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  • 151.
    Forsling, Willis
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sterte, Johan
    Skogsindustrin satsar på forskning och utbildning i Luleå: professur i Kemisk Apparatteknik inrättad1997In: Svensk papperstidning, Nordisk cellulosa, ISSN 1101-766X, no 9, p. 49-50Article in journal (Other academic)
  • 152.
    Forsling, Willis
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Su, Fen-Wei
    Luleå tekniska universitet.
    Sun, Zheng-Xi
    Luleå tekniska universitet.
    Samskog, Per-Olof
    LKAB utveckling.
    Forsmo, Seija
    LKAB utveckling.
    Karakterisering av magnetitytor i vattensuspension1994In: Konferens i mineralteknik: Luleå, 2-4 februari 1993 / [ed] Marianne Thomaeus; Eric Forssberg, MinFo , 1994, p. 231-244Conference paper (Other academic)
  • 153.
    Forsling, Willis
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sun, Zhong-Xi
    Luleå tekniska universitet.
    Use of surface complexation models in sulphide mineral flotation1997In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 51, no 1-4, p. 81-95Article in journal (Refereed)
    Abstract [en]

    Surface complexation modelling is introduced to investigate the surface reactions in a mixed galena and sphalerite flotation system. Computer-assisted calculations based on surface complexation modelling (SCM) are performed to obtain the mineral surface distribution of ethyl xanthate as well as carbonate and excess sulphide ions as a function of pH. The significance of pe is demonstrated by computing the mineral surface speciation in a flotation system with xanthate and excess of sulphide ions. The results are used to evaluate the influences of pH, pe, the concentration of xanthate, sulphide or carbonate ions to the mineral flotability. The flotation mechanisms in galena-sphalerite system are discussed based on SCM.

  • 154.
    Forsling, Willis
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wu, Liuming
    Luleå tekniska universitet.
    Adsorptionsmekanism för organisk tryckare på apatit och kalcit1992In: Konferens i mineralteknik: Luleå, 4-5 februari, 1992 / [ed] Börje Sköld; Eric Forssberg, MinFo , 1992, p. 65-74Conference paper (Other academic)
  • 155. Fredriksson, Andreas
    Adsorption of heptyl xanthate at the metal sulphide/aqueousinterface2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In sulphide mineral flotation a sufficient hydrophobicity of the mineral surfaces is obtained by the adsorption of collector chemicals at the metal sulphide/aqueous interface. This surface alteration is of fundamental and applied interest. In this thesis, attenuated total reflection infrared spectroscopy has been used to monitor the adsorption kinetics and the orientation of heptyl xanthate when adsorbed onto three solid surfaces - germanium, zinc sulphide and lead sulphide in-situ. The choice of using the ATR technique is because it is very suitable when working with water as solvent, and the choice of germanium as internal reflection element is because of its small penetration depth due to a high refraction index. The Chemical Bath Deposition method has been used to deposit metal sulphides onto germanium internal reflection elements. For determining the adsorption of heptyl xanthate onto lead sulphide a novel method has been tested, and verified as capable in recovering information about surface reactions at a lead sulphide/aqueous interface. In the study of surface reactions the substrate is of vast importance, implying that the chemistry of the surface has to be well characterised. This work has utilized X-ray Photoelectron spectroscopy, and ATR spectroscopy, in the characterisation of the different surfaces. The adsorption kinetics has been followed to adsorption equilibrium at different concentrations. In the case of heptyl xanthate adsorbed at the zinc sulphide/aqueous interface, an adsorption isotherm has been calculated from the equilibrium data. On the assumption that the adsorption step was rate controlling a second order rate equation was derived and adsorption rate data tested according to this equation. In addition, an orientation study of the heptyl xanthate molecule at the different interfaces was performed, which requires polarised infrared light. In the case of heptyl xanthate adorbed onto germanium, both surface excess and a degree of alignment of the alkyl chain from the surface normal has been calculated.

  • 156.
    Fredriksson, Andreas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kinetics of collector in-situ adsorption on metal sulphide surfaces studied by ATR-FTIR spectroscopy2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In sulphide mineral flotation, a sufficient hydrophobicity of the mineral surfaces is obtained by the adsorption of collector chemicals at the metal sulphide/aqueous interface. This surface alteration is of fundamental and applied interest. In this thesis, attenuated total reflection infrared spectroscopy has been used to monitor the adsorption kinetics and the orientation of heptyl xanthate when adsorbed onto three solid surfaces - germanium, zinc sulphide and lead sulphide in-situ. The Chemical Bath Deposition method has been used to deposit metal sulphides onto germanium internal reflection elements, and verified as capable in synthesizing metal sulphide surfaces for adsorption studies recovering information about surface reactions at metal sulphide/solution interfaces. In the study of surface reactions the substrate is of great importance, implying that the chemistry of the surface has to be well characterised. This work has utilized X-ray photoelectron spectroscopy in the characterisation of the different surfaces. The adsorption kinetics has been followed to monitor the adsorption equilibria at different concentrations. In the case of heptyl xanthate adsorbed at the zinc sulphide/aqueous interface, an adsorption isotherm has been calculated from the equilibrium data. On the assumption that the adsorption step was rate controlling a pseudo-first order equation was derived and adsorption rate data, in all the three studied systems, tested according to this equation. In addition, an orientation study of the heptyl xanthate molecule at the different interfaces was performed, which requires polarised infrared light. Density Functional calculations of a free heptyl xanthate molecule, and a heptyl xanthate molecule adsorbed on a pure Ge(111) were utilized to get more information about the in-situ adsorption of heptyl xanthate on a germanium surface. The important vibration bands were assigned to different vibrations, and the theoretical infrared spectra were compared with the experimentally analyzed spectra. This study shows the strengths of using advanced first-principle Density Functional Theory in the interpretation of real surface adsorption systems.

  • 157. Fredriksson, Andreas
    et al.
    Hellström, Pär
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Comparison between in situ total internal reflection vibrational spectroscopy of an adsorbed collector and spectra calculated by ab initio density functional theory methods2007In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 26, p. 9299-9304Article in journal (Refereed)
    Abstract [en]

    In this investigation, adsorbed heptyl xanthate on a Ge(111) surface was studied, as well as the free heptyl xanthate molecule, by means of first-principle density functional theory calculations. The modeled results were compared with the in situ total internal reflection vibrational spectroscopy spectra of heptyl xanthate adsorbed on a germanium internal reflection element and the transmission infrared spectrum of a heptyl xanthate ion in aqueous solution. The assignments of the vibrational frequencies were done for the adsorbed xanthate. The region between 1150 and 1000 cm(-1) seems suitable for discussing differences between an adsorbed xanthate and its corresponding ion. The modeled spectra for both the adsorbed xanthate and the xanthate ion are in good agreement with the experimentally retrieved spectra. This investigation shows the strength of using DFT calculations in the interpretation of absorption bands from molecules adsorbed at surfaces in situ.

  • 158. Fredriksson, Andreas
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    An in situ ATR-FTIR investigation of adsorption and orientation of heptyl xanthate at the lead sulphide/aqueous solution interface2007In: Proceedings of Flotation 07: Cape Town, South Africa, Nov. 6-9, 2007 / [ed] Barry Wills, Minerals Engineering International , 2007Conference paper (Refereed)
  • 159. Fredriksson, Andreas
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    An in situ ATR-FTIR investigation of adsorption and orientation of heptyl xanthate at the lead sulphide/aqueous solution interface2008In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 21, no 12-14, p. 1000-1004Article in journal (Refereed)
    Abstract [en]

    A lead sulphide film precipitated on a zinc sulphide layer of an ATR crystal has been used to study in situ surface reactions of heptyl xanthate adsorption. The lead sulphide film was made by the chemical bath deposition method and was analyzed by X-ray photoelectron spectroscopy. In turn deposited layers make it possible to study the PbS/aqueous solution interface in situ and open up interesting areas for attenuated total reflection spectroscopy. Monitoring the adsorption of heptyl xanthate from a 0.1 mM aqueous solution using the vibration band at 1200 cm-1 has shown the existence of adsorbed molecules on the lead sulphide surface as well as precipitated lead xanthate on the surface at bulk concentrations higher than 1 mM. At lower concentrations, the adsorbed species are dominant as is the precipitate at higher concentrations. The rate of adsorption is in accordance with pseudo first-order kinetics with a rate constant of 0.21 s-1. The Dichroic ratio for heptyl xanthate adsorbed on PbS indicates the hydrocarbon chain of the heptyl xanthate to be preferentially orientated perpendicular to the surface normal of the internal reflection element.

  • 160. Fredriksson, Andreas
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    An in situ ATR-FTIR study of the adsorption kinetics of xanthate on germanium2007In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 302, no 1-3, p. 96-101Article in journal (Refereed)
    Abstract [en]

    The in situ adsorption of n-heptyl xanthate on a germanium multiple internal reflection element was studied at constant ionic strength and X-ray photoelectron spectroscopy was used in the investigation of the germanium surface. The kinetics of heptyl xanthate adsorption was evaluated using the integrated absorbance of a sub-band under the vibration at 1200 cm−1. This vibration was assigned to the adsorbed xanthate molecule. It was shown that the adsorption of heptyl xanthate can be represented by a pseudo-first-order rate law and a monodentate binding of the xanthate to the germanium surface is proposed. During the adsorption of xanthate, the dimeric form of xanthate was simultaneously formed.

  • 161. Fredriksson, Andreas
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Kinetics of collector adsorption on mineral surfaces2005In: Centenary of flotation symposium / [ed] Graeme J. Jameson, The Australian Institute of Mining and Metallurgy , 2005, p. 433-437Conference paper (Refereed)
    Abstract [en]

    In the present study infrared attenuated total reflection (IR-ATR) was used to monitor the rate of in situ adsorption of heptyl xanthate on a layer of zinc sulfide synthesised on a germanium ATR crystal. The zinc sulfide surface was characterised using x-ray photoelectron spectroscopy (XPS). The absorbance of heptyl xanthate measured increased with increasing bulk concentration of the adsorbate up to an equilibrium plateau value corresponding to a fractional coverage of the surface sites of the substrate. For the adsorption from solutions of concentrations between 10-3 and 10-5 M, the rate of adsorption increased with increasing bulk concentration. At higher concentrations the measured absorbance should be corrected for the absorbance due to the concentration of xanthate in bulk solution. The present work provides a discussion of this correction. Assuming the adsorption stage to be rate-controlling and proportional both to the concentration of the adsorbing species in solution and unreacted surface area, a rate law governing this type of transient adsorption kinetics was derived. By means of absorbance data for the concentrations 0.1 and 0.01 mM, die rate constant of adsorption was calculated. From the initial part of a Langmuir adsorption isotherm, the absorbance at monolayer coverage and the equilibrium constant of adsorption could be estimated.

  • 162. Fredriksson, Andreas
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Kinetics of collector adsorption on mineral surfaces2006In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 19, no 6-8, p. 784-789Article in journal (Refereed)
    Abstract [en]

    In the present study infrared attenuated total reflection (IR-ATR) was used to monitor the rate of in situ adsorption of heptyl xanthate on a layer of zinc sulphide synthesized on a germanium ATR crystal. The zinc sulphide surface was characterized using X-ray photoelectron spectroscopy (XPS). The absorbance of heptyl xanthate measured increased with increasing bulk concentration of the adsorbate up to an equilibrium plateau value corresponding to a fractional coverage of the surface sites of the substrate. For the adsorption from solutions of concentrations between 10−3 and 10−5 M, the rate of adsorption increased with increasing bulk concentration. At higher concentrations the measured absorbance should be corrected for the absorbance due to the concentration of xanthate in bulk solution. The present work provides a discussion of this correction. Assuming the adsorption stage to be rate-controlling and proportional both to the concentration of the adsorbing species in solution and unreacted surface area, a rate law governing this type of transient adsorption kinetics was derived. By means of absorbance data for the concentrations 0.1 and 0.01 mM, the rate constant of adsorption was calculated. From the initial part of a Langmuir adsorption isotherm, the absorbance at monolayer coverage and the equilibrium constant of adsorption could be estimated.

  • 163. Fredriksson, Andreas
    et al.
    Lidström-Larsson, Margareta
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kinetics of xanthate adsorption on metal sulphides2004In: Konferens i mineralteknik / [ed] Marianne Thomaeus; Eric Forssberg, Föreningen Mineralteknisk Forskning / Swedish Mineral Processing Research Association , 2004Conference paper (Other academic)
  • 164. Fredriksson, Andreas
    et al.
    Lidström-Larsson, Margareta
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    n-Heptyl xanthate adsorption on a ZnS layer synthesized on germanium: an in situ attenuated total reflection IR study2005In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 286, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Adsorption of n-heptyl xanthate on synthesized zinc sulfide was followed in situ by monitoring the methylene absorption band at 2925 cm-1. The zinc sulfide surface used in the adsorption experiments was synthesized on a germanium internal reflection element using the chemical bath deposition method. Characterization of the adsorbent surface was performed by X-ray photoelectron spectroscopy. The time needed to reach adsorption equilibrium varied with the initial concentration of the aqueous potassium heptyl xanthate solution. The amount of adsorbed xanthate ions increased with the concentration of the solution within the range studied (10 μM-50 mM). The experimental data are reasonably well described by the Langmuir adsorption isotherm. Polarized infrared attenuated total reflection (ATR) was used to determine the average orientation of the heptyl chains by measuring the absorbance of the infrared beam polarized perpendicularly and parallely to the plane of incidence. Measured absorbances were corrected for contribution from heptyl xanthate in bulk solution.

  • 165.
    Frost, Ray L.
    et al.
    Queensland University of Technology.
    Forsling, Willis
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kloprogge, Theo
    Queensland University of Technology.
    Kristof, Janos
    University of Veszprem.
    Raman spectroscopy at temperatures between 298 and 423 K and at 77 K of kaolinites intercalated with formamide1998In: Journal of Raman Spectroscopy, ISSN 0377-0486, E-ISSN 1097-4555, Vol. 29, no 12, p. 1065-1069Article in journal (Refereed)
    Abstract [en]

    Raman spectra of kaolinite and of the formamide-intercalated kaolinite were obtained at both 298 and 77 K using a Raman microprobe equipped with a thermal stage. Upon cooling to 77 K, the band attributed to the inner hydroxyl shifts by 5 cm-1 to lower wavenumbers and the bands assigned to the inner surface hydroxyls move to higher wavenumbers. Upon intercalation of the kaolinite with formamide, an additional Raman band attributed to the formation of a hydrogen-bonded complex between the inner surface hydroxyls and the carbonyl group of the formamide is observed at 3627 cm-1 at 298 K and at 3631 cm-1 at 77 K. Raman spectra of the deintercalation of the formamide-intercalated kaolinite are obtained by using the thermal stage to heat the intercalated kaolinite in situ. A decrease in intensity of the bands formed through intercalation and at the same time an increase in intensity of the inner surface hydroxyl bands are observed. A loss of intensity of the low-wavenumber region of the formamide-intercalated kaolinite is also observed.

  • 166.
    Frost, Ray L.
    et al.
    Centre for Instrumental and Developmental Chemistry, Queensland University of Technology.
    Johansson, Ursula
    Luleå tekniska universitet.
    Combination bands in the infrared spectroscopy of kaolins: a drift spectroscopic study1998In: Clays and clay minerals, ISSN 0009-8604, E-ISSN 1552-8367, Vol. 46, no 4, p. 466-477Article in journal (Refereed)
    Abstract [en]

    Kaolinites with varying degrees of defect structures have been studied by both mid-infrared (IR) and near-IR diffuse reflectance spectroscopy (DRIFT). Difference bands were observed in the 2650to 2750-cm-1 region. This region coincides with the kaolinite-deuterated hydroxyl stretching region. Summation bands were observed in the near-IR spectra in the 4500- to 4650-cm-1 and in the 7050- to 7250cm-1 region. Each of the spectral regions of the summation and difference bands is both kaolin polytype and sample dependent. It is proposed that each of these sets of bands arises from the combination of the hydroxyl stretching frequencies and the hydroxyl deformation frequencies and, to a lesser extent, the silicon-oxygen symmetric stretching vibration of the siloxane layer. Additional difference bands of very low intensity were also observed at 2930 and 2856 cm-1. Combination bands were observed in all kaolinites at 2137 and 2227 cm-1. Each of the 3 major combination spectral regions was composed of 5 component bands corresponding to the 4 IR active and the 1 Raman active kaolinite hydroxyl stretching frequencies. Combination bands were also observed at ∼1932 and 1821 cm-1.

  • 167.
    Geng, Shiyu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Plasticizing and crosslinking effects of borate additives on the structure and properties of poly(vinyl acetate)2017In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 13, p. 7483-7491Article in journal (Refereed)
    Abstract [en]

    As an environmentally friendly, low-cost and widely used polymer, poly(vinyl acetate) (PVAc) is worth modifying to achieve better properties. Here, we report on the influence of borate additives on the structure and properties of partially hydrolysed PVAc. In addition to the general crosslinking function of borate additives, an extraordinary plasticizing effect was found. By controlling the pH from 4 to 11 during sample preparation, the plasticizing and crosslinking effects can be shifted. In alkaline conditions, the degree of crosslinking in the PVAc/borate sample is increased; however, this increase declines gradually with an increase in the borate additive content, which impacts the morphology of the PVAc latex particles, as well as the mechanical and thermal properties of the PVAc/borate films. In contrast, in acidic conditions, the PVAc/borate films are plasticized by borate additives; thus, their ultimate mechanical strength, elastic moduli and thermal stabilities decrease, while the water diffusivities increase.

  • 168.
    Gergely, Andras
    et al.
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia, Egyetem, Hungary .
    Szabó, Péter
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, Egyetem, Hungary .
    Krojer, Antal
    Department of Inspection and Maintenance, Mol Nyrt., Olajmunkás, Hungary .
    Nagy, Bence
    Refining Research and Innovation, Mol Nyrt., Hungary .
    Kristof, Tamas
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia, Egyetem, Hungary .
    Hydrogen Sulfide Corrosion of Carbon and Stainless Steel Alloys in Mixtures of Renewable Fuel Sources under Co-Processing Conditions2018In: Modern Applied Science, ISSN 1913-1844, E-ISSN 1913-1852, Vol. 12, no 4, p. 227-255Article in journal (Refereed)
    Abstract [en]

    Corrosion rates of steel alloys were investigated in gas oil and its mixture with waste cooking oil and animal waste lard over 1, 3, 7 and 21 days under desulfurizing condition. Co-processing conditions were attempted to simulate by batch-reactor experiment at temperatures between 200 and 300oC and pressures between 20 and 90 bar in the presence of 2 volume% hydrogen sulfide. Integral and differential corrosion rates were defined by weight losses. Intense sulfide corrosion of carbon steels was less impacted by the biomass sources. Thinner scales in gas oil was probably due to frequent cohesive failure, whereas thicker layers in biomass mixtures were allowed to form to afford limited physical protection. The high corrosion rate of low alloy steel with temperature over time is related to inefficient protection by the metal sulfide scales. Greater activation energy and enthalpy balance in the formation of activated complex is expected to reflect in thick cohesive scales. Loose layers and the less unfavorable entropy balance in the transition state did not lead to valuable barrier protection. High sulfide corrosion resistance of stainless steels is in chemical in nature markedly impacted by the biomass fuel sources and contributed especially by the acidic species. Corrosion rates increased with temperature by magnitude similar to those of carbon steels, which probably owes to the less unfavorable entropy and free energy balance between the initial and transition states of the reactants.

  • 169.
    Gergely, András
    et al.
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia.
    Locskai, Roland
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia.
    Szabo, Peter
    Krójer, Antal
    Department of Inspection and Maintenance.
    Kristóf, Tamás
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia.
    Hydrogen Sulphide Corrosion of Carbon and Stainless Steel Alloys Immersed in Mixtures of Renewable Fuel Sources and Tested Under Co-processing Conditions2016In: Hungarian Journal of Industry and Chemistry, ISSN 2450-5102, Vol. 44, no 1, p. 55-70Article in journal (Refereed)
    Abstract [en]

    In accordance with modern regulations and directives, the use of renewable biomass materials as precursors for the production of fuels for transportation purposes is to be strictly followed. Even though, there are problems related to processing, storage and handling in wide range of subsequent uses, since there must be a limit to the ratio of biofuels mixed with mineral raw materials. As a key factor with regards to these biomass sources pose a great risk of causing multiple forms of corrosion both to metallic and non-metallic structural materials. To assess the degree of corrosion risk to a variety of engineering alloys like low-carbon and stainless steels widely used as structural metals, this work is dedicated to investigating corrosion rates of economically reasonable engineering steel alloys in mixtures of raw gas oil and renewable biomass fuel sources under typical co-processing conditions. To model a desulphurising refining process, corrosion tests were carried out with raw mineral gasoline and its mixture with used cooking oil and animal waste lard in relative quantities of 10% (g/g). Co-processing was simulated by batch-reactor laboratory experiments. Experiments were performed at temperatures between 200 and 300ºC and a pressure in the gas phase of 90 bar containing 2% (m3/m3) hydrogen sulphide. The time span of individual tests were varied between 1 and 21 days so that we can conclude about changes in the reaction rates against time exposure of and extrapolate for longer periods of exposure. Initial and integral corrosion rates were defined by a weight loss method on standard size of coupons of all sorts of steel alloys. Corrosion rates of carbon steels indicated a linear increase with temperature and little variation with composition of the biomass fuel sources. Apparent activation energies over the first 24-hour period remained moderate, varying between 35.5 and 50.3 kJ mol−1. Scales developed on carbon steels at higher temperatures were less susceptible to spall and detach. Nonetheless, moderate deceleration of corrosion rates as a function of time are due to the less coherent, frequently spalling and low compactness, higher porosity of the scales evolved at lower and higher temperatures, respectively. On the surface of high alloy steels, sulphide scales of an enhanced barrier nature formed during the induction periods and the layer formation mechanism was found to be assisted by the increasing temperature as initial reaction rates considerably decreased over time. Nevertheless, corrosion-related sulphide conversion of metals and mass loss of the high alloys are strongly affected by the composition of the biomass fuel sources especially animal waste lard. Thermal activation in the first 24 hours decreased from 68.9 to 35.2 kJ mol−1. A greater degree of failure to develop protective sulphide scales was experienced by changing to composition of the biomass fuel sources than the impact of thermal activation between a narrow temperature range at around 100ºC. In accordance with the literature, high free fatty acid contents lead to high corrosion rates accounted for direct corrosion of high alloy steels and assisted solubilisation of corrosion products. In addition, the pronounced acceleration of sulphide corrosion is connected to the diminishing inhibition effect of the sulphide scales

  • 170.
    Golets, M.
    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.
    Wang, Y-L
    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, KTH, Royal Institute of Technology , Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden, Department of Physics, Warwick University, Coventry.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Understanding the thermal decomposition mechanism of a halogen-free chelated orthoborate-based ionic liquid: a combined computational and experimental study2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, p. 22458-22466Article in journal (Refereed)
    Abstract [en]

    In the last few decades, ionic liquids (ILs) have gained significant attention as lubricants and lubricant additives due to their polar nature, low vapour pressure and tunable physicochemical properties. In this work, quantum chemistry calculations and atomistic Molecular Dynamics (MD) simulations were employed to predict thermal degradation mechanisms of a potential lubricating agent - the tributyloctylphosphonium bis(oxalato)borate ([P4,4,4,8][BOB]) IL. It was found that the onset of decomposition of the studied IL coincides with a cleavage of the B-O bonds in the [BOB](-) anion. Consequently, a series of chemical reactions of the [P4,4,4,8](+) cation with the [BOB](-) anion was triggered yielding alkylboranes, alkenes, trialkylphosphines, CO and CO2. Another ionic system, consisting of [P4,4,4,8][Cl], was also tested for a comparison. Thermogravimetric measurements have shown a higher thermal stability of [P4,4,4,8][BOB] compared to that of [P4,4,4,8][Cl] at least at the initial stage of decomposition, in accord with the presented calculations. Quantum chemical frequency calculations also agreed with the experimental Fourier Transform Infrared (FTIR) spectroscopy results.

  • 171. Goryan, Alexander
    et al.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Solid state NMR studies on bentonites2007Conference paper (Other academic)
  • 172. Goryan, Alexander
    et al.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Solid state NMR studies on bentonites2007Conference paper (Other academic)
  • 173.
    Goryan, Alexander S.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Nuclear magnetic resonance studies on bentonite in complex mixed systems2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this work 23Na MAS NMR was validated as a successful quantitative method for studies of exchanging sodium in bentonites useful, in particular, for studies of ion-exchange kinetics. Na-enriched bentonites equilibrated in a re-circulated process water at iron-oxide pelletizing plants may acquire properties of Ca-bentonites after already 20 minutes of the equilibration time, since >50 % of sodium ions will be exchanged by calcium ions during first minutes of bentonite placed in contact with the process water. It was shown that all sodium activated bentonites used in this study exchange >50% of sodium in Na+/Ca2+ and ca 20 % of sodium in binary Na+/Mg2+ systems with the same bentonite/solution ratio and same concentrations of these ions in aqueous solutions as in the process water at a pelletizing plant. In total, approximately 50 % of the exchangeable sodium in original bentonites was exchanged after equilibrating of bentonites in the process water already after 20 minutes. Experimental Na+/Ca2+ exchange curves for ‘model’ Ca2+(aq) solutions and for process water are very similar as Ca2+ is the dominant constituent in the process water. Since bivalent ions (Ca2+ and Mg2+) that present in the process water readily replace Na+ ions, Na-bentonite transforms into Ca- or Mg- bentonite, which have worse rheological, swelling and, therefore, binding properties. This ion-exchange process can influence the binder performance in the pelletizing process. Taking into account that fluorapatite is one of the components present in a blend of minerals processed, possible interactions between orthophosphate (the principal anionic component of apatites) and bentonites in aqueous suspensions are considered. It was found that sorption of orthophosphate on Ca-montmorillonite follows a different pattern from sorption of orthophosphate on aluminum oxides and kaolinite. While there is a small amount of sorption below pH 7, which may involve inner-sphere complexation and precipitation of AlPO4 to Al-OH edge sites on the montmorillonite crystals, most sorption of orthophosphate occurs at higher pH. Both macroscopic sorption measurements and solid-state 31P MAS NMR suggest that above pH 7 there is precipitation of proton depleted calcium phosphate phases. Based on both 31P chemical shifts and 31P chemical shift anisotropies it was concluded that the principal precipitated phased are most likely ‘brushite-like’ phases. Very short spin-lattice T2(31P) relaxation times (≤100 μs) for the orthophosphate/bentonite systems can possibly be explained by the presence of paramagnetic Fe in bentonites. Since there are insufficient concentrations of soluble Fe species in the supernatant solution that may give rise to the observed effects, it is likely that orthophosphate is precipitated as thin layers on the surfaces of montmorillonite crystals, where phosphorus may interact with Fe atoms present in the crystal lattice. PO4-tetrahedra in sorbed species can be also distorted giving rise to a larger 31P CSA than for pure ‘apatite-like phases’. 29Si MAS and 1H-29Si CP/MAS NMR experiments on bentonite samples also performed in this work provide information about impurities of quartz in bentonites, a level of substitution of aluminum by iron atoms in the structure of montmorillonite and about the degree of hydration of montmorillonite. 29Si NMR experiments on bentonite incubated with waterglass in aqueous suspensions at concentrations of sodium silicates as in the process water demonstrated that one can follow the process of polymerization of waterglass in solutions and also detect sodium silicates polymerized on surfaces of bentonites already after 1 hour of incubation. Polymerized waterglass sorbed on bentonite surfaces may also alter rheological, swelling and, therefore, binding properties of sodium-activated bentonites used in pelletization of iron-oxide ores.

  • 174.
    Gowda, Vasantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Combined experimental and theoretical studies of dithiocarbamate complexes of yttrium, lanthanum and bismuth2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Metal-dithiocarbamate complexes find wide-ranging applications in nanomaterial and metalseparation science, and have potential use as chemotherapeutic, pesticides, and as additives tolubricants. A highly versatile dialkyldithiocarbamate (R2NCS2–) ligand can form stablecomplexes with all the transition elements and also the majority of main group, lanthanide andactinide elements. Here we present structural investigations of the molecular and electronicstructures of dialkyldithiocarbamate complexes with yttrium(III), lanthanum(III), andbismuth(III) of molecular formula [Y{S2CN(C2H5)2}3PHEN], [La{S2CN(C2H5)2}3PHEN], and[Bi2{S2CN-n(C4H9)2}6] (where PHEN=1,10-Phenanthroline) . The experimental solid-state 13Cand 15N cross polarization magic-angle-spinning (CP-MAS) NMR results are reported for allthese three complexes. We also report new single-crystal X-ray structures of heterolepticyttrium, lanthanum, and homoleptic bismuth dialkyldithiocarbamate complexes. Thecomparative analysis of powder XRD patterns and solid-state 13C and 15N CP-MAS spectra ofpolycrystalline yttrium(III) and lanthanum(III) diethyldithiocarbamato-phenanthrolinecomplexes shows the presence of significant structural differences. The diethyldithiocarbamatophenanthrolinecomplex of yttrium has a very similar structural type to a previously reported Xraydiffraction structure for [Nd{S2CN(C2H5)2}3PHEN] whereas, the crystal structure of[La{S2CN(C2H5)2}3PHEN] is considerably more complex. Our NMR and single-crystal X-raydiffraction results suggested polymorphism for bismuth di-n-butyldithiocarbamate complex.Finally, the experimental NMR results are complemented by chemical shifts obtained usingquantum chemical methods and verified the spectral assignments. Overall, our workdemonstrates how different experimental and theoretical methods can be combined that canafford insights into the solid-state structure and bonding environments of metal complexes.

  • 175.
    Gowda, Vasantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Experimental and Computational Magnetic Resonance Studies of Selected Rare Earth and Bismuth Complexes2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The rare-earth elements (REEs) and bismuth, being classified as the ‘most critical raw materials’ (European Raw Materials Initiatives, 2017), have a high economic importance to the EU combined with a high relative supply risk. REEs are highly important for the evolving technologies such as clean-energy applications, high-technology components, rechargeable batteries, permanent magnets, electric and hybrid vehicles, and phosphors monitors.This scientific research work aims at building a fundamental knowledge base concerning the electronic/molecular structure and properties of rare-earth element (REE) and bismuth complexes with dithiocarbamate (DTC) and 1,10-phenanthroline (PHEN) by employing state-of-the-art experimental techniques such as nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction (XRD) techniques together with ab initioquantum mechanical computational methods. This combination of methods has played a vital role in analysing the direct and significant effect of the heavy metal ions on the structural and magnetic resonance properties of the complexes, thereby, providing a framework of structure elucidation. This is of special importance for REEs, which are known to exhibit similar chemical and physical properties. The objectives of the work involve i) a systematic investigation of series of REE(III) as well as bismuth(III) complexes to get a profound understanding of the structure-properties relationship and ii) to find an appropriate theoretical modelling and NMR calculation methods, especially, for heavy metal systems in molecular and/or solid-state. This information can later be used in surface interaction studies of REE/bismuth minerals with DTC as well as in design and development of novel ligands for extraction/separation of metal ions.The REE(III) and bismuth(III) complexes with DTC and PHEN ligands have all provided aunique NMR fingerprint of the metal centre both in liquid and solid phase. The solid-state 13C and 15NNMR spectra of the diamagnetic REE(III) and bismuth(III) complexes were in accord with their structural data obtained by single crystal XRD. The density functional theory (DFT) methods were used to get complementary and refined structural and NMR parameters information for all diamagnetic complexes in the solid-state. The relativistic contributions due to scalar and spin-orbit correlations for the calculated 1H/13C/15N chemical shifts of REE complexes were analysed using two-component zeroth-order regular approximation (ZORA)/DFT while the ‘crystal-lattice’ effects on the NMR parameters were calculated by combining DFT calculations on molecular and periodic solid-state models. The paramagnetic REE complexes display huge differences in their 1H and 13C NMR spectral patterns. The experimental paramagnetic NMR (pNMR) chemical shifts, as well as the sizable difference of the 1H and 13C NMR shifts for these isoelectronic complexes, are well reproduced by the advanced calculations using ab initio/DFT approach. The accuracy of this approach is very promising for further applications to demanding pNMR problems involving paramagnetic f-block elements.The results presented in this thesis demonstrate that a multidisciplinary approach of combined experimental NMR and XRD techniques along with computational modelling and property calculations is highly efficient in studying molecular complexes and solids containing heavy metal systems, such as rare-earths and bismuth.

  • 176.
    Gowda, Vasantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Project: Solid-State NMR and DFT calculations on rare earth metal complexes2013Other (Other (popular science, discussion, etc.))
  • 177.
    Gowda, Vasantha
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Laitinen, Risto S.
    Laboratory of Inorganic Chemistry, University of Oulu.
    Telkki, Ville-Veikko
    NMR Research Unit, University of Oulu.
    Larsson, Anna-Carin
    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.
    Lantto, Perttu
    NMR Research Unit, University of Oulu.
    DFT calculations in the assignment of solid-state NMR and crystal structure elucidation of a lanthanum(iii) complex with dithiocarbamate and phenanthroline2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 48, p. 19473-19484Article in journal (Refereed)
    Abstract [en]

    The molecular, crystal, and electronic structures as well as spectroscopic properties of a mononuclear heteroleptic lanthanum(iii) complex with diethyldithiocarbamate and 1,10-phenanthroline ligands (3 : 1) were studied by solid-state 13C and 15N cross-polarisation (CP) magic-angle-spinning (MAS) NMR, X-ray diffraction (XRD), and first principles density functional theory (DFT) calculations. A substantially different powder XRD pattern and 13C and 15N CP-MAS NMR spectra indicated that the title compound is not isostructural to the previously reported analogous rare earth complexes with the space group P21/n. Both 13C and 15N CP-MAS NMR revealed the presence of six structurally different dithiocarbamate groups in the asymmetric unit cell, implying a non-centrosymmetric packing arrangement of molecules. This was supported by single-crystal X-ray crystallography showing that the title compound crystallised in the triclinic space group P1[combining macron]. In addition, the crystal structure also revealed that one of the dithiocarbamate ligands has a conformational disorder. NMR chemical shift calculations employing the periodic gauge including projector augmented wave (GIPAW) approach supported the assignment of the experimental 13C and 15N NMR spectra. However, the best correspondences were obtained with the structure where the atomic positions in the X-ray unit cell were optimised at the DFT level. The roles of the scalar and spin-orbit relativistic effects on NMR shielding were investigated using the zeroth-order regular approximation (ZORA) method with the outcome that already the scalar relativistic level qualitatively reproduces the experimental chemical shifts. The electronic properties of the complex were evaluated based on the results of the natural bond orbital (NBO) and topology of the electron density analyses. Overall, we apply a multidisciplinary approach acquiring comprehensive information about the solid-state structure and the metal-ligand bonding of the heteroleptic lanthanum complex.

  • 178.
    Gowda, Vasantha
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Larsson, Anna-Carin
    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.
    Lantto, P.
    University of Oulu.
    Telkki, V-V
    University of Oulu.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Structural investigations of rare earth dialkyl dithiocarbamate complexes: solid-state NMR, X-ray diffraction and DFT calculation studies2013Conference paper (Other academic)
    Abstract [en]

    In this study, we made an attempt to qualitatively study the structures of few rare earth metal complexes by employing solid state NMR, X-Ray Diffraction, and preliminary DFT calculations. High resolution 13C and 15N solid state CP/MAS NMR spectra were recorded for six diamagnetic polycrystalline rare earth dialkyldithiocarbamates of the general formula [(RE2S2CNR2)3 PHEN] (where RE=La or Y, R=C2H5, C3H7, and i-C3H7) [1]. Different isotropic 13C and 15N chemical shifts for the three dialkyldithiocarbamato groups were observed. Regulacio et al. (2005) inferred that irrespective of the alkyl chains, rare earth complexes of dialkyldithiocarbamates and phenanthroline (3:1) ligands always crystallize in a monoclinic system with a space P21/c group. However, comparative analysis of solid state 13C/15N CPMAS spectra of polycrystalline yttrium and lanthanum diethyldithiocarbamate complexes shows the presence of significant differences, indicating structural variations of these complexes. Also, quite different X-Ray diffraction powder pattern was observed for the above two complexes. Finally, the computational geometry optimization of Y and La complexes, followed by the preliminary calculation of 13C and 15N chemical shifts and shielding contributions with the ADF program [2], found to be very near to the experimental results.

  • 179.
    Gowda, Vasantha
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Larsson, Anna-Carin
    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.
    Lantto, Perttu
    University of Oulu.
    Modelling and structrual optimizations of rare earth coordination: First principles calculations2013Conference paper (Other academic)
    Abstract [en]

    An approximate 3D structure for the yttrium diethyldithiocarbamato-phenanthroline complex 1, obtained by manually replacing the Nd3+ ion with Y3+ion of the reported crystal structure for neodymium diethyldithiocarbamato-phenanthroline complex 2 followed by DFT geometry optimization using periodic boundary conditions with dispersion corrected functional, has been compared with DFT optimized structure for 1. The quality of the method is discussed by comparing predicted PXRD pattern, high resolution solid state 13C and 15N CP/MAS NMR data and calculated chemical shift tensor eigenvalues for optimized structures for 1 and 2. We have observed an excellent agreement between the ‘modeled’ and experimental structures. Finally, to take into account the relativistic effects on NMR shielding calculations, we have employed the zeroth-order regular approximation (ZORA) formalism using Slater-type orbital (STO) basis sets implemented in Amsterdam Density Functional (ADF) package. The present approach can be further extended to study other complexes of rare earth metals in general, particularly those having similar crystal structure.

  • 180.
    Gowda, Vasantha
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. NMR Research Unit, University of Oulu.
    Sarma, Bipul
    Department of Chemical Sciences, Tezpur University.
    Laitinen, Risto S.
    Laboratory of Inorganic Chemistry, University of Oulu.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ivanov, Alexander V.
    Institute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences .
    Iuga, Dinu
    Department of Physics, Warwick University.
    Lantto, Perttu
    NMR Research Unit, University of Oulu.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Warwick University.
    Structural insights into the polymorphism of bismuth(III) di-n-butyldithiocarbamate by X-ray diffraction, solid-state (13C/15N) CP-MAS NMR and DFT calculations2017In: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 129, p. 123-132Article in journal (Refereed)
    Abstract [en]

    Two crystalline polymorphs of a binuclear tris(di-n-butyldithiocarbamato)bismuth(III) complex, I and II, with an empirical formula of [Bi{S2CN(n-C4H9)2}3] were synthesised and characterised by X-ray diffraction (XRD), solid-state NMR and density functional theory (DFT) calculations. At the supramolecular level, these mononuclear molecular units interact in pairs via secondary Bi⋯S bonds, yielding binuclear formations of [Bi2{S2CN(n-C4H9)2}6]. The polymorph I () contains two isomeric non-centrosymmetric binuclear molecules of [Bi2{S2CN(n-C4H9)2}6], which are related to each other as conformers, therefore having four structurally inequivalent bismuth atoms and twelve inequivalent dithiocarbamate ligands. In contrast, the structurally simpler polymorph II (P21/n) exists as a single molecular form of the corresponding centrosymmetric binuclear formation, comprising two structurally equivalent bismuth atoms and three structurally different dithiocarbamate groups. The polymorphs I and II were found to be interconvertible by altering the solvent system during the recrystallisation process. Sun et al. (2012) has reported a crystalline form of the title compound which resembles, but is not identical with, polymorph II. Experimental solid-state 13C and 15N cross-polarisation (CP) magic-angle-spinning (MAS) NMR spectra of both polymorphs I and II were in accord with the direct structural data on these complexes. Assignments of the resonance lines in the solid-state 13C and 15N NMR spectra were assisted by chemical shift calculations of the crystals using periodic DFT.

  • 181.
    Gowda, Vasantha
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sarma, Bipul
    Department of Chemical Sciences, Division of Chemical Engineering, Tezpur University, Tezpur, Assam.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Telkki, Ville-Veikko
    University of Oulu, NMR Research Group, Division of Chemical Engineering, Faculty of Science, University of Oulu.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Lantto, Perttu
    University of Oulu, NMR Research Group, Division of Chemical Engineering, Faculty of Science, University of Oulu.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Structure Elucidation of an Yttrium Diethyldithiocarbamato-Phenanthroline Complex by X-ray Crystallography, Solid-State NMR, and ab-initio Quantum Chemical Calculations2016In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 20, p. 3278-3291Article in journal (Refereed)
    Abstract [en]

    We present a structural analysis method for molecular and electronic structure of yttrium diethyldithiocarbamato-phenanthroline complex {[Y(S2CNR2)3PHEN] with R = C2H5 and PHEN = 1,10-phenanthroline} combining solid-state NMR spectroscopy, XRD, and first principles DFT calculations. Replacing the Nd3+ ion with Y3+ in the reported crystal structure of [Nd(S2CNR2)3PHEN] complex generated an approximate 3D structure of the title complex. The structure was then subjected to first principles quantum chemical geometry optimisation using periodic DFT method. The quality of the method is discussed by comparing predicted and experimental powder XRD patterns. Full assignment of 13C and 15N solid-state CP-MAS NMR spectra as well as analyses of the principal values of the chemical shift tensors were carried out using periodic scalar relativistic DFT modelling. Spin-orbit relativistic effects, estimated by SO-ZORA formalism for one molecular unit, were evaluated. Finally, the X-ray structure of the title complex was determined, which proved that the former procedure is appropriate. The most important orbital interactions were investigated by Natural Bond Orbital analysis. The isotropic shielding values for S2CN-carbons were analysed by Natural Localised Molecular Orbital analysis. The present approach can be further extended to study other rare earth metal complexes, particularly those having similar but not yet solved crystal structures

  • 182.
    Grahn, Mattias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Hedlund, Jonas
    Adsorption of n-hexane and p-xylene in thin silicalite-1 films studied by FTIR/ATR spectroscopy2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 20, p. 7717-7724Article in journal (Refereed)
    Abstract [en]

    Adsorption isotherms for p-xylene and n-hexane in silicalite-1 films with a thickness of 200 nm were determined at 323, 343, 368, 393, and 423 K using Fourier transform infrared/attenuated total reflection (FTIR/ATR) spectroscopy. For both adsorbates, the low-pressure data agreed with literature data for MFI powder and the estimated Henry's constant and adsorption enthalpy were close to previously reported results. The upper region of the n-hexane isotherm (p > 2 kPa at 323 K) was likely influenced by micropores in open grain boundaries, as expected for a polycrystalline film of small (<200 nm) crystals. As for n-hexane, the first part (0 ≤ p ≤ 65 Pa at 323 K) of the p-xylene isotherm agreed with data for powder. However, the saturation capacity was only about half of that previously reported for powders, which indicates that p-xylene molecules do not adsorb in the sinusoidal channels in the film. We speculate that the small crystals used in the present work may behave differently from the larger crystals in previous works. Another explanation for the lower saturation capacity may be the bonding of crystals to the supports, which are known to induce strain in the attached crystals.

  • 183.
    Grahn, Mattias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lobanova, Antonia
    Luleå tekniska universitet.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A novel experimental technique for estimation of molecular orientation in zeolite2007In: Studies in Surface Science and Catalysis, ISSN 0167-2991, Vol. 170, p. 724-731Article in journal (Refereed)
    Abstract [en]

    FTIR spectroscopy in combination with polarized light and an ATR probe coated with a b-oriented ZSM-5 film was for the first time used to determine the orientation of adsorbed molecules in the ZSM-5 structure. Two adsorbates were studied, n-hexane and p-xylene and the results agreed with previously reported results obtained by other experimental techniques.

  • 184.
    Grahn, Mattias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lobanova, Antonina
    Luleå tekniska universitet.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Orientational analysis of adsorbates in molecular sieves by FTIR/ATR spectroscopy2008In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, no 19, p. 6270-6276Article in journal (Refereed)
    Abstract [en]

    ZnS ATR elements were coated with well-defined b-oriented ZSM-5 films by in situ growth. Both adsorption isotherms, as well as molecular orientation of p-xylene adsorbed in the films, were measured at 323 and 373 K by FTIR/ATR spectroscopy. The observed isotherms for the b-oriented ZSM-5 films in the present work were very similar to previously reported isotherms of supported MFI films, albeit the crystals in the latter films were aluminum free (silicalite-1) and orientated differently relative to the support surface than the crystals in the films studied in the present work. The novel technique facilitated, for the first time, the examination of how the tilt angle varies with loading and temperature. The data obtained in the present work showed that the p-xylene molecules were mainly oriented with their long axis parallel to the b-direction of the MFI crystals in concert with previously reported results based on FTIR microscopy, Monte Carlo simulations, NMR, and XRD data. At high concentrations, the tilt angle was in good agreement with observations by FTIR microscopy. It was also found that the orientation of the molecules changed with loading, this might be due to different adsorption geometries in the channel intersection as reported previously. The observed tilt angles may also be influenced from competitive adsorption on silanol groups, as was also indicated in the spectra. The results also indicate that the adsorption properties of zeolite films and powders may differ. Hence, adsorption parameters determined for zeolite powders may not necessarily be applicable to films.

  • 185.
    Grahn, Mattias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wang, Zheng
    Luleå tekniska universitet.
    Lidström-Larsson, Margareta
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Sterte, Johan
    Silicalite-1 coated ATR elements as sensitive chemical sensor probes2005In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 81, no 1-3, p. 357-363Article in journal (Refereed)
    Abstract [en]

    A novel sensitive chemical sensor probe has been fabricated. The sensor principle is based on silicalite-1 coated ATR (attenuated total reflection) elements and FTIR spectroscopy. The microporous silicalite-1 film enriches the analyte to the probe surface, thus increasing the sensitivity. At a relative pressure of n-hexane in helium of 6 × 10−5 the sensitivity of the probe is approximately 85 times higher for the silicalite-1 coated element compared to a 10 cm transmission gas cell and ca. 180 times higher compared to an uncoated element. The performance of the probe is illustrated by determination of an adsorption isotherm for n-hexane in silicalite-1.

  • 186.
    Grubbström, Göran
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Silane-crosslinking of recycled low-density polyethylene/wood composites2010In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 41, no 5, p. 678-683Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to study silane-crosslinking of recycled low-density polyethylene wood composites and its effect on composites properties. The composites were produced in a one-step twin-screw extrusion process and the silane-peroxide solution was pumped into the extruder. Degree of crosslinking, mechanical properties, short-term creep, fractured surfaces and nature of crosslinking were studied to understand the relationship between composite structure and properties. The results showed that crosslinked composite strength, toughness and creep resistance were improved compared to uncrosslinked composites. The flexural strength was doubled compared to uncrosslinked samples and the creep strain was reduced. The crosslinked composites stored under room conditions showed the highest strength, whereas storage in a sauna resulted in a higher degree of crosslinking. The Fourier transform infrared spectroscopy indicated formation of silane-bridges between wood and polyethylene, accordingly improving the interfacial adhesion between the wood and LDPE. The low concentration of peroxide in the silane-solution was shown to be a preferred composition to limit unintentional crosslinking during the process.

  • 187.
    Gu, TR
    et al.
    Beijing University.
    Huang, Z
    Beijing University.
    Sun, Zhong-Xi
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The ionic exchange coefficients of surfactant counterions at the solid liquid interface .1: The ionic exchange coefficients of F- and CL- on adsorbed Cetyltrimethylammonium Bromide at the Silica water interface1991In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 45, no 5, p. 526-528Article in journal (Refereed)
  • 188. Gunneriusson, Lars
    Aqueous speciation and surface complexation to goethite (α-FeOOH), of divalent mercury, lead and cadmium1993Doctoral thesis, comprehensive summary (Other academic)
  • 189. Gunneriusson, Lars
    Composition and stability of Cd(II)-chloro and -hydroxo complexes at the goethite (α-FeOOH)/water interface1994In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 163, no 2, p. 484-492Article in journal (Refereed)
    Abstract [en]

    The surface complexation of Cd(II) to goethite (α-FeOOH) in the absence and presence of chloride has been investigated. Equilibrium measurements have been performed as potentiometric titrations at 298.2 K, within the range 2.7 < -log[H+] < 9.0, in 0.1 mol dm-3 NaNO3, NaCl, and a mixture (1:1) of both these media. The data were evaluated according to the electrostatic constant capacitance model, including a previously determined model for the acid-base reactions of the goethite surface. The following model is presented (errors ± 3σ): equivalent FeOH + Cd2+ <=> equivalent FeOHCd2+; log β0,1,1,0s(int) = 6.43 ± 0.05; equivalent FeOH + Cd2+ <=> equivalent FeOCd+ + H+; log β-1,1,1,0s(int) = -2.22 ± 0.05; equivalent FeOH + Cd2+ + H2O <=> equivalent FeOCdOH + 2H+; log β-2,1,1,0s(int) = -12.01 ± 0.08; equivalent FeOH + Cd2+ + Cl- <=> equivalent FeOHCdCl+; log β0,1,1,1s(int) = 6.85 ± 0.02; equivalent FeOH + Cd2+ + Cl- <=> equivalent FeOCdCl + H+; log β-1,1,1,1s(int) = -2.38 ± 0.04. In the presence of excess Cd(II) ions to surface hydroxyl groups, it was found that the results could be explained by including bulk precipitation of Cd(OH)2. The calculated formation constant for Cd(OH)2 (s) was within an order of magnitude from the literature value for the stable phase in solution, β-Cd(OH)2. Modeling of natural water conditions showed that relatively high concentrations of goethite have to be present to influence the concentrations of Cd(II). Furthermore, the reactions were found to be nearly fully reversible, which means that adsorbed Cd(II) can be released to the environment by a relatively moderate lowering of pH

  • 190.
    Gunneriusson, Lars
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Baxter, Douglas
    Emteborg, Håkan
    Umeå universitet.
    Complexation at low concentrations of methyl and inorganic mercury(II) to a hydrous goethite (α-FeOOH) surface1995In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 169, no 2, p. 262-266Article in journal (Refereed)
    Abstract [en]

    Surface complexation of inorganic mercury(II) and monomethyl mercury onto a hydrous goethite surface was studied. The pH was varied and low total mercury concentrations were used. The inorganic mercury distribution was evaluated based on the constant capacitance concept. The surface complexation model was derived using about 103 times higher mercury concentrations. A model calculation describing the surface complexation of methyl mercury was also performed

  • 191. Gunneriusson, Lars
    et al.
    Lövgren, Lars
    Sjöberg, Staffan
    Complexation of Pb(II) at the goethite (α-FeOOH)/water interface: the influence of chloride1994In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 58, no 22, p. 4973-4983Article in journal (Refereed)
  • 192.
    Gunneriusson, Lars
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sandström, Åke
    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.
    Kuzmann, Ernő
    Laboratory of Nuclear Chemistry, Institute of Chemistry, Eötvös Loránd University.
    Kovacs, Krisztina
    Laboratory of Nuclear Chemistry, Institute of Chemistry, Eötvös Loránd University.
    Vertes, Attila
    Laboratory of Nuclear Chemistry, Institute of Chemistry, Eötvös Loránd University.
    Jarosite inclusion of fluoride and its potential significance to bioleaching of sulphide minerals2009In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 96, no 1-2, p. 108-116Article in journal (Refereed)
    Abstract [en]

    Incorporation of fluoride ions into the structure of jarosite, a common precipitate in bioleaching, was studied. Crystalline jarosite was synthesized in the presence of various concentrations of fluoride ions and characterized by spectroscopic- and chemical analysis.The results showed that substantial amounts of fluoride were sorbed to jarosite, increasing with pH and fluoride concentration. FTIR, XRD and Mössbauer analysis supported a structural incorporation of the fluoride. Due to the size similarity between fluoride and hydroxide ions, a probable mechanism is an exchange of hydroxide ions and fluoride ions within the jarosite, giving the composition KFe3(SO4)2(OH)6 - xFx(s). For the maximum concentration of fluoride used during synthesis, 200 mM, about 25% of the hydroxide ions were exchanged for fluoride ions. The mass of jarosite precipitated shown to be highly dependent on the fluoride concentration, with approximately half the yield using 200 mM potassium fluoride compared to in the absence of fluoride ions.To test the influence on toxicity of the incorporation of fluoride in jarosite, a bioleaching study was performed at 65 °C. A suspension of pyrite concentrate with 4% solid content (w/v) in the modified 9 K medium was bioleached under additions of potassium fluoride. The results indicated a higher tolerance for fluoride ions, as compared to earlier reported studies on fluoride toxicity during bioleaching.

  • 193. Gunneriusson, Lars
    et al.
    Sjöberg, Staffan
    Equilibrium Speciation Models for Hg, Cd, and Pb in the Gulf of Bothnia and its Catchment Area1991In: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 22, no 1, p. 67-80Article in journal (Refereed)
  • 194. Gunneriusson, Lars
    et al.
    Sjöberg, Staffan
    Surface Complexation in the H+-Goethite (α-FeOOH)-Hg (II)-Chloride System1993In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 156, no 1, p. 121-128Article in journal (Refereed)
  • 195.
    Gusain, Rashi
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Chemical Science Division, CSIR-Indian Institute of Petroleum, Dehradun.
    Panda, Somenath
    Department of Chemistry, Indian Institute of Technology Madras, Chennai.
    Bakshi, Paramjeet Singh
    Chemical Science Division, CSIR-Indian Institute of Petroleum, Dehradun.
    Gardas, Ramesh L.
    Department of Chemistry, Indian Institute of Technology Madras, Chennai.
    Khatri, Om Prakash
    Chemical Science Division, CSIR-Indian Institute of Petroleum, Dehradun.
    Thermophysical properties of trioctylalkylammonium bis(salicylato)borate ionic liquids: Effect of alkyl chain length2018In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 269, p. 540-546Article in journal (Refereed)
    Abstract [en]

    Thermophysical properties of halogen-free ionic liquids are gaining significant attention for industrial applications. In this context, trioctylalkylammonium bis(salicylato)borate (N888n-BScB) ionic liquids having variable alkyl chain length (n = 4, 8, 12, 16) are synthesized to explore the effect of chain length and temperature on their physicochemical properties. The density (ρ), refractive index (nD), and speed of sound (u) are measured in the temperature range of 293.15 to 333.15 K. The tetraoctylammonium-BScB is found to be highly dense ionic liquid, and it was attributed to the closer packing of symmetric structure of tetraoctylammonium cation. Furthermore, derived thermodynamic properties such as isentropic compressibility (βs), coefficient of thermal expansion (α), standard entropy (S°), intermolecular free length (Lf) and lattice energy (UPOT) are calculated for the N888n-BScB ionic liquids using the experimental data and shown the effect of variable chain length. This study provides a comprehensive insight on the thermophysical properties of halogen-free ionic liquids.

  • 196.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Classical calculations of radiative association in absence of electronic transitions2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 7, article id 74308Article in journal (Refereed)
    Abstract [en]

    A formula for the cross section of radiative association where no electronic transitions take place is derived and tested for diatomic molecules. The approach is based on classical mechanics and therefore it is valid for direct, i.e., non-resonant, radiative association. For the formation of carbon monoxide (CO) and the cyano radical (CN), in the X 1Σ+ and A 1Π states, respectively, the treatment reproduces the baselines of the cross sections obtained using quantum mechanical perturbation theory. The method overestimates the formation cross section of potassium sodide (NaK) by about 8%. For the lower mass diatoms hydrogen fluoride (HF) and deuterium hydride (HD), the formula overestimates the cross sections by 12% and 60%, respectively. The formula can be used alone for estimates of radiative association rate constants, or in combination with Breit-Wigner theory to include resonance contributions.

  • 197.
    Gärd, Rune
    Luleå tekniska universitet.
    FT-IR and FT-Raman studies of colloidal ZnS1995Licentiate thesis, comprehensive summary (Other academic)
  • 198.
    Gärd, Rune
    Luleå tekniska universitet.
    Spectroscopic studies of colloidal ZnS1997Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is a summary and discussion of four papers, mainly dealing with reactions at the ZnS/water interface. The main analysis method has been spectroscopy. In mineral concentration plants valuable minerals are rendered hydrophobic by the action of certain surface active molecules, so called collectors. Other molecules, depressors, are used to prevent the collectors from acting also on the less desirable minerals. Even if many potent reagents are available the selectivity is not always satisfying. To design new, selective molecules an understanding of the fundamental reactions at the ZnS/water interface is essential. The acidic and alkaline sites of Zns have been identified by FI-IR spectroscopy. The dependence of stoichiometry and pH has been determined. Adsorption onto ZnS of one common collector, amyl xanthate, one potential collector, thionalide an one depressor has been investigated. The conditions for adsorption with regard to pH, concentration, stoichiometry and temperature have been determined. Adsorption mechanisms are proposed.

  • 199.
    Gärd, Rune
    et al.
    Luleå University of Technology.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Spectroscopic Studies of Dextrin Adsorption onto Colloidal ZnS1997In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 194, no 2, p. 319-325Article in journal (Refereed)
    Abstract [en]

    The interaction of dextrin with colloidal ZnS has been investigated through adsorption studies and FT-IR spectroscopy in the 4000-400 cm-1range. The adsorption capacity is estimated to be around 1 mg/m2. Maximum adsorption is found to be constant below pH ≈7 and to increase with pH at least up to pH 11. Eighty percent of maximum adsorption is achieved within 3 min after addition of the dextrin. Based upon FT-IR studies and titration data, an adsorption mechanism is proposed.

  • 200.
    Gärd, Rune
    et al.
    Luleå University of Technology.
    Sun, Zhong-Xi
    Luleå University of Technology.
    Forsling, Willis
    FT-IR and FT-Raman studies of colloidal ZnS 1.: Acidic and alkaline sites at the ZnS/water interface1995In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 169, no 2, p. 393-399Article in journal (Refereed)
    Abstract [en]

    The surface complexes of colloidal ZnS have been studied using FT-IR and FT-Raman techniques. The absorption bands at 2500 and 1475-1375 cm-1, which are identified as the S-H bond and the Zn-OHCO2 entity, respectively, can be observed under varied conditions of sample stoichiometry and pH. The correlation between surface spectra and the complexation model is evaluated. The relation between the intensities of FT-IR and FT-Raman spectra and particle size is discussed.

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