Experiments and theory

Liang, Xiaoliang; Lin, Xiaoju; Wei, Gaoling; Ma, Longlong; He, Hongping; Santos‐Carballal, David; Zhu, Jianxi; Leeuw, Nora H. de

doi:10.2138/am-2020-7350

Cited by 32 publications

(12 citation statements)

References 95 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Additionally, according to recent studies, UiO-66 is an excellent phosphate adsorbent (up to a 415 mg/g phosphate uptake capacity, a higher capacity than most phosphate adsorbents) and the presence of phosphate can severely impact adsorption of arsenate by UiO-66. , For this study, the focus is narrowed on species present at neutral pH, i.e., H 2 AsO 4 – vs H 2 PO 4 – and HAsO 4 2– vs HPO 4 2– , and the double monodentate adsorption mode (Figure ). Our results show that adsorption of phosphates is thermodynamically competitive with arsenate adsorption, in agreement with previous computational studies on other materials − as well as the observed competitive behavior of phosphates for adsorption sites on UiO-66. , Additionally, we found that phosphate coadsorption with arsenate is also thermodynamically viable and competitive, e.g., HAsO 4 2– /HPO 4 2– double monodentate binding mode is only 2.4 kcal/mol less favorable than both the HAsO 4 2– /HAsO 4 2– and HPO 4 2– /HPO 4 2– binding modes, thus potentially also contributing to decreased arsenate adsorption. Factors other than the binding strength between UiO-66 and the oxyanions may help further explain the detrimental effect of phosphates on arsenic adsorption.…”

Section: Resultssupporting

confidence: 92%

Computational Insights into As(V) Removal from Water by the UiO-66 Metal–Organic Framework

2021

View full text Add to dashboard Cite

Metal–organic frameworks (MOFs) such as UiO-66 have shown great promise for the removal of toxic As(V) species from water, but the precise adsorption mechanism is not yet well understood. In this study, we use density functional theory calculations and cluster models to determine accurate energetics and geometries for the adsorption of As(V) species present under varying pH conditions, namely, arsenic acid and related oxyanions. As a result of this analysis, we identify a new adsorption mode in which two As(V) molecules adsorb in a monodentate fashion on two neighboring Zr open metal sites resulting from capping ligand displacement. This mode is preferred over other adsorption modes previously proposed in the literature at acidic and neutral pH. Multidentate adsorption modes involving adsorption of a single As(V) molecule onto both neighboring Zr sites become more competitive as the pH increases, consistent with the lower adsorption performance observed at basic pH. Additionally, we study the influence of the ligands capping the Zr sites on As(V) adsorption thermodynamics. We show that the hydroxide–water ligand pair is the capping ligand most easily displaced by adsorbing As(V) species, suggesting that defects present in the aqueous environment are the ideal site for As(V) species adsorption. Furthermore, we find that adsorption of phosphate oxyanions can thermodynamically compete with As(V) adsorption, thus potentially explaining the observed decreased As(V) adsorption performance in the presence of phosphates. The molecular-level insights gained in this study are used to draw general design principles for the development of new MOFs that can be employed to remove toxic oxyanions from water.

show abstract

Section: Resultssupporting

confidence: 92%

Computational Insights into As(V) Removal from Water by the UiO-66 Metal–Organic Framework

2021

View full text Add to dashboard Cite

show abstract

“…We note that the model underestimated the suppression of arsenate adsorption to gibbsite when phosphate was present. Given the EXAFS analysis showed more evidence for outer-sphere surface complexes of arsenate on gibbsite (e.g., lower CN Al ) and the recent observation of arsenate outer-sphere complex on magnetite surfaces by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrum, we speculate that the outer-sphere complexation, which is not specifically accounted for in the present models, may provide additional capacity for arsenate uptake when phosphate is competing.…”

Section: Resultsmentioning

confidence: 67%

Effects of Phosphate Competition on Arsenate Binding to Aluminum Hydroxide Surfaces

Wang

et al. 2021

ACS Earth Space Chem.

View full text Add to dashboard Cite

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.

show abstract

“…The D2 semiempirical method of Grimme was included in our calculations to correct the long-range dispersion interactions, 75 which is particularly important for an appropriate description of materials and interface properties. 59,68,[76][77][78][79][80][81][82][83][84][85] periodic plane-wave basis set with an upper kinetic energy threshold fixed at 400 eV was employed to expand the Kohn-Sham valence states. The electronic ground state was determined using a preconditioned conjugate gradients minimisation algorithm, which optimises completely and self-consistently the total (free) energy, which is the variational quantity within this methodology.…”

Section: Calculation Detailsmentioning

confidence: 99%

Catalytic formation of oxalic acid on the partially oxidised greigite Fe₃S₄(001) surface

Santos‐Carballal

Leeuw

2022

Phys. Chem. Chem. Phys.

Self Cite

View full text Add to dashboard Cite

show abstract

Competitive adsorption geometries for the arsenate As(V) and phosphate P(V) oxyanions on magnetite surfaces: Experiments and theory

Abstract: This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

Cited by 32 publications

References 95 publications

Computational Insights into As(V) Removal from Water by the UiO-66 Metal–Organic Framework

Computational Insights into As(V) Removal from Water by the UiO-66 Metal–Organic Framework

Effects of Phosphate Competition on Arsenate Binding to Aluminum Hydroxide Surfaces

Catalytic formation of oxalic acid on the partially oxidised greigite Fe₃S₄(001) surface

Contact Info

Product

Resources

About

Competitive adsorption geometries for the arsenate As(V) and phosphate P(V) oxyanions on magnetite surfaces: Experiments and theory

Abstract: This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

Cited by 32 publications

References 95 publications

Computational Insights into As(V) Removal from Water by the UiO-66 Metal–Organic Framework

Computational Insights into As(V) Removal from Water by the UiO-66 Metal–Organic Framework

Effects of Phosphate Competition on Arsenate Binding to Aluminum Hydroxide Surfaces

Catalytic formation of oxalic acid on the partially oxidised greigite Fe3S4(001) surface

Contact Info

Product

Resources

About

Catalytic formation of oxalic acid on the partially oxidised greigite Fe₃S₄(001) surface