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Sökning: WFRF:(Boily Jean François)

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1.
  • Henriksson, Nils, et al. (författare)
  • Improved in vivo measurement of alternative oxidase respiration in field-collected pine roots
  • 2019
  • Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 167, s. 34-47
  • 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)
  • 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
  • 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)
  • 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)
  • 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)
  • 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)
  • 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
  • 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
  • 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)
  • 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)
  • 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
  • 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)
  • 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
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society Publications. - 1932-7447 .- 1932-7455. ; 113:38, s. 16568-16570
  • 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)
  • Elucidation of oxyanion coordination geometries at solid surfaces of varied electric field strengths
  • 2009
  • Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : RSC Publishing. - 1463-9076 .- 1463-9084. ; 11:37, s. 8133-5
  • 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)
  • FTIR spectral components of schwertmannite
  • 2010
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 44:4, s. 1185-1190
  • 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
  • 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)
  • Hydrothermal solutions
  • 2017
  • 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)
  • Inner-Helmholtz potential development at the hematite (α-Fe2O3) (0 0 1) surface
  • 2011
  • Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 75:15, s. 4113-4124
  • 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)
  • Modeling proton binding at the goethite (-FeOOH)-water interface
  • 2001
  • Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. ; 179:1, s. 11-27
  • 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)
  • Particle Morphological and Roughness Controls on Mineral Surface Charge Development
  • 2014
  • Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier. - 0016-7037 .- 1872-9533. ; 141:15 September, s. 567-578
  • 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)
  • Proton binding to humic acids and sorption of Pb(II) and humic acid to the corundum surface
  • 2000
  • Ingår i: Chemical Geology. ; 168:3-4, s. 239-53
  • 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)
  • Solubility
  • 2017
  • Ingår i: Encyclopedia of geochemistry. - Cham : Springer. - 9783319391939 ; , s. 1-9
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
  •  
23.
  • Boily, Jean-François, et al. (författare)
  • Structures and stabilities of Cd(II) and Cd(II)-phthalate complexes at the goethite/water interface
  • 2005
  • Ingår i: GEOCHIMICA ET COSMOCHIMICA ACTA. - : Elsevier BV. - 0016-7037. ; 69:13, s. 3219-35
  • 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)
  • The Variable Capacitance Model : A Strategy for Treating Contrasting Charge-Neutralizing Capabilities of Counterions at the Mineral/Water Interface
  • 2014
  • Ingår i: Langmuir. - Washington : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:8, s. 2009-2018
  • 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)
  • Thin Water Films at Multifaceted Hematite Particle Surfaces
  • 2015
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:48, s. 13127-13137
  • 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.
  •  
26.
  • Boily, Jean-Francois (författare)
  • Water Structure and Hydrogen Bonding at Goethite/Water Interfaces : Implications for Proton Affinities
  • 2012
  • Ingår i: The Journal of Physical Chemistry C. - Washington, DC : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:7, s. 4714-4724
  • Tidskriftsartikel (refereegranskat)abstract
    • Molecular dynamics simulations of four crystallographic terminations of goethite (alpha-FeOOH) in contact with liquid water (300 K, 1 bar) were performed to resolve interfacial water structures in the vicinity of surface (hydr)oxo groups. Interfacial water molecules adopted highly surface-specific configurations on (010), 100), (110), and (021) planes of goethite. Water molecules generally had weaker hydrogen bond numbers and strengths, as well as smaller self-diffusion coefficients, than their bulk liquid counterparts. Relaxed surface Fe-O and H acceptor distances and populations were used to estimate proton affinity constants of singly-, and triply-coordinated (hydr)oxo groups using the multisite complexation model. These calculations confirmed that singly coordinated groups are mainly responsible for charge uptake under normal environmental conditions. However, revised proton affinity constants showed that protonation of doubly-coordinated hydroxo groups and one type of triply-coordinated oxo group may be favored in the presence of strongly binding negatively charged ligands. These calculations should facilitate elucidation of surface complexation mechanisms on this environmentally important material.
  •  
27.
  • Boily, Jean-Francois, et al. (författare)
  • X-ray photoelectron spectroscopy of fast-frozen hematite colloids in aqueous solutions. 2. tracing the relationship between surface charge and electrolyte adsorption
  • 2010
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:6, s. 2613-2616
  • Tidskriftsartikel (refereegranskat)abstract
    • Colloidal-sized hematite spheroids exposed to aqueous NaCl solutions were investigated by X-ray photoelectron spectroscopy using the fast-frozen technique. The O 1s region provided evidence for (de)protonation reactions of surface (hydr)oxo groups of OH-enriched/O-depleted hematite Surfaces. These results were also correlated to changes in sodium (Na 1s) and chloride (Cl 2p) contents with pH. Electrolyte ion surface loadings were successfully predicted using a classic thermodynamic adsorption model normalized for surface site density. These efforts pointed to ion-specific inner-Helmholtz plane capacitances.
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28.
  • Bottone, Anna, et al. (författare)
  • Sodium hypochlorite as an oxidizing agent for removal of soil organic matter before microplastics analyses
  • 2021
  • Ingår i: Journal of Environmental Quality. - : John Wiley & Sons. - 0047-2425 .- 1537-2537. ; 51:1, s. 112-122
  • Tidskriftsartikel (refereegranskat)abstract
    • The omnipresence of microplastics (MPs) across Earth's surface has raised concerns about their environmental impact and created an urgent need for methods to identify them in complex soil and sedimentary matrices. However, detecting MPs in the O horizons of soils is difficult because plastic polymers share many physical and chemical properties with natural soil organic matter (SOM). In this study, we assessed whether sodium hypochlorite (NaOCl), a reagent that can oxidize SOM and simultaneously preserve mineral constituents, can be used for MP analysis and characterization in soil environments. In addition, we scrutinized how factors such as MP size, polymer type, extraction methods, and soil matrix affect the recovery of microplastic particles. We used both hydrophobic and density-dependent separation methods to assess the effects of our oxidation treatment on the recovery of MP. We observed that NaOCl effectively removed SOM without greatly altering the surface properties of resistant MP polymers (polypropylene, polylactic acid, low-density polyethylene, and polyethylene terephthalate), which were characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy after SOM removal. The NaOCl treatment caused some chlorination and formation of additional C–OH bonds on polymer surfaces, which likely contributed to the reduced efficiency of the hydrophobic-based (oil) extraction. We conclude that NaOCl treatment can improve detection of MPs in SOM-rich soil and that recovery of MPs from soils is influenced by MP size, polymer type, extraction method, and soil type, which makes it challenging to develop a universal analytical method.
  •  
29.
  • Chang, Ribooga (författare)
  • Design and Optimization of CO2 sorbents for Point Source Emissions and Direct Air Capture
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis presents a comprehensive study on the design and optimization of CO2 sorbents, targeting two distinct applications: CO2 capture from point source emissions and Direct Air Capture (DAC). The research first introduces Na2HfO3 as a potential CO2 sorbent for point source emissions, using the molten salt effects of Na2CO3 and the thermal stability of HfO2. This combination results in a CO2 sorbent with impressive thermal and cyclic stability, through various optimization steps to enhance CO2 capture performance and efficiency. The study then shows into the structural disorder in Na2ZrO3, a chemically similar CO2 sorbent. This investigation fills a knowledge gap, offering new insights into the sorbent's behavior in CO2 capture. For DAC applications, the thesis explores the design of inorganic anion pillared metal-organic frameworks, focusing on the adjustment of M5+−F− bond lengths in inorganic anion pillars within M5+OFFIVE-1-Ni samples. These structural modifications impact the CO2 capture properties, particularly in terms of capacity and kinetics, demonstrating the potential of structural tuning in enhancing sorbent effectiveness. The synthesized samples exhibit good cyclic and water stability, suggesting their potential for practical DAC applications.
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30.
  • Cheng, Wei, et al. (författare)
  • Competitive Carboxylate-Silicate Binding at Iron Oxyhydroxide Surfaces
  • 2021
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 37:44, s. 13107-13115
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissolved silicate ions in wet and dry soils can determine the fate of organic contaminants via competitive binding. While fundamental surface science studies have advanced knowledge of binding in competitive systems, little is still known about the ranges of solution conditions, the time dependence, and the molecular processes controlling competitive silicate-organic binding on minerals. Here we address these issues by describing the competitive adsorption of dissolved silicate and of phthalic acid (PA), a model carboxylate-bearing organic contaminant, onto goethite, a representative natural iron oxyhydroxide nanomineral. Using surface complexation thermodynamic modeling of batch adsorption data and chemometric analyses of vibrational spectra, we find that silicate concentrations representative of natural waters (50-1000 μM) can displace PA bound at goethite surfaces. Below pH ∼8, where PA binds, every bound Si atom removes ∼0.3 PA molecule by competing with reactive singly coordinated hydroxo groups (-OH) on goethite. Long-term (30 days) reaction time and a high silicate concentration (1000 μM) favored silicate polymer formation, and increased silicate while decreasing PA loadings. The multisite complexation model predicted PA and silicate binding in terms of the competition for -OH groups without involving PA/silicate interactions, and in terms of a lowering of outer-Helmholtz potentials of the goethite surface by these anions. The model predicted that silicate binding lowered loadings of PA species, and whose two carboxylate groups are hydrogen- (HB) and metal-bonded (MB) with goethite. Vibrational spectra of dried samples revealed that the loss of water favored greater proportions of MB over HB species, and these coexisted with predominantly monomeric silicate species. These findings underscored the need to develop models for a wider range of organic contaminants in soils exposed to silicate species and undergoing wet-dry cycles.
  •  
31.
  • Cheng, Wei, et al. (författare)
  • Effects of organic matter-goethite interactions on reactive transport of nalidixic acid : Column study and modeling
  • 2020
  • Ingår i: Environmental Research. - : Elsevier. - 0013-9351 .- 1096-0953. ; 191
  • Tidskriftsartikel (refereegranskat)abstract
    • The fractionation of natural organic matter (NOM) and its impact on the binding of quinolones to mineral surfaces and transport behavior under flow-through conditions have been scarcely investigated. In this study, the sorption and transport of a widely used quinolone antibiotic, Nalidixic acid (NA), were investigated in goethite-coated sand (GCS) columns over a wide concentration range (5-50 mg/L) of Leonardite humic acid (LHA), a representative NOM. Simultaneous injection of NA and LHA in GCS columns mutually alter transport of each other, i.e. NA mobility and LHA molecular fractionation. Preloading of GCS column with LHA dramatically facilitated the transport behavior of NA, where nonspecific interactions with LHA-covered goethite surfaces controlled NA mobility. Simulations using a two-site nonequilibrium model showed that a modified sorption rate constant was required to accurately describe the breakthrough curves of NA under these conditions. This altered rate constant suggests that nonspecific interactions of NA on bound LHA may take place as an additional binding mechanism affecting adsorption kinetics. NOM fractionation alters sorption mechanisms and kinetics of quinolone antibiotics, which in turn affect their fractionation. These results may have important implications for an accurate assessment of the fate of these types of antibiotics in aquatic environments.
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32.
  • Cheng, Wei, et al. (författare)
  • Nalidixic acid and Fe(II)/Cu(II) coadsorption at Goethite and Akaganéite surfaces
  • 2023
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 57:41, s. 15680-15692
  • Tidskriftsartikel (refereegranskat)abstract
    • Interactions between aqueous Fe(II) and solid Fe(III) oxy(hydr)oxide surfaces play determining roles in the fate of organic contaminants in nature. In this study, the adsorption of nalidixic acid (NA), a representative redox-inactive quinolone antibiotic, on synthetic goethite (α-FeOOH) and akaganéite (β-FeOOH) was examined under varying conditions of pH and cation type and concentration, by means of adsorption experiments, attenuated total reflectance-Fourier transform infrared spectroscopy, surface complexation modeling (SCM), and powder X-ray diffraction. Batch adsorption experiments showed that Fe(II) had marginal effects on NA adsorption onto akaganéite but enhanced NA adsorption on goethite. This enhancement is attributed to the formation of goethite-Fe(II)-NA ternary complexes, without the need for heterogeneous Fe(II)-Fe(III) electron transfer at low Fe(II) loadings (2 Fe/nm2), as confirmed by SCM. However, higher Fe(II) loadings required a goethite-magnetite composite in the SCM to explain Fe(II)-driven recrystallization and its impact on NA binding. The use of a surface ternary complex by SCM was supported further in experiments involving Cu(II), a prevalent environmental metal incapable of transforming Fe(III) oxy(hydr)oxides, which was observed to enhance NA loadings on goethite. However, Cu(II)-NA aqueous complexation and potential Cu(OH)2 precipitates counteracted the formation of ternary surface complexes, leading to decreased NA loadings on akaganéite. These results have direct implications for the fate of organic contaminants, especially those at oxic-anoxic boundaries.
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33.
  • Cheng, Wei, et al. (författare)
  • Nanoscale hydration in layered manganese oxides
  • 2021
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 37:2, s. 666-674
  • Tidskriftsartikel (refereegranskat)abstract
    • Birnessite is a layered MnO2 mineral capable of intercalating nanometric water films in its bulk. With its variable distributions of Mn oxidation states (MnIV, MnIII, and MnII), cationic vacancies, and interlayer cationic populations, birnessite plays key roles in catalysis, energy storage solutions, and environmental (geo)chemistry. We here report the molecular controls driving the nanoscale intercalation of water in potassium-exchanged birnessite nanoparticles. From microgravimetry, vibrational spectroscopy, and X-ray diffraction, we find that birnessite intercalates no more than one monolayer of water per interlayer when exposed to water vapor at 25 °C, even near the dew point. Molecular dynamics showed that a single monolayer is an energetically favorable hydration state that consists of 1.33 water molecules per unit cell. This monolayer is stabilized by concerted potassium–water and direct water–birnessite interactions, and involves negligible water–water interactions. Using our composite adsorption–condensation–intercalation model, we predicted humidity-dependent water loadings in terms of water intercalated in the internal and adsorbed at external basal faces, the proportions of which vary with particle size. The model also accounts for additional populations condensed on and between particles. By describing the nanoscale hydration of birnessite, our work secures a path for understanding the water-driven catalytic chemistry that this important layered manganese oxide mineral can host in natural and technological settings.
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34.
  • Cheng, Wei, et al. (författare)
  • Water Vapor Binding on Organic Matter-Coated Minerals
  • 2019
  • Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:3, s. 1252-1257
  • Tidskriftsartikel (refereegranskat)abstract
    • Atmospheric water vapor binding to soils is a key process driving water availability in unsaturated terrestrial environments. Using a representative hydrophilic iron oxyhydroxide, this study highlights key mechanisms through which water vapor (i) adsorbs and (ii) condenses at mineral surfaces coated with Leonardite humic acid (LHA). Microgravimetry and vibrational spectroscopy showed that liquid-like water forms in the three-dimensional array of mineral-bound LHA when present at total C/Fe ratios well exceeding similar to 73 mg C per g Fe (26 C atoms/nm(2)). Below these loadings, minerals become even less hydrophilic than in the absence of LHA. This lowering in hydrophilicity is caused by the complexation of LHA water-binding sites to mineral surfaces, and possibly by conformational changes in LHA structure removing available condensation environments for water. An empirical relationship predicting the dependence of water adsorption densities on LHA loadings was developed from these results. Together with the molecular-level description provided in this work, this relationship should guide efforts in predicting water availability, and thereby occurrences of water-driven geochemical processes in terrestrial environments.
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35.
  • Ding, Xiangbin, et al. (författare)
  • Identification of fluoride and phosphate binding sites at FeOOH surfaces
  • 2012
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:41, s. 21939-21947
  • Tidskriftsartikel (refereegranskat)abstract
    • Iron oxyhydroxide minerals occur widely in nature and play important roles in environmental and industrial processes. Owing to their high reactivity, these minerals can act as sinks and/or transformation centers for a variety of inorganic and organic ions. Interfacial reactions are often mediated by surface (hydr)oxo groups. These groups can be singly, doubly, or triply coordinated with respect to underlying Fe atoms. In order to investigate the reactivity of these differently coordinated groups, Fourier transform infrared (FTIR) spectroscopy was used to examine adsorption products formed on iron oxyhydroxide surfaces. The absence of water was required to probe the O-H stretching region after initial reactions in aqueous media. This work was specifically focused on synthetic, submicrometer-sized lepidocrocite and goethite particles reacted with aqueous solutions of sodium fluoride and monosodium phosphate. Langmuir-Freundlich adsorption isotherms were calibrated on adsorption data in aqueous media at various pH values to obtain the maximum sorption densities for these ions under these conditions. FTIR measurements of the resulting solids dried under N-2(g) show that fluoride and phosphate ions preferentially exchange with singly coordinated hydroxyls. Doubly coordinated groups can, however, be exchanged with fluoride ions at relatively high loading densities. Triply coordinated groups remain, in contrast, resilient to exchange. They may, however, stabilize phosphate species by hydrogen bonding. These findings add further constraints to our understanding of adsorption reactions and to the formulation of molecularly adequate thermodynamic models.
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36.
  • Feng, Wenting, et al. (författare)
  • Millennia-old organic carbon in a boreal paleosol : chemical properties and their link to mineralizable carbon fraction
  • 2016
  • Ingår i: Journal of Soils and Sediments. - : Springer Science and Business Media LLC. - 1439-0108 .- 1614-7480. ; 16:1, s. 85-94
  • Tidskriftsartikel (refereegranskat)abstract
    • Little is known about the biogeochemical properties of millennia-old soil organic matter (SOM) in boreal forest paleosols and whether these properties contribute to the persistence of several millennia-old SOM. In this study, we assessed the physicochemical properties of a well-drained paleosol and looked for links between these properties and the mineralizable carbon (C) fraction. We studied a well-drained paleosol located under a typical forest podzol in Northern Sweden, in which up to 7-kyr-old SOM was preserved according to C-14 dating. We assessed the elemental compositions of the outermost 2-mu m and 10-nm soil particle surfaces by using energy-dispersive X-ray scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. We also conducted a 5-week laboratory incubation of samples from both the paleosol and the podzol to quantify their mineralizable C fractions and analyzed the thermal stability of soil samples before and after incubation by using temperature-programmed desorption coupled with mass spectrometry techniques. Proxies for weathering (i.e., total mineral surface area and Al/Si and Fe/Si ratios of particle surfaces) suggested that the paleosol was at the same weathering stage as the contemporary forming podzol. Mineral soil particle surfaces of both the paleosol and podzol were dominated by aliphatic and ether/alcohol C functional groups. The incubation and thermal analysis showed that the mineralizable C fraction of the paleosol was smaller than that of the podzol, and losses of thermally labile SOM due to microbial degradation during the incubations were only detected in the mineral free O horizon of the podzol. Moreover, the mineralizable C fraction of the sampled podzol-paleosol sequence was correlated to the proportion of ether/alcohol C functional groups at the outermost 10-nm soil particle surfaces. Based on the links between microbial decomposition and the chemistry of soil particle surfaces and the thermal stability difference between organic and mineral soils induced by microbial decomposition, we conclude that the intrinsic chemical properties of SOM and its chemical surroundings is important for SOM preservation over a millennia timescale in the studied soil.
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37.
  • Feng, Wenting, et al. (författare)
  • Thermal Stability of Goethite-Bound Natural Organic Matter Is Impacted by Carbon Loading
  • 2015
  • Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 119:51, s. 12790-12796
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissolved natural organic matter (NOM) sorption at mineral surfaces can significantly affect the persistence. of organic carbon in soils and sediments. Consequently, determining the mechanisms that stabilize sorbed NOM is crucial for predicting the persistence of carbon in nature. This study determined the effects of loadings and pH on the thermal stability of NOM associated: With synthetic goethite (alpha-FeOOH) particle surfaces, as a proxy for NOM mineral interactions taking place in nature.. NOM thermal stability was investigated using temperature programmed desorption (TPD) in the 30-700 degrees C range to collect vibration spectra of thermally decomposing goethite NOM assemblages, and to concomitantly analyze evolved gases using mass spectrometry Results showed that NOM thermal stability, indicated by the range of temperatures in which CO2 evolved during thermal decomposition, was greatest in unbound NOM and lowest when NOM was bound to goethite. NOM thermal Stability was also loading dependent. It decreased:when loadings were in increased the 0.01 to 042 mg C m(-2) range, where the upper value corresponds to a Langmuirian adsorption maximum. Concomitant Fourier transform infrared (FTIR) spectroscopy measurement showed that these lowered stabilities could be ascribed to direct NOM-goethite interactions that dominated the NOM binding environment. Mineral surface interactions at larger loadings involved, on the contrary, a smaller fraction of the sorbed NOM, thus increasing thermal stability toward that of its unbound counterpart. This study thus identifies a sorption threshold below which NOM sorption to goethite decreases NOM thermal stability, and above which no strong effects are Manifested. This should likely influence the fate of organic carbon exposed to thermal gradients in natural environments.
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38.
  • Hakobyan, Shoghik, 1981- (författare)
  • Antivirulent and antibiofilm salicylidene acylhydrazide complexes in solution and at interfaces
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The growing bacterial resistance against antibiotics creates a limitation for using traditional antibiotics and requests development of new approaches for treatment of bacterial infections. Among the bacterial infections that are most difficult to treat, biofilm-associated infections are one of the most hazardous. Consequently, the prevention of biofilm formation is a very important issue. One of the techniques that are widely investigated nowadays for this purpose is surface modification by polymer brushes that allows generating antifouling antibacterial surfaces. Previously, it was reported that salicylidene acylhydrazides (hydrazones) are good candidates as antivirulence drugs targeting the type three secretion system (T3SS). This secretion system is used by several Gramnegative pathogens, including Pseudomonas aeruginosa, to deliver toxins into a host cell. Furthermore, the chemical structure of these substances allows formation of complexes with metal ions, such as Fe3+ and Ga3+. The antibacterial activity of Ga3+ is well known and attributed to its similarity to the Fe3+ ion. It has also been shown that Ga3+ ions are able to suppress biofilm formation and growth in bacteria. In this thesis the chemistry of antibacterial and antivirulence Ga3+-Hydrazone complexes in solution was studied. First, to get insights in the solution chemistry, the protonation and the stability constants as well as the speciation of the Ga3+-Hydrazone complexes were determined. Additionally, a procedure for anchoring one of the hydrazone substances to antifouling polymer brushes was optimized, and the resulting surfaces were characterized. Results showed that the complexation with Ga3+ ions stabilizes the ligand and increases its solubility. Ga3+ ion binds to the hydrazone molecule forming a strong chelate that should be stable at physiological conditions. The different biological assays, such as Ga3+ uptake, antivirulence and antibiofilm effects, indicated very complex interaction of these complexes with the bacterial cell. Negatively charged and zwitterionic surfaces strongly reduced protein adsorption as well as biofilm formation. Therefore, the antifouling zwitterionic poly-[2-(methacryloyloxy)ethyl]dimethyl-3- sulfopropyl)-ammonium hydroxide (pMEDSAH) brushes were post-modified and successfully functionalized with bioactive substances via a block-copolymerization strategy. However, in order to maintain the availability of the bioactive substance after functionalization, the hydrophobic polyglycidylmethacrylate (pGMA) top block is probably better to functionalize with a lipophilic molecules to reduce diblock copolymer brush rearrangement.
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39.
  • Hakobyan, Shoghik, et al. (författare)
  • Influence of Chelation Strength and Bacterial Uptake of Gallium Salicylidene Acylhydrazide on Biofilm Formation and Virulence by Pseudomonas aeruginosa
  • 2016
  • Ingår i: Journal of Inorganic Biochemistry. - : Elsevier. - 0162-0134 .- 1873-3344. ; 160, s. 24-32
  • Tidskriftsartikel (refereegranskat)abstract
    • Development of antibiotic resistance in bacteria causes major challenges for our society and has prompted a great need for new and alternative treatment methods for infection. One promising approach is to target bacterial virulence using for example salicylidene acylhydrazides (hydrazones). Hydrazones coordinate metal ions such as Fe(III) and Ga(III) through a five-membered and a six-membered chelation ring. One suggested mode of action is via restricting bacterial Fe uptake. Thus, it was hypothesized that the chelating strength of these substances could be used to predict their biological activity on bacterial cells. This was investigated by comparing Ga chelation strength of two hydrazone complexes, as well as bacterial Ga uptake, biofilm formation, and virulence in the form of production and secretion of a toxin (ExoS) by Pseudomonas aeruginosa. Equilibrium constants for deprotonation and Ga(III) binding of the hydrazone N′-(5-chloro-2-hydroxy-3-methylbenzylidene)-2,4-dihydroxybenzhydrazide (ME0329), with anti-virulence effect against P. aeruginosa, were determined and compared to bacterial siderophores and the previously described Ga(III) 2-oxo-2-[N-(2,4,6-trihydroxy-benzylidene)-hydrazino]-acetamide (Ga-ME0163) and Ga-citrate complexes. In comparison with these two complexes, it was shown that the uptake of Ga(III) was higher from the Ga-ME0329 complex. The results further show that the Ga-ME0329 complex reduced ExoS expression and secretion to a higher extent than Ga-citrate, Ga-ME0163 or the non-coordinated hydrazone. However, the effect against biofilm formation by P. aeruginosa, by the ME0329 complex, was similar to Ga-citrate and lower than what has been reported for Ga-ME0163.
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40.
  • Hakobyan, Shoghik, et al. (författare)
  • Proton and gallium(III) binding properties of a biologically active salicylidene acylhydrazide
  • 2014
  • Ingår i: Journal of Inorganic Biochemistry. - : Elsevier. - 0162-0134 .- 1873-3344. ; 138, s. 9-15
  • Tidskriftsartikel (refereegranskat)abstract
    • Bacterial biofilm formation causes a range of problems in our society, especially in health care. Salicylidene acylhydrazides (hydrazones) are promising antivirulence drugs targeting secretion systems used during bacterial infection of host cells. When mixed with the gallium ion they become especially potent as bacterial and biofilm growth-suppressing agents, although the mechanisms through which this occurs are not fully understood. At the base of this uncertainty lies the nature of hydrazone-metal interactions. This study addresses this issue by resolving the equilibrium speciation of hydrazone-gallium aqueous solutions. The protonation constants of the target 2-oxo-2-[N-(2,4,6-trihydroxy-benzylidene)-hydrazino]-acetamide (ME0163) hydrazone species and of its 2,4,6-trihydroxybenzaldehyde and oxamic acid hydrazide building blocks were determined by UV-visible spectrophotometry to achieve this goal. These studies show that the hydrazone is an excessively strong complexing agent for gallium and that its antivirulence properties are predominantly ascribed to monomeric 1:1Ga-ME0163 complexes of various Ga hydrolysis and ME0163 protonation states. The chelation of Ga(III) to the hydrazone also increased the stability of the compounds against acid-induced hydrolysis, making this group of compounds very interesting for biological applications where the Fe-antagonist action of both Ga(III) and the hydrazone can be combined for enhanced biological effect.
  •  
41.
  • Hanna, K., et al. (författare)
  • Sorption of Phthalic Acid at Goethite Surfaces under Flow-Through Conditions
  • 2014
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:23, s. 6800-6807
  • Tidskriftsartikel (refereegranskat)abstract
    • The objectives of this investigation were to improve our understanding of organic acid transport in porous media by focusing on a model system involving phthalic acid and goethite-coated sand (GCS). This was specifically made by first recalibrating a molecularly sound phthalate surface complexation model to GCS and then applying this model to describe breakthrough curves (BTC) in a GCS packed column. ATR-FTIR spectra of phthalic acid adsorbed at goethite surfaces at pH 3.0 and 6.0 and at loadings from 2.0 to 40.8 mu mol/m(2) confirmed the coexistence of metal-bonded (MB) and hydrogen-bonded (HB) complexes at low pH and the predominance of HB complexes at high pH. This concept was incorporated into a surface complexation model used to describe BTC at influent pH (pH(in)) values of 3.0, 6.0, and 7.8. The BTC revealed strongly pH-dependent behaviors. At pH(in) 3.0, the BTC revealed one front/plateau behavior while at pH(in) 6.0 two fronts/plateaus occurred. The existence of a second front/plateau led to an overestimation of the sorbed amount compared to that observed in the batch and caused a failure in the prediction of BTC. Additional column investigations suggested that surface loadings of nonspecifically adsorbed complexes could vary with pH and ionic strength and that the two-step breakthrough behavior may have emerged as a result of the formation of surface species of different natures than those during the first step, with the latter even serving as attachment sites corresponding to the second step. These findings call for refinements in current day modeling approaches used in reactive transport studies.
  •  
42.
  • Hanna, K, et al. (författare)
  • Sorption of two naphthoic acids to goethite surface under flow through conditions
  • 2010
  • Ingår i: Environmental Science and Technology. - : ACS Publications. - 0013-936X .- 1520-5851. ; 44:23, s. 8863-8869
  • Tidskriftsartikel (refereegranskat)abstract
    • While the transport of low molecular weight organic acids was widely investigated, little is known about the mobility of the carboxylated aromatic compounds containing double rings in natural porous media. This study combines macroscopic (batch and column), microscropic (vibration spectroscopy), and surface complexation modeling to evaluate the mobility of two PAH degradation products: naphthoic acid (1-naphthoic acid (NA) and 1-hydroxy-2-naphthoic acid (HNA)), in porous media consisting of goethite-coated sand. The loss of ligands from aqueous solution was attributed to (1) a hydrogen-bonded surface complex present over the entire 3−10 pH range as well as protonated (2) surface and (3) bulk precipitates below pH 5. Mobility in column experiments was strongly affected by ligand functionality. Adsorption breakthrough predictions that make use of surface complexation parameters accurately predicted NA mobility. Those for HNA however predicted much less adsorption reactions than in the batch sorption experiments. Additional breakthrough experiments and test calculations confirmed that these differences were not related to sorption kinetics. HNA adsorption breakthrough data could only be predicted by lowering intrinsic complexation constant of the formation of hydrogen-bonded species, thereby suggesting modifications of the diffuse layer properties under flow conditions. These findings have strong implications in the assessment and prediction of contaminant transport and environmental remediation.
  •  
43.
  • Haziri, Veton, et al. (författare)
  • A gateway for ion transport on gas bubbles pinned onto solids
  • 2021
  • Ingår i: Communications Chemistry. - : Nature Publishing Group. - 2399-3669. ; 4:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Gas bubbles grown on solids are more than simple vehicles for gas transport. They are charged particles with surfaces populated with exchangeable ions. We here unveil a gateway for alkali metal ion transport between oxygen bubbles and semi-conducting (iron oxide) and conducting (gold) surfaces. This gateway was identified by electrochemical impedance spectroscopy using an ultramicroelectrode in direct contact with bubbles pinned onto these solid surfaces. We show that this gateway is naturally present at open circuit potentials, and that negative electric potentials applied through the solid enhance ion transport. In contrast, positive potentials or contact with an insulator (polytetrafluoroethylene) attenuates transport. We propose that this gateway is generated by overlapping electric double layers of bubbles and surfaces of contrasting (electro)chemical potentials. Knowledge of this ion transfer phenomenon is essential for understanding electric shielding and reaction overpotential caused by bubbles on catalysts. This has especially important ramifications for predicting processes including mineral flotation, microfluidics, pore water geochemistry, and fuel cell technology.
  •  
44.
  • Haziri, Veton, et al. (författare)
  • Oxygen Interactions with Covalently Grafted 2D Nanometric Carboxyphenyl Thin Films : An Experimental and DFT Study
  • 2022
  • Ingår i: Coatings. - : MDPI. - 2079-6412. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Surface modification is a hot topic in electrochemistry and material sciences because it affects the way materials are used. In this paper, a method for covalently attaching carboxyphenyl (PhCOOH) groups to a gold electrode is presented. These groups were grafted onto the electrode surface electrochemically via reduction of aryldiazonium salt. The resulting grafted surface was characterized using cyclic voltammetry (CV) before and after the functionalization procedure to validate the presence of the grafted layer. The grafting of PhCOOH groups was confirmed by analyzing electrode thickness and composition by ellipsometry and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations indicated that the grafted layers provide a stable platform and resolved, for the first time, their interactions with oxygen.
  •  
45.
  • Ilton, Eugene S, et al. (författare)
  • Influence of Dynamical Conditions on the Reduction of U(VI) at the Magnetite-Solution Interface
  • 2010
  • Ingår i: Environmental Science and Technology. - Washington : American Chemical Society. - 0013-936X .- 1520-5851. ; 44:1, s. 170-6
  • Tidskriftsartikel (refereegranskat)abstract
    • The heterogeneous reduction of U(VI) to U(IV) by ferrous iron is believed to be a key process influencing the fate and transport of U in the environment. The reactivity of both sorbed and structural Fe(II) has been studied for numerous substrates, including magnetite. Published results from U(VI)-magnetite experiments have been variable, ranging from no reduction to clear evidence for the formation of U(IV). In this contribution, we used XAS and high resolution (+/-cryogenic) XPS to study the interaction of U(VI) with nanoparticulate magnetite. The results indicated that U(VI) was partially reduced to U(V) with no evidence of U(IV). However, thermodynamic calculations indicated that U phases with average oxidation states below (V) should have been stable, indicating that the system was not in redox equilibrium. A reaction pathway that involves incorporation and stabilization of U(V) and U(VI) into secondary phases is invoked to explain the observations. The results suggest an important and previously unappreciated role of U(V) in the fate and transport of uranium in the environment.
  •  
46.
  • Ilton, Eugene S, et al. (författare)
  • The Effect of pH and Time on the Extractability and Speciation of Uranium(VI) Sorbed to SiO(2)
  • 2012
  • Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 46:12, s. 6604-6611
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of pH and contact time on uranium extractability from quartz surfaces was investigated using either acidic or carbonate (CARB) extraction solutions, time-delayed spikes of different U isotopes ((238)U and (233)U), and liquid helium temperature time-resolved laser-induced fluorescence spectroscopy (TRLFS). Quartz powders were reacted with (238)U(VI) bearing solutions equilibrated with atmospheric CO(2) at pH 6, 7, and 8. After 42 days, the suspensions were spiked with (233)U(VI) and reacted for an additional 7 days. Sorbed U was then extracted with either dilute nitric acid or CARB. For the CARB, but not the acid, extraction there was a systematic decrease in extraction efficiency for both isotopes from pH 6 to 8, which was mimicked by less desorption of (238)U, after the (233)U spike, from pH 6 to 8. The efficiency of (233)U extraction was consistently greater than that of (238)U, indicating a strong temporal component to the strength of U association with the surface that was accentuated with increasing pH. TRLFS revealed a strong correlation between CARB extraction efficiency and sorbed U speciation as a function of pH and time. Collectively, the observations show that aging and pH are critical factors in determining the form and strength of uranium-silica interactions.
  •  
47.
  • Jolsterå, Rickard (författare)
  • Surface reactions of magnetite and maghemite with dissolved and added ions in process water
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Reactions between mineral surfaces and dissolved species in process water, both inorganic and organic play an important role in mineral processing. Reverse flotation of finely comminuted iron ore is sometimes employed in order to remove the phosphorous mineral apatite. An anionic collector, designed to specifically adsorb at the calcium specific surface sites of apatite is added, rendering the apatite particles hydrophobic properties. However, some of the collector adsorbs also at the magnetite surfaces, thereby introducing undesired characteristics to the upgraded iron ore concentrate.Of this reason, magnetite and maghemite surfaces and their interactions with the most abundant and important ions in the process water during flotation, and their potential influence on collector adsorption at magnetite was studied. Maghemite was included in the experiments, since previous work had shown that oxidation of the magnetite surface into maghemite may occur during the processing of the iron ore concentrate. The complex system that the dissolved ions in the process water and the iron oxide particles constitute at flotation and agglomeration was divided into smaller subsystems.The protolytic characteristics for the magnetite-H+ and maghemite-H+ systems proved to be similar when their modelled intrinsic surface complexation constants were compared. However, the surface site density of magnetite was found to be 50 % greater than for maghemite. Both potentiometric titrations and ATR-FTIR spectroscopy were used to study and characterize the adsorption of silicate. The results from the surface complexation modelling suggested that the silicate adsorbed as monodentate surface complexes at the maghemite surfaces. The results showed a silicate adsorption maximum at pH 8.5 to 9.5 for both iron oxides. Within this range pH, the surface complex ΞFeOSiO(OH)2 - was proposed as the dominating surface specie in the maghemite-silicate system.The iron ore pellet additive olivine proved to release substantial amounts of Mg2+ when immersed in water, indicating that olivine probably is the main source of Mg2+ to the process water. Thus, the surface characteristic of olivine particles in water suspensions was studied. Since olivine proved to be a significant source of magnesium ions, adsorption of Mg2+ at maghemite and magnetite was studied and modelled. The results suggested that magnesium ions adsorbed as a mix of mono- and bidentate surface complexes when the number of surface sites was in excess. Increased amounts of Mg2+ i.e., ≥1 Mg2+ site-1, resulted in a model including only monodentate surface complexes.Experiments involving competitive adsorption of carbonate and silicate showed that added silicate replaced adsorbed carbonate. Other competitive experiments, with Mg2+ and Ca2+, showed that Mg2+ had a stronger affinity for the magnetite surface than Ca2+. The preferential adsorption of Mg2+ at the iron oxide surface may then have protective properties, by preventing adsorption of the calcium specific collector. Results from both in-situ ATR-FTIR spectroscopy and contact angle measurements indicated also that added Mg2+ reduced the adsorption of collector and thereby increased the wettability of the magnetite surfaces.
  •  
48.
  • Kanematsu, Masakazu, et al. (författare)
  • Silicate Binding and Precipitation on Iron Oxyhydroxides
  • 2018
  • Ingår i: Environmental Science and Technology. - : AMER CHEMICAL SOC. - 0013-936X .- 1520-5851. ; 52:4, s. 1827-1833
  • Tidskriftsartikel (refereegranskat)abstract
    • Silica-bearing waters in nature often alter the reactivity of mineral surfaces via deposition of Si complexes and solids. In this work, Fourier transform infrared (FTIR) spectroscopy was used to identify hydroxo groups at goethite (alpha-FeOOH) and lepidocrocite (gamma-FeOOH) surfaces that are targeted by ligand exchange reactions with monomeric silicate species. Measurements of samples first reacted in aqueous solutions then dried under N-2(g) enabled resolution of the signature O-H stretching bands of singly (-OH), doubly (mu-OH), and triply coordinated (mu(3)-OH) groups. Samples reacted with Si for 3 and 30 d at pH 4 and 7 revealed that -OH groups were preferentially exchanged by silicate and that mu-OH and mu(3)-OH groups were not exchanged. Based on knowledge of the disposition of -OH groups on the major crystallographic faces of goethite and lepidocrocite, and the response of these groups to ligand exchange prior oligomerization, our work points to the predominance of rows of mononuclear monodentate silicate species, each separated by at least one -OH group. These species are the attachment sites from which oligomerization and polymerization reactions occur, starting at loadings exceeding similar to 1 Si/nm(2) and corresponding to soluble Si concentrations that can be as low as similar to 0.7 mM after 30 d reaction time. Only above such loadings can reaction products grow away from rows of -OH groups and form hydrogen bonds with nonexchangeable mu-OH and mu(3)-OH groups. These findings have important repercussions for our understanding of the fate of waterborne silicate ions exposed to minerals.
  •  
49.
  •  
50.
  • Kozin, Philipp A., 1987- (författare)
  • Charge Development at Iron Oxyhydroxide Surfaces : The Interplay between Surface Structure, Particle Morphology and Counterion Identity
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Iron (oxyhydr)oxide (FeOOH) minerals play important roles in various natural, technological and societal settings. The widespread abundance of these minerals has prompted numerous studies on their surface reactivity in aqueous media. Surface charge development, one that namely takes place through the adsorption of potential determining ions (p.d.i.; H+, OH-) and coadsorption of counterions (e.g. Cl-, ClO4-, Na+), is particularly interesting in this regard. Mineral surface charge development is determined by numerous factors related to the interplay of mineral surface structure, particle morphology and counterion identity.In this thesis the interplay between these factors is resolved by monitoring charge development on submicron-sized synthetic iron oxyhydroxide particles of different structures and sizes in aqueous media with counteranions of contrasting charge-to-size ratio (i.e. NaCl, NaClO4). This work, which is summarized in an introductory chapter and detailed in five appendices, is focused on three types of synthetic lepidocrocite (ã- FeOOH) of different shapes and surface roughness, three types of goethite (á-FeOOH) of different levels of surface roughness, and finally akaganéite (â-FeOOH), a mineral representing unique ion exchange properties due to its hollandite-type structure. While charge development was chiefly monitored by high precisition potentiometric titrations, these efforts were supported by a range of techniques including electrolyte ion uptake by cryogenic X-ray photoelectron spectroscopy, particle imaging by (high resolution) transmission electron microscopy, porosity analysis by N2 adsorption/desorption, surface potential development by electrokinetics, as well as thermodynamic adsorption modeling.These efforts showed that lepidocrocite particles of contrasting morphology and surface roughness acquired highly comparable pH and ionic strength p.d.i. loadings. Equilibriation times required to develop these loadings were however altered when particles became aggregated by aging.Goethite particles of contrasting surface roughness also acquired incongruent p.d.i. loadings, which were predominantly explained by the different charge-neutralizing capabilities of these surfaces, some of which were related to pore size distributions controlling the entrance of ions of contrasting sizes. Such size exclusion effects were also noted for the case of akaganéite where its bulk 0.4×0.4 nm wide channels permitted chloride diffusion but blocked perchlorate. Charge development at goethite surfaces in binary mixtures of NaCl and NaClO4 solutions also showed that the larger size-to-charge ratio chloride ion exerted a strong effect on these results even when present as a minor species. Many of these aforementioned effects were also modeled using variable, counterion- and loading-specific, Stern layer capacitance values.The findings summarized in this thesis are providing a better understanding of surface processes occurring at iron oxyhydroxide surfaces. They should impact our ability in designing uses of such particles, for example, effective sorption in aquatic media, as well as to understand how they behave in natural systems.
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