| 1. |
- Henriksson, Nils, et al.
(författare)
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Improved in vivo measurement of alternative oxidase respiration in field-collected pine roots
- 2019
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 167, s. 34-47
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Tidskriftsartikel (refereegranskat)abstract
- Cellular respiration via the alternative oxidase pathway (AOP) leads to a considerable loss in efficiency. Compared to the cytochrome pathway (COP), AOP produces 0-50% as much ATP per carbon (C) respired. Relative partitioning between the pathways can be measured in vivo based on their differing isotopic discriminations against O-18 in O-2. Starting from published methods, we have refined and tested a new protocol to improve measurement precision and efficiency. The refinements detect an effect of tissue water content (P < 0.0001), which we have removed, and yield precise discrimination endpoints in the presence of pathway-specific respiratory inhibitors [CN- and salicylhydroxamic acid (SHAM)], which improves estimates of AOP/COP partitioning. Fresh roots of Pinus sylvestris were sealed in vials with a CO2 trap. The air was replaced to ensure identical starting conditions. Headspace air was repeatedly sampled and isotopically analyzed using isotope-ratio mass spectrometry. The method allows high-precision measurement of the discrimination against O-18 in O-2 because of repeated measurements of the same incubation vial. COP and AOP respiration discriminated against O-18 by 15.1 +/- 0.3 parts per thousand and 23.8 +/- 0.4 parts per thousand, respectively. AOP contributed to root respiration by 23 +/- 0.2% of the total in an unfertilized stand. In a second, nitrogen-fertilized, stand AOP contribution was only 14 +/- 0.2% of the total. These results suggest the improved method can be used to assess the relative importance of COP and AOP activities in ecosystems, potentially yielding information on the role of each pathway for the carbon use efficiency of organisms.
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| 2. |
- Shimizu, Kenichi, et al.
(författare)
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X-ray photoelectron spectroscopy of fast-frozen hematite colloids in aqueous solutions. 4. Coexistence of alkali metal (Na+, K+, Rb+, Cs+) and chloride ions
- 2012
-
Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 606:13-14, s. 1005-1009
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal suspensions of hematite in contact with aqueous solutions of 50 mM alkali metal chloride electrolytes (NaCl, KCl, RbCl, CsCl) were investigated by cryogenic X-ray photoelectron spectroscopy (XPS) and electrophoretic mobility. Suspension pH values were varied from 2 to 11 in order to evaluate effects of positively- and negatively-charged hematite surfaces. XPS revealed coexisting cations and chloride ions both below and above the point of zero charge. Concentration profiles of adsorbed cations point to a Hofmeister series in the order of Na+ > K+ > Rb+ ≈ Cs+. Binding energies of photoelectrons emitted from electrolyte ions increased with pH at roughly 0.04 eV per pH unit. This shift was attributed to variations in the surface electric potential of hematite. This effect, compounded by rises in aliphatic carbon signals with pH, called for referencing of all spectra to the 530.0 eV oxide component of the hematite O1s spectrum. This departure from the traditional use of the external C 1s 285.0 eV peak is hereby proposed for cryogenic XPS studies of interfacial reactions involving hematite.
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| 3. |
- Adeniyi, Omotayo, et al.
(författare)
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Engineering of layered iron vanadate nanostructure for electrocatalysis : simultaneous detection of methotrexate and folinic acid in blood serum
- 2023
-
Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859.
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, nanostructure kazakhstanite-like iron vanadate (FexV3xOy.H2O) was synthesized and calcined at different temperatures (100-800 °C) in a nitrogen atmosphere. The material was used to modify screen-printed carbon electrodes to achieve an electrocatalytic effect on the surface. The relationship between calcination conditions and the catalytic performance of the electrode towards the oxidation of chemotherapeutic drugs, including methotrexate (MTX) and folinic acid (FA), was studied. Various spectroscopic, microscopic, and electrochemical methods were used to characterize the synthesized materials. The results show that calcination induces changes in the electronic structure, nanostructure morphology, electroactive surface area, and electrocatalytic performance of the material. Screen-printed carbon electrode modified with FexV3xOy calcinated at 450 °C (SPC/FexV3xOy-450) was used to develop a voltammetric sensor for the determination of MTX and FA in blood serum. The response of the SPC/FexV3xOy-450 towards the electrooxidation of MTX and FA was the highest in comparison to the bare SPC and SPC/FexV3xOy calcined at other temperatures. The SPC/FexV3xOy-450 exhibited a linear relationship over a wide concentration range: 0.005-200 µM for MTX and 0.05-200 µM for FA. The detection limit was 2.85 nM for MTX and 7.79 nM for FA. Compared to conventional methods, the SPC/FexV3xOy-450 sensor had a short response time (5 min) for simultaneous detection of MTX and FA without signal interferences from coexisting electroactive compounds. The accurate and precise determination of MTX in the presence of FA confirmed the potential clinical applications of SPC/FexV3xOy-450 for therapeutic drug monitoring during chemotherapy.
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| 4. |
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| 5. |
- Annamalai, Alagappan, et al.
(författare)
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Influence of Sb5+ as a Double Donor on Hematite (Fe3+) Photoanodes for Surface-Enhanced Photoelectrochemical Water Oxidation
- 2018
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:19, s. 16467-16473
-
Tidskriftsartikel (refereegranskat)abstract
- To exploit the full potential of hematite (α-Fe2O3) as an efficient photoanode for water oxidation, the redox processes occurring at the Fe2O3/electrolyte interface need to be studied in greater detail. Ex situ doping is an excellent technique to introduce dopants onto the photoanode surface and to modify the photoanode/electrolyte interface. In this context, we selected antimony (Sb5+) as the ex situ dopant because it is an effective electron donor and reduces recombination effects and concurrently utilize the possibility to tuning the surface charge and wettability. In the presence of Sb5+ states in Sb-doped Fe2O3 photoanodes, as confirmed by X-ray photoelectron spectroscopy, we observed a 10-fold increase in carrier concentration (1.1 × 1020 vs 1.3 × 1019 cm–3) and decreased photoanode/electrolyte charge transfer resistance (∼990 vs ∼3700 Ω). Furthermore, a broad range of surface characterization techniques such as Fourier-transform infrared spectroscopy, ζ-potential, and contact angle measurements reveal that changes in the surface hydroxyl groups following the ex situ doping also have an effect on the water splitting capability. Theoretical calculations suggest that Sb5+ can activate multiple Fe3+ ions simultaneously, in addition to increasing the surface charge and enhancing the electron/hole transport properties. To a greater extent, the Sb5+- surface-doped determines the interfacial properties of electrochemical charge transfer, leading to an efficient water oxidation mechanism.
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| 6. |
- Arbid, Yara, et al.
(författare)
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Use of iron-bearing waste materials in laundry wastewater treatment
- 2024
-
Ingår i: Journal of Water Process Engineering. - : Elsevier. - 2214-7144. ; 57
-
Tidskriftsartikel (refereegranskat)abstract
- This study evaluates the efficiency of a steel waste-derived magnetite (WM) for the treatment of laundry wastewater under various irradiation conditions (ultraviolet-A and C: UVA and UVC), both in the presence and absence of H2O2. Because WM can contain magnetite and elemental iron phases, its ability to remove ciprofloxacin and phenol, here used as model pollutants, and total organic carbon (TOC) from laundry wastewater was compared with that of synthetic magnetite (SM) and zero-valent iron (ZVI). We show that the mixed ZVI/H2O2 system under UVC degraded up to 80 % of the pollutant and 70 % of the TOC. WM had, on the other hand, a lower reactivity for pollutants due to the presence of inorganic impurities, yet removed up to 60 % of TOC. In all cases considered in this work, a higher degradation rate was observed under UVC irradiation than under UVA. Moreover, iron-based materials can adsorb heavy metals co-existing in the laundry wastewater. Recyclability tests showed no significant loss in the activity of WM or SM for up to 5 cycles in laundry wastewater. This study can have strong implications for the development of new remediation technologies relying on industrial solid wastes, especially in the context of a circular economy.
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| 7. |
- Boily, Jean-François, et al.
(författare)
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An independent confirmation of the correlation of Uf4 primary peaks and satellite structures of UVI, UV and UIV in mixed valence uranium oxides by two-dimensional correlation spectroscopy
- 2008
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 602:24, s. 3637-46
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) correlation spectroscopy was used to resolve the positions and correlations among U4f primary peaks and satellite structures of UIV, UV and UVI components on a dry mica surface. These different species resulted from the reduction of UVI, initially sorbed/precipitated from solution, upon exposure to a high flux of monochromatic Al Kα X-rays during X-ray photoelectron spectroscopy. Synchronous and asynchronous 2D maps of these results are consistent with previous assignments to UIV, UV and UVI components of the solid. The synchronous spectra confirmed the negative correlation between UVI and UIV components and the asynchronous spectra confirmed the role of UV as a reactive intermediate in the reduction reaction of UVI to UIV. Simulations of 2D correlation maps using synthetic spectra of the primary peaks showed that the presence of highly overlapped peaks centered within 2 eV of each other cannot be distinguished without the presence of additional cross-peaks. The maps have therefore confirmed the existence of three dominant oxidation states, and identified positions of UIV, UV and UVI U4f primary peaks and satellite structures that are consistent with previous peak-fitting efforts. Satellite structures also showed out-of-phase correlations among the different oxidation states, further confirming their use as reliable indicators of oxidation state.
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| 8. |
- Boily, Jean-Francois, et al.
(författare)
-
Benzenecarboxylate surface complexation at the goethite (-FeOOH)/water interface: II. Linking IR spectroscopic observations to mechanistic surface complexation models for phthalate, trimellitate, and pyromellitate
- 2000
-
Ingår i: Geochimica et Cosmochimica Acta. ; 64:20, s. 3453-70
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Tidskriftsartikel (refereegranskat)abstract
- A study combining information from infrared spectroscopy and adsorption experiments was carried out to investigate phthalate, trimellitate, and pyromellitate complexes at the goethite (-FeOOH)/water interface. Infrared spectra showed evidence for inner-sphere complexes below pH 6 and outer-sphere complexes in the pH range 3 to 9. Normalized infrared peak areas were used as a semi-quantitative tool to devise diagrams showing the molecular level surface speciation as a function of pH. Surface complexation models that simultaneously predict these diagrams, the proton balance data and the ligand adsorption data were developed with surface complexation theory. Surface complexation modeling was carried out with a Charge Distribution Multisite Complexation Model (CD-MUSIC), assuming goethite particles with surfaces represented by the {110} plane (90% of total particle surface area) and by the {001} plane (10% of total particle surface area). Inner-sphere complexes were described as mononuclear chelates at the {001} plane, whereas outer-sphere complexes were described as binuclear complexes with singly coordinated sites on the {110} plane. The Three-Plane Model (TPM) was used to described surface electrostatics and to distribute the charges of the inner- and the outer-sphere complexes on different planes of adsorption.
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| 9. |
- Boily, Jean-Francois, et al.
(författare)
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Benzenecarboxylate surface complexation at the goethite (α-FEOOH)/water interface. III. The influence of particle surface area and the significance of modeling parameters
- 2000
-
Ingår i: Journal of colloid and interface science. ; 227:1, s. 132-40
-
Tidskriftsartikel (refereegranskat)abstract
- A surface complexation model describing the adsorption of three benzenecarboxylates (phthalate, trimellitate, and pyromellitate) on goethite (α-FeOOH) was calibrated on data using goethite particles of 37 and 43 m[2]/g surface area. The models predict potentiometric titration and batch adsorption data with the multisite complexation model coupled with the three-plane model to account for surface electrostatics. The modeling parameters were found to be similar to those calibrated on benzenecarboxylate adsorption data on goethite particles of 90 m[2]/g (Boily et al. Geochim. Cosmochim. Acta, in press). The significance of the benzenecarboxylate-dependent values of the modeling parameters is also discussed. The values of the capacitances of the inner- and outer-Helmholtz planes were shown to be important modeling parameters to model the benzenecarboxylate-dependent slopes of the adsorption edges. It was shown that the larger the charge of the ligand, the larger the capacitance of the outer-Helmholtz plane.
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| 10. |
- Boily, Jean-Francois
(författare)
-
Colloids
- 2017
-
Ingår i: Encyclopedia of geochemistry. - Cham : Springer. - 9783319391939 ; , s. 1-4
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Colloids are inorganic and organic fines of diverse compositions and sources. They are of widespread occurrence in continental, oceanic, and atmospheric environments. The high surface-to-bulk mass ratio of these particles is especially responsible for their large chemical reactivity and for their important roles in the biogeochemical cycling of elements in nature and even in atmospheric processes.
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| 11. |
- Boily, Jean-François, et al.
(författare)
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Crystallographic controls on uranyl binding at the quartz/water interface
- 2011
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : RSC Publishing. - 1463-9076 .- 1463-9084. ; 13:17, s. 7845-7851
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics methods were used to simulate UO(2)(OH)(2)(0) binding to pairs of oxo sites (O(S)) on three low-index planes of α-SiO(2) in contact with water. Differences in binding site distributions on the (001), (010) and (101) planes produced distinct sets of stable U inner-sphere species. Steric constraints prevented bidentate coordination to the (001) surface, resulting in a mononuclear monodentate complex, [UO(2)(OH)(2)(H(2)O)(n)O(S)] (90% for n = 1 and 10% for n = 2 over 5 ns production runs). Binuclear bidentate coordination, [UO(2)(OH)(2)(H(2)O)(n)(O(S))(2)], was however favored on the (010) (99% for n = 0 and 1% for n = 1) and the (101) (72% for n = 0 and 28% for n = 1) planes. These results underscore a predominant four-coordinated equatorial shell for U when complexed to the quartz/water interface. Potential of mean force calculations uncovered a diversity of metastable outer- and inner-sphere complexes at local energy minima up to ∼0.4 nm from the surface. These calculations point to important differences in both energetic requirements and mechanisms for the approach of UO(2)(OH)(2)(0) to different quartz surfaces. Binding strengths are affected by binding site distribution, steric freedom, U hydration and OH orientation, and increase in the order (001) (3.7 kJ mol(-1)) < (101) (5.6 kJ mol(-1)) < (010) (6.5 kJ mol(-1)). A general binding mechanism involves (1) formation of monodentate outer-sphere complexes, (2) removal of oxo-bound waters, (3) formation of one (monodentate), then two (bidentate) direct U-O(S) bonds (inner-sphere), and (4) expulsion of excessive waters from the equatorial shell of U.
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| 12. |
- Boily, Jean-Francois, et al.
(författare)
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Direct identification of reaction sites on ferrihydrite
- 2020
-
Ingår i: Communications Chemistry. - : Nature Publishing Group. - 2399-3669. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Hydroxyl groups are the cornerstone species driving catalytic reactions on mineral nanoparticles of Earth's crust, water, and atmosphere. Here we directly identify populations of these groups on ferrihydrite, a key yet misunderstood iron oxyhydroxide nanomineral in natural sciences. This is achieved by resolving an enigmatic set of vibrational spectroscopic signatures of reactive hydroxo groups and chemisorbed water molecules embedded in specific chemical environments. We assist these findings by exploring a vast array of configurations of computer-generated nanoparticles. We find that these groups are mainly disposed along rows at edges of sheets of iron octahedra. Molecular dynamics of nanoparticles as large as 10 nm show that the most reactive surface hydroxo groups are predominantly free, yet are hydrogen bond acceptors in an intricate network formed with less reactive groups. The resolved vibrational spectroscopic signatures open new possibilities for tracking catalytic reactions on ferrihydrite, directly from the unique viewpoint of its reactive hydroxyl groups. Ferrihydrite nanoparticles have many hydroxyl sites which can react with environmental contaminants and nutrients, but the surface structure of this common mineral is still not fully understood. Here, a combination of vibrational spectroscopy and molecular simulations identify hydroxyl groups exposed along rows at the edges of sheets of iron octahedra.
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| 13. |
- Boily, Jean-Francois, et al.
(författare)
-
Electrostatic cooperativity of hydroxyl groups at metal oxide surfaces
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society Publications. - 1932-7447 .- 1932-7455. ; 113:38, s. 16568-16570
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Tidskriftsartikel (refereegranskat)abstract
- The O−H bond distribution of hydroxyl groups at the {110} goethite (α-FeOOH) surface was investigated by molecular dynamics. This distribution was strongly affected by electrostatic interactions with neighboring oxo and hydroxo groups. The effects of proton surface loading, simulated by emplacing two protons at different distances of separation, were diverse and generated several sets of O−H bond distributions. DFT calculations of a representative molecular cluster were also carried out to demonstrate the impact of these effects on the orientation of oxygen lone pairs in neighboring oxo groups. These effects should have strong repercussions on O−H stretching vibrations of metal oxide surfaces.
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| 14. |
- Boily, Jean-François
(författare)
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Elucidation of oxyanion coordination geometries at solid surfaces of varied electric field strengths
- 2009
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : RSC Publishing. - 1463-9076 .- 1463-9084. ; 11:37, s. 8133-5
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Tidskriftsartikel (refereegranskat)abstract
- Density functional theory calculations of oxyanions exposed to external electric fields revealed systematic variations in molecular geometries and vibration stretching frequencies. These variations can be used in laboratory studies to determine coordination geometries of oxyanions adsorbed on solid surfaces using infrared spectroscopy.
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| 15. |
- Boily, Jean-François, et al.
(författare)
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FTIR spectral components of schwertmannite
- 2010
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 44:4, s. 1185-1190
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Tidskriftsartikel (refereegranskat)abstract
- Fourier transform infrared (FTIR) spectral components of three dominant groups of sulfate species in synthetic schwertmannite (Fe8O8(OH)6-x(SO4)x*nH2O) are presented. These components were extracted by multivariate curve resolution analysis of spectra obtained from N2(g)-dry samples initially reacted in aqueous solutions (pH 3-9) at room temperature. Each component contains complex sets of bands that correspond to mixtures of similar species. We tentatively assign these components to sulfate ions that are hydrogen- (components I and III) and iron-bonded (component I) to schwertmannite. Another component (II) is assigned to protonated sulfate species. Heating experiments to 130 degrees C moreover confirmed this possibility for component II. The spectral components extracted from this study can be used to identify dominant sulfate species in FTIR spectra of naturally occurring schwertmannite samples.
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| 16. |
- Boily, Jean-Francois, et al.
(författare)
-
Hydrogen bonding and molecular orientations across thin water films on sapphire
- 2019
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 555, s. 810-817
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Water vapor binding to metal oxide surfaces produces thin water films with properties controlled by interactions with surface hydroxo sites. Hydrogen bonding populations vary across films and induce different molecular orientations than at the surface of liquid water. Identifying these differences can open possibilities for tailoring film-mediated catalytic reactions by choice of the supporting metal oxide substrate.Experiments: The (0001) face of a single sapphire (α-Al2O3) sample exposed to water vapor and the surface of liquid water were probed by polarization dependent Sum Frequency Generation-Vibration Spectroscopy (SFG-VS). Molecular dynamics (MD) provided insight into the hydrogen bond populations and molecular orientations across films and liquid water.Findings: SFG-VS revealed a submonolayer film on sapphire exposed to 43% relative humidity (R.H.), and a multilayer film at 78% R.H. Polarization dependent SFG-VS spectra showed that median tilt angles of free OH bonds on the top of films are at ∼43° from the normal of the (0001) face but at 38° on neat liquid water. These values align with MD simulations, which also show that up to 36% of all OH bonds on films are free. This offers new means for understanding how interfacial reactions on sapphire-supported water films could contrast with those involving liquid water.
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| 17. |
- Boily, Jean-Francois
(författare)
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Hydrothermal solutions
- 2017
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Ingår i: Encyclopedia of geochemistry. - Cham : Springer. - 9783319391939 ; , s. 1-6
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 18. |
- Boily, Jean-François, et al.
(författare)
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Inner-Helmholtz potential development at the hematite (α-Fe2O3) (0 0 1) surface
- 2011
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 75:15, s. 4113-4124
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Tidskriftsartikel (refereegranskat)abstract
- Electric potentials of the (0 0 1) surface of hematite were measured as a function of pH and ionic strength in solutions of sodium nitrate and oxalic acid using the single-crystal electrode approach. The surface is predominantly charge-neutral in the pH 4–14 range, and develops a positive surface potential below pH 4 due to protonation of μ-OH0 sites (pK1,1,0,int = −1.32). This site is resilient to deprotonation up to at least pH 14 (−pK−1,1,0,int ≫ 19). The associated Stern layer capacitance of 0.31–0.73 F/m2 is smaller than typical values of powders, and possibly arises from a lower degree of surface solvation. Acid-promoted dissolution under elevated concentrations of HNO3 etches the (0 0 1) surface, yielding a convoluted surface populated by sites. The resulting surface potential was therefore larger under these conditions than in the absence of dissolution. Oxalate ions also promoted (0 0 1) dissolution. Associated electric potentials were strongly negative, with values as large as −0.5 V, possibly from metal-bonded interactions with oxalate. The hematite surface can also acquire negative potentials in the pH 7–11 range due to surface complexation and/or precipitation of iron species (0.0038 Fe/nm2) produced from acidic conditions. Oxalate-bearing systems also result in negative potentials in the same pH range, and may include ferric-oxalate surface complexes and/or surface precipitates. All measurements can be modeled by a thermodynamic model that can be used to predict inner-Helmholtz potentials of hematite surfaces.
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| 19. |
- Boily, Jean-Francois, et al.
(författare)
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Modeling proton binding at the goethite (-FeOOH)-water interface
- 2001
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. ; 179:1, s. 11-27
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Tidskriftsartikel (refereegranskat)abstract
- The basic charging behaviours of goethite particles with different surfaces area (23, 37 and 85 m2 g-1) in 0.003-2.0 M NaNO3 were interpreted using surface complexation theory with the basic Stern model (BSM). The affinity of the goethite surface functional groups for protons was evaluated using the multisite complexation model (MUSIC) framework considering singly, doubly, and triply-coordinated surface oxygens with respect to underlying Fe(III) atoms. The affinity of these functional groups for protons was investigated first by using a calibration curve devised in Hiemstra et al. [J. Colloid Interface Science, 184 (1996) 680]. The calibration curve correlates the proton affinity constants of aqueous metal monomers to the undersaturation of the coordination environment of oxygens by considering the actual bond valences of Fe&unknown;O bonds in goethite, short hydroxyl bonds and hydrogen bonds. The results show that the predictions are sensitive to the range of short hydroxyl bonds/hydrogen bonds found in the literature. The singly- and one type of the triply coordinated sites are, however, most likely responsible for the basic charging behavior of goethite in the pH 2-11. The proton affinity constants of the singly- and triply coordinated sites were also optimized using titration data at different ionic strengths by co-optimizing values for electrolyte ion pairs and the capacitance of the Stern Layer. The optimal proton binding constants were in the range of the predicted values using the aforementioned calibration curve, although the modeling parameters are interdependent. A narrow range of CStern and electrolyte ion pairs was chosen to model the charging behavior of goethite by considering, (i), the range of proton binding constants from the aforementioned calibration curve; and (ii), the success of the models to predict zeta potential measurements assuming that the shear plane coincides with the head of the diffuse layer. Modeling parameters were also produced with the '1pK approximation' whereby the proton affinity constant of the singly- and of the triply-coordinated sites were set to the pH of zero charge and CStern and the electrolyte ion binding constants were co-optimized. In both cases, the values of CStern and of the electrolyte ion binding constants are slightly larger for the 23 and 37 m2 g-1 goethites than for the 85 m2 g-1. This indicates a larger proton uptake capacity of the 23 and 37 m2 g-1 goethites, putatively resulting from the larger surface roughness at the termination of the particles.
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| 20. |
- Boily, Jean-Francois, et al.
(författare)
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Particle Morphological and Roughness Controls on Mineral Surface Charge Development
- 2014
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier. - 0016-7037 .- 1872-9533. ; 141:15 September, s. 567-578
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Effects of mineral particle morphology and roughness on potential determining ion (p.d.i.; H+, OH−) loadings achieved at synthetic lepidocrocite (γ-FeOOH) surfaces were predominantly investigated by potentiometry and thermodynamic modeling. Nanosized rod- (RL) and lath-shaped (LL) particles exhibiting different proportions of the same predominant crystallographic faces acquired largely comparable pH, ionic strength and counterion (NaCl, NaClO4) dependencies on p.d.i. loadings. These results supported previous claims that faces ideally containing proton silent sites only, are likely populated by additional proton active sites. This concept was supported further by results of roughened LL-like particles (LLR) also showing highly congruent pH-, ionic strength- and composition-dependent p.d.i. loadings with those of LL and RL. These loadings thereby correspond to maximal levels allowed by net attractive and repulsive forces at each solution composition, irrespective of particle morphology. Contrasting equilibration times required to achieve these loadings revealed considerably slower exchange of p.d.i. and electrolyte ions near the point of zero charge in the rough LLR than in the more idealized LL and RL particles.Thermodynamic modeling was used to test various concepts accounting for these results. The model made use of a novel framework capable of isolating electrostatic contributions from different faces, and of accounting for ion-specific double-layer properties within a single crystallographic face. These efforts made use of capacitance values for each electrolyte ions within the framework of a recently developed Variable Capacitance Model. Attempts at modeling all three particle types were used to suggest that the (0 1 0) face contains ∼0.9 site nm−2 of proton active sites, a value notably constrained by recently published Na+, Cl−, and ClO4− loadings derived by cryogenic X-ray photoelectron spectroscopy. The model presented in this work thus provides a means to predict p.d.i. loadings on multifaceted mineral particle surfaces, and can therefore be used to constrain further our understanding of mineral/water interface reactivity.
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| 21. |
- Boily, Jean-François, et al.
(författare)
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Proton binding to humic acids and sorption of Pb(II) and humic acid to the corundum surface
- 2000
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Ingår i: Chemical Geology. ; 168:3-4, s. 239-53
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Tidskriftsartikel (refereegranskat)abstract
- An experimental investigation of proton binding to a humic acid, and of the co-adsorption of humic acid and Pb(II) to the corundum surface was conducted in 0.01 M NaNO3. We attempt to model the acid–base properties of the humic acid using both discrete and continuous distributions of proton affinity constants, also testing both nonelectrostatic and electrostatic approaches. The best-fitting models indicate that an average of three dominant proton-active functional groups are present on the humic acid with proton affinity constant logβ1,1,0 (int) equal to 2.6, 5.2 and 7.6. These values may be applied as intrinsic constants in a Constant Capacitance Model (CCM) or as means of distribution functions in a Langmuir–Freundlich isotherm where the humate is treated as a mixture of three monoprotic acids. The adsorption of humic acid onto corundum is best described using a Surface Complexation Model (SCM) with the Extended Constant Capacitance Model. The humate surface complexes, which best describe the experimental data, are the outer-sphere (>AlOH2+)0.1Hf1∑L(0.1–3.0+f1) and (>AlOH2+)0.1(H(f1+f2)∑L)(0.1–3.0+f1+f2) complexes, where f1 and f2 are the mole fractions of the sites with logβ1,1,0 (int)=7.6 and logβ1,1,0 (int)=5.2, respectively. Experimental data also show that the presence of calcium increases the adsorption of humate. The adsorption of Pb in the presence of humate was interpreted to proceed by the formation of the surface ternary complex >AlOH2+–L−z–Pb+2 at low to circumneutral pH. At high pH, aqueous Pb–humate complexation competes with Pb surface complexes and significantly reduces Pb adsorption.
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| 22. |
- Boily, Jean-Francois
(författare)
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Solubility
- 2017
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Ingår i: Encyclopedia of geochemistry. - Cham : Springer. - 9783319391939 ; , s. 1-9
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 23. |
- Boily, Jean-François, et al.
(författare)
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Structures and stabilities of Cd(II) and Cd(II)-phthalate complexes at the goethite/water interface
- 2005
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Ingår i: GEOCHIMICA ET COSMOCHIMICA ACTA. - : Elsevier BV. - 0016-7037. ; 69:13, s. 3219-35
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Tidskriftsartikel (refereegranskat)abstract
- The complexation of Cd(II) and Cd(II)-phthalate at the goethite/water interface were investigated by EXAFS and IR spectroscopy, by batch adsorption experiments and by potentiometric titrations at 298.15 K. The EXAFS spectra showed Cd(II) to form only inner-sphere corner-sharing complexes with the goethite surface sites in the presence and absence of phthalate. EXAFS spectra also showed the presence of Cd(II)-chloride complexes in 0.1 mol/L NaCl. IR spectra also showed phthalate to form (1) an inner-sphere complex with adsorbed corner-sharing Cd(II) surface complexes in the pH 3.5 to 9.5 and (2) an outer-sphere complex with the same type of corner-sharing Cd(II) complex however at pH > 6, in addition to the inner- and outer-sphere complexes of phthalate reported in a previous study. The potentiometric titration and the batch adsorption data were used to constrain the formation constants of the different Cd(II)-phthalate surface complexes on the dominant {110} and the {001} planes of the goethite. The models were carried out with the Charge Distribution Multisite Complexation model coupled to the Three Plane Model and can predict the molecular-scale speciation of cadmium and phthalate in the presence of goethite. Cd(II) adsorption models calibrated on a 90 m2/g goethite also could accurately predict experimental data for a 37 m2/g goethite of slightly different basic charging properties.
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| 24. |
- Boily, Jean-Francois
(författare)
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The Variable Capacitance Model : A Strategy for Treating Contrasting Charge-Neutralizing Capabilities of Counterions at the Mineral/Water Interface
- 2014
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Ingår i: Langmuir. - Washington : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:8, s. 2009-2018
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Tidskriftsartikel (refereegranskat)abstract
- Thermodynamic models predicting ion adsorption at mineral/water interfaces can have limitations from the simplifying assumptions that compact plane thicknesses and capacitance values are constant, and that charge densities of electrolyte counterions of different charge-to-size ratios lie at the same planes of adsorption, or split between different planes. To address these limitations a thermodynamic adsorption modeling framework was developed to account for coexisting compact planes for each type of counterion complexes formed on a single mineral surface. This framework was developed to predict charge development at lepidocrocite (gamma-FeOOH) particle surfaces suspended in aqueous solutions of NaCl and NaClO4. The model incorporates properties of Cl-, ClO4-, and Na+ complexes formed at the (001) and (010) faces of this mineral obtained by molecular dynamics (MD) simulations. This concept was incorporated in a thermodynamic adsorption model that predicts an overall variable compact plane capacitance in terms of a linear combination of the capacitances of ion-specific EDL structures scaled for their relative surface loadings. These capacitance values are in turn constrained by compact plane thicknesses of every Cl-, ClO4-, and Na+ complex, based on their MD-derived structures and atomic densities. The model predicts experimental potential-determining (H+, OH-) data for submicrometer-sized synthetic lepidocrocite particles exhibiting both (001) and (010) faces. It also isolates electrostatic contributions from these faces. A computer code solving for this Variable Capacitance Model-VCM-is provided in the Supporting Information section of this article, and can be readily modified to predict molecular-level details of any other mineral/water interface systems using this methodology.
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| 25. |
- Boily, Jean-Francois, et al.
(författare)
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Thin Water Films at Multifaceted Hematite Particle Surfaces
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:48, s. 13127-13137
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Tidskriftsartikel (refereegranskat)abstract
- Mineral surfaces exposed to moist air stabilize nanometer- to micrometer-thick water films. This study resolves the nature of thin water film formation at multifaceted hematite (alpha-Fe2O3) nanoparticle surfaces with crystallographic faces resolved by selected area electron diffraction. Dynamic vapor adsorption (DVA) in the 0-19 Torr range at 298 K showed that these particles stabilize water films consisting of up to 4-5 monolayers. Modeling of these data predicts water loadings in terms of an adsorption regime (up to 16 H2O/nm(2)) involving direct water binding to hematite surface sites, and of a condensation regime (up to 34 H2O/nm(2)) involving water binding to hematite-bound water nanodusters. Vibration spectroscopy identified the predominant hematite surface hydroxo groups (-OH, mu-OH, mu(3)-OH) through which first layer water molecules formed hydrogen bonds, as well as surface iron sites directly coordinating water molecules (i.e., as geminal eta-(OH2)(2) sites). Chemometric analyses of the vibration spectra also revealed a strong correspondence in the response of hematite surface hydroxo groups to DVA-derived water loadings. These findings point to a near-saturation of the hydrogen-bonding environment of surface hydroxo groups at a partial water vapor pressure of similar to 8 Torr (similar to 40% relative humidity). Classical molecular dynamics (MD) resolved the interfacial water structures and hydrogen bonding populations at five representative crystallographic faces expressed in these nanoparticles. Simulations of single oriented slabs underscored the individual roles of all (hydro)oxo groups in donating and accepting hydrogen bonds with first layer water in the adsorption regime. These analyses pointed to the preponderance of hydrogen bond-donating -OH groups in the stabilization of thin water films. Contributions of mu-OH and mu(3)-OH groups are secondary, yet remain essential in the stabilization of thin water films. MD simulations also helped resolve crystallographic controls on water water interactions occurring in the condensation regime. Water water hydrogen bond populations are greatest on the (001) face, and decrease in importance in the order (001) > (012) approximate to (110) > (014) >> (100). Simulations of a single (similar to 5 nm x similar to 6 nm x similar to 6 nm) nanometric hematite particle terminated by the (001), (110), (012), and (100) faces also highlighted the key roles that sites at particle edges play in interconnecting thin water films grown along contiguous crystallographic faces. Hydroxo water hydrogen bond populations showed that edges were the preferential loci of binding. These simulations also suggested that equilibration times for water binding at edges were slower than on crystallographic faces. In this regard, edges, and by extension roughened surfaces, are expected to play commanding roles in the stabilization of thin water films. Thus, in focusing on the properties of nanometric-thick water layers at hematite surfaces, this study revealed the nature of interactions between water and multifaced particle surfaces. Our results pave the way for furthering our understanding of mineral-thin water film interfacial structure and reactivity on a broader range of materials.
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