Temperature-Dependent Evolution of the Molecular Configuration of Oxo-Tungsten(VI) Species Deposited on the Surface of Titania

Tribalis, Antonios; Panagiotou, George D.; Tsilomelekis, George; Kalampounias, Angelos G.; Bourikas, Kyriakos; Kordulis, Christos; Boghosian, Soghomon; Lycourghiotis, Alexis

doi:10.1021/jp500909x

Cited by 18 publications

(29 citation statements)

References 69 publications

(155 reference statements)

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“…For clarity, only final equilibrated W (VI) spectrum was shown in Figure 2A. This spectrum illustrated IR bands associated with W-O symmetric (930 cm -1 ) and antisymmetric (830 cm -1 ) stretching due to strong inner-sphere type surface complexation of W (VI) with hematite surface as reported by earlier studies (Zorina and Syritso, 1972;Charton et al, 2002;Tomaszewicz et al, 2009;Kumar and Mohanta, 2011;Tribalis et al, 2014;Davantes and Lefevre, 2015;Rakshit et al, 2017). Subsequent time series spectra after 100 µM and 200 µM P additions were depicted to indicate the gradual growth of 1097 cm -1 IR band due to P surface complexation on hematite in the W +P mixed system (Figure 2A).…”

Section: Resultssupporting

confidence: 52%

“…In our earlier study, we found strong W-O-W stretching band at 875 cm -1 for the pH envelope of W (VI) sorption on hematite in the pH range of 6 to 4.6 (Rakshit et al, 2017). Other researchers indicated that the presence of this band represents the formation of polytungstate species (Tribalis et al, 2014). Inspection of the IR bands in the present study reveal similar IR bands at 875-877 cm -1 in the difference spectra of pH (4.6-8.05, 5.05-8.05, and 6.05-8.05).…”

Section: Analysis Of In Situ Atr-ftir Spectra Of W (Vi) and P Binding Onmentioning

confidence: 72%

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Influence of phosphate on tungstate sorption on hematite: A macroscopic and spectroscopic evaluation of the mechanism

2018

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Environmental fate of tungstate (VI) oxyanion [i.e. mono tungstate and several polytungstate, generally expressed by W (VI)] is largely controlled by sorption on soil minerals, especially on iron oxide minerals. Molecular scale evaluation of W (VI) retention on iron oxides in the presence of competing oxyanions is scarce in the literature. Here we report surface interaction mechanisms of W (VI) on hematite in the presence of phosphorus (P) using macroscopic and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic experiments. Batch sorption experiments were conducted using 2g L-1 hematite and 100 µM W (VI) and P, in single ion system and in binary mixtures as a function of pH (4-11). In situ ATR-FTIR spectroscopic evaluation of P and W (VI) sorption on hematite was also carried out. The results from macroscopic experiments indicated that W (VI) sorption on hematite was not affected when W (VI) was added first. The influence of P on W (VI) sorption was noticed when W (VI) & P were added simultaneously or P was added first. The in situ ATR-FTIR spectroscopic data corroborated this finding. In addition, the spectroscopic data revealed that in the presence of P, surface complexation mode of W (VI) differed as noted from either the absence of W-O antisymmetric infrared (IR) band or the W-O-W stretching band. This study provides useful information on molecular level understanding of W (VI) surface complexation on hematite in the presence of competing ions such as P.

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Section: Resultssupporting

confidence: 52%

Section: Analysis Of In Situ Atr-ftir Spectra Of W (Vi) and P Binding Onmentioning

confidence: 72%

Influence of phosphate on tungstate sorption on hematite: A macroscopic and spectroscopic evaluation of the mechanism

2018

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“…For higher concentrations, WO 3 nanoparticles (amorphous and crystallized) are evidenced. This contrasts with other supports (Al 2 O 3 [53,54], TiO 2 [55,56], ZrO 2 [57][58][59]) for which tungsten impregnation up to 4-5 W nm −2 leads to well-dispersed catalysts. On these supports, WO 3 nanocrystals are generally observed in the 4.5-9 W nm −2 loading range, while large bulklike WO 3 crystals can be observed beyond 9 W nm −2 [60].…”

Section: Structure Of Supported Tungsten Oxidesmentioning

confidence: 61%

Tungsten-Based Catalysts for Environmental Applications

2021

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This review aims to give a general overview of the recent use of tungsten-based catalysts for wide environmental applications, with first some useful background information about tungsten oxides. Tungsten oxide materials exhibit suitable behaviors for surface reactions and catalysis such as acidic properties (mainly Brønsted sites), redox and adsorption properties (due to the presence of oxygen vacancies) and a photostimulation response under visible light (2.6–2.8 eV bandgap). Depending on the operating condition of the catalytic process, each of these behaviors is tunable by controlling structure and morphology (e.g., nanoplates, nanosheets, nanorods, nanowires, nanomesh, microflowers, hollow nanospheres) and/or interactions with other compounds such as conductors (carbon), semiconductors or other oxides (e.g., TiO2) and precious metals. WOx particles can be also dispersed on high specific surface area supports. Based on these behaviors, WO3-based catalysts were developed for numerous environmental applications. This review is divided into five main parts: structure of tungsten-based catalysts, acidity of supported tungsten oxide catalysts, WO3 catalysts for DeNOx applications, total oxidation of volatile organic compounds in gas phase and gas sensors and pollutant remediation in liquid phase (photocatalysis).

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“…Specifically, for W-adsorbed Fh samples at pH 6.5 and 4.5, and all W-adsorbed Fh-HA composite samples, the IR peak broadens towards higher frequencies. Interestingly, the W−O−W stretching vibrations, which are characteristic of polymeric tungstate species can appear at ~860−880 cm −1 (Davantès et al, 2016;Rakshit et al, 2017;Tribalis et al, 2014). Results therefore suggest the presnece of poly tungstate species on Fh and Fh-HA at pH≤6.5.…”

Section: Molecular W(vi) Adsorption Characteristicsmentioning

confidence: 80%

Natural organic matter decreases uptake of W(VI), and reduces W(VI) to W(V), during adsorption to ferrihydrite

et al. 2020

Chemical Geology

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Tungsten is both naturally occurring and an anthropogenically released contaminant metal in soils, sediments and water systems that typically exits as the soluble tungstate oxyanions, W(VI)O4 2− . Tungsten mobility and fate are strongly dependent on the adsorption of tungstate to mineral surfaces. However, environmental mineral surfaces are commonly coated with natural organic matter (NOM), and the role of this coating in the tungsten adsorption process, and thus in controlling tungsten reactivity and transport, is unclear. This study investigates W(VI) adsorption to ferrihydrite (Fh), a ubiquitous iron (hydr)oxide in soils and sediments, both in the absence and presence of humic acid (HA), a widely occurring type of NOM, using batch experiments coupled with spectroscopic and thermodynamic techniques. Kinetic results indicate that access to the adsorption sites for W(VI) on the organomineral surfaces is limited when Fh is coprecipitated with HA. Commensurate with this observation, batch experiments show that HA decreases W(VI) adsorption to Fh over a wide pH range (4-11), and this inhibitory effect is more pronounced at higher HA concentration. X-ray photoelectron spectroscopy (XPS) measurements demonstrate the formation of inner-sphere type W complexes on both the Fh and HA fraction of the Fh-HA binary composite. In particular, ~40% of the adsorbed W(VI) species is reduced to W(V) in the presence of HA. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) results show the presence of poly tungstate species on Fh, particularly at lower pH and in the presence of HA. Isothermal titration calorimetry shows that W(VI) adsorption to Fh is an exothermic process both in the presence and absence of HA, and that process is accompanied by a positive entropy. The findings of this work suggest that NOM not only mobilizes tungstate but also reduces tungstate from W(VI) to W(V) at environmental iron (hydr)oxide-water interfaces, which is of significance for evaluating the migration and bioavailability of tungsten in both natural and contaminated environments.

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Temperature-Dependent Evolution of the Molecular Configuration of Oxo-Tungsten(VI) Species Deposited on the Surface of Titania

Cited by 18 publications

References 69 publications

Influence of phosphate on tungstate sorption on hematite: A macroscopic and spectroscopic evaluation of the mechanism

Influence of phosphate on tungstate sorption on hematite: A macroscopic and spectroscopic evaluation of the mechanism

Tungsten-Based Catalysts for Environmental Applications

Natural organic matter decreases uptake of W(VI), and reduces W(VI) to W(V), during adsorption to ferrihydrite

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