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  • 1. Acharya, Shravan S.
    et al.
    Easton, Christopher D.
    McCoy, Thomas M.
    Spiccia, Leone
    Ohlin, C. André
    Umeå University, Faculty of Science and Technology, Department of Chemistry. School of Chemistry, Monash University, Clayton, Australia.
    Winther-Jensen, Bjorn
    Diverse composites of metal-complexes and PEDOT facilitated by metal-free vapour phase polymerization2017In: Reactive & functional polymers, ISSN 1381-5148, E-ISSN 1873-166X, Vol. 116, p. 101-106Article in journal (Refereed)
    Abstract [en]

    Abstract Oxidative polymerization for the manufacture of conducting polymers such as poly(3,4-ethylenedioxy-thiophene) has traditionally employed iron(III) salts. Demonstrated in this study is vapour phase polymerization of 3,4-ethylenedio- xythiophene using a metal-free oxidant, ammonium persulfate, leading to films with an estimated conductivity of 75 S/cm. Additionally, a route for embedding active transition metal complexes into these poly(3,4-ethylenedioxythiophene)/-poly(styrene-4-sulfonate) (PEDOT/PSS) films via vapour assisted complexation is outlined. Here, the vapour pressure of solid ligands around their melting temperatures was exploited to ensure complexation to metal ions added into the oxidant mixture prior to polymerization of PEDOT. Four composite systems are discussed, viz. PEDOT/PSS embedded with tris(8-hydroxyquinolinato)cobalt(III), tris(2,2-bipyridine)cobalt(II), tris(1,10- phenanthroline)cobalt(II) and tris(8-hyd-roxyquinolinato)aluminium(III). Using these composites, electrochemical reduction of nitrite to ammonia with a faradaic efficiency of 61% was reported.

  • 2. Acharya, Shravan
    et al.
    Winther-Jensen, Bjorn
    Spiccia, Leone
    Ohlin, André C.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Rates of water exchange in 2,2'-bipyridine and 1,10-phenanthroline complexes of CoII and MnII2017In: Australian journal of chemistry (Print), ISSN 0004-9425, E-ISSN 1445-0038, Vol. 70, no 6, p. 751-754Article in journal (Refereed)
    Abstract [en]

    The rates and activation parameters of water exchange at pH 3.0 have been determined using variable temperature 17O NMR spectroscopy for four CoII complexes and one MnII complex: [Co(bpy)(H2O)4]2+, [Co(bpy)2 (H2O)2]2+, [Co(phen)-(H2O)4]2+, [Co(phen)2 (H2O)2]2+, and [Mn(bpy)(H2O)4]2+ (bpy = 2,2′-bipyridyl and phen = 1,10-phenanthroline). Substitution of aquo ligands with 1,10-phenanthroline or 2,2′-bipyridyl leads to an increase in the rate of exchange in the manganese complexes, from k298 (1.8 ± 0.1) × 107 s-1 for [Mn(H2O)6]2+ to (7.2 ± 0.3) × 107 s-1 for [Mn(phen)2 (H2O)2]2+, whereas the trends are more complex for the cobalt complexes. We have used the new data in conjunction with literature data for similar complexes to analyse the effect of M–OH2 distance and degree of substitution.

  • 3.
    Andersson, Kristoffer
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Selective detection of TNT withmodified SERS-surfaces: Investigation of TNT adsorption and detection using goldand silver nano structured surfaces modified by cysteineand cysteamine2010Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the search for trace amounts of explosives in various environmental samples, the

    analytical procedure is in need of improvements. If it is for national security or for

    environmental purposes the detection of trace amounts of for example 2,4,6-

    trinitrotoluene (TNT) is a costly and time consuming procedure. The use of Raman

    spectrometry for trace amounts detection is one of the research areas that are in the

    advancement and mainly because of the discovery of Surface-Enhanced Raman

    spectroscopy (SERS). Raman spectrometry detects the inelastically scattered light

    from molecules giving a fingerprint spectrum that can be interpreted and species can

    be detected. The inelastically scattering of light only occurs in a small amount of the

    molecules making the signal low and sensitive for interferences. SERS enhances the

    signal from the molecules making it possible to detect very low concentrations. The

    surfaces used in SERS need to be selective for the wanted species to be useful for the

    analysis of environmental samples that often contains a wide variety of compounds.

    This project’s aim was to investigate the possibility of modifying gold- and silvercoated

    SERS surfaces (provided by DTU Nanotech) to get a selective detection of

    trace amounts of TNT in water and air samples.

    The results from the modification indicated some problems with the surfaces. The

    modification molecules were cysteine or cysteamine. The hypothesis was that both of

    them should bind to the surface by sulphur bond. But for cysteine this was not the

    case. The results indicated a binding of the carboxyl group making the use of the

    modification for the selective detection of TNT impossible. The modification by

    cysteamine was more successful but the detection of TNT in water samples was hard

    to get clear results from. The detection of TNT in air samples was carried out by a

    method never tested before using a so-called Linkam cell in conjunction with a TNT

    treated GC-column which together create a controlled environment. The results from

    this experiment were very positive where a clear SERS-signal from TNT could be

    detected.

  • 4. Andrew, Rhiann E.
    et al.
    Ferdani, Dominic W.
    Ohlin, C. Andre
    Chaplin, Adrian B.
    Coordination Induced Atropisomerism in an NHC-Based Rhodium Macrocycle2015In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 34, no 5, p. 913-917Article in journal (Refereed)
    Abstract [en]

    Reversible interaction with carbon monoxide results in the onset of dynamic atropisomerism at 298 K in an otherwise static NHC-based rhodium pincer complex, [Rh(C boolean AND N boolean AND C-(CH2)(12))(CO)][BArF4] (1, ArF = 3,5-C6H3(CF3)(2)). The mechanism of this process has been comprehensively interrogated by a combination of variable-temperature NMR spectroscopy, IR spectroscopy, and computational modeling. In addition, a structural analogue of a high-energy symmetrical intermediate species-invoked in the process but not directly observed spectroscopically-has been prepared and characterized in solution and the solid-state.

  • 5. Aureliano, M.
    et al.
    Ohlin, C. Andre
    Decavanadate in vitro and in vivo effects: facts and opinions2014In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 137, p. 123-130Article in journal (Refereed)
    Abstract [en]

    This review covers recent advances in the understanding of the in vitro and in vivo effects of decavanadate, (V10O28)(6-), particularly in mitochondria. In vivo toxicological studies involving vanadium rarely account for the fact that under physiological conditions some vanadium may be present in the form of the decavanadate ion, which may behave differently from ortho- and metavanadates. It has for example been demonstrated that vanadium levels in heart or liver mitochondria are increased upon decavanadate exposure. Additionally, in vitro studies have shown that mitochondrial depolarization (IC50, 40 nM) and oxygen consumption (IC50, 99 nM) are strongly affected by decavanadate, which causes reduction of cytochrome b (complex III). We review these recent findings which together suggest that the observed cellular targets, metabolic pathway and toxicological effects differ according to the species of vanadium present. Finally, the toxicological effects of decavanadate depend on several factors such as the mode of administration, exposure time and type of tissue. (C) 2014 Elsevier Inc. All rights reserved.

  • 6. Aureliano, Manuel
    et al.
    Fraqueza, Gil
    Ohlin, C. Andre
    Ion pumps as biological targets for decavanadate2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 33, p. 11770-11777Article in journal (Refereed)
    Abstract [en]

    The putative applications of poly-, oligo-and mono-oxometalates in biochemistry, biology, pharmacology and medicine are rapidly attracting interest. In particular, these compounds may act as potent ion pump inhibitors and have the potential to play a role in the treatment of e. g. ulcers, cancer and ischemic heart disease. However, the mechanism of action is not completely understood in most cases, and even remains largely unknown in other cases. In the present review we discuss the most recent insights into the interaction between mono-and polyoxometalate ions with ion pumps, with particular focus on the interaction of decavanadate with Ca2+-ATPase. We also compare the proposed mode of action with those of established ion pump inhibitors which are currently in therapeutic use. Of the 18 classes of compounds which are known to act as ion pump inhibitors, the complete mechanism of inhibition is only known for a handful. It has, however, been established that most ion pump inhibitors bind mainly to the E2 ion pump conformation within the membrane domain from the extracellular side and block the cation release. Polyoxometalates such as decavanadate, in contrast, interact with Ca2+-ATPase near the nucleotide binding site domain or at a pocket involving several cytoplasmic domains, and therefore need to cross through the membrane bilayer. In contrast to monomeric vanadate, which only binds to the E2 conformation, decavanadate binds to all protein conformations, i.e. E1, E1P, E2 and E2P. Moreover, the specific interaction of decavanadate with sarcoplasmic reticulum Ca2+-ATPase has been shown to be non-competitive with respect to ATP and induces protein cysteine oxidation with concomitant vanadium reduction which might explain the high inhibitory capacity of V-10 (IC50 = 15 mu M) which is quite similar to the majority of the established therapeutic drugs.

  • 7. Aureliano, Manuel
    et al.
    Ohlin, C. André
    Vieira, Michele O.
    Marques, M. Paula M.
    Casey, William H.
    Batista de Carvalho, Luis A. E.
    Characterization of decavanadate and decaniobate solutions by Raman spectroscopy2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 17, p. 7391-7399Article in journal (Refereed)
    Abstract [en]

    The decaniobate ion, (Nb-10 = [Nb10O28](6-)) being isoelectronic and isostructural with the decavanadate ion (V-10 = [V10O28](6-)), but chemically and electrochemically more inert, has been useful in advancing the understanding of V-10 toxicology and pharmacological activities. In the present study, the solution chemistry of Nb-10 and V-10 between pH 4 and 12 is studied by Raman spectroscopy. The Raman spectra of V-10 show that this vanadate species dominates up to pH 6.45 whereas it remains detectable until pH 8.59, which is an important range for biochemistry. Similarly, Nb-10 is present between pH 5.49 and 9.90 and this species remains detectable in solution up to pH 10.80. V-10 dissociates at most pH values into smaller tetrahedral vanadate oligomers such as V-1 and V-2, whereas Nb-10 dissociates into Nb-6 under mildly (10 > pH > 7.6) or highly alkaline conditions. Solutions of V-10 and Nb-10 are both kinetically stable under basic pH conditions for at least two weeks and at moderate temperature. The Raman method provides a means of establishing speciation in the difficult niobate system and these findings have important consequences for toxicology activities and pharmacological applications of vanadate and niobate polyoxometalates.

  • 8.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    MALIbase: Termodynamisk data för föreningar i systemet CaO-K2O-P2O52015Other (Other (popular science, discussion, etc.))
  • 9. Behravesh, Erfan
    et al.
    Kumar, Narendra
    Balme, Quentin
    Roine, Jorma
    Salonen, Jarno
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Process Chemistry Centre, Åbo Akademi University, FI-20500 Turku/Åbo, Finland.
    Peurla, Markus
    Aho, Atte
    Eränen, Kari
    Murzin, Dmitry Yu.
    Salmi, Tapio
    Synthesis and characterization of Au nano particles supported catalysts for partial oxidation of ethanol: Influence of solution pH, Au nanoparticle size, support structure and acidity2017In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 353, p. 223-238Article in journal (Refereed)
    Abstract [en]

    Partial oxidation of ethanol to acetaldehyde was carried out over gold catalysts supported on various oxides and zeolites by deposition precipitation. The special focus of this work was on the influence of H-Y zeolite surface charge on Au cluster size and loading linking it to activity and selectivity in ethanol oxidation and comparing with other studied catalysts. The catalysts were characterized by nitrogen physisorption, transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and zeta potential measurements. pH of the solution governed the Au NPs size within the range of 5.8–13.2 nm with less negatively charged surfaces leading to formation of smaller clusters. Au loading on H-Y zeolite with silica to alumina ratio of 80 was increased by raising the pH. In fact, H-Y-12 and H-Beta-25 were selective towards diethyl ether while acetaldehyde was the prevalent product on less acidic H-Y-80. The results demonstrated strong dependency of the catalytic activity on the Au cluster size. Namely turn over frequency (TOF) decreased with an increase in metal size from 6.3 to 9.3 nm on H-Y-80. Selectivity towards acetaldehyde and ethyl acetate did not change significantly on H-Y-80 within 6.3–9.3 nm Au particle size range. On Al2O3 support, however, selectivity towards acetaldehyde increased considerably upon diminishing Au average particle size from 3.7 to 2.1 nm.

  • 10.
    Björnberg, Arne
    Umeå University, Faculty of Science and Technology.
    Crystal structure studies of a new series of molybdovanadate polyanions and some related vanadates1980Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The determination of complexes formed in weakly acidic aqueous solutions containing pentavalent vanadium as well as hexavalent molybdenum has proved diffi cui t due to slow equilibria and 1 imi ted sol ubi 1 i ty of especially the vanadium species. The formation of several different polynuclear complexes with a very varied molybdenum/vanadium ratio also complicates the interpretation of Potentiometrie data. In order to clarify the picture of complexes formed and provide starting points for equilibrium calculations single-crystal X-ray studies were made on crystals obtained from âqueous solutions. In addition, these studies can provide information on bonding conditions and possibly formation mechanisms for molybdovanadate polyanions. Crystals were synthesized by slow evaporation of aqueous solutions. Solutions with varied molybdenum/vanadium ratios and also varied pH values were prepared and used in the synthesis experiments. The X-ray measurements were performed with Philips PAILRED, Syntex P21 and Syntex R3 automatic diffractometers. All data sets were corrected for absorption. Five of the structures were solved with heavy-atom methods and one by direct methods. The structures were refined by computer-performed least-squares methods. The following crystals were obtained and structurally determined: NaV03•1.89H2O, which contains chains of VO5 trigonal bipyramids. Na4V2O7 (H2O)18 , containing discrete V2O74- anions which are completely surrounded by sodium-coordinated water molecules. Discrete molybdovanadate polyanions were found in the structures of the compounds Na6Mo6\/2O26 (H2O)16 , K7Mo8V5O40 • 8H2O, K8Mo4,V8O36 - 12H20 and K6 (V2 , Mo10) VO40 • 13H20. The last substance belongs to a class of compounds named 'heteropoly blues', which contain metal atoms in mixed-valence states, and has one unpaired electron on the polyanion. This compound was also investigated with electron spin resonance spectroscopy. The bonding configurations of oxygen atoms coordinated to molybdenum or vanadium are described and discussed. As the Mo4V8O368-, Mo8V5O407- (which is an isomer of the Keggin anion but has a quite different structure) and Mo6V2O266- anions all contain remnants of mononuclear molybdate and vanadate anions, it seems likely that these polyanions are formed mainly through the condensation of mononuclear species.An electrostatic model for the simulation of bond distances in polyions, starting with perfectly regular idealized models, is presented.

  • 11.
    Boily, Jean-Francois
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kozin, Philipp A.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Particle Morphological and Roughness Controls on Mineral Surface Charge Development2014In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 141, no 15 September, p. 567-578Article in journal (Other academic)
    Abstract [en]

    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.

  • 12.
    Boström, Dan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Ash transformation chemistry during energy conversion of biomass2010In: Impacts of Fuel Quality on Power Production and the Environment, Saariselkä, Finland, August 29–September 3, 2010, 2010Conference paper (Refereed)
  • 13.
    Boulanger, Nicolas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Nano-Engineered Materials and Organic Electronics Laboratory.
    Yu, Victor
    Hilke, Michael
    Toney, Michael F.
    Barbero, David R.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Nano-Engineered Materials and Organic Electronics Laboratory.
    In situ probing of the crystallization kinetics of rr-P3HT on single layer graphene as a function of temperature2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 12, p. 8496-8503Article in journal (Refereed)
    Abstract [en]

    We studied the molecular packing and crystallization of a highly regio-regular semiconducting polymer poly(3-hexylthiophene) (P3HT) on both single layer graphene and silicon as a function of temperature, during cooling from the melt. The onset of crystallization, crystallites' size, orientation, and kinetics of formation were measured in situ by synchrotron grazing incidence X-ray diffraction (GIXD) during cooling and revealed a very different crystallization process on each surface. A favored crystalline orientation with out of plane pi-pi stacking formed at a temperature of 200 degrees C on graphene, whereas the first crystallites formed with an edge-on orientation at 185 degrees C on silicon. The crystallization of face-on lamellae revealed two surprising effects during cooling: (a) a constant low value of the pi-pi spacing below 60 degrees C; and (b) a reduction by half in the coherence length of face-on lamellae from 100 to 30 degrees C, which corresponded with the weakening of the 2nd or 3rd order of the in-plane (k00) diffraction peak. The final ratio of face-on to edge-on orientations was 40% on graphene, and 2% on silicon, revealing the very different crystallization mechanisms. These results provide a better understanding of how surfaces with different chemistries and intermolecular interactions with the polythiophene polymer chains lead to different crystallization processes and crystallites orientations for specific electronic applications.

  • 14.
    Chorell, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bengtsson, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sainte-Luce Banchelin, Thomas
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Das, Pralay
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Uvell, Hanna
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sinha, Arun K
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pinkner, Jerome S
    Department of Molecular Microbiology, Washington University, School of Medicine, St. Louis, Missouri 63110, USA.
    Hultgren, Scott J
    Department of Molecular Microbiology, Washington University, School of Medicine, St. Louis, Missouri 63110, USA.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Synthesis and application of a bromomethyl substituted scaffold to be used for efficient optimization of anti-virulence activity2011In: European Journal of Medicinal Chemistry, ISSN 0223-5234, E-ISSN 1768-3254, Vol. 46, no 4, p. 1103-1116Article in journal (Refereed)
    Abstract [en]

    Pilicides are a class of compounds that attenuate virulence in Gram negative bacteria by blocking the chaperone/usher pathway in Escherichia coli. It has also been shown that compounds derived from the peptidomimetic scaffold that the pilicides are based on can prevent both Aβ aggregation and curli formation. To facilitate optimizations towards the different targets, a new synthetic platform has been developed that enables fast and simple introduction of various substituents in position C-7 on the peptidomimetic scaffold. Importantly, this strategy also enables introduction of previously unattainable heteroatoms in this position. Pivotal to the synthetic strategy is the synthesis of a C-7 bromomethyl substituted derivative of the ring-fused dihydrothiazolo 2-pyridone pilicide scaffold. From this versatile and reactive intermediate various heteroatom-linked substituents could be introduced on the scaffold including amines, ethers, amides and sulfonamides. In addition, carbon-carbon bonds could be introduced to the sp(3)-hybridized bromomethyl substituted scaffold by Suzuki-Miyaura cross couplings. Evaluation of the 24 C-7 substituted compounds in whole-bacterial assays provided important structure-activity data and resulted in the identification of a number of new pilicides with activity as good or better than those developed previously.

  • 15.
    Ding, Xiangbin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Identity of Fluoride and Phosphate-Binding Sites at FeOOH Surfaces2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Iron oxyhydroxides are of widespread occurrence in nature and play essential roles in both environmental as well as industrial processes. Due to their high reactivity, these minerals can act as sinks and/or transformation centers for a variety of inorganic and organic ions. These reactions are often mediated by various surface hydroxyl groups that are in turn singly-, doubly- or triply-coordinated with respect to underlying Fe atoms. In an effort to follow the reactivity of these different groups, attenuated total reflectance (ATR) - Fourier transform infrared (FTIR) spectroscopy was used to monitor adsorption reactions of on iron oxyhydroxide minerals.

    This work was specifically focused on synthetic submicron-sized lepidocrocite and goethite particles reacted to aqueous solutions of sodium fluoride and sodium phosphate. Langmuir-Freundlich adsorption isotherms were calibrated on adsorption data at various pH values to provide independent clues to the maximum sorption density achieved by these ions. When compared to theoretical site densities, these values suggested that although singly-coordinated groups are by far the more reactive groups on all surfaces, doubly-coordinated groups could be substituted by fluoride ions. FTIR measurements of dry mineral samples equilibrated with fluoride and phosphate confirmed these findings and also showed that triply-coordinated groups cannot be exchanged.

    Key words

    : goethite, lepidocrocite, FTIR, surface, adsorption, isotherm, modeling

  • 16. Domashevskaya, EP
    et al.
    Ryabtsev, SV
    Turishchev, S Yu
    Kashkarov, VM
    Yurakov, Yu A
    Chuvenkova, OA
    Shchukarev, Andrey V
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    XPS and XANES studies of SnOx nanolayers2008In: Journal of Structural Chemistry, ISSN 0022-4766, E-ISSN 1573-8779, Vol. 49, no Suppl 1, p. 80-91Article in journal (Refereed)
    Abstract [en]

    This paper presents the results of our XPS (X-ray photoelectron spectroscopy) and XANES (X-ray absorption near edge structure) Studies of tin oxide nanolayers obtained by magnetron spraying of the metal and its further oxidation in air at different temperatures. It was shown that at 240 degrees C (annealing temperature), tin monoxide was dominant in the surface layer of the samples. When the temperature was increased to 450 degrees C, the phase composition corresponded to tin dioxide. Increased sorption ability was found for the samples oxidized at 450 degrees C. The band structure model of SnOx nanolayers obtained by superposition of the XANES and XPS data revealed cross transitions with energy similar to 3.7 eV in the presence of the SnO and SnO, phases. Surface doping of nanolayers with palladium gave the Pd, PdO, and PdO2 components, among which PdO was most intense. Alternate treatments with O-2 and H-2 gases led to the disappearance of palladium dioxide and the reduction of PdO to the Pd metal. After the volume doping of nanoplayers with palladium, the surface layer contained PdO and PdO2; the latter was represented by two types of particles with different sizes.

  • 17.
    Ekspong, Joakim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sharifi, Tiva
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen-Doped Carbon Nanotubes for Hydrogen Evolution Reaction2016In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 37, p. 6766-6776Article in journal (Refereed)
    Abstract [en]

    Finding an abundant and cost-effective electrocatalyst for the hydrogen evolu-tion reaction (HER) is crucial for a global production of hydrogen from water electrolysis. This work reports an exceptionally large surface area hybrid catalyst electrode comprising semicrystalline molybdenum sulfi de (MoS 2+ x) catalystattached on a substrate based on nitrogen-doped carbon nanotubes (N-CNTs), which are directly grown on carbon fiber paper (CP). It is shown here that nitrogen-doping of the carbon nanotubes improves the anchoring of MoS 2+ xcatalyst compared to undoped carbon nanotubes and concurrently stabilizes a semicrystalline structure of MoS 2+ x with a high exposure of active sites for HER. The well-connected constituents of the hybrid catalyst are shown to facilitate electron transport and as a result of the good attributes, the MoS 2+ x/N-CNT/CPelectrode exhibits an onset potential of −135 mV for HER in 0.5 M H2SO4, a Tafel slope of 36 mV dec −1, and high stability at a current density of −10 mA cm −2.

  • 18. Filinchuk, Yaroslav
    et al.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hagemann, Hans
    Dmitriev, Vladimir
    Chernyshov, Dmitry
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cation Size and Anion Anisotropy in Structural Chemistry of Metal Borohydrides. The Peculiar Pressure Evolution of RbBH42010In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, no 11, p. 5285-5292Article in journal (Refereed)
    Abstract [en]

    The pressure evolution of RbBH4 has been characterized by synchrotron powder X-ray diffraction and Raman spectroscopy up to 23 GPa. Diffraction experiments at ambient temperature reveal three phase transitions, at 3.0, 10.4, and 18 GPa (at 2.6, 7.8, and 20 GPa from Raman data), at which the space group symmetry changes in the order Fm-3m(Z=4) → P4/nmm(2) → C222(2) → I-42m(4). Crystal structures and equations of state are reported for all four phases. The three high-pressure structure types are new in the crystal chemistry of borohydrides. RbBH4 polymorphs reveal high coordination numbers (CNs) for cation and anion sites, increasing with pressure from 6 to 8, via an intermediate 4 + 4 coordination. Different arrangements of the tetrahedral BH4 group in the Rb environment define the crystal symmetries of the RbBH4 polymorphs. The structural evolution in the MBH4 series is determined by the cation’s size, as it differs drastically for M = Li (CNs = 4, 6), Na (CN = 6), and Rb. The only structure common to the whole MBH4 family is the cubic one. Its bulk modulus linearly decreases as the ionic radius of M increases, indicating that the compressibility of the material is mainly determined by the repulsive BH4···BH4 interactions.

  • 19. Fischer, A I
    et al.
    Kuznetsov, V A
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Belyaev, A N
    Crystal and molecular structures of mixedvalence octanuclear cobalt(II,III) propionate and butyrate with an etagerelike core2012In: Russian chemical bulletin, ISSN 1066-5285, E-ISSN 1573-9171, Vol. 61, no 4, p. 821-827Article in journal (Refereed)
    Abstract [en]

    The new mixed-valence octanuclear cobalt carboxylate complexes [CoII4CoIII4(μ4-O)4-(μ3-OMe)4(μ-O2CR)6(O2CR)2(H2O)6]·4H2O, where R = Et (3) or n-Pr (4), were investigated by X-ray diffraction analysis. Complexes 3 and 4 have a molecular octanuclear structure, and they are valence trapped, and contain four cobalt atoms Co3+ in the central cubane fragment with four cobalt atoms Co2+ at the periphery of the molecules. The molecules of the complexes are stabilized by four intramolecular hydrogen bonds and are linked, together with water solvent molecules, by intermolecular hydrogen bonds to form a three-dimensional supramolecular system.

  • 20. Fraqueza, G.
    et al.
    Carvalho, L.
    Marques, P.
    Ohlin, C. Andre
    Casey, W.
    Aureliano, M.
    Functional and structural interactions of Nb, V, Mo and W oxometalates with the sarcoplasmic reticulum Ca2(+) -ATPase reveal new insights into inhibition processes: a combination of NMR, Raman, AA and EPR spectroscopie with kinetic studies2012In: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 279, no 1, SIArticle in journal (Refereed)
  • 21. Fraqueza, Gil
    et al.
    Batista de Carvalho, Luis A. E.
    Marques, M. Paula M.
    Maia, Luisa
    Ohlin, C. Andre
    Casey, William H.
    Aureliano, Manuel
    Decavanadate, decaniobate, tungstate and molybdate interactions with sarcoplasmic reticulum Ca2+-ATPase: quercetin prevents cysteine oxidation by vanadate but does not reverse ATPase inhibition2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 41, p. 12749-12758Article in journal (Refereed)
    Abstract [en]

    Recently we demonstrated that the decavanadate (V-10) ion is a stronger Ca2+-ATPase inhibitor than other oxometalates, such as the isoelectronic and isostructural decaniobate ion, and the tungstate and molybdate monomer ions, and that it binds to this protein with a 1 : 1 stoichiometry. The V-10 interaction is not affected by any of the protein conformations that occur during the process of calcium translocation (i.e. E1, E1P, E2 and E2P) (Fraqueza et al., J. Inorg. Biochem., 2012). In the present study, we further explore this subject, and we can now show that the decaniobate ion, [Nb-10 = Nb10O28](6-), is a useful tool in deducing the interaction and the non-competitive Ca2+-ATPase inhibition by the decavanadate ion [V-10 = V10O28](6-). Moreover, decavanadate and vanadate induce protein cysteine oxidation whereas no effects were detected for the decaniobate, tungstate or molybdate ions. The presence of the antioxidant quercetin prevents cysteine oxidation, but not ATPase inhibition, by vanadate or decavanadate. Definitive V(IV) EPR spectra were observed for decavanadate in the presence of sarcoplasmic reticulum Ca2+-ATPase, indicating a vanadate reduction at some stage of the protein interaction. Raman spectroscopy clearly shows that the protein conformation changes that are induced by V-10, Nb-10 and vanadate are different from the ones induced by molybdate and tungstate monomer ions. Here, Mo and W cause changes similar to those by phosphate, yielding changes similar to the E1P protein conformation. The putative reduction of vanadium(V) to vanadium(IV) and the non-competitive binding of the V-10 and Nb-10 decametalates may explain the differences in the Raman spectra compared to those seen in the presence of molybdate or tungstate. Putting it all together, we suggest that the ability of V-10 to inhibit the Ca2+-ATPase may be at least in part due to the process of vanadate reduction and associated protein cysteine oxidation. These results contribute to the understanding and application of these families of mono-and polyoxometalates as effective modulators of many biological processes, particularly those associated with calcium homeostasis.

  • 22. Fraqueza, Gil
    et al.
    Ohlin, C. Andre
    Casey, William H.
    Aureliano, Manuel
    Sarcoplasmic reticulum calcium ATPase interactions with decaniobate, decavanadate, vanadate, tungstate and molybdate2012In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 107, no 1, p. 82-89Article in journal (Refereed)
    Abstract [en]

    Over the last few decades there has been increasing interest in oxometalate and polyoxometalate applications to medicine and pharmacology. This interest arose, at least in part, due to the properties of these classes of compounds as anti-cancer, anti-diabetic agents, and also for treatment of neurodegenerative diseases, among others. However, our understanding of the mechanism of action would be improved if biological models could be used to clarify potential toxicological effects in main cellular processes. Sarcoplasmic reticulum (SR) vesicles, containing a large amount of Ca(2+)-ATPase, an enzyme that accumulates calcium by active transport using ATP, have been suggested as a useful model to study the effects of oxometalates on calcium homeostasis. In the present article, it is shown that decavanadate, decaniobate, vanadate, tungstate and molybdate, all inhibited SR Ca(2+)-ATPase, with the following IC(50) values: 15, 35, 50, 400 mu M and 45 mM, respectively. Decaniobate (Nb(10)), is the strongest P-type enzyme inhibitor, after decavanadate (V(10)). Atomic-absorption spectroscopy (AAS) analysis, indicates that decavanadate binds to the protein with a 1:1 decavanadate:Ca(2+)-ATPase stoichiometry. Furthermore, V10 binds with similar extension to all the protein conformations, which occur during calcium translocation by active transport, namely El, El P, E2 and E2P, as analysed by MS. In contrast, it was confirmed that the binding of monomeric vanadate (H(2)VO(4)(2-):V(1)) to the calcium pump is favoured only for the E2 and E2P conformations of the ATPase, whereas no significant amount of vanadate is bound to the E1 and E1P conformations. Scatchard plot analysis, confirmed a 1:1 ratio for decavanadate-Ca(2+)-ATPase, with a dissociation constant, k(d) of 1 mu M(-1). The interaction of decavanadate V(10)O(28)(6-) (V(10)) with Ca(2+)-ATPase is prevented by the isostructural and isoelectronic decaniobate Nb(10)O(28)(6-) (Nb(10)), whereas no significant effects were detected with ATP or with heparin, a known competitive ATP binding molecule, suggesting that V(10) binds non-competitively, with respect to ATP, to the protein. Finally, it was shown that decaniobate inhibits SR Ca(2+)-ATPase activity in a non competitive type of inhibition, with respect to ATP. Taken together, these data demonstrate that decameric niobate and vanadate species are stronger inhibitors of the SR calcium ATPase than simple monomeric vanadate, tungstate and molybdate oxometalates, thus affecting calcium homeostasis, cell signalling and cell bioenergetics, as well many other cellular processes. The ability of these oxometalates to act either as phosphate analogues, as a transition-state analogue in enzyme-catalysed phosphoryl group transfer processes and as potentially nucleotide-dependent enzymes modulators or inhibitors, suggests that different oxometalates may reveal different mechanistic preferences in these classes of enzymes. (C) 2011 Elsevier Inc. All rights reserved.

  • 23. Gordon, C M
    et al.
    Ohlin, C A
    Ritchie, C
    Ionic liquids: Clean solvents for organic synthesis.2001Other (Refereed)
  • 24.
    Gorzsás, András
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Vanadate and Peroxovanadate Complexes of Biomedical Relevance: A speciation approach with focus on diabetes2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Diabetes mellitus is one of the most threatening epidemics of modern times with rapidly increasing incidence. Vanadium and peroxovanadium compounds have been shown to exert insulin–like actions and, in contrast to insulin, are orally applicable. However, problems with side–effects and toxicity remain. The exact mechanism(s) by which these compounds act are not yet fully known. Thus, a better understanding of the aqueous chemistry of vanadates and peroxovanadates in the presence of various (bio)ligands is needed.

    The present thesis summarises six papers dealing mainly with aqueous speciation in different vanadate – and peroxovanadate – ligand systems of biological and medical relevance. Altogether, five ligands have been studied, including important blood constituents (lactate, citrate and phosphate), a potential drug candidate (picolinic acid), and a dipeptide (alanyl serine) to model the interaction of (peroxo)vanadate in the active site of enzymes. Since all five ligands have been studied both with vanadates and peroxovanadates, the number of systems described in the present work is eleven, including the vanadate – citrate – lactate mixed ligand system. The pH–independent formation constants have been determined for 33 ternary vanadate – ligand, 41 quaternary peroxovanadate – ligand and two vanadate – mixed ligand species in addition to the pKa values of all five ligands. These constants have been used to model physiological conditions, and the biomedical relevance of the different species is discussed.

    The studies have been performed at 25 ºC in the physiological medium of 0.150 M Na(Cl), i.e. the ionic strength of human blood. No buffers have been used, and wide pH–ranges have usually been covered. The applied experimental techniques comprise mostly 51V NMR and potentiometry, but 31P, 13C, 1H and 14N NMR as well as EPR and ESI–MS have also been used to gain additional information. Multimethod data have been treated by the least–squares program LAKE and modelling has been carried out by the software package WinSGW.

    Whenever possible, solution structures of the species have been proposed. In addition, simple biological tests have been carried out to determine the stability of the formed peroxovanadate complexes in the presence of human catalase. A brief comparison is given of the different vanadate – ligand and peroxovanadate – ligand systems with emphasis on observed trends and general features.

  • 25.
    Grimm, Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bed agglomeration characteristics in fluidized quartz bed combustion of phosphorus-rich biomass fuels2011In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, no 3, p. 937-947Article in journal (Refereed)
    Abstract [en]

    The bed agglomeration characteristics during combustion of phosphorus-rich biomass fuels and fuel mixtures were determined in a fluidized (quartz) bed reactor (5 kW). The fuels studied (separately and in mixtures) included logging residues, bark, willow, wheat straw, and phosphorus-rich fuels, like rapeseed meal (RM) and wheat distillers dried grain with solubles (DDGS). Phosphoric acid was used as a fuel additive. Bed material samples and agglomerates were studied by means of scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDX), in order to analyze the morphological and compositional changes of coating/reaction layers and necks between agglomerated bed particles. Furthermore, bed ash particles were separated by sieving from the bed material samples and analyzed with SEM/EDS and powder X-ray diffraction (XRD). For logging residues, bark, and willow, with fuel ash rich in Ca and K but with low contents of P and organically bound Si, the bed layer formation is initiated by reactions of gaseous or liquid K compounds with the surface of the bed material grains, resulting in the formation of a potassium silicate melt. The last process is accompanied by the diffusion/dissolving of Ca into the melt and consequent viscous flow sintering and agglomeration. The addition of high enough phosphorus content to convert the available fuel ash basic oxides into phosphates reduced the amount of K available for the reaction with the quartz bed material grains, thus preventing the formation of an inner bed particle layer in the combustion of logging residues, bark, and willow. Some of the phosphate-rich ash particles, formed during the fuel conversion, adhered and reacted with the bed material grains to form noncontinuous phosphate−silicate coating layers, which were found responsible for the agglomeration process. Adding phosphorus-rich fuels/additives to fuels rich in K and Si (e.g., wheat straw) leads to the formation of alkali-rich phosphate−silicate ash particles that also adhered to the bed particles and caused agglomeration. The melting behavior of the bed particle layers/coatings formed during combustion of phosphorus-rich fuels and fuel mixtures is an important controlling factor behind the agglomeration tendency of the fuel and is heavily dependent on the content of alkaline earth metals in the fuel. A general observation is that phosphorus is the controlling element in ash transformation reactions during biomass combustion in fluidized quartz beds because of the high stability of phosphate compounds.

  • 26. Grivel, J-C
    et al.
    Pitillas, A.
    Namazkar, S.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Department of Energy Conversion and Storage, Technical University of Denmark, 4000-Roskilde, Denmark.
    Alexiou, A.
    Holte, O. J.
    Preparation and characterization of MgB2 with Pd, Pt and Re doping2016In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 520, p. 37-41Article in journal (Refereed)
    Abstract [en]

    Samples with Mg1-xDxB2.04 (D = Pt, Pd or Re) nominal compositions have been synthesised by a solid-state route. None of these doping elements can be substituted for Mg in a detectable amount and their presence in the samples has no influence on the critical temperature and on the lattice parameters of the MgB2 superconductor. Impurity phases are formed by reaction mostly with Mg. The microstructure of the Pt, Pd and Re-based phases depends on the elements. Re-rich particles with large sizes up to 8 mu m form, whereas Pt- and Pd-containing impurities are finely dispersed with a particle size that does not exceed 1 mu m. The field dependence of the normalised critical current density is improved when Pt, Pd or Re are present in the samples. (C) 2015 Elsevier B.V. All rights reserved.

  • 27.
    Gustafsson, Tomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Saxin, Maria
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kihlberg, Jan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Synthesis of a C-glycoside analogue of β-D -galactosyl threonine2003In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 68, no 6, p. 2506-2509Article in journal (Refereed)
    Abstract [en]

    C-linked analogue of β-d-galactosylthreonine has been prepared from 2,3,4,6-tetra-O-benzyl-d-galactopyranolactone (1) in 14 steps. Three stereogenic centers were created during the synthesis, with the anomeric center of the C-glycoside being generated first by addition of a Grignard reagent to 1 and subsequent reduction of the intermediate hemiacetal with triethylsilane. The two stereogenic centers in the threonine moiety were both established by alkylation of Evans' chiral N-acyloxazolidinone enolates.

  • 28.
    Hagman, Henrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Perstorp Specialty Chemicals AB.
    Co-firing animal waste, sludge, residue wood, peat and forest fuels in a 50MWth CFB boiler: ash transformation, availability and process improvements2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The direct variable costs for heat and electricity production based on solid biomass fuel combustion is approximately 3-5 times lower than the costs in a fossil fuel-oil based boiler in Sweden. In addition waste derived biomass fuels are typically much cheaper than biomass not classified as waste. The introduction of the waste derived fuels; wastewater treatment sludge, demolition wood, and animal waste in a 50MWth circulating fluidized bed (CFB) biomass boiler located in Perstorp, Sweden, led to rapid deposit buildup in superheaters, heavy ash accumulation in economizers and failing boiler tubes and vortex finders that forced frequent boiler shutdowns. This in turn increased the use of expensive oil (fossil fuel) in backup boilers and the CO2 footprint of the on-site energy conversion system. This work aims to increase the general mechanistic understanding of combustion systems using complex fuels, and includes: A mapping of the boiler failure and preventive maintenance statistics; elemental composition analysis of ash, deposits and fuel fractions; flue-gas composition measurements; chemical speciation analysis; an attempt to describe the overall ash transformation reactions and mass balance throughout the combustion process. Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) was used to analyze the elemental composition of ash and deposits. The SEM-EDS results were used together with data from X-ray powder diffraction (XRD) analysis, thermodynamic phase data, and equilibrium calculations in an attempt to quantify the crystalline phases and the overall ash transformation of the process. Based on the findings concerning ash transformation and the failure statistics, it has been possible to identify generic key parameters regarding boiler design and process parameters, enabling major improvements of the CFB boiler availability, a lower overall energy conversion cost and a reduced CO2 footprint.

  • 29. Harley, Steven J.
    et al.
    Ohlin, C. Andre
    Casey, William H.
    Geochemical kinetics via the Swift-Connick equations and solution NMR2011In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 75, no 13, p. 3711-3725Article in journal (Refereed)
    Abstract [en]

    Signal analysis in Nuclear Magnetic Resonance spectroscopy is among the most powerful methods to quantify reaction rates in aqueous solutions. To this end, the Swift-Connick approximations to the Bloch-McConnell equations have been used extensively to estimate rate parameters for elementary reactions. The method is primarily used for O-17 NMR in aqueous solutions, but the list of geochemically relevant nuclei that can be used is long, and includes Si-29, Al-27, F-19, C-13 and many others of particular interest to geochemists. Here we review the derivation of both the Swift-Connick and Bloch-McConnell equations and emphasize assumptions and quirks. For example, the equations were derived for CW-NMR, but are used with modern pulse FT-NMR and can be applied to systems that have exchange rates that are shorter than the lifetime of a typical pulse. The method requires a dilute solution where the minor reacting species contributes a negligible amount of total magnetization. We evaluate the sensitivity of results to this dilute-solution requirement and also highlight the need for chemically well-defined systems if reliable data are to be obtained. The limitations in using longitudinal relaxation to estimate reaction rate parameters are discussed. Finally, we provide examples of the application of the method, including ligand exchanges from aqua ions and hydrolysis complexes, that emphasize its flexibility. Once the basic requirements of the Swift-Connick method are met, it allows geochemists to establish rates of elementary reactions. Reactions at this scale lend themselves well to methods of computational simulation and could provide key tests of accuracy. (C) 2011 Elsevier Ltd. All rights reserved.

  • 30. Harley, Steven J.
    et al.
    Ohlin, C. Andre
    Johnson, Rene L.
    Panasci, Adele F.
    Casey, William H.
    The Pressure Dependence of Oxygen Isotope Exchange Rates Between Solution and Apical Oxygen Atoms on the [UO2(OH)(4)](2-) Ion2011In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, no 19, p. 4467-4469Article in journal (Refereed)
  • 31. Hawley, Andrew L.
    et al.
    Ohlin, C. André
    Umeå University, Faculty of Science and Technology, Department of Chemistry. School of Chemistry, Melbourne, Australia).
    Fohlmeister, Lea
    Stasch, Andreas
    Heavier Group 13 Metal(I) Heterocycles Stabilized by Sterically Demanding Diiminophosphinates: a Structurally Characterized Monomer–Dimer Pair For Gallium2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 2, p. 447-455Article in journal (Refereed)
    Abstract [en]

    We have synthesized and characterized the monomeric diiminophosphinate-stabilized Group 13 metal(I) complexes [DipLE:], DipL=Ph2P(NDip)2, Dip=2,6-iPr2C6H3; E=Ga (1), In (2) and Tl (3). In addition, we structurally characterized the dimeric complex [(DipLGa)2], 12. Similar synthetic attempts using MesL=Ph2P(NMes)2, Mes=2,4,6-Me3C6H2 afforded product mixtures from which the mixed oxidation state species [(MesL)3Ga4I3] 4 was isolated. [DipLGa:] 1 is converted with dry air to the gallium(III) oxide species [(DipLGaO)2] 5. Density Functional Theory studies on [DipLE:] and [(DipLE)2], E=Al−Tl, shed light on the bonding in these compounds and show that the newly formed E−E bonding interactions can be described as weak single σ-bond with no significant π-bonding contribution for E=Al, Ga. A large contribution to the dimer binding enthalpies results from London dispersion forces.

  • 32.
    Holmgren, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Entrained flow studies on biomass fuel powder conversion and ash formation2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Reducing the global dependence on fossil fuels is of paramount importance in tackling the environmental challenges we face, not only tomorrow, but already today. Biomass offers a renewable supply of CO2-neutral raw material that can be converted into many different forms of fuels and valuable chemicals, making it a prime candidate for the technologies of tomorrow. However, the heterogeneous nature and distinctly different elemental composition of biomass compared to traditional fossil sources present new challenges to be solved. When it comes to thermochemical technologies, key issues concern fuel conversion efficiency, ash formation, ash/fuel interactions and ash/reactor material interactions.

    The objective of the present thesis was to provide new knowledge and insights into thermochemical fuel conversion, in particular its application in entrained flow technologies. A laboratory-scale reactor was constructed, evaluated and was used to study several aspects of high-temperature entrained flow biomass fuel conversion. Pulverized fuel particles from different biomass sources were used, and their physical and chemical interactions with the surrounding atmosphere, the concurrent ash element release, ash formation, and phase interactions were also studied in detail. In addition to the entrained flow reactor designed and constructed for this purpose, the main method for data collection was in situ optical studies of converting particles, either while entrained in the flow or when impacting upon surfaces. Elemental composition analysis of collected samples and gas analysis were also performed, allowing for a deeper understanding of ash element fractionation and interactions and thus explaining the observed properties of the resulting deposits or slag.

    The degree of conversion of fuels with very low ash content, such as stem wood, was well described and modeled by a novel method using optical data, offering a non-intrusive and non-destructive alternative to traditional techniques. Coupling computational fluid dynamics with optical data allowed for improved experimental data interpretation and provided improved accuracy for fuel particle residence time estimations, which is an important parameter when studying fast chemical reactions such as those taking place in reactors for entrained flow conditions. The results from studies on ash formation gave new insights into the feasibility of using dry-mixed K-rich additives for improving slag properties during gasification of Ca-rich and Si-rich fuels. Interpretations of the experimental results were supported by thermodynamic equilibrium calculations, and the conclusions highlight both possibilities and challenges in gasification with high fuel flexibility while at the same time producing a flowing slag. Applications and future implications are discussed, and new topics of interest are presented.

  • 33.
    Holmgren, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå Universitet.
    Carlborg, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå Universitet.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå Universitet.
    Slag Formation During Entrained Flow Gasification: Calcium Rich Bark Fuel with KHCO3 AdditiveManuscript (preprint) (Other academic)
    Abstract [en]

    Managing slag properties is of utmost importance for successful operation of entrained flow gasifiers. The present study details some aspects of slag formed from a softwood bark fuel, and especially the situation with only small amounts of mineral contaminants, meaning composition is shifted from Si- towards P-dominated ash. Wood bark with and without KHCO3 additive was gasified between 850 °C and 1300 °C at O2 stoichiometric ratio (λ) 0.6 to study the resulting ash properties and the influence of the additive. The ash particles collided with a flat impact probe inside the hot reactor, with particle impact angles varied between 90° to 30°. The reactor and probe were constructed to allow for long-distance microscope data collection close to the surface of the probe. In situ PIV and SEM-EDS of deposit samples from lab scale entrained flow gasification experiments were used for evaluation, while XRD was used to characterize carbonates. High potassium release was found but numerous spherical ash particles indicated lower ash melting temperatures than expected from the bulk ash composition. These new findings propose a mechanism for melt formations involving carbonates rich in potassium and phosphorous, followed by K-release and calcination leading to solidification.

  • 34. Isidorova, Anastasija
    et al.
    Bravo, Andrea G.
    Riise, Gunnhild
    Bouchet, Sylvain
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sobek, Sebastian
    The effect of lake browning and respiration mode on the burial and fate of carbon and mercury in the sediment of two boreal lakes2016In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, no 1, p. 233-245Article in journal (Refereed)
    Abstract [en]

    In many northern temperate regions, the water color of lakes has increased over the past decades (lake browning), probably caused by an increased export of dissolved organic matter from soils. We investigated if the increase in water color in two lakes in Norway has resulted in increased burial of organic carbon (OC) and mercury (Hg) in the sediments and if the Hg was prone to methylation. Lake Solbergvann experienced a threefold water color increase, and OC burial increased approximately twofold concomitant to the water color increase. This lake had prolonged periods of anoxic bottom water, and anoxic OC mineralization rates were only about half of the oxic OC mineralization rates (7.7 and 17.5g C m(-2)yr(-1), respectively), contributing to an efficient OC burial. In Lake Elvaga, where water color increase was only approximately twofold and bottom water was oxygenated, no recent increase in OC burial could be observed. Hg burial increased strongly in both lakes (threefold and 1.6-fold in Lake Solbergvann and Lake Elvaga, respectively), again concomitant to the recent water color increase. The proportion of methylated Hg (MeHg) in surficial sediment was 1 order of magnitude higher in Lake Elvaga (up to 6% MeHg) than in Lake Solbergvann (0.2-0.6% MeHg), probably related to the different oxygenation regimes. We conclude that lake browning can result in increased OC and Hg burial in lake sediments, but the extent of browning and the dominating mode of sediment respiration (aerobic or anaerobic) strongly affect burial and fate of OC and Hg in sediments.

  • 35. Ivanova, T M
    et al.
    Shchukarev, Andrey V
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Linko, R V
    Kiskin, M A
    Sidorov, A A
    Novotortsev, V M
    Eremenko, I L
    X-ray photoelectron spectra of heterometallic 3d-metal carboxylate complexes2011In: Russian Journal of Inorganic Chemistry, ISSN 0036-0236, E-ISSN 1531-8613, Vol. 56, no 1, p. 104-109Article in journal (Refereed)
    Abstract [en]

    The electronic structure and magnetic states in the heterometallic hexanuclear complex Mn4II Fe2III4-O)2(Piv)10 · MeCN4 have been studied by X-ray photoelectron spectroscopy (XPS). The substitution of two Mn atoms for two Fe atoms in the hexanuclear complex was found to have an effect on the patterns of iron and manganese X-ray photoelectron spectra. XPS data are evidence of the high-spin paramagnetic state of MnII and FeIII atoms, as well as of the ligand-metal charge transfer upon complex formation. In the heteroatomic complex, the degree of bond covalence increased for both the manganese and iron atoms. The results obtained are in good agreement with X-ray diffraction data.

  • 36. Ivanova, TM
    et al.
    Kochur, AG
    Shchukarev, Andrey V
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Linko, RV
    Terebova, NS
    Kiskin, MA
    Sidorov, AA
    Novotortsev, VM
    Eremenko, IL
    XPS study of the electronic structure of binuclear 3d transition metal pivalate complexes2012In: Russian Journal of Inorganic Chemistry, ISSN 0036-0236, E-ISSN 1531-8613, Vol. 57, no 11, p. 1484-1489Article in journal (Refereed)
    Abstract [en]

    Binuclear pivalate complexes of 3d transition metals (manganese, iron, cobalt, and nickel) with the same ligand environment and a lantern structure have been studied by X-ray photoelectron spectroscopy. The M2p, M3s, C1s, O1s, and N1s X-ray photoelectron spectra have been examined. A redistribution of electron density in the OCO group has been revealed. It has been shown that the theory fits the experimental data on the energy separation between the high- and low-spin components in the M3s spectra and between the spin doublet components in the M2p spectra. It has been demonstrated that the iron, cobalt, and nickel complexes are paramagnetic at room temperature, whereas the manganese complex exhibits antiferromagnetic properties. There is a correlation between the size of the 3d subshell of the transition metal atom and the M-O and M-N bond lengths.

  • 37. Johnson, Rene L.
    et al.
    Harley, Stephen J.
    Ohlin, C. Andre
    Panasci, Adele F.
    Casey, William H.
    Multinuclear NMR Study of the Pressure Dependence for Carbonate Exchange in the UO2(CO3)34-(aq) Ion2011In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 12, no 16, p. 2903-2906Article in journal (Refereed)
  • 38. Johnson, Rene L.
    et al.
    Ohlin, C. Andre
    Pellegrini, Kristi
    Burns, Peter C.
    Casey, William H.
    Dynamics of a Nanometer-Sized Uranyl Cluster in Solution2013In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 29, p. 7464-7467Article in journal (Refereed)
  • 39. Johnson, Rene L.
    et al.
    Villa, Eric M.
    Ohlin, C. Andre
    Rustad, James R.
    Casey, William H.
    O-17 NMR and Computational Study of a Tetrasiliconiobate Ion, [H2+xSi4Nb16O56]((14-x)-)2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 34, p. 9359-9367Article in journal (Refereed)
    Abstract [en]

    Rates of oxygen-isotope exchange were measured in the tetrasiliconiobate ion [H2+xSi4Nb16O56]((14-x)-) to better understand how large oxide ions interact with water. The molecule has 19 nonequivalent oxygen sites and is sufficiently complex to evaluate hypotheses derived from our previous work on smaller clusters. We want to examine the extent to which individual oxygen atoms react independently with particular attention given to the order of protonation of the various oxygen sites as the pH decreases from 13 to 6. As in our previous work, we find that the set of oxygen sites reacts at rates that vary over approximately 104 across the molecule at 6 < pH < 13 but with similar pH dependencies. There is NMR evidence of an intra-or intermolecular reaction at pH similar to 7, where new peaks began to slowly form without losing the O-17 isotopic tag, and at pH <= 6 these new peaks formed rapidly. The oxygen atoms bonded to silicon atoms began to isotopically exchange at pH 9 and below. The 17O NMR peak positions also vary considerably with pH for some, but not all, nonequivalent oxygen sites. This variation could be only partly accounted by electronic calculations, which indicate that oxygen atoms should shift similarly upon protonation. Instead, we see that some sites change enormously with pH, whereas other, similarly coordinated oxygen atoms are less affected, suggesting that either some protons are exchanging so rapidly that the oxygen sites are seeing an averaged charge, or that counterions are modulating the effect of the coordinated protons.

  • 40.
    Jönsson, Jörgen
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Phase transformation and surface chemistry of secondary iron minerals formed from acid mine drainage2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The mining of sulphidic ore to extract metals such as zinc and copper produces huge quantities of waste material. The weathering and oxidation of the waste produces what is commonly known as Acid Mine Drainage (AMD), a dilute sulphuric acid rich in Fe(II) and heavy metals. This thesis serves to summarise five papers reporting how the precipitation of Fe(III) phases can attenuate the contamination of heavy metals by adsorption processes.

    Schwertmannite (Fe8O8(OH)6SO4) is a common Fe(III) mineral precipitating in AMD environments at pH 3-4. The stability and surface chemistry of this mineral was investigated. It was shown that the stability depended strongly on pH and temperature, an increase in either promoted transformation to goethite (α-FeOOH). Two pH dependent surface species of SO42- were detected with infrared (ATR-FTIR) spectroscopy.

    The adsorption of Cu(II), Pb(II) and Zn(II) to schwertmannite occurred at lower pH than to goethite, whereas Cd(II) adsorption occurred in a similar pH range on both schwertmannite and goethite. Extended x-ray absorption fine structure (EXAFS) spectroscopy suggests two surface species for Cu(II) and Cd(II) at the schwertmannite surface. Cu(II) adsorbs monodentately and Cd(II) bridging bidentately to adsorbed SO42-. Both metal ions also adsorb in a bridging bidentate mode to the surface hydroxyl groups. At pH 7.5 up to 2.7 μmol Cd(II) m-2 could be adsorbed to schwertmannite, indicating a large adsorption capacity for this mineral.

    The acid-base properties of two NOM samples were characterised and could be well described as diprotic acids below pH 6. The adsorption of NOM to schwertmannite and goethite was very similar and adsorption occured in a very wide pH range.

    High concentrations of NOM increased the adsorption of Cu(II) to goethite at low pH whereas a slight decrease was noted at low concentrations of NOM. No effect was detected in the schwertmannite system.

    The formation of Fe(III) phases from precipitation of AMD was shown to be very pH dependent. At pH 5.5 a mixture of minerals, including schwertmannite, formed whereas at pH 7 only lepidocrocite (γ-FeOOH) formed. The concentration of Zn(II) in AMD could by adsorption/coprecipitation be reduced to environmentally acceptable levels.

  • 41. Knighton, Richard C.
    et al.
    Emerson-King, Jack
    Rourke, Jonathan P.
    Ohlin, C. André
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Chaplin, Adrian B.
    Solution, Solid-State, and Computational Analysis of Agostic Interactions in a Coherent Set of Low-Coordinate Rhodium(III) and Iridium(III) Complexes2018In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 19, p. 4927-4938Article in journal (Refereed)
    Abstract [en]

    A homologous family of low‐coordinate complexes of the formulation trans‐[M(2,2′‐biphenyl)(PR3)2][BArF4] (M=Rh, Ir; R=Ph, Cy, iPr, iBu) has been prepared and extensively structurally characterised. Enabled through a comprehensive set of solution phase (VT 1H and 31P NMR spectroscopy) and solid‐state (single crystal X‐ray diffraction) data, and analysis in silico (DFT‐based NBO and QTAIM analysis), the structural features of the constituent agostic interactions have been systematically interrogated. The combined data substantiates the adoption of stronger agostic interactions for the IrIII compared to RhIII complexes and, with respect to the phosphine ligands, in the order PiBu3>PCy3>PiPr3>PPh3. In addition to these structure–property relationships, the effect of crystal packing on the agostic interactions was investigated in the tricyclohexylphosphine complexes. Compression of the associated cations, through inclusion of a more bulky solvent molecule (1,2‐difluorobenzene vs. CH2Cl2) in the lattice or collection of data at very low temperature (25 vs. 150 K), lead to small but statistically significant shortening of the M−H−C distances.

  • 42. Kochur, A. G.
    et al.
    Ivanova, T. M.
    Shchukarev, Andrey V.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Linko, R. V.
    Terebova, N. G.
    Sidorov, A. A.
    Eremenko, I. L.
    Study of the electronic structure of polynuclear cobalt trimethylacetate complexes by Co3s and Co3p X-ray photoelectron spectroscopy2011In: Russian Journal of Inorganic Chemistry, ISSN 0036-0236, E-ISSN 1531-8613, Vol. 56, no 3, p. 402-408Article in journal (Refereed)
    Abstract [en]

    The electronic structure of mono-, hexa-, and nonanuclear cobalt trimethylacetate complexes was studied by XPS. The Co3s- and Co3p X-ray photoelectron spectra of the complexes were recorded. The Co3p spectrum of bivalent cobalt was calculated in the isolated-ion intermediate-coupling approximation. Spectrum analysis showed that the [Co(N-Phobsqdi)2(eta'-N-Ph-opda)(OOCCMe(3))] complex is a strong-field complex with Co(III) in the diamagnetic state; the [Co(dipy)(2)(OOCCMe(3))(2)], [Co(dipyam)(OOCCMe(3))(2)], and [Co(9)(mu(3)-OH)(6)(mu-OOCCMe(3))(12)(OCMe(2))(4)] are high-spin weak-field Co(II) complexes; and the [Co(6)(mu(4)-O)(2)(OOCCMe(3))(10)(THF)(4)] complex contains both the Co(II) and Co(III) atoms. The energy position of major Co3s- and Co3p spectral maxima were found to be sensitive to the nature of the nearest environment of cobalt atoms. The data correlate well with X-ray crystallographic data.

  • 43.
    Koroidov, Sergey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Anderlund, Magnus F
    Styring, Stenbjörn
    Thapper, Anders
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles2015In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 8, no 8, p. 2492-2503Article in journal (Refereed)
    Abstract [en]

    Co-oxides are promising water oxidation catalysts for artificial photosynthesis devices. Presently, several different proposals exist for how they catalyze O-2 formation from water. Knowledge about this process at molecular detail will be required for their further improvement. Here we present time-resolved O-18-labelling isotope-ratio membrane-inlet mass spectrometry (MIMS) experiments to study the mechanism of water oxidation in Co/methylenediphosphonate (Co/M2P) oxide nanoparticles using [Ru(bpy)(3)](3+) (bpy = 2,2'-bipyridine) as chemical oxidant. We show that O-16-Co/M2P-oxide nanoparticles produce O-16(2) during their first turnover after simultaneous addition of (H2O)-O-18 and [Ru(bpy)(3)](3+), while sequential addition with a delay of 3 s yields oxygen reflecting bulk water O-18-enrichment. This result is interpreted to show that the O-O bond formation in Co/M2P-oxide nanoparticles occurs via intramolecular oxygen coupling between two terminal Co-OHn ligands that are readily exchangeable with bulk water in the resting state of the catalyst. Importantly, our data allow the determination of the number of catalytic sites within this amorphous nanoparticular material, to calculate the TOF per catalytic site and to derive the number of holes needed for the production of the first O-2 molecule per catalytic site. We propose that the mechanism of O-O bond formation during bulk catalysis in amorphous Co-oxides may differ from that taking place at the surface of crystalline materials.

  • 44.
    Kozin, Philipp A.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Charge Development at Iron Oxyhydroxide Surfaces: The Interplay between Surface Structure, Particle Morphology and Counterion Identity2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 45.
    Kozin, Philipp A.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boily, Jean-François
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mineral surface charge development in mixed electrolyte solutions2014In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 418, p. 246-253Article in journal (Refereed)
    Abstract [en]

    Abstract Effects of competing counterions with different charge-to-size ratios on potential-determining ion (pdi; H+, OH−) adsorption at mineral/water interfaces were resolved in mixtures of aqueous solutions of NaCl and NaClO4 solutions. These effects were monitored on two synthetic goethite (α-FeOOH) particle preparations with distinct charge uptake capacities arising from differences in surface roughness. Charge development at these mineral surfaces was chiefly explored by high precision potentiometric titrations at 25 °C. These measurements confirmed that the greater charge-to-size ratio chloride ion not only promoted greater surface charge, but also had pronounced effects in perchlorate-dominated solutions. Cryogenic X-ray photoelectron spectroscopic measurements confirmed that perchlorate retains significant loadings at the goethite surface, even in the presence of chloride. Molecular dynamics simulations of the (1 1 0) plane of goethite exposed to these mixed solutions showed that chloride compressed the interfacial region containing electrolyte ions. Perchlorate, on the other hand, is not only present over a thicker region of the interface but also promotes an additional outer-sphere sodium species. These findings were used to develop a thermodynamic adsorption model predicting charge development at these mineral surfaces. The model involves a new formulation accounting for coexisting ion-specific regions each with their distinct compact plane capacitance values. The model can predict charge development in any mixtures of NaCl and NaClO4 contacted with goethite particles of contrasting charge uptake capacities without any additional parameters. This model can also be applied to a broader range of material surfaces.

  • 46.
    Kozin, Philipp A
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boily, Jean-François
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Proton Binding and Ion Exchange at the Akaganéite/Water Interface2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 12, p. 6409-6419Article in journal (Refereed)
    Abstract [en]

    Proton exchange in nanosized synthetic akaganéite particles suspended in aqueous media and in ionic strengths of 3–100 mM NaCl and NaClO4 was monitored by high precision potentiometry at 25 °C. Proton budgets in the pH 3–10 range pertain to simultaneously occurring surface complexation and bulk ionic exchange reactions. Surface complexation reactions involve proton binding to (hydr)oxo groups of the dominant crystallographic planes of the particles. These are responsible for the colloidal attributes of the akaganéite particles, as confirmed by electrophoretic mobility measurements. Bulk ionic exchange involves the codiffusion of protons and chloride ions through the tunnel structure of the hollandite-type akaganéite bulk. Chloride ions migrate to bulk complexation sites that are ideally defined by eight surrounding hydroxyl groups, ≡(OH)8. Protons are in turn considered to be bound to neighboring oxo groups, ≡O. Collectively, the complexes are referred as [≡(OH)8···Cl······HO≡]. A thermodynamic model accounting for these two processes was developed to predict the pH (3–9), ionic strength (3–100 mM), and ionic medium (NaCl, NaClO4) dependence of the potentiometric data. This model is supported by new zeta potential data pointing to an isoelectric point of 9.6–10.3 for pristine akaganéite particles and by Fourier transform infrared spectra showing the impact of pH and ionic medium on bulk proton-chloride loadings. Our proposed stoichiometry for a chloride-rich solid of β-FeOOH·(HCl)0.192 corresponds to a maximal occupancy of 75% for chloride ions in the [≡(OH)8···Cl······HO≡] bulk complexation sites. Samples equilibrated in pure aqueous solutions should have a composition of β-FeOOH·(HCl)0.151, corresponding to a 60% occupancy for chloride ions due to a partial exchange of HCl. Our model can be used to predict compositional changes in the akaganéite bulk and surfaces upon any variations in pH and ionic media considered in this work.

  • 47.
    Kozin, Philipp A.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Salazar-Alvarez, German
    Boily, Jean-François
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Oriented Aggregation of Lepidocrocite and Its Impact on Surface Charge DevelopmentManuscript (preprint) (Other academic)
  • 48.
    Kuba, Matthias
    et al.
    Technische Universität Wien, Institute of Chemical Engineering.
    He, Hanbing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Kirnbauer, Friedrich
    Technische Universität Wien, Institute of Chemical Engineering.
    Skoglund, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Hofbauer, Hermann
    Technische Universität Wien, Institute of Chemical Engineering.
    Mechanism of Layer Formation on Olivine Bed Particles in Industrial-Scale Dual Fluid Bed Gasification of Wood2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 9, p. 7410-7418Article in journal (Refereed)
    Abstract [en]

    Utilization of biomass as feedstock in dual fluidized bed steam gasification is a promising technology for the substitution of fossil energy carriers. Experience from industrial-scale power plants showed an alteration of the olivine bed material due to interaction with biomass ash components. This change results mainly in the formation of Ca-rich layers on the bed particles. In this paper, a mechanism for layer formation is proposed and compared to the better understood mechanism for layer formation on quartz bed particles. Olivine bed material was sampled at an industrial-scale power plant before the start of operation and at predefined times after the operation had commenced. Therefore, time-dependent layer formation under industrial-scale conditions could be investigated. The proposed mechanism suggests that the interaction between wood biomass ash and olivine bed particles is based on a solid–solid substitution reaction, where Ca2+ is incorporated into the crystal structure. As a consequence, Fe2+/3+ and Mg2+ ions are expelled as oxides. This substitution results in the formation of cracks in the particle layer due to a volume expansion in the crystal structure once Ca2+ is incorporated. The results of this work are compared to relevant published results, including those related to quartz bed particles.

  • 49.
    Kuba, Matthias
    et al.
    Technische Universität Wien, Institute of Chemical Engineering.
    He, Hanbing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Kirnbauer, Friedrich
    Technische Universität Wien, Institute of Chemical Engineering.
    Skoglund, Nils
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Hofbauer, Hermann
    Technische Universität Wien, Institute of Chemical Engineering.
    Thermal stability of bed particle layers on naturally occurring minerals from dual fluid bed gasification of woody biomass2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 10, p. 8277-8285Article in journal (Refereed)
    Abstract [en]

    The use of biomass as feedstock for gasification is a promising way of producing not only electricity and heat but also fuels for transportation and synthetic chemicals. Dual fluid bed steam gasification has proven to be suitable for this purpose. Olivine is currently the most commonly used bed material in this process due to its good agglomeration performance and its catalytic effectiveness in the reduction of biomass tars. However, as olivine contains heavy metals such as nickel and chromium, no further usage of the nutrient-rich ash is possible, and additional operational costs arise due to necessary disposal of the ash fractions. This paper investigates possible alternative bed materials and their suitability for dual fluid bed gasification systems focusing on the behavior of the naturally occurring minerals olivine, quartz, and K-feldspar in terms of agglomeration and fracturing at typical temperatures. To this end, samples of bed materials with layer formation on their particles were collected at the industrial biomass combined heat and power (CHP) plant in Senden, Germany, which uses olivine as the bed material and woody biomass as feedstock. The low cost logging residue feedstock contains mineral impurities such as quartz and K-feldspar, which become mixed into the fluidized bed during operation. Using experimental and thermochemical analysis, it was found that the layers on olivine and K-feldspar showed a significantly lower agglomeration tendency than quartz. Significant fracturing of particles or their layers could be detected for olivine and quartz, whereas K-feldspar layers were characterized by a higher stability. High catalytic activity is predicted for all three minerals once Ca-rich particle layers are fully developed. However, quartz may be less active during the buildup of the layers due to lower amounts of Ca in the initial layer formation.

  • 50.
    Kumpiene, Jurate
    et al.
    Luleå University of Technology.
    Brännvall, Evelina
    Luleå University of Technology.
    Wollters, Martin
    Skoglund, Nils
    Energy Engineering, Department of Engineering Sciences & Mathematics, Luleå University of Technology, SE-97187 Luleå, Sweden.
    Čirba, Stasys
    Aksamitauskas, Vladislovas Česlovas
    Phosphorus and cadmium availability in soil fertilized with biosolids and ashes2016In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 151, p. 124-132Article in journal (Refereed)
    Abstract [en]

    The recycling of hygienized municipal sewage sludge (biosolids) to soil as the source of phosphorus (P) is generally encouraged. The use of biosolids, however, has some concerns, such as the presence of elevated concentrations of potentially toxic trace elements, and the possible presence of pathogens, hormones and antibiotics. Organic substances are destroyed during combustion whereas trace elements could partly be separated from P in different ash fractions. Biomass combustion waste (ash) can instead be considered as an alternative P source. This study evaluates and compares the impact of biosolids and their combustion residues (ashes), when used as fertilizers, on P and Cd solubility in soil, plant growth and plant uptake of these elements. Biosolids were also amended with K and Ca to improve the composition and properties of P in ashes, and incinerated at either 800 °C or 950 °C. Combustion of biosolids improved the Cd/P ratio in ashes by 2–5 times, compared with the initial biosolids. The low Cd content in ashes (4–9 mg Cd (kg P)−1) makes this material a particularly attractive alternative to mineral fertilizers. Significantly higher pore water P (as well as total N) was measured in soils containing biosolids, but plants produced a higher biomass in soil fertilized with ashes. The K and Ca amendments prior to biosolids combustion generally decreased the total Cd in ash, but had little effect on P and Cd uptake and biomass growth. Similarly, the combustion temperature had negligible effect on these factors as well.

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