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  • 551.
    Usachev, K.S.
    et al.
    Kazan (Volga Region) Federal University, Kazan.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Filippova, E.A.
    Kazan (Volga Region) Federal University, Kazan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Klochkov, V.V.
    Kazan (Volga Region) Federal University, Kazan.
    Solution structures of Alzheimer’s amyloid Aβ13-23 peptide: NMR studies in solution and in SDS2013In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1049, p. 436-440Article in journal (Refereed)
    Abstract [en]

    To be believed that interaction of amyloid peptides with the cellular membrane is one of the mechanisms for the neurotoxicity of Aβ. Therefore, structural studies of beta-amyloid in solution and in a “peptide - bio-membrane” complex are of intense interest. The aim of this study was to acquire a better understanding of the mechanism of “Aβ peptide-micelle surface” complex formation. Previous studies of Aβ peptides binding on the micelle surface show the presence of helical region between 15-24 residues and that fragment between 11-28 residues have a tendency to exit the hydrophobic environment of the micelle core and to bind to the micelle surface. In present paper we considered the fragment of Aβ from 13 to 23 residues and found that L17, F19 and F20 residues region play a great role in the process of binding of Aβ to the micelle surface.

  • 552.
    Verma, Priya
    et al.
    Department of Physics, University of Lucknow, Lucknow, Uttar Pradesh, India.
    Srivastava, Anubha
    Department of Physics, University of Lucknow, Lucknow, Uttar Pradesh, India.
    Shukla, Anuradha
    Department of Physics, University of Lucknow, Lucknow, Uttar Pradesh, India.
    Tandon, Poonam
    Department of Physics, University of Lucknow, Lucknow, Uttar Pradesh, India.
    Shimpi, Manishkumar R.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Vibrational spectra, hydrogen bonding interactions and chemical reactivity analysis of nicotinamide–citric acid cocrystals by an experimental and theoretical approach2019In: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 43, no 40, p. 15956-15967Article in journal (Refereed)
    Abstract [en]

    Nicotinamide (NIC), also called vitamin B-3, is commonly known as a pellagra-preventive drug. Citric acid (CA) is a weak tribasic acid, generally used as a flavouring and chelating agent. Herein, a combined experimental and quantum chemical approach was adopted to study the structural properties and spectroscopic signatures of nicotinamide–citric acid (NIC–CA) cocrystals using monomer (2NIC + CA) and cluster (4NIC + CA) models. In the cluster model, two additional NIC molecules were attached to cover the nearest possible interactions to understand the complete molecular geometries and hydrogen bonding interactions present in the cocrystal. In addition to this, our strategy was to calculate and analyse the physicochemical properties of NIC and CA along with improved properties after NIC–CA cocrystal formation. The observed red shift in the stretching modes of CO and N–H of the NH2 groups of NIC and the CO and O–H groups of CA along with the elongation in bond lengths in the cluster model of NIC–CA indicated the presence of hydrogen bonding interactions as well as the formation of cocrystals. Moreover, natural bond orbital (NBO) analysis was performed to obtain information about the interactions that were responsible for the stability and formation of the NIC–CA cocrystal. The ‘quantum theory of atoms in molecules’ (QTAIM) calculations revealed that all the intra- and intermolecular hydrogen bonding interactions present in the NIC–CA (monomer) and NIC–CA (cluster) model were partially covalent in nature. The molecular electrostatic potential (MESP) map of NIC and CA shows that the carbonyl (CO) group and C–N of the pyridine ring in NIC are prone to electrophilic attack, and the hydroxyl (O–H) group of CA is prone to nucleophilic attack. The chemical reactivity parameters calculated using both models show that the NIC–CA cocrystal is more reactive and softer than NIC (API) and CA (co-former) since the band gap of the cocrystal is less than that of both NIC and CA.

  • 553.
    Viveka, Shivapura
    et al.
    Department of Studies in Chemistry, Mangalagangotri, Mangalore University, Konaje.
    Gowda, Vasantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Dinesha, Dinesha
    Department of Studies in Chemistry, Mangalagangotri, Mangalore University, Konaje.
    Naveen, Shivalingegowda
    Institution of Excellence, Vijnana Bhavana, Manasagangotri, University of Mysore.
    Lokanath, Neratur Krishnappagowda
    Department of Studies in Physics, Manasagangotri, University of Mysore.
    Nagaraja, Gundibasappa Karikannar
    Department of Studies in Chemistry, Mangalagangotri, Mangalore University, Konaje.
    Structural, spectral, and theoretical investigations of 5-methyl-1-phenyl-1H-pyrazole-4-carboxylic acid2016In: Research on chemical intermediates (Print), ISSN 0922-6168, E-ISSN 1568-5675, Vol. 42, no 5, p. 4497-4511Article in journal (Refereed)
    Abstract [en]

    The present research work has focused on combined experimental and theoretical studies of one of the biologically important pyrazole-4-carboxylic acid derivatives, viz. 5-methyl-1-phenyl-1H-pyrazole-4-carboxylic acid (C11H10N2O2). The starting material 5-methyl-1-phenyl-1H-4-pyrazolecarboxylate (1) was obtained by the cyclocondensation of ethyl acetoacetate, N,N-dimethylformamide dimethyl acetal (DMF-DMA), and phenylhydrazine, which upon basic hydrolysis yielded the corresponding acid (2). The target compound (2) was characterized by 1H and 13C NMR (solution in DMSO), Fourier transform infrared (FT-IR) spectroscopy, thermo gravimetric analysis, and by single-crystal X-ray diffraction technique. The single crystals of compound (2) were obtained at room temperature by slow evaporation of ethanol as solvent and crystallized in the space group P2 1/n of monoclinic system. The experimental FT-IR and 1H and 13C NMR chemical shifts have been compared to those calculated by means of density functional theory (DFT) at the B3LYP/TZ2P level of theory. The continuum-like screening model was used for geometry optimization of a single molecule and for subsequent calculations of NMR shielding constants in solution (DMSO). Finally, the HOMO–LUMO energy levels were also constructed to study the electronic transition within the molecule by time-dependent TD-DFT method.

  • 554.
    Viveka, Shivapura
    et al.
    Department of Studies in Chemistry, Mangalagangotri, Mangalore University, Konaje.
    Gowda, Vasantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Dinesha, Dinesha
    Department of Studies in Chemistry, Mangalagangotri, Mangalore University, Konaje.
    Naveen, Shivalingegowda
    Institution of Excellence, Vijnana Bhavana, Manasagangotri, University of Mysore.
    Lokanath, Neratur Krishnappagowda
    Department of Studies in Physics, Manasagangotri, University of Mysore.
    Nagaraja, Gundibasappa Karikannar
    Department of Studies in Chemistry, Mangalagangotri, Mangalore University, Konaje.
    Synthesis, characterization, single crystal X-ray diffraction and DFT studies of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate2016In: Molecular Crystals and Liquid Crystals, ISSN 1542-1406, E-ISSN 1563-5287, p. 135-145Article in journal (Refereed)
    Abstract [en]

    The present study describes the synthesis, spectroscopic, and single crystal X-ray structural analysis of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate. The pyrazole ester of formula [C13H14N2O2] was prepared from the three-component one-pot condensation reaction of ethyl acetoacetate, N,N-dimethyldimethoxymethanamine, and phenyl hydrazine. The product was crystallized by using ethanol as solvent. The structure of the compound was confirmed by elemental analysis, Fourier transforms infrared (IR), thermogravimetric analysis, UV-visible (UV-Vis), 1H NMR, and single-crystal X-ray diffraction studies. The gas-phase molecular geometry and the electronic structure-property of the molecule were calculated at the density functional theory. The frontier molecular orbitals, theoretical UV-Vis, and IR stretching vibrations were also reported. The compound crystallizes in the monoclinic system with the space group P21/c and Z = 4. The unit cell parameters are a = 12.141(3) Å, b = 13.934(4) Å, c = 7.2777(18) Å, and β = 97.816(14)0. The structure is stabilized by an intermolecular interaction of type C-H···O and the structure also involves C-H···π interactions

  • 555.
    Wang, Feiyue
    et al.
    Peking University.
    Chen, Jingsheng
    Peking University.
    Chen, Jianglin
    Peking University.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Surface properties of natural aquatic sediments1997In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 31, no 7, p. 1796-1800Article in journal (Refereed)
    Abstract [en]

    Eleven geographically and hydrologically diverse sediment samples were collected from major rivers of China and determined for the surface properties. The results indicate the sediments have a large variation in surface area (6.9-16.0 m(2)/g of SSA(N2), 35.6-73.2 m(2)/g Of SSA(CPB), surface site density (10.3-149.8 mu mol/g) and surface acidity constants (1.56-2.50 of pK(s.a1)(int), and 3.75-5.58 of pK(s.a2)(int)) but a small difference in PZSE (3.0-4.0). Within the pH range 3.0-9.0, all sediments present negative surface charges. Their surface charge distribution curves with pH extend between these of SiO2, montmorillonite. kaolinite, alpha-MnO2, calcite and gamma-Al2O3;. Correlation analysis reveals that surface area and surface site density of the sediments are correlated strongly with reactive and amorphous iron oxides, total aluminum, clay and total organic carbon, while surface acidity constants, PZSE and the permanent structural charge only show a weak correlation with total aluminum in the sediments.

  • 556.
    Wang, Feiyue
    et al.
    Peking University.
    Chen, Jingsheng
    Peking University.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Modeling Sorption of Trace Metals on Natural Sediments by Surface Complexation Model1997In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 31, no 2, p. 448-453Article in journal (Refereed)
    Abstract [en]

    The potential possibility of the surface complexation models to describe the sorption of trace metals on natural sediments has been suggested since the late 1980s, which should be of natural importance to predict the bioavailability of trace metals in aquatic sediments. This possibility was tested based on 11 geographically and hydrologically diverse natural aquatic sediment samples. The sorption of Cu(II), Zn(II), Pb(II), and Cd(II) on these sediments was studied by both sorption isotherm and pH-edge sorption experiments. The experimental sorption data were fit well by the surface complexation model (the double-layer model). The linear free energy relationship (LFER) between the surface complexation constants (Ks) of trace metals on the sediments and the corresponding first-hydrolysis constants (*K1) was observed, which could be expressed as log Ks = a log *K1 + b. The slope of the linear regression, a, was dependent on the sediment composition: a = 0.19TOC - 0.09Oxides + 1.31 (n = 11), where TOC (%) is the total organic carbon and Oxides (%) include reactive iron oxide, amorphous iron oxide, cryptocrystalline manganese oxide, and aluminum oxide. The results strongly suggest that the sorption of trace metals on natural sediments could be described reasonably by the surface complexation model and predicted potentially from the relationships between Ks and *K1 and the sediment composition.

  • 557.
    Wang, Y.L.
    et al.
    Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology.
    Sarman, Sten
    Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology.
    Kloo, Lars
    Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Glavatskih, Sergei
    System and Component Design, Department of Machine Design, KTH Royal Institute of Technology.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Solvation structures of water in trihexyltetradecylphosphonium-orthoborate ionic liquids2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, no 6, article id 064507Article in journal (Refereed)
    Abstract [en]

    Atomistic molecular dynamics simulations have been performed to investigate effective interactions of isolated water molecules dispersed in trihexyltetradecylphosphonium-orthoborate ionic liquids (ILs). The intrinsic free energy changes in solvating one water molecule from gas phase into bulk IL matrices were estimated as a function of temperature, and thereafter, the calculations of potential of mean force between two dispersed water molecules within different IL matrices were performed using umbrella sampling simulations. The systematic analyses of local ionic microstructures, orientational preferences, probability and spatial distributions of dispersed water molecules around neighboring ionic species indicate their preferential coordinations to central polar segments in orthoborate anions. The effective interactions between two dispersed water molecules are partially or totally screened as their separation distance increases due to interference of ionic species in between. These computational results connect microscopic anionic structures with macroscopically and experimentally observed difficulty in completely removing water from synthesized IL samples and suggest that the introduction of hydrophobic groups to central polar segments and the formation of conjugated ionic structures in orthoborate anions can effectively reduce residual water content in the corresponding IL samples

  • 558.
    Wang, Yonglei
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Sarman, Sten S.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Glavatskih, Sergei
    System and Component Design, KTH, Royal Institute of Technology , Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden, Department of Physics, Warwick University, Coventry.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rutland, Mark W.
    Surface and Corrosion Science, School of Chemical Science and Engineering, KTH – Royal Institute of Technology, Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Atomistic insight into tetraalkylphosphonium-bis(oxalato)borate ionic liquid/water mixtures: I. Local microscopic structure2015In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 119, no 16, p. 5251-5264Article in journal (Refereed)
    Abstract [en]

    Atomistic simulations have been performed to investigate the microscopic structural organization of aqueous solutions of trihexyltetradecylphosphonium bis(oxalato)borate ([P6,6,6,14][BOB]) ionic liquid (IL). The evolution of the microscopic liquid structure and the local ionic organization of IL/water mixtures as a function of the water concentration is visualized and systematically analyzed via radial and spatial distribution functions, coordination numbers, hydrogen bond network, and water clustering analysis. The microscopic liquid structure in neat IL is characterized by a connected apolar network composed of the alkyl chains of [P6,6,6,14] cations and isolated polar domains consisting of the central segments of [P6,6,6,14] cations and [BOB] anions, and the corresponding local ionic environment is described by direct contact ion pairs. In IL/water mixtures with lower water mole fractions, the added water molecules are dispersed and embedded in cavities between neighboring ionic species and the local ionic structure is characterized by solvent-shared ion pairs through cation-water-anion triple complexes. With a gradual increase in the water concentration in IL/water mixtures, the added water molecules tend to aggregate and form small clusters, intermediate chain-like structures, large aggregates, and eventually a water network in water concentrated simulation systems. A further progressive dilution of IL/water mixtures leads to the formation of self-organized micelle-like aggregates characterized by a hydrophobic core and hydrophilic shell consisting of the central polar segments in [P6,6,6,14] cations and [BOB] anions in a highly branched water network. The striking structural evolution of the [P6,6,6,14][BOB] IL/water mixtures is rationalized by the competition between favorable hydrogen bonded interactions and strong electrostatic interactions between the polar segments in ionic species and the dispersion interactions between the hydrophobic alkyl chains in [P6,6,6,14] cations

  • 559.
    Wang, Yong-Lei
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Glavatskih, Sergei
    System and Component Design, KTH, Royal Institute of Technology.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Atomistic insight into orthoborate-based ionic liquids: force field development and evaluation2014In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 29, p. 8711-8723Article in journal (Refereed)
    Abstract [en]

    We have developed an all-atomistic force field for a new class of halogen-free chelated orthoboratephosphonium ionic liquids. The force field is based on an AMBER framework with determination of force field parameters for phosphorus and boron atoms, as well as refinement of several available parameters. The bond and angle force constants were adjusted to fit vibration frequency data derived from both experimental measurements and ab initio calculations. The force field parameters for several dihedral angles were obtained by fitting torsion energy profiles deduced from ab initio calculations. To validate the proposed force field parameters, atomistic simulations were performed for 12 ionic liquids consisting of tetraalkylphosphonium cations and chelated orthoborate anions. The predicted densities for neat ionic liquids and the [P6,6,6,14][BOB] sample, with a water content of approximately 2.3−2.5 wt %, are in excellent agreement with available experimental data. The potential energy components of 12 ionic liquids were discussed in detail. The radial distribution functions and spatial distribution functions were analyzed and visualized to probe the microscopic ionic structures of these ionic liquids. There are mainly four high-probability regions of chelated orthoborate anions distributed around tetraalkylphosphonium cations in the first solvation shell, and such probability distribution functions are strongly influenced by the size of anions.

  • 560.
    Wang, Yonglei
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Shimpi, Manishkumar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sarman, Sten S.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Glavatskih, Sergei
    System and Component Design, KTH, Royal Institute of Technology , Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden, Department of Physics, Warwick University, Coventry.
    Kloo, Lars
    Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Atomistic insight into tetraalkylphosphonium-bis(oxalato)borate ionic liquid/water mixtures: 2. Volumetric and Dynamic Properties2016In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 120, no 30, p. 7446-7455Article in journal (Refereed)
    Abstract [en]

    Atomistic simulations have been performed to investigate the microscopic structural organization of aqueous solutions of trihexyltetradecylphosphonium bis(oxalato)borate ([P6,6,6,14][BOB]) ionic liquid (IL). The evolution of the microscopic liquid structure and the local ionic organization of IL/water mixtures as a function of the water concentration is visualized and systematically analyzed via radial and spatial distribution functions, coordination numbers, hydrogen bond network, and water clustering analysis. The microscopic liquid structure in neat IL is characterized by a connected apolar network composed of the alkyl chains of [P6,6,6,14] cations and isolated polar domains consisting of the central segments of [P6,6,6,14] cations and [BOB] anions, and the corresponding local ionic environment is described by direct contact ion pairs. In IL/water mixtures with lower water mole fractions, the added water molecules are dispersed and embedded in cavities between neighboring ionic species and the local ionic structure is characterized by solvent-shared ion pairs through cation-water-anion triple complexes. With a gradual increase in the water concentration in IL/water mixtures, the added water molecules tend to aggregate and form small clusters, intermediate chain-like structures, large aggregates, and eventually a water network in water concentrated simulation systems. A further progressive dilution of IL/water mixtures leads to the formation of self-organized micelle-like aggregates characterized by a hydrophobic core and hydrophilic shell consisting of the central polar segments in [P6,6,6,14] cations and [BOB] anions in a highly branched water network. The striking structural evolution of the [P6,6,6,14][BOB] IL/water mixtures is rationalized by the competition between favorable hydrogen bonded interactions and strong electrostatic interactions between the polar segments in ionic species and the dispersion interactions between the hydrophobic alkyl chains in [P6,6,6,14] cations

  • 561.
    Wang, Zeng
    et al.
    Luleå tekniska universitet.
    Lidström-Larsson, Margareta
    Grahn, Mattias
    Holmgren, Allan
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Zeolite coated ATR crystals for new applications in FTIR-ATR spectroscopy2004In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 24, p. 2888-2889Article in journal (Refereed)
  • 562.
    Wang, Zheng
    et al.
    Luleå tekniska universitet.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lidström-Larsson, Margareta
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Sterte, Johan
    Zeolite coated ATR crystal probes2006In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 115, no 2, p. 685-690Article in journal (Refereed)
    Abstract [en]

    Thin and well-defined MFI type molecular sieve films were grown on a range of ATR crystals by employing a seeding method. The type of ATR crystal does not influence film morphology. FTIR spectroscopy was used to evaluate the coated ATR crystals as sensor probes. These novel sensor probes could be used to detect low concentrations of organic molecules in a gas flow.

  • 563.
    Wang, Zhou
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Temperature dependent changes of physicochemical and tribological properties of NBR elastomer upon ageing in hexadecane and DGDE2012In: 15th Nordic Symposium on Tribology - NordTrib 2012: 12 - 15 June 2012 - Trondheim, Norway, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2012Conference paper (Refereed)
    Abstract [en]

    Acrylonitrile-butadiene rubber (NBR) elastomers are widely used in seal and tire industries. Physiochemical, surface and tribological properties of NBR exposed to a lubricant in a sealed mechanical contact may gradually change, in particular, at elevated temperatures. In this study, industrial-grade NBR elastomers were aged in two model non-additivated base oils, namely non-polar hexadecane (HEX) and polar Diethylene Glycol Dibutyl Ether (DGDE) at both ambient (298 K) and elevated (398 K) temperatures from 1 to 168 hours. Mass changes of NBR before and after ageing indicated that NBR had distinct ageing dynamics in different model base oils and at different temperatures. For NBR aged in nonpolar HEX, the rate of weight loss of the rubber was larger at 398 K compared to that at 298 K. On the contrary, distinct weight-gaining (swelling) dynamics were observed for NBR aged in polar DGDE at 298 and 398 K. Based on Fourier Transform Infrared (FTIR), liquid and solid-state Nuclear Magnetic Resonance (NMR) spectroscopy and Energy Dispersive Spectroscopy (EDS) analysis it was found that aldehydes and sulfur- and zinc-containing compounds were leached out from NBR aged in both HEX and DGDE. The results of tribological studies showed that the non-aged NBR has a good wear-resistance. NBR samples had a very similar surface topography before and after tribo-tests. However, the worn surfaces of NBR samples were characterized by fine scoring (abrasion) marks after ageing in both model base oils. This has been attributed to changes in the steel-rubber contact environment during the sliding process and degradation of mechanical properties of NBR after ageing. For one NBR sample (after ageing in HEX at 398 K) very stable friction in the steel-rubber contact was observed.

  • 564.
    Wang, Zhou
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Temperature-dependent changes of physicochemical and tribological properties of acrylonitrile-butadiene rubber elastomer upon ageing in hexadecane and diethylene glycol dibutyl ether2013In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 227, no 8, p. 826-836Article in journal (Refereed)
    Abstract [en]

    Acrylonitrile-butadiene rubber elastomers are widely used in seal and tire industries. Physiochemical, surface and tribological properties of acrylonitrile-butadiene rubber exposed to a lubricant in a sealed mechanical contact may gradually change, in particular, at elevated temperatures. In this study, industrial-grade acrylonitrile-butadiene rubber elastomers were aged in two model non-additivated base oils, namely non-polar hexadecane and polar diethylene glycol dibutyl ether at both ambient (298 K) and elevated (398 K) temperatures from 1 to 168 h. Mass changes of acrylonitrile-butadiene rubber before and after ageing indicated that acrylonitrile-butadiene rubber had distinct ageing dynamics in different model base oils and at different temperatures. For acrylonitrile-butadiene rubber aged in nonpolar hexadecane, the rate of weight loss of the rubber was larger at 398 K compared to that at 298 K. On the contrary, distinct weight-gaining (swelling) dynamics were observed for acrylonitrile-butadiene rubber aged in polar diethylene glycol dibutyl ether at 298 and 398 K. Based on Fourier transform infrared spectroscopy, liquid and solid-state nuclear magnetic resonance spectroscopy and energy dispersive spectroscopy analyses, it was found that aldehydes and sulfur- and zinc-containing compounds were leached out from acrylonitrile-butadiene rubber aged in both hexadecane and diethylene glycol dibutyl ether. The results of tribological studies showed that the non-aged acrylonitrile-butadiene rubber has a good wear-resistance. Acrylonitrile-butadiene rubber samples had a very similar surface topography before and after tribo-tests. However, the worn surfaces of acrylonitrile-butadiene rubber samples were characterized by fine scoring (abrasion) marks after ageing in both model base oils. This has been attributed to changes in the steel–rubber contact environment during the sliding process and degradation of mechanical properties of acrylonitrile-butadiene rubber after ageing. For one acrylonitrile-butadiene rubber sample (after ageing in hexadecane at 398 K), very stable friction in the steel–rubber contact was observed.

  • 565.
    Wei, Juan
    et al.
    Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Iuga, Dinu
    Department of Physics, Warwick University, Coventry, Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Lam, Pui Yiu
    Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Barrow, Mark P.
    Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Dupree, Ray
    University of Warwick, Department of Physics, Warwick University, Coventry, Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Brown, Steven P.
    Department of Physics, Warwick University, Coventry, Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    O'Connor, Peter B.
    Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Amyloid Hydrogen Bonding Polymorphism Evaluated by 15N{17O}REAPDOR Solid-State NMR and Ultra-High Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry2016In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 55, no 14, p. 2065-2068Article in journal (Refereed)
    Abstract [en]

    A combined approach, using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and solid-state NMR (Nuclear Magnetic Resonance), shows a high degree of polymorphism exhibited by Aβ species in forming hydrogen-bonded networks. Two Alzheimer’s Aβ peptides, Ac-Aβ16–22-NH2 and Aβ11–25, selectively labeled with 17O and 15N at specific amino acid residues were investigated. The total amount of peptides labeled with 17O as measured by FTICR-MS enabled the interpretation of dephasing observed in 15N{17O}REAPDOR solid-state NMR experiments. Specifically, about one-third of the Aβ peptides were found to be involved in the formation of a specific >C═17O···H–15N hydrogen bond with their neighbor peptide molecules, and we hypothesize that the rest of the molecules undergo ± n off-registry shifts in their hydrogen bonding networks.

  • 566.
    Westerstrand, Magnus
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    The impact of process water on the surface properties of magnetite as measured by the zeta potential and through leaching experiments2012In: Minerals & metallurgical processing, ISSN 0747-9182, Vol. 29, no 4, p. 199-206Article in journal (Refereed)
  • 567.
    Widerlund, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Roos, Per
    Lund University.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ingri, Johan
    Holmström, Henning
    Envipro Miljöteknik AB, Linköping.
    Early diagenesis and isotopic composition of lead in Lake Laisan, northern Sweden2002In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 189, no 3-4, p. 183-197Article in journal (Refereed)
    Abstract [en]

    Water column (dissolved/suspended phase, sediment traps) and sediment data (pore-water, solid-phase sediment) were combined with stable Pb and 210Pb isotope data to trace the early diagenetic behaviour and geochemical cycling of Pb in Lake Laisan, a lake which has received large quantities of anthropogenic Pb since the early 1940s. Early diagenetic remobilisation of Pb is indicated by a subsurface pore-water Pb maximum (120 μg l-1) in the oxic surface layer of the sediment, where the solid-phase Pb concentration is 3400-4600 μg g-1. The remobilisation of Pb appears to be caused by a pH-controlled desorption of Pb from solid-phase sediment, which is consistent with a model describing surface complexation of Pb(II) on hydrous goethite surfaces. The diffusive Pb flux from the subsurface pore-water maximum towards the sediment surface (36 μg cm-2 year-1) exceeds the depositional Pb flux (8.6 μg cm-2 year-1) by approximately a factor of four, indicating that Pb is highly mobile in the sediment. Stable Pb isotope data and a mass balance calculation suggest that Pb diffusing upwards is, to a large extent, trapped in the surface sediment. Lead that may diffuse into the slightly alkaline lake water appears to be efficiently sorbed to suspended particulate matter, resulting in low dissolved Pb concentrations in the water column (0.040-0.046 μg l-1). Sorption of Pb to suspended particulate matter is consistent with the elevated suspended particulate Pb concentrations in the hypolimnion (3800-4000 μg g-1), and the fact that the stable Pb isotopic compositions of suspended matter and pore-water are similar.

  • 568.
    Wu, Liu-Ming
    Luleå tekniska universitet.
    Acid-base and complexation properties of hydrous flourapatite surfaces1992Licentiate thesis, comprehensive summary (Other academic)
  • 569. Wu, Liuming
    Surface complexation at calcium mineral-water interfaces1994Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Surface reactions occurring at solid-water interfaces in calcium mineral-ligands systems have been studied. Both hydrous apatite and fluorite surfaces show clear amphoteric properties. An ion exchange process between lattice ions of F- on fluorite and OH- ions in bulk solution is discovered. The surface adsorption of Alizarin Red S and sodium oleate are determined. Surface chemical reaction models are established based on acidbase potentiometric titrations, solubility, adsorption and zeta-potential measurements in 0. 1 mol dm-3 ionic media at 25'C. Experimental data are evaluated using the computer program FITEQL assuming a constance capacitance model for the electric double layer. Surface complexes identities are obtained from FT-IR, FT-Raman, and UV/visible spectroscopy studies. A series of surface equilibrium constants in the system are presented. The correlation between surface complex formation and mineral flotation is discussed.

  • 570.
    Wu, Liuming
    et al.
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Acid-base and complexation properties of hydrous fluorapatite surfaces1993In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 205, no 1, p. 125-GEOCArticle in journal (Other academic)
  • 571.
    Wu, Liuming
    et al.
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Surface complexation at hydrous fluorapatite1993In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 55, no 4, p. 336-346Article in journal (Refereed)
    Abstract [en]

    The adsorption of H+, OH- and ARS (Alizarin Red S) onto hydrous fluorapatite surfaces and Ca2+-ARS complexation in solution were studied by means of combined potentiometric and spectrophotometric titrations, as well as zeta potential and FT-IR measurements. Corresponding equilibrium constants of surface and solution reactions are determined. The application in flotation processes is discussed.

  • 572.
    Wu, Liuming
    et al.
    Luleå University of Technology.
    Forsling, Willis
    Surface complexation of calcium minerals in aqueous solution III. ion exchange and acid-base properties of hydrous fluorite surfaces1995In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 174, no 1, p. 178-184Article in journal (Refereed)
    Abstract [en]

    The acid-base properties of hydrous fluorite surfaces and ion exchange reactions between surface lattice ions of F- and OH- ions in bulk solution have been investigated. The measurements were performed as potentiometric titrations with varied solid concentrations in 0.1 mol dm-3 KCl medium at 25.0°C using a glass electrode for -log[H+] and a fluoride ion selective electrode for -log[F-]. The experimental data could be explained by a model that assumes the surface equilibria(≡CaOH12≡F ≡CnOH≡F + H+ logβs-1100 (int) = -9.5 ± 0.1≡CaOH+2≡F + H+ ≡CaOH+2≡FH logβs-1100 (int) = 4.4 ± 0.1≡CaOH+2≡F + H+ + H2O+ ≡CaOH≡OH + 2H+ + F- logβs-210-1(int) = -20.3 ± 0.1The equilibrium constants were evaluated using the computer program FITEQL assuming a constant capacitance model for the electric double layer.

  • 573.
    Wu, Liuming
    et al.
    Luleå University of Technology.
    Forsling, Willis
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Surface complexation of calcium minerals in aqueous solution: 4. The complexation of alizarin red S at fluorite-water interfaces2000In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 224, no 2, p. 211-218Article in journal (Refereed)
    Abstract [en]

    The complexation of Alizarin Red S (ARS) at the surface of hydrous fluorite particles has been investigated by means of potentiometric titrations, adsorption experiments, and ζ-potential measurements in 0.1 mol dm-3 KCl ionic medium at 25.0°C, as well as by UV/visible specular reflectance, FT-IR, and FT-Raman spectroscopy. Chemical reaction models describing the equilibria of ARS (HA2-) at the aqueous fluorite surfaces (≡X) have been established as follows:[formula] Experimental data were evaluated using the computer program FITEQL on the basis of a constant capacitance model for the electric double layer. Surface complexation mechanisms involving the R-SO3-, R-β-OH, and R-α-OH active groups of the ARS molecule are proposed to describe coordination to the fluorite surface.

  • 574.
    Wu, Liuming
    et al.
    Luleå tekniska universitet.
    Forsling, Willis
    Schindler, Paul W.
    University of Bern.
    Surface complexation of calcium minerals in aqueous solution: 1. Surface protonation at fluorapatite-water interfaces1991In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 147, no 1, p. 178-185Article in journal (Refereed)
    Abstract [en]

    The amphoteric properties of hydrous fluorapatite surfaces have been investigated. The measurements were performed as potentiometric titrations in 0.1M NaCl medium at 25°C using a glass electrode. The experimental data could be explained by a model that assumes the surface equilibria equivalent P-O- + H+ = equivalent P-OH log β101s(int.) = 6.6 ± 0.1 (3σ) equivalent Ca-OH2+ - H+ = equivalent Ca-OH log β-110s(int.) = -9.7 ± 0.1 (3σ). The equilibrium constants were evaluated using the computer program FITEQL by Westall (Report 82-01, Department of Chemistry. Oregon State University, Corvallis, 1982), assuming a constant capacitance model for the electric double layer. The acidity constants result in a value of log [H+]pzc = -8.15, which shifts to log [H+]pzc = -7.13 upon exposure to atmospheric carbon dioxide

  • 575.
    Wu, Liuming
    et al.
    Luleå tekniska universitet.
    Sun, Zhong-Xi
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tang, Hongxiao
    A flexible method of carbonate determination using an automatic gas analyzer equipped with an FTIR photoacoustic measurement chamber1999In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 124, no 3, p. 361-365Article in journal (Refereed)
  • 576. Wu, Luiming
    et al.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Potentiometric and spectrophotometric study of calcuim and alizarin red-S complexation1992In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 46, no 5, p. 418-422Article in journal (Refereed)
    Abstract [en]

    Equilibria in the system H+, Ca2+ and Alizarin Red S have been studied by means of potentiometric (glass electrode) and spectrophotometric measurements in a 0.1 M NaCl medium at 25-degrees-C. Calcium complexation is characterized by the formation of ternary species according to the reaction: pH+ + qCa2+ + rHA2- half-arrow-right-over-half-arrow-left H(p)Ca(q)(HA)r(p+2q-2r) Equilibrium constants were evaluated within the range 3.3 less-than-or-equal-to -log[H] less-than-or-equal-to 10.3 and the wavelength interval 300 less-than-or-equal-to lambda less-than-or-equal-to 700 nm with the following results: log-beta(012) = 8.04 +/- 0.04 (pot.); log-beta(012) = 8.20 +/- 0.12 (spectr.); log-beta(-111) = -3.72 +/- 0.12 (pot.); log-beta(-111) -3.74 +/- 0.15 (spectr.); log-beta(-212) = 10.11 +/- 0.20 (pot.).All errors reported are 3-sigma (log-beta(pqr)). The protonation constants for Alizarin Red S were also determined. Data were analysed using the least-squares computer programs LETAGROPVRID (ETITR and SPEFO).

  • 577.
    Yang, Xiaofang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Interaction of magnetite with soluble silicates and bentonite: implications for wet agglomeration of magnetite concentrate2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Iron ore green pellets are produced by agglomeration of moist magnetite concentrates. The quality of green pellets is essential for the transportability and metallurgical benefits of the final product. The agglomeration behavior of magnetite concentrate particles is strongly influenced by its surface properties which are affected by the interactions with flotation reagents (i.e. water glass and collector) and species in process water. However, the mechanisms of these interactions and the influence on the following agglomeration process are still not completely understood. The present work has been focused on the interaction of magnetite with water glass (sodium silicate) and bentonite clay (silicate mineral) aiming for better fundamental knowledge of the magnetite surface properties in order to improve the agglomeration behavior of the magnetite concentrate. Water glass is used as a dispersing or depressing agent in flotation of magnetite. The former function is to improve the separation of mineral particles in the pulp, while the latter function is to protect the magnetite surfaces from attachment of the collector which is known to cause problems in the subsequent agglomeration process. Sodium activated bentonite clay is commonly used as an external binder in iron ore agglomeration owing to its swelling properties. The particle interaction between magnetite and bentonite platelets, which is expected to be affected by the surface properties of magnetite, is of importance for the wet and dry strength of the pellets. Sorption mechanisms of sodium silicate onto the magnetite surface at the molecular scale were studied at various pH and silicate concentrations using in-situ ATR-FTIR spectroscopy. Silicate concentration, pH, and conditioning time are the most important factors for silicate sorption and speciation at the surface of magnetite. A maximum sorption was observed in the pH range 8.5 - 9.5. Oligomeric or polymeric silicate species are formed and dominate at high surface loading of silicate. These oligomeric or polymerized species have stronger affinity for the magnetite as compared to monomeric species, resulting in a slower and less extent of desorption and implying a higher depressing efficiency in flotation. Sodium silicate makes the magnetite surface more negatively charged, while adsorbed calcium ions on the surface compensate this negative surface charge. Calcium ions promote the oligomerization of silicate on the surface of magnetite at high pH (pH > 10) possibly due to the increased local silicate concentration by additional sorption of silicate on adsorbed calcium at the surface. The competitive sorption between sodium silicate and collector (sodium oleate) for the magnetite surface was studied using the in situ ATR-FTIR technique. It was confirmed that oleate could still be adsorbed onto a sodium silicate modified magnetite surface but the amount of adsorbed oleate decreased with increasing concentration of silicate (0.1 - 5 mmol•L-1). This depression effect became much more significant when the concentration of sodium silicate was higher than 0.4 mmol•L-1 above which more dimers or oligomeric silicate species were formed at the magnetite surface. However, when the magnetite surface was pre-treated firstly with sodium oleate, the addition of sodium silicate only slightly reduced the adsorption of oleate. Meanwhile, the sorption of silicate anions was depressed and resulted in a lower degree of oligomerization or polymerization at high silicate dosage. Sessile drop method and Wilhelmy method were used to measure the water contact angle of synthesized magnetite, and Washburn method was used for contact angle measurements of magnetite concentrate. The synthesized magnetite has lower contact angle compared to mineral particles. Nevertheless, similar tendency of changes in wettability upon interaction with calcium, sodium silicate and collector was observed for synthesized magnetite and magnetite concentrate. Sorption of calcium and silicate increased the wettability of the surface, while adsorption of collector made the surface more hydrophobic. Further exposure of the collector modified magnetite surface to sodium silicate could restore the surface wettability. Therefore, an interesting implication for magnetite flotation and agglomeration is that the decreased hydrophilicity of magnetite by attachment of collector could be improved by further chemical conditioning with sodium silicate (water glass). The interaction of bentonite with magnetite was investigated by means of settling of bentonite platelets onto a layer of magnetite nano-particles. The magnetite layer was deposited on a horizontal ZnSe crystal to be able to examine the orientation of the platelets by polarized ATR-FTIR. The measured dichroic ratio of the bentonite platelets decreased with time in wet film and approached a minimum value in the dry bentonite film regardless of the pH of the bentonite suspension. This tendency is in good agreement with the results observed for settling on bare crystal, indicating a more ordered structure of platelets upon evaporation of water. The bentonite platelets in dry film were evidently tending to orient with their basal plane surfaces to the magnetite layer, whilst wet films adopted a much more disordered structure. Similarly, a rather disordered wet bentonite film was formed on the calcium and sodium silicate modified magnetite layer. These bentonite platelets became more ordered when the wet film was dried.

  • 578.
    Yang, Xiaofang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Interactions between iron oxides and silicates2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main objective of this Licentiate thesis was to acquire a better understanding of the mechanisms involved in the sorption of dissolved silicate from aqueous solutions onto iron oxide surfaces by using Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and subsequently to develop a method to monitor the orientation of bentonite platelets settling onto the bare iron oxide using polarized ATR-FTIR technique. The infrared spectra show that the silicate concentration and pH both determine the species of sorbed silicate on the iron oxide surfaces. In the last part of this thesis, the orientation of bentonite platelets on a ZnSe ATR crystal as well as on a layer of magnetite particles deposited on the crystal was analyzed with polarized horizontal ATR-FTIR Spectroscopy.The iron oxide layer contributed to an increased order of the settled bentonite platelets.

  • 579. Yang, Xiaofang
    et al.
    Dongsheng, Wang
    Chinese Academy of Sciences, Research Center Ecoenvironmental Science, Beijing.
    Zhongxi, Sun
    Jinan University, Department of Chemistry & Chemical Engineering, Jinan.
    Huijuan, Liu
    Chinese Academy of Sciences, Research Center Ecoenvironmental Science, Beijing.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Application of ATR-FTIR spectroscopy in the study of adsorption on environmental micro-interfaces2010In: Huaxue jinzhan, ISSN 1005-281X, Vol. 22, no 6, p. 1185-1194Article in journal (Refereed)
    Abstract [en]

    Interfacial adsorption process is the initial step or key step for most of environmental micro-interface reactions. The online study of environmental micro-interfacial adsorption by in situ research methods provides direct information about interface reactions and reliable evidence for the detection of reaction mechanisms which are of great importance to understand the rule of transformation and distribution of pollutants in the environment. Because of its unique sampling principle, convenient sample pre-treatment and wide applicability, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) is becoming a powerful tool for investigating the interface reactions. Based on a brief introduction of the working principle of ATR-FTIR, the application of this technique in the investigation of adsorption on environmental interfaces, especially mineral-water interfaces, is summarized. Furthermore, the perspective of this method is discussed as well.

  • 580. Yang, Xiaofang
    et al.
    Roonasi, Payman
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A study of sodium silicate in aqueous solution and sorbed by synthetic magnetite using in situ ATR-FTIR spectroscopy2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 328, no 1, p. 41-47Article in journal (Refereed)
    Abstract [en]

    The sorption of sodium silicate by synthetic magnetite (Fe3O4) at different pH conditions (pH 7-11) and initial silicate concentrations (1×10-3 and 10 x 10-3 mol L-1) was studied using in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The analysis of infrared spectra of sodium silicate in solution as well as adsorbed on magnetite nano-particles clearly showed the evolution of different silicate species depending on pH and silica concentration. The silicate concentration studied (10 x 10-3 mol L-1 ) contained polymeric or condensed silicate species at lower pH as well as monomers at high pH, as evident from infrared spectra. Condensation of monomers resulted in an increased intensity of absorptions in the high frequency part (>1050 cm-1) of the spectral region, which contains information about both silicate in solution and sorbed silicate viz. 1300 cm-1-850 cm-1. In the pH range studied, infrared spectra of sorbed silicate and sorbed silicate during desorption both indicated the presence of different types of surface complexes at the magnetite surface. The sorption mechanism proposed is in accordance with a ligand exchange reaction where both monodentate and bidentate complexes could exist at low surface loading level, the relative proportion of the complexes being due to both pH and concentration in solution. Oligomerization occurred on the magnetite surface at higher surface loading.

  • 581.
    Yang, Xiaofang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Roonasi, Payman
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Jolsterå, Rickard
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kinetics of silicate sorption on magnetite and maghemite: an in-situ ATR-FTIR study2008Conference paper (Other academic)
  • 582. Yang, Xiaofang
    et al.
    Roonasi, Payman
    Jolsterå, Rickard
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kinetics of silicate sorption on magnetite and maghemite: an in-situ ATR-FTIR study2009In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 343, no 1-3, p. 24-29Article in journal (Refereed)
    Abstract [en]

    Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to monitor the in situ sorption of sodium metasilicate from aqueous solution onto synthesized magnetite and maghemite particles in the pH range 10.8-7.0 using silicate concentrations between 0.1 mM and 5 mM. The spectral data showed that both pH and silicate concentration had great influence on the interfacial reaction between soluble silicate and the iron oxide surfaces, regarding the amount adsorbed per unit mass of iron oxide and the surface species formed. A pH dependent sorption of silicate on iron oxides was observed, implying that a maximum sorption took place in the pH range of 9.5 - 7.0. All experiments showed a fast initial increase in the absorption intensity followed by a slower sorption stage which was strongly dependent on the concentration of silicate in solution and the pH value. The amount of sorption onto magnetite was 3 to 5 times larger than onto maghemite, but there was no significant difference in the line shape of corresponding absorption bands. At pH 8.5 and low concentration (≤ 0.1 mM), the silicate monomers dominate in solution and on the iron oxide surface also monomeric species were dominating as evident from the infrared band at 950 cm-1. However, at higher concentration (0.4-5.0 mM), the dominating absorption band at about 1000 cm-1 shifted to higher frequency during the sorption indicating that oligomeric surface silicate species were formed on the iron oxide surface. Desorption of silicate from the surface of the iron oxides was easier to accomplish at low silicate concentration, whilst the highest concentration showed a comparatively low relative amount of desorbed silicate, suggesting that polymerized species had a stronger affinity for the iron oxide surface as compared to monomeric species.

  • 583.
    Yang, Xiaofang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Sun, Zhongxi
    Department of Chemistry and Chemical Engineering, Jinan University.
    Wang, Dongsheng
    Research Centre for Eco-Environmental Sciences, Chinese Academy of Science, Beijing.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Surface acid-base properties and hydration/dehydration mechanisms of aluminum (hydr)oxides2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 308, no 2, p. 395-404Article in journal (Refereed)
    Abstract [en]

    In this paper, surface physiochemical properties of three typical aluminas, γ-Al(OH)3, γ-Al2O3, and α-Al2O3, were investigated by means of XRD, SEM, TEM, BET surface area, TG/DTA, and potentiometric titration techniques. Based on the titration data, surface protonation and deprotonation constants were determined using the constant capacitance model (CCM). The emphasis of this research was laid on the comparison of the crystal structure, surface hydration/dehydration and acid-base properties of these three typical alumina minerals. The calculation results revealed that the surface acidity of the aluminas is in the order of α-Al2O3>γ-Al(OH)3>γ-Al2O3 after being hydrated for 1 h. The correlation between the hydration/dehydration mechanisms of alumina and its acid/base properties is discussed.

  • 584.
    Yin, Y. G.
    et al.
    University of Shantou.
    Forsling, Willis
    Bodström, D.
    Umeå university.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lindberg, Mats
    Ivanov, Alexander V.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Polymeric structure and solid P-31, Cd-113 NMR spectra of cadmium(11) dialkyldithiophosphate (alkyl = n-butyl and i-butyl)2003In: Chinese Chemical Letters, ISSN 1001-8417, E-ISSN 1878-5964, Vol. 14, no 2, p. 188-190Article in journal (Refereed)
    Abstract [en]

    Two polymeric complexes, [Cd(BTP)(2)](n) and [Cd(i-BTP)(2)](n) 2, were prepared and investigated by solid P-31 and Cd-113 NMR spectroscopies. The crystal structure of 2 was determined by X-ray diffraction.

  • 585.
    Yin, Y-G
    et al.
    Department of Chemistry, Faculty of Science, Shantou University, Shantou, Guangdong.
    Forsling, Willis
    Bodström, D.
    Department of Chemistry, Umeå University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lindberg, Mats
    Ivanov, Alexander V.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Polymeric structure and solid NMR spectra of cadmuim (II) dialkyldithiophosphates (alkyl = propyl, butyl, isopropyl and isobutyl)2003In: Chinese journal of chemistry, ISSN 1001-604X, E-ISSN 1614-7065, Vol. 21, no 3, p. 291-295Article in journal (Refereed)
    Abstract [en]

    By dropwise adding thio ligands to concentrated aqueous solutions of Cd(ClO4)26H2O, polymeric complexes, Cd(II) O,O′-dipropyl-dithiophosphate (1), O,O′-dibutyl- dithiophosphate (2), O,O′-diisopropyi-dithiophosphate (3) and O,O′-diisobutyl-dithiophosphate (4) were obtained. The structure of 4 was determined by X-ray diffraction analysis, showing that the metal ion sits in distorted tetrahedral sulphur coordination sphere and that the eight-membered bimetallic rings take the twist chair and boat conformations, alternately. Based on facts that the S(1)-Cd bond length [0.25099(12) nm] is shorter than the other S-Cd bond length [0.25399(12)-0.25701(18) nm] and that the S(1)-involving angles [113.45(4)°-118.43(5)°] are systematically larger than the normal angles of a tetrahedron, the ligands are hypothesized to be erratically functionalized to Cd(II). To certify the steric nonequivalence of ligands, the compounds were investigated by solid 13C, 31P and 113Cd NMR spectroscopy.

  • 586.
    Zaeva, Anna S.
    et al.
    Institute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences,Blagoveschensk, Amur Region, Russia.
    Ivanov, Maxim A.
    Institute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences,Blagoveschensk, Amur Region, Russia.
    Gerasimenko, Andrey V.
    Institute of Chemistry, Far Eastern Branch of the Russian Academy of Sciences,Vladivostok, Russia.
    Ivanov, Alexander V.
    Institute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences, Blagoveschensk, Amur Region, Russia.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Warwick University, Coventry, UK.
    Dialkyldithiocarbamate platinum(II) complexes of [Pt(S2CNR2)2] (R = iso-C3H7iso-C4H9): Preparation, 13C CP-MAS NMR, molecular structure, supramolecular self-assembly and thermal behaviour2020In: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 175, article id 114166Article in journal (Refereed)
    Abstract [en]

    Two new dialkyldithiocarbamato platinum(II) complexes of [Pt(S2CNR)2], R = iso-C3H7 (1) and iso-C4H9 (2), have been prepared and characterised using 13C CP-MAS NMR. The crystal and molecular structures of the isolated compounds were established by single-crystal X-ray diffraction. The unit cell of 1 contains four centrosymmetric discrete molecules of [Pt{S2CN(iso-C3H7)2}2], of which the pairs are structurally inequivalent to each other (hereafter denoted as molecules 1a and 1b). At the supramolecular level, due to numerous intermolecular C–H···S hydrogen bonds, the 1a molecules form linear polymeric ribbons, whose interaction with the 1b molecules results in a two-dimensional polymeric network. In the structure of 2, the construction of supramolecular zigzag chains by non-centrosymmetric molecules of [Pt{S2CN(iso-C4H9)2}2] is determined by intermolecular C–H···Pt anagostic interactions. The thermal behaviour of crystalline compounds 1 and 2 was studied by simultaneous thermal analysis (STA), a combination of the TG and DSC techniques, under an argon atmosphere. In both cases, platinum(II) sulphide (PtS) was identified as the main end-product upon thermal decomposition of the complexes at 600 °C.

  • 587.
    Zhang, Wei-Min
    et al.
    University of Jinan.
    Li, Hui-Min
    University of Jinan.
    Sun, Zhong-Xi
    School of Chemistry and Chemical Engineering, University of Jinan.
    Zhang, Qi
    University of Jinan.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Synthesis of mesoporous ZnS synergistically templated by butylamine and alkanols2012In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 147, no 1, p. 222-228Article in journal (Refereed)
    Abstract [en]

    Pore size and pore volume adjustable mesoporous ZnS was synthesized through a co-template method, which was achieved by the combined interaction between butylamine and some alkanols with proper lengths of the straight carbon chain. The pore size for mesoporous ZnS templated by butyl amine alone was 4.29 nm, and could be enlarged to 6.96 and 8.33 nm respectively through adding certain amounts of hexanol and octanol. Correspondingly, the pore volume also exhibited an augmentation with increasing carbon chain lengths of alkanols from C6 to C8. However, the pore size and pore volume dropped abruptly when decanol was added as the auxiliary agent. The formation of mesopores for ZnS prepared using butylamine molecules as the only templating agent is considered to be attributed to the coordination between N atoms in amines and Zn2+ ions at the surfaces of zinc suphide. The templating effect of butylamines might be improved by adding hexanols and octanols to form aggregates through solubilization to tailor the pore size and pore volume of ZnS effectively, while the function of decanols for changing the porous structure is restricted by its low solubility.

  • 588.
    Zhang, Wei-Min
    et al.
    University of Jinan.
    Liu, Jia
    University of Jinan.
    Sun, Zhong-Xi
    University of Jinan.
    Fan, Bao-Qiang
    University of Jinan.
    Yang, Zhen-Dong
    University of Jinan.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Synthesis of mesoporous silica by a surface charge reversal route2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 349, no 2, p. 473-476Article in journal (Refereed)
    Abstract [en]

    Pore size adjustable mesoporous silica was synthesized by adsorption of varying amount of sodium dodecyl benzenesulfonate at the surface of silica activated by zinc ion via a novel surface charge reversal route. The pore size and volume can be adjusted from 5.9 to 13.76 nm and 0.88 to 1.08 cm3·g-1 respectively with increasing the SDBS concentration from 0.77 to 3.08 mmol·L-1. Adsorption of Zn2+ as a function of pH and N2 adsorption/desorption isotherms demonstrated that the metal ions such as Zn2+ could be readily removed with dilute nitric acid without apparent collapse of the pore structure at the proper range of SDBS concentration.

  • 589. Zheng, Ting-Ting
    et al.
    Sun, Zhong-Xi
    Yang, Xiaofang
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sorption of phosphate onto mesoporous gamma-alumina studied with in-situ ATR-FTIR spectroscopy2012In: Chemistry Central Journal, ISSN 1752-153X, E-ISSN 1752-153X, Vol. 6Article in journal (Refereed)
  • 590.
    Zhou, Han
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Farzaneh, Amirfarrokh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Colloidal Defect-Free Silicalite-1 Single Crystals: Preparation, Structure Characterization, Adsorption, and Separation Properties for Alcohol/Water Mixtures2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 30, p. 8488-8494Article in journal (Refereed)
    Abstract [en]

    In this work, colloidal silicalite-1 single crystals are for the first time synthesized using fluoride as mineralizing agent at near neutral pH. SEM, TEM, DLS, XRD, solid-state 29Si MAS NMR, and adsorption/desorption experiments using nitrogen, water, n-butanol, and ethanol as adsorbates were used to characterize the crystals. The single crystals have a platelike habit with a length of less than 170 nm and an aspect ratio (length/width) of about 1.2, and the thickness of the crystals is less than 40 nm. Compared with silicalite-1 crystals grown using hydroxide as mineralizing agent, the amount of structural defects in the lattice is significantly reduced and the hydrophobicity is increased. Membrane separation and adsorption results show that the synthesized defect-free crystals present high selectivity to alcohols from alcohol/water mixtures. The n-butanol/water adsorption selectivities were ca. 165 and 14 for the defect-free crystals and a reference sample containing defects, respectively, illustrating the improvement in n-butanol/water selectivity by eliminating the polar silanol defects.

  • 591.
    Ziegler, Ildiko Mohammedne
    Luleå tekniska universitet.
    Adsorption of pinosylvin onto the structure of wood: mechanism and adsorption parameters2000Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Pinosylvin and polyhydroxybenzene derivatives are natural components of wood, known for their fungicidal/fungistatic properties. These components were used as adsorbates in the present investigation. Lignin and a-cellulose powder were used as model substrates in order to aquire information about the attachment of the adsorbates to the structure of wood. The adsorbate-substrate interaction was investigateded by the diffuse reflectance technique, commonly known as DRIFT. Furthermore, the adsorption of pinosylvin onto twelve different types of wood was studied, by means of the Raman microprobe technique. The effects of the solvents used, B.E.T. specific surface area, heat treatment and lignin content (as measured by the k-value), have been quantified by means of the Raman intensity ratios of characteristic peaks. The amount of solvent residue in each sample has been measured by the DRIFT technique. The morphology of the samples was investigated with the aid of scanning electron microscopy. In this licentiate work it was found that the adsorption is mainly due to the formation of hydrogen bonds. The lignin content and the composition of wood have significant effects on the surface concentration of pinosylvin adsorbed. The specific surface area of wood, as measured by the B.E.T. method, is rather low and does not diretly correlate with the amount adsorbed. The chemical changes after prolonged wood storage cause an increase in the hydrophobicity of wood, resulting in reduced adsorption efficiency.

  • 592.
    Zsirka, Balázs
    et al.
    University of Pannonia, Institute of Environmental Engineering, Hungary.
    Horváth, Erzsébet
    University of Pannonia, Institute of Environmental Engineering, Hungary.
    Szabó, Péter
    University of Pannonia, Department of Analytical Chemistry, Hungary.
    Juzsakova, Tatjána
    University of Pannonia, Institute of Environmental Engineering, Hungary.
    Szilágyi, Róbert K.
    Department of Chemistry and Biochemistry, Montana State University, USA.
    Fertig, Dávid
    University of Pannonia, Department of Analytical Chemistry, Hungary.
    Makó, Éva
    University of Pannonia, Institute of Materials Engineering, Hungary.
    Varga, Tamás
    University of Szeged, Department of Applied and Environmental Chemistry, Hungary.
    Kónya, Zoltán
    University of Szeged, Department of Applied and Environmental Chemistry, Hungary; MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Hungary .
    Kukovecz, Ákos
    University of Szeged, Department of Applied and Environmental Chemistry, Hungary; MTA-SZTE “Lendület” Porous Nanocomposites Research Group, Hungary.
    Kristóf, János
    University of Pannonia, Department of Analytical Chemistry, Hungary.
    Thin-walled nanoscrolls by multi-step intercalation from tubular halloysite-10 Å and its rearrangement upon peroxide treatment2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 399, p. 245-254Article in journal (Refereed)
    Abstract [en]

    Surface modification of the halloysite-10 Å mineral with tubular morphology can be achieved by slightly modified procedures developed for the delamination of kaolinite minerals. The resulting delaminated halloysite nanoparticles have unexpected surface/morphological properties that display, new potentials in catalyst development. In this work, a four-step intercalation/delamination procedure is described for the preparation of thin-walled nanoscrolls from the multi-layered hydrated halloysite mineral that consists of (1) intercalation of halloysite with potassium acetate, (2) replacement intercalation with ethylene glycol, (3) replacement intercalation with hexylamine, and (4) delamination with toluene. The intercalation steps were followed by X-ray diffraction, transmission electron microscopy, N2adsorption-desorption, thermogravimetry, and infrared spectroscopy. Delamination eliminated the crystalline order and the crystallite size along the ‘c’-axis, increased the specific surface area, greatly decreased the thickness of the mineral tubes to a monolayer, and shifted the pore diameter toward the micropore region. Unexpectedly, the removal of residual organics from intercalation steps adsorbed at the nanoscroll surface with a peroxide treatment resulted in partial recovery of crystallinity and increase of crystallite size along the ‘c’-crystal direction. The d(001) value showed a diffuse pattern at 7.4–7.7 Å due to the rearrangement of the thin-walled nanoscrolls toward the initial tubular morphology of the dehydrated halloysite-7 Å mineral.

  • 593.
    Österlund, Helene
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Rodushkin, Ilya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ylinenjärvi, Karin
    ALS Scandinavia AB.
    Baxter, Douglas
    Determination of total chlorine and bromine in solid wastes by sintering and inductively coupled plasma-sector field mass spectrometry2009In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 29, no 4, p. 1258-1264Article in journal (Refereed)
    Abstract [en]

    A sample preparation method based on sintering, followed by analysis by inductively coupled plasma-sector field mass spectrometry (ICP-SFMS) for the simultaneous determination of chloride and bromide in diverse and mixed solid wastes, has been evaluated. Samples and reference materials of known composition were mixed with a sintering agent containing Na2CO3 and ZnO and placed in an oven at 560 °C for 1 h. After cooling, the residues were leached with water prior to a cation-exchange assisted clean-up. Alternatively, a simple microwave-assisted digestion using only nitric acid was applied for comparison. Thereafter the samples were prepared for quantitative analysis by ICP-SFMS. The sintering method was evaluated by analysis of certified reference materials (CRMs) and by comparison with US EPA Method 5050 and ion chromatography with good agreement. Median RSDs for the sintering method were determined to 10% for both chlorine and bromine, and median recovery to 96% and 97%, respectively. Limits of detection (LODs) were 200 mg/kg for chlorine and 20 mg/kg for bromine. It was concluded that the sintering method is suitable for chlorine and bromine determination in several matrices like sewage sludge, plastics, and edible waste, as well as for waste mixtures. The sintering method was also applied for determination of other elements present in anionic forms, such as sulfur, arsenic, selenium and iodine.

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