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  • 51.
    Hellström, Pär
    et al.
    Luleå University of Technology.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Fredriksson, Andreas
    Luleå University of Technology.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A theoretical and experimental study of vibrational properties of alkyl xanthates2006In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 65, no 3-4, p. 887-895Article in journal (Refereed)
    Abstract [en]

    Geometrical structure and vibrational modes of potassium and sodium ethyl/heptyl xanthates were studied, using both theoretical and experimental methods. Both Hartree-Fock and density functional theory were used. The experimental method used was infrared absorption spectroscopy (FTIR). Our work showed that vibrational frequencies calculated with density functional theory, using the local density approximation, are in very good agreement with experiments. The results were not improved by using the more sophisticated and computationally demanding B3LYP functional.

  • 52.
    Holmgren, Allan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Bergström, B.
    Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology.
    Gref, R.
    Ericsson, A.
    Detection of pinosylvins in solid wood of Scots pine using Fourier transform Raman and infrared spectroscopy1999In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 19, no 1-2, p. 139-150Article in journal (Refereed)
    Abstract [en]

    Diffuse reflectance Fourier transform infrared (DRIFT) and near infrared (NIR) FT-Raman spectroscopy were used to detect pinosylvins in the wood of Pinus sylvestris L. trees. NIR FT-Raman spectroscopy offered the possibility of revealing pinosylvins simply by visual inspection of Raman spectra whereas DRIFT spectra needed a more complicated evaluation. Pinosylvin and resin acids from Scots pine were examined as to the possibility of their being the cause of observed spectral differences between sapwood and heartwood. Since pinosylvins are important compounds for the decay resistance of Scots pine wood, the detection of pinosylvins with Raman spectroscopy might be used to assess durability of wood products.

  • 53.
    Holmgren, Allan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    A prestudy of the recycling properties of aircraft de-/anti-icing fluids1995Report (Other academic)
  • 54.
    Holmgren, Allan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Polubotko, A. M.
    Russian Adademy of Sciences.
    SER spectra analysis of molecules with D-3h and D-6h symmetry groups1998In: Pure and Applied Optics, ISSN 0963-9659, Vol. 7, no 1, p. 115-117Article in journal (Refereed)
    Abstract [en]

    On the basis of the theory of SER spectra, proposed in a previous paper, the SER spectra of 1,3,5-trifluorobenzene, 1,3,5-trideuteriobenzene, benzene and hexafluorobenzene are analysed. It is demonstrated that the bands, caused by the totally symmetric modes and by the mode transforming as the d(z) moment experience large enhancement. The existence of a large number of forbidden bands in the SER spectra is pointed out. Some anomalies in the enhanced spectra are explained by qualitative ideas and by the 'interference phenomenon' of various contributions. It is pointed out that all the observed lines and regularities of the SER spectra can be explained within the framework of the quadrupole and dipole electrodynamical mechanism of the enhancement.

  • 55.
    Holmgren, Allan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Luleå University of Technology.
    Wu, Liuming
    Luleå University of Technology.
    An FT-IR study of Alizarin Red S adsorbed at the fluorapatite-water interface1997In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. Suppl. 14, p. 197-199Article in journal (Refereed)
    Abstract [en]

    The diffuse reflectance infrared Fourier transform (DRIFT) technique was used to study sodium 1,2-dihydroxyanthraquinone-3-sulphonate (ARS) adsorbed onto the surface of fluorapatite mineral. The acidity of the water solution was varied between pH 5.4 and pH 8.4. In this pH range the infrared spectra of adsorbed ARS show that the fluorapatite surface contains precipitated calcium-ARS. The chelation of calcium strongly affects the resonance structure of the ARS molecule.

  • 56.
    Holmgren, Allan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Lidström-Larsson, Margareta
    Luleå University of Technology.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sterte, Johan
    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.
    Wang, Zheng
    Luleå University of Technology.
    Sensor for spectroscopic analysis of gases or liquids, comprises attenuated total reflection element with molecular sieve layer2004Patent (Other (popular science, discussion, etc.))
  • 57.
    Holmgren, Allan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wu, Liuming
    Luleå University of Technology.
    Forsling, Willis
    Luleå University of Technology.
    Fourier transform infrared and Raman study of Alizarin Red S adsorbed at the fluorite-water interface1999In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 55, no 9, p. 1721-1730Article in journal (Refereed)
    Abstract [en]

    The adsorption of 1,2-dihydroxyanthraqinone-3-sulphonate (ARS) onto the surface of fluorite mineral was studied using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and Fourier transform (FT) Raman spectroscopy. The FT-Raman method proved to be more appropriate for this study when ARS was adsorbed from alkaline solution. At pH 6 both DRIFT and Raman spectra indicate non-precipitated ARS on the fluorite surface. At higher pH Raman spectra indicate ARS to be attached to the fluorite surface through the quinoid group at the 9-position and the α-phenolic oxygen.

  • 58.
    Holmgren, Allan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wu, Liuming
    Luleå University of Technology.
    Forsling, Willis
    Luleå University of Technology.
    Surface hydration of aqueous calcium minerals as studied by Fourier transform Raman and infrared spectroscopy1994In: Spectrochimica Acta. Part A, Molecular Spectroscopy, ISSN 0584-8539, Vol. 50, no 11, p. 1857-1869Article in journal (Refereed)
    Abstract [en]

    Rapid hydration reactions of several calcium minerals are studied using Fourier transform (FT) Raman and infrared (IR) spectroscopy. Oleate adsorption over aqueous synthetic fluorite, calcite and gypsum (pH 9) is investigated and adsorption mechanisms are discussed.

  • 59.
    Holmgren, Allan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Yang, Xiaofang
    A polarized Fourier transform infrared spectrometry attenuated total reflection study of bentonite settled onto magnetite2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 42, p. 16609-16615Article in journal (Refereed)
    Abstract [en]

    Sodium bentonite in aqueous suspension was allowed to settle onto a layer of magnetite, and the orientation of the bentonite platelets was monitored using the Fourier transform infrared spectrometry-attenuated total reflection technique. This study is the first reported use of polarized IR to study the in situ settling of delaminated bentonite platelets onto a thin layer of magnetite nanoparticles. The experiment was performed at a pH value (pH 5.6) close to the point of zero charge for the edge surfaces of the bentonite platelets in order to possibly enhance the probability for the (001) surface of bentonite to adhere to the positively charged magnetite particles. The order parameter (S) of the platelets was calculated both for the dry film and the film formed during water evaporation. These results were compared with the orientation of bentonite platelets on the internal reflection element (ZnSe) without magnetite particles, a system where the three layer model is valid. During settling of the bentonite, the tilt angle of the normal to the (001) surface of the platelets decreases and reaches a minimum value for the dry film. When the film is still covered by a layer of water, the tilt angles indicate the film to be at least partly built up of so-called card-house structures, implying that the edge surfaces of the platelets are at least partly adhering to the basal (001) surfaces.

  • 60.
    Johansson, U.
    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
    Luleå University of Technology.
    Frost, R.L.
    Centre for Instrumental and Developmental Chemistry, Queensland University of Technology, Queensland, Australia.
    Adsorption of silane coupling agents onto kaolinite surfaces1999In: Clay minerals, ISSN 0009-8558, E-ISSN 1471-8030, Vol. 34, no 2, p. 239-246Article in journal (Refereed)
    Abstract [en]

    The adsorption of the silane coupling agents N-(2-amino-ethyl)-3-aminopropyltrimethoxysilane (Z-6020), N-(2-(vinylbenzyl-amino)-ethyl)-3-amino-propyl-trimethoxysilane (Z-6032) and 3-glycidoxy-propyl-trimethoxysilane (Z-6040) onto the surface of kaolinite has been studied using the solvents water and ethanol. The adsorbed silanes were analysed using diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy and FT-Raman spectroscopy. When the silane coupling agents are dissolved in water, silanol groups are formed. Raman spectra of aqueous solutions of the silanes show that condensation of the silanols into oligomers occurred. The peak at 1000 cm(-1) assigned to Si-O-Si vibrations indicates that polymerization has occurred. A similar behaviour is observed when the silanes are dissolved in ethanol. The DRIFT spect-ra show that the silane coupling agents adsorb onto the surface of kaolinite, It is proposed that the oligomers are bonded to the kaolinite surface only by hydrogen bondings with no covalent bonds formed.

  • 61.
    Johansson, Ursula
    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
    Luleå University of Technology.
    Frost, Ray L.
    Centre for Instrumental and Developmental Chemistry, Queensland University of Technology, Brisbane, Queensland, Australia.
    Isotopic exchange of kaolinite hydroxyl protons: a diffuse reflectance infrared Fourier transform spectroscopy study1998In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 123, no 4, p. 641-645Article in journal (Refereed)
    Abstract [en]

    Specific surface reactions on kaolinite were investigated by deuterium exchange of the hydroxyl protons of kaolinite, The kaolinite samples were reacted with deuterium oxide for 48 h and 2.5 and 5 weeks, at various pH values (3, natural and 8) and at different temperatures (ambient, and 30, 60 and 100 degrees C), Analyses were performed using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The spectral results show that it is very difficult at room temperature to exchange the hydroxyl protons isotopically with deuterons at the surface of kaolinite, The temperature and the reaction time must be increased for successful exchange. It was found that the most suitable temperature for isotopic exchange was 60 degrees C. The pH did not significantly influence the deuteration, Only at high pH were changes of the OD bands in the DRIFT spectra observed, This study shows that it is possible to deuterate kaolinite without using intercalation. All three types of hydroxyl protons from the inner, inner surface and edge were exchanged.

  • 62.
    Jolsterå, Rickard
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gunneriusson, Lars
    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.
    Surface complexation modeling of Fe3O4-H+ and Mg(II) sorption onto maghemite and magnetite2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 386, no 1, p. 260-267Article in journal (Refereed)
    Abstract [en]

    The surface acid/base properties of magnetite (Fe3O4) particles and the sorption of Mg2+ onto magnetite and maghemite (γ-Fe2O3), have been studied using high precision potentiometric titrations, batch experiments and zeta potential measurements. The acid/base properties of magnetite were found to be very similar to maghemite except for the difference in surface site density, Ns (sites nm-2), 1.50±0.08 for magnetite and 0.99±0.05 for maghemite. The experimental proton exchange of the magnetite surface increased from pH 10 and above, indicating dissolution/transformation reactions of magnetite at alkaline conditions. Thus, magnetite with its Fe(II) content proved to be less stable towards dissolution in comparison with pure Fe(III) oxides also at high pH values.Three different ratios between surface sites and added Mg2+ were used in the sorption experiments viz. 0.5, 1 and 2 Mg2+ site-1. Surface complexation modeling of the Mg2+ sorption onto maghemite and magnetite, was restricted to pH conditions where the interference from Mg(OH)2(s) precipitation could be ruled out. The model calculations showed that Mg2+ sorb onto the magnetite and maghemite surfaces as a mixture of mono- or bidentate surface complexes at 0.5 Mg2+ site-1 and as monodentate complexes at 1 and 2 Mg2+ site-1 conditions. Mg2+ was also found to adsorb more readily at the maghemite surfaces in comparison with magnetite surfaces. For experiments with excess Mg2+ relative to the number of surface sites, the calculations suggested the formation of polynuclear surface complexes on maghemite.

  • 63.
    Karimi, Somayeh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran, Tehran, Iran.
    Mortazavi, Yadollah
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran, Tehran, Iran.
    Khodadadi, Abbas Ali
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran, Tehran, Iran.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Korelskiy, Danil
    Materials Technology and Chemistry, Alfa Laval Tumba AB, Tumba, Sweden.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Functionalization of silica membranes for CO2 separation2020In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 235, article id 116207Article in journal (Refereed)
    Abstract [en]

    Five organic CO2-philic functional groups were incorporated in silica matrixes for preparation of functionalized silica membranes to explore the CO2 separation performance. Chemical groups including acetate, trifluoromethyl, methacrylate, urea and vinyl groups were anchored in the silica network using the co-condensation method.

    The information from 29Si solid-state NMR and FTIR analyses indicates the successful formation of a covalent bond between functional groups and the silica network. The thickness of the functionalized silica layers was measured by SEM and the thermal stability of the organic groups was determined by thermogravimetric analysis (TGA).

    The gas permeance and mixed gas selectivity of CO2/N2 was measured in the temperature range of 253–373 K with a feed pressure of 9 bar. A maximum selectivity of as high as 10 was observed for a trifluoromethyl functionalized silica membrane with a CO2 permeance of 5.5 × 10−7 mol s−1 m−2 Pa−1. Permporometry measurements indicated that the contribution of flow through micropores to the total flow for all the functionalized silica membranes varied between 62 and 82%. All membranes were CO2 selective.

     

  • 64. Lidström-Larsson, Margareta
    et al.
    Fredriksson, Andreas
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Direct observation of a self-assembled monolayer of heptyl xanthate at the germanium/water interface: a polarized FTIR study2004In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 273, no 2, p. 345-349Article in journal (Refereed)
    Abstract [en]

    The adsorption of heptyl xanthate on germanium has been studied by the attenuated total reflection (ATR) technique. Polarized infrared light was used in situ to determine the average orientation of the alkyl chain in heptyl xanthate adsorbed at the germanium/solution interface. Spectra reveal the formation of closely packed xanthate ions with the alkyl chains in the all-trans conformation. The average tilt angle of the alkyl chains of heptyl xanthate was approximately 47° from the surface normal.

  • 65. Lidström-Larsson, Margareta
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Reversible phase transition in Zn₂(O,O-di(cyclohexyl)dithiophosphate)₄, studied by Raman spectroscopy and compared with NMR results2004In: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 34, no 2, p. 243-246Article in journal (Refereed)
    Abstract [en]

    It was recently shown by solid state ³¹P NMR spectroscopy that the number of phosphorous signals from the complex Zn₂(O,O-di(cyclohexyl)DTP)₄ varied reversibly with the temperature. According to the present study, Raman spectra of the same metal complex were also temperature dependent. Spectral features affected by the temperature changed reversibly upon raising and lowering the temperature. It was shown that conformational change of the hexyl rings and the P---O---C entities occurred in the temperature range between 40 and 55°C.

  • 66. Lidström-Larsson, Margareta
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Structure and orientation of collectors adsorbed at the ZnS/water interface2001In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 242, no 1, p. 25-30Article in journal (Refereed)
    Abstract [en]

    The adsorption of O,O-dibutyldithiophosphate and 2-mercaptobenzothiazole on the surface of ZnS has been studied by using the attenuated total reflection (ATR) technique. By utilizing polarized infrared radiation, we got qualitative information about the orientation of the adsorbed collectors. The difference between the absorbance of the s-polarized light and the absorbance of p-polarized light was used to draw conclusions about the orientation. The influence on the orientation of O,O-dibutyldithiophosphate and 2-mercaptobenzothiazole when adsorbing from a mixture of the two collectors is also reported, as well as the influence of these collectors on the hydrophobicity of the ZnS surface obtained by contact angle measurements.

  • 67. Lidström-Larsson, Margareta
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Xanthate adsorbed on ZnS studied by polarized FTIR-ATR spectroscopy2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, no 21, p. 8129-8133Article in journal (Refereed)
    Abstract [en]

    The structure and orientation of heptylxanthate adsorbed on a ZnS surface have been studied by the FTIR-ATR technique. By using polarized light and the dichroic ratio, we found the average tilt angle to be approximately 44 degrees. The adsorbed layer studied was prepared by self-assembly from solution or by spraying the solution onto the surfaces of the ATR crystal for a short time and then rinsing with water. From the spectra we can conclude that there is a mixture of adsorbed heptylxanthate and formed diheptyldixanthogen on the ZnS surface. A bridging coordination of the adsorbed heptylxanthate is proposed.

  • 68.
    Mihailova, B.
    et al.
    Luleå University of Technology.
    Engström, V.
    Luleå University of Technology.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Sterte, Johan
    A vibrational spectroscopic study of the growth of silicalite-1 films on seeded gold surfaces1999In: Porous materials in environmentally friendly processes: proceedings of the 1st International FEZA Conference / [ed] I. Kiricsi, Amsterdam: Elsevier, 1999, p. 221-228Conference paper (Refereed)
  • 69.
    Mihailova, B.
    et al.
    Luleå University of Technology.
    Engström, V.
    Luleå University of Technology.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Luleå University of Technology.
    Sterte, Johan
    Luleå University of Technology.
    Infrared spectroscopic study of a γ-mercaptopropyltrimethoxysilane monolayer on a gold surface1999In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 9, no 7, p. 1507-1510Article in journal (Refereed)
    Abstract [en]

    Reflectance-absorption infrared spectra of ?-mercaptopropyltrimethoxysilane (?-MPT) adsorbed on Au (111)-oriented films are analyzed on the basis of the calculated vibrational modes of a monomer, a dimer and n-membered rings of SiO3R (R=CH2CH2CH2SAu). The results show that the ?-MPT molecules adsorbed on the Au surface are partially hydrolyzed and that the orientation of the methyl groups and propyl chains are near perpendicular to the surface. After a hydrolysis procedure, the SiO3 groups in ?-MPT form a quasi two-dimensional system built predominantly of 6-membered puckered Si-O rings. Additional treatment of the ?-MPT monolayer with a surface-charge-reversing cationic polymer disrupts the connectivity and increases the topological disorder in the silicate system.

  • 70.
    Mihailova, B.
    et al.
    Luleå University of Technology.
    Engström, V.
    Luleå University of Technology.
    Hedlund, Jonas
    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.
    Sterte, Johan
    Luleå University of Technology.
    Vibrational spectroscopy study of the structure of silicalite-1 films on a gold surface1999In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 32, no 3, p. 297-304Article in journal (Refereed)
    Abstract [en]

    The structure of silicalite-1 films grown on seeded gold surfaces is investigated by modelling the observed changes in the infrared reflection absorption (IRRA) spectra of samples treated for different times in the synthesis solution. The results show that a gradual deformation of the five-membered silicon-oxygen rings occurs during the first 11 h of the hydrothermal treatment which leads to breaking of Si---O---Si linkages and to formation of linear defects along the c-axis. Interactions between the dislocations and the grain boundaries during the further growth of the film provoke the appearance of void spaces in the grain boundary interface which may cause incipient cracking in the silicalite-1 films on seeded gold surfaces. The range 1000-1300 cm-1 in the IRRA spectra is found to be appropriate for estimating the quality of silicalite-1 films grown on metal surfaces.

  • 71.
    Mohammed-Ziegler, Ildiko
    et al.
    Luleå University of Technology. Hemercy KKT, Csolnok, Hungary.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Luleå University of Technology.
    Ranheimer, Maine
    Luleå University of Technology.
    Adsorption of pinosylvin onto different species of fresh and stored wood2010In: Materials Science: An Indian Journal, ISSN 0974-7486, Vol. 6, no 4Article in journal (Refereed)
    Abstract [en]

    The adsorption of pinosylvin- a natural antifungal agent - on wood was studied byRamanmicroprobe technique. The adsorption properties of twelve different European wood species were compared. The effect of solvents used, heat treatment, and prolonged storage of the samples on pinosylvin adsorption ability was analysed by means of the Raman intensity ratios of characteristic lines. Itwas found that the surface concentration of pinosylvin increased when the Lewis acidity of the solvent increased. Besides, adsorption of pinosylvin was less efficient on during prolonged storage the surface of wood became more hydrophobic after prolonged sample storage. In case of heat treatment (120C, 3 h) no remarkable effect on the amount of adsorbed pinosylvin was observed. Simultaneously, the intensity of the fluorescence background increases. Moreover, the possible influence of B.E.T. specific surface area and lignin content (described by the kappavalue) on the amount of adsorbed pinosylvin was investigated.As revealed, B.E.T. specific surface area did not vary significantly between the different wood species, and therefore it has no significant effect on the efficiency of pinosylvin adsorption. However, the surface concentration of pinosylvin seems to increas with the lignin content. The amount of solvent residue in each sample wasmeasured by diffuse reflectance infrared Fourier transform (DRIFT) technique. For a few wood samples (e.g. pine heartwood, ash, and Hungarian oak) UV-Raman scattering was used to characterize the aromatic components of these wood species. The morphology of the samples was investigated with the aid of scanning electron microscopy (SEM) images. Furthermore, the B.E.T. specific surface area was found not to vary significantly between the different wood species, and therefore it has no significant effect on the efficiency of pinosylvin adsorption. However, the surface concentration of pinosylvin seems to increas with the lignin content. DRIFT spectroscopy was found to be useful to detect solvent residue in the wood samples and the evaporation of polar solvents is a rather slow process. However, it was not possible to detect adsorbed pinosylvin by DRIFT measurements, due to the low concentration and the lack of characteristic frequencies differing from other wood constituents.

  • 72.
    Mohammed-Ziegler, Ildiko
    et al.
    Arany J. u.28., Csolnok.
    Hórvölgyi, Zoltán
    Department of Physical Chemistry, Budapest University of Technology and Economics, Budapest.
    Tóth, András
    Research Laboratory of Materials and Environmental Chemistry, Chemical Research Center of the Hungarian Academy of Sciences, Budapest.
    Forsling, Willis
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wettability and spectroscopic characterization of silylated wood samples2006In: Polymers for Advanced Technologies, ISSN 1042-7147, E-ISSN 1099-1581, Vol. 17, no 11-12, p. 932-939Article in journal (Refereed)
    Abstract [en]

    Surfaces of three European wood species (namely, English oak, Hungarian oak, and Scots pine) and two tropical wood species (namely, teak and cloves) were silylated with dichlorodimethylsilane (DDS), dichlorodiphenylsilane (DPS) and octadecyltrichlorosilane (OTS) in the first step, and with chlorotrimethylsilane (CTMS) as a monofunctional reagent in a second step. Attenuated total reflection-Fourier transform infrared (ATR-FT-IR) and electron spectroscopy for chemical analysis (ESCA) measurements were performed in order to characterize the surface composition of the treated samples. The progress of surface modification was also monitored by contact angle measurements of different test liquids (water, formamide and diiodomethane). The water contact angles were found to be in the range of 80� to 145�. The most hydrophobic surface was obtained by two-step silylation by OTS and CTMS (water contact angles were between 131� and 140�). Interestingly, the hydrophobicity of DDS-treated samples showed a significant decrease after additional silylation by CTMS. The surface free energy values were evaluated in terms of the Lifshitz-van der Waals/acid-base theory. The results obtained by the surface analytical methods (i.e. FT-IR and ESCA measurements) were compared with the contact angle data. These results suggest that in the case of DDS-treated samples, CTMS molecules substitute partly the DDS molecules, thus only physisorption of the silylating agents is supposed at room temperature.

  • 73.
    Mohammed-Ziegler, Ildiko
    et al.
    Institute of Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest.
    Oszlanczi, Agnes
    Department of Physical Chemistry, Budapest University of Technology and Economics, Budapest.
    Somfai, B.
    Department of Physical Chemistry, Budapest University of Technology and Economics, Budapest.
    Hórvölgyi, Z.
    Department of Physical Chemistry, Budapest University of Technology and Economics, Budapest.
    Pászli, I.
    Department of Colloid Chemistry, Loránd Eötvös University.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Surface free energy of natural and surface-modified tropical and European wood species2004In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 18, no 6, p. 687-713Article in journal (Refereed)
    Abstract [en]

    To describe the wetting properties of various wood types from a practical point of view, the surface free energy of six tropical (guava, almond, teak, cloves, mango and neem) and six European wood species (English oak, Norway maple, hazel, ash, alder and Scots pine) were calculated using contact angles by the sessile-drop method. In order to provide water-repellent characteristics to the samples, they were silanized by a less used silylating reagent (using chloroform solution of trimethylsilyl N,N-dimethylcarbamate) and the results were compared with the effect of two commonly used reagents (chloroform solutions of chlorotrimethylsilane and octadecyltrichlorosilane). Since the Lifshitz-van der Waals/acid-base model is widely used in studies of biological surfaces, the energetics of the resultant wood surfaces were quantitatively described in terms of this model. For the mainly hydrophobic wood samples, anomalous surface behaviour (i.e. extremely high water contact angles (130-145°) and in certain cases unreasonably low surface free energy values) was found. Since the Lifshitz-van der Waals/acid-base model did not yield numerical results in some cases and the calculated surface free energies depended on the test liquid triplet used, the limitations in the applicability of this model are also discussed. For comparison, we analyzed our data also in terms of the Chang model.

  • 74.
    Mohammed-Ziegler, Ildikó
    et al.
    Luleå University of Technology. Chemical Research Center of the Hungarian Academy of Sciences, Institute of Chemistry, Budapest, Hungary.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Luleå University of Technology.
    Lindberg, Mats
    Luleå University of Technology.
    Ranheimer, Maine
    Luleå University of Technology.
    Mechanism of the adsorption process of pinosylvin and some polyhydroxybenzenes onto the structure of lignin2004In: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 36, no 1, p. 65-72Article in journal (Refereed)
    Abstract [en]

    The lignin Induline AT was used as model substrate to observe the adsorption of pinosylvin, trans-stilbene, pyrocatechol, resorcinol, hydroquinone, pyrogallol and phloroglucinol. Prior to adsorption the adsorbates were dissolved in diethylether. Infrared spectra of adsorbed compounds were recorded using the diffuse reflectance infrared Fourier transform (DRIFTS) technique. Far IR spectra of the adsorbed pinosylvin and polyhydroxybenzenes were used to facilitate the interpretation on the mechanism of adsorption. Vibrational analysis by quantum chemical calculations, available for most of the polyhydroxybenzenes, were utilized. The interaction between adsorbed species and lignin was found to be mainly mediated through the formation of hydrogen bonds.

  • 75.
    Nilsson, A.
    et al.
    Department of Physical Chemistry, Umeå University, Umeå, Sweden.
    Holmgren, Allan
    Department of Physical Chemistry, Umeå University, Umeå, Sweden.
    Lindblom, G.
    Department of Physical Chemistry, Umeå University, Umeå, Sweden.
    An FTIR study of the hydration and molecular ordering at phase transitions in the monooleoylglycerol/water system1994In: Chemistry and Physics of Lipids, ISSN 0009-3084, E-ISSN 1873-2941, Vol. 71, no 2, p. 119-131Article in journal (Refereed)
    Abstract [en]

    The liquid-crystalline phases of monooleoylglycerol and water have been investigated by FTIR spectroscopy. The use of polarized IR radiation made it possible to obtain the order parameters of transition moments in the lipid molecule. The order parameters as a function of the temperature and water content have been studied for the lamellar liquid-crystalline phase (L(α)). The decrease in the ordering of the C=O and C-O-CO stretching vibrations in the polar headgroup started earlier than for the CH=CH and CH2 stretching vibrations in the acyl chain region at the phase transition between lamellar and non-lamellar structures. The hydration of the ester carbonyl group increased with the water content. The ordering of the acyl chain decreases drastically in the two-phase regions, while it is nearly constant in the L(α) phase.

  • 76.
    Ohlin, Lindsay
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Berezovsky, Vladimir
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Farzaneh, Amirfarrokh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Holmgren, Allan
    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.
    Effect of Water on the Adsorption of Methane and Carbon Dioxide in Zeolite Na-ZSM-5 Studied Using in Situ ATR-FTIR Spectroscopy2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 51, p. 29144-29152Article in journal (Refereed)
    Abstract [en]

    Methane is the main component in biogas and natural gas along with contaminants such as water and carbon dioxide. Separation of methane from these contaminants is therefore an important step in the upgrading process. Zeolite adsorbents and zeolite membranes have great potential to be cost-efficient candidates for upgrading biogas and natural gas, and in both of these applications, knowing the nature of the competitive adsorption is of great importance to further develop the properties of the zeolite materials. The binary adsorption of methane and carbon dioxide in zeolites has been studied to some extent, but the influence of water has been much less studied. In the present work, in situ ATR (attenuated total reflection)–FTIR (Fourier transform infrared) spectroscopy was used to study the adsorption of water/methane and water/carbon dioxide from binary mixtures in a high-silica Na-ZSM-5 zeolite film at various gas compositions and temperatures. Adsorbed concentrations for all species were determined from the recorded IR spectra, and the experimental values were compared to values predicted using the ideal adsorbed solution theory (IAST). At lower temperatures (35, 50, and 85 °C), the IAST was able to predict the binary adsorption of water and methane, whereas the values predicted by the IAST deviated from the experimental data at the highest temperature (120 °C). For the binary adsorption of water and carbon dioxide, the IAST could not predict the adsorption values accurately. This discrepancy was assigned to the particular adsorption behavior of water in high-silica MFI forming clusters at hydrophilic sites. However, the predicted values did follow the same trend as the experimental values. The adsorption selectivity was determined, and it was found that the H2O/CH4 adsorption selectivity was decreasing with increasing water content in the gas phase at low temperatures whereas the selectivity was increasing at higher temperatures. The H2O/CO2 adsorption selectivity was increasing with increasing water content at all temperatures.

  • 77.
    Ohlin, Lindsay
    et al.
    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.
    Holmgren, Allan
    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.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ternary Adsorption of Methane, Water and Carbon Dioxide in Zeolite Na-ZSM-5 Studied Using in Situ ATR-FTIR Spectroscopy2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 27, p. 14703-14711Article in journal (Refereed)
    Abstract [en]

    The main component in biogas and natural gas is methane but these gases also contain water and carbon dioxide that often have to be removed in order to increase the calorific value of the gas. Membrane and adsorbent-based technologies using zeolites are interesting alternatives for efficient separation of these components. To develop efficient processes, it is essential to know the adsorption properties of the zeolite. In the present work, adsorption of methane, carbon dioxide and water from ternary mixtures in high silica zeolite Na-ZSM-5 was studied using in-situ ATR (Attenuated Total Reflection) – FTIR (Fourier Transform Infrared) spectroscopy. Adsorbed concentrations were extracted from the infrared spectra and the obtained loadings were compared to values predicted by the Ideal Adsorbed Solution Theory (IAST). The IAST could not fully capture the adsorption behavior of this ternary mixture, indicating that the adsorbed phase is not behaving as an ideal mixture. The CO2/CH4 adsorption selectivities determined for the ternary mixtures were compared to selectivities determined for binary mixtures in our previous work, indicating that the presence of water slightly improves the CO2/CH4 adsorption selectivity at lower temperatures. Further, the results show that water and carbon dioxide are adsorbed preferentially over methane in high silica zeolite Na-ZSM-5.

  • 78.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindberg, Henrik
    Luleå University of Technology.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The nature and location of SEBS-MA compatibilizer in polyethylene-wood flour composites1998In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 69, no 1, p. 201-209Article in journal (Refereed)
    Abstract [en]

    A maleic-anhydride-grafted styrene-ethylene - butylene-styrene (SEBS-MA) triblock copolymer has been used as a compatibilizer in low-density polyethylene-wood flour (LDPE-WF) composite system. The location of compatibilizer was studied using transmission electron microscopy (TEM). The unsaturated parts of the copolymer were stained with osmium tetraoxide (OsO4) to enhance contrast between the different phases. TEM micrographs indicated that part of the compatibilizer was located at the interface between the wood particles and PE matrix and that wood was also stained by the OsO4. The nature of the interface between the wood surface and the SEBS-MA was studied using Fourier transform infrared spectroscopy (FTIR). The results indicated that MA reacts with wood through esterification and hydrogen bonding and also possibly through interaction between the styrene and wood.

  • 79.
    Potapova, Elisaveta
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Carabante, Ivan
    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.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Studies of collector adsorption on iron oxides by in-situ ATR-FTIR spectroscopy2010In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 49, no 4, p. 1493-1502Article in journal (Refereed)
    Abstract [en]

    In this work, the adsorption of three model collectors, viz., poly(ethylene glycol) monooleate (PEGMO), ethyl oleate, and maleic acid, as well as the commercial fatty-acid-type collector Atrac 1563, was studied in situ on synthetic hematite using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The adsorption behavior of the studied compounds on hematite was determined to a large extent by the polar headgroup. Adsorption of Atrac and PEGMO as a function of concentration showed good agreement with the Freundlich adsorption model, suggesting energetically heterogeneous adsorption. In situ desorption experiments revealed that a large fraction of the Atrac was weakly attached to the hematite surface, as it was partially removed by flushing with water at pH 8.5 and 10. These results suggest that a separate washing unit after the flotation step could be beneficial in reducing the contamination of iron ore by flotation chemicals.

  • 80.
    Potapova, Elisaveta
    et al.
    Luleå University of Technology.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Luleå University of Technology.
    Hedlund, Jonas
    Luleå University of Technology.
    The effect of calcium ions and sodium silicate on the adsorption of a model anionic flotation collector on magnetite studied by ATR-FTIR spectroscopy2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 345, no 1, p. 96-102Article in journal (Refereed)
    Abstract [en]

    Previous studies have shown that agglomeration of the magnetite concentrate after reverse flotation of apatite is negatively affected by the collector species adsorbed on the surface of magnetite. In this work, the effect of ionic strength, calcium ions and sodium silicate on the unwanted adsorption of a model anionic flotation collector on synthetic magnetite was studied in-situ using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The amount of collector adsorbed was found to increase with increasing ionic strength at pH 8.5 providing evidence to the contribution of electrostatic forces to the adsorption of the collector. Adding sodium silicate to the system resulted in a three-fold decrease in the amount of collector adsorbed compared to when no sodium silicate was added, confirming the depressing activity of sodium silicate on magnetite. Calcium ions were shown to increase the adsorption of both the collector and sodium silicate on magnetite. The depressing effect of sodium silicate on collector adsorption was completely suppressed in the presence of calcium ions under the conditions studied. Furthermore, the amount of collector adsorbed on magnetite from the silicate-collector solution increased 14 times upon addition of calcium ions suggesting that calcium ions in the process water may increase undesired adsorption of the collector on the iron oxide.

  • 81.
    Potapova, Elisaveta
    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.
    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.
    The effect of polymer adsorption on the wetting properties of partially hydrophobized magnetite2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 367, no 1, p. 478-484Article in journal (Refereed)
    Abstract [en]

    Upon reverse flotation of iron ore, the surface of the iron ore concentrate may become partially hydrophobized due to adsorption of flotation collector, which is facilitated by the calcium ions present in the process water. Hydrophobic areas on the concentrate surface may introduce problems in subsequent pelletization of the concentrate. A possible way to restore the wettability of the surface could be by modifying the surface with a hydrophilic polymer. The effect of hydrophilic polymers of different types, viz. cationic, anionic, and non-ionic, on the wettability of the magnetite surface after adsorption of a surfactant was investigated. Although all the polymers could adsorb on magnetite at pH 8.5, the contact angle measurements revealed that only anionic ammonium polyacrylate could decrease the contact angle of synthetic magnetite after surfactant adsorption to a level close to that of as-synthesized magnetite. Such effect was probably achieved due to shielding of the hydrophobic surfactant chains from the aqueous phase by hydrophilic polyacrylate molecules. The fact that polyacrylate adsorption on magnetite occurred via calcium ions makes polyacrylate suitable for application in calcium-rich process water. The results presented in this work illustrate that ammonium polyacrylate could be successfully used to improve the wettability of magnetite after adsorption of surfactants.

  • 82.
    Potapova, Elisaveta
    et al.
    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.
    Surface modification of magnetite for improved pelletization of iron ore2012Conference paper (Refereed)
  • 83.
    Potapova, Elisaveta
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical 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.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    In-situ spectroscopic study of surfactants adsorption onto hematite from binary mixtures and the effect of inorganic ions2014In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 46, no 10-11, p. 1110-1114Article in journal (Refereed)
    Abstract [en]

    Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy has proven to be a powerful tool for surfactant adsorption studies. In many practical applications, surfactant mixtures and waters with different chemistry are employed, which significantly complicates adsorption studies. In this work, we investigate the effect of calcium and carbonate ions, frequently found in natural waters, on the co-adsorption of sodium dodecylbenzenesulfonate (SDBS) and a non-ionic primary alcohol ethoxylate (NEODOL 25–7) onto hematite at pH 8 and 10.5 using ATR-FTIR spectroscopy. Adsorption of SDBS was affected by pH and the presence of inorganic ions to a greater extent than the adsorption of NEODOL 25–7. A larger amount of SDBS was adsorbed at pH 8 than at pH 10.5 in all the experiments. The effect of co-adsorbing ions on the amount of SDBS adsorbed was significant only at pH 10.5 and not at pH 8. Calcium ions promoted adsorption of SBDS onto hematite, whereas addition of carbonate decreased the amount of SDBS adsorbed. In the presence of both calcium and carbonate ions, calcium carbonate precipitate was formed on the hematite surface, promoting accumulation of NEODOL 25–7 at the surface. NEODOL 25–7 was found to have a strong effect on the hydrophilicity of the hematite film when adsorbed in combination with SDBS. A more hydrophilic surface was obtained upon adsorption of the surfactants in the presence of sodium chloride, film dispersion occurred in the presence of calcium chloride, and a less hydrophilic surface was obtained in the presence of both calcium chloride and sodium carbonate

  • 84.
    Potapova, Elisaveta
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Jolsterå, Rickard
    Luossavaara-Kiirunavaara AB, 983 81 Malmberget, Sweden.
    Holmgren, Allan
    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.
    The effect of inorganic ions on dodecylbenzenesulfonate adsorption onto hematite: an ATR-FTIR study2014In: Journal of Surfactants and Detergents (JSD), ISSN 1097-3958, E-ISSN 1558-9293, Vol. 17, no 5, p. 1027-1034Article in journal (Refereed)
    Abstract [en]

    Linear alkylbenzenesulfonates (LAS) are an important group of anionic surfactants within the detergent industry and have also been suggested for use in mineral flotation and enhanced oil recovery. Because of its great industrial importance, there are a number of publications on the adsorption of LAS on metal oxides; however, the effect of co-adsorbing inorganic species on LAS adsorption has rarely been addressed. In this study we investigated the effect of calcium and carbonate ions on the adsorption of sodium dodecylbenzenesulfonate (DBS) onto hematite at pH 8 and 10.5 using in-situ ATR-FTIR spectroscopy. DBS adsorption on hematite was found to increase as pH was decreased from 10.5 to 8. Calcium ions promoted accumulation of DBS on hematite, with a larger amount of DBS on the surface at pH 10.5. Carbonate ions did not have any major effect on DBS adsorption on hematite. In the presence of both calcium and carbonate, the amount of DBS on the hematite surface was higher than without the two co-adsorbing ions but lower than with calcium ions alone. Likely, precipitation of calcite reduced the total concentration of calcium ions available for the interaction with DBS on the hematite surface. The results presented in this work clearly indicate the importance of water chemistry for DBS adsorption and allow predicting adsorption behavior of DBS on iron oxides from natural and process waters of different chemistry, which is important for the industrial applications of DBS and the fate of DBS in the environment.

  • 85.
    Potapova, Elisaveta
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Yang, X.
    Research Centre for Eco-Environmental Sciences, Chinese Academy of Science, Beijing.
    Westerstrand, Magnus
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Grahn, Mattias
    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.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Interfacial properties of natural magnetite particles compared with their synthetic analogue2011In: 5th International Flotation Conference 2011: (Flotation '11) ; Cape Town, South Africa, 14 - 17 November 2011, Red Hook: Curran Associates, Inc., 2011Conference paper (Refereed)
    Abstract [en]

    Understanding of the interactions between iron oxides and flotation reagents is important both for flotation and agglomeration of iron ore. Model systems comprising synthetic iron oxides and pure chemical reagents are commonly applied in experimental work in order to obtain high quality data and to ease the interpretation of the empirical data. Whether the results obtained using model systems are valid for iron ore minerals and commercial reagents is a question seldom addressed in the literature. It is shown in this work that previously reported results obtained from a model system, concerning adsorption of a carboxylate surfactant and sodium metasilicate onto synthetic magnetite nanoparticles, as obtained by in-situ ATR-FTIR spectroscopy and contact angle measurements, are applicable to adsorption of flotation reagents on magnetite concentrate. Additionally, the problem of restoring magnetite wetting after flotation is addressed since good wetting of a magnetite concentrate is required to produce iron ore pellets by wet agglomeration. The results from the present work indicate that the wettability of both synthetic magnetite coated with surfactant and magnetite concentrate after flotation can be improved by adsorbing a hydrophilizing agent such assilicate or polyacrylate.

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  • 86.
    Potapova, Elisaveta
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Yang, Xiaofang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Grahn, Mattias
    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.
    Forsmo, Seija
    LKAB.
    Fredriksson, Andreas
    LKAB.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The effect of calcium ions, sodium silicate and surfactant on charge and wettability of magnetite2011In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 386, no 1-3, p. 79-86Article in journal (Refereed)
    Abstract [en]

    Anionic carboxylate surfactants and sodium silicate are used in the reverse flotation of iron ore to separate magnetite from apatite. In this work, consecutive adsorption of sodium silicate and an anionic surfactant on synthetic magnetite modified with calcium ions was studied in the pH range 7.5–9.5 using in situ ATR-FTIR spectroscopy. The effect of these chemicals on the zeta-potential and wetting properties of magnetite was also investigated. While adsorption of silicate increased with increasing pH, subsequent surfactant adsorption went through a maximum at pH 8.5. Surfactant adsorption in the presence of calcium ions was not affected by the amount of silicate adsorbed on magnetite. Calcium ions were found to render the magnetite surface positive in the pH range 3–10 and could reduce the dispersing effect of silicate in flotation of apatite from magnetite. While treatment with calcium chloride and sodium silicate made magnetite more hydrophilic, subsequent adsorption of the anionic surfactant increased the water contact angle on the magnetite surface from about 10° to 40–50°. Although the latter values are not high enough to make magnetite float, the hydrophobic areas on the magnetite surface could result in the incorporation of air bubbles inside the iron ore pellets produced by wet agglomeration, lowering the pellet strength.

  • 87.
    Potapova, Elisaveta
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Yang, Xiaofang
    Luleå University of Technology.
    Sammelin, Desiré
    Department of Physics, Umeå University, Umeå, Sweden.
    Grahn, Mattias
    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.
    Fredriksson, Andreas
    LKAB, Kiruna, Sweden.
    Surfactant adsorption at the iron oxide/water interface: the effect of pH and calcium ions2010Conference paper (Other academic)
  • 88.
    Potapova, Elisaveta
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Yang, Xiaofang
    Research Centre for Eco-Environmental Sciences, Chinese Academy of Science, Beijing 100085, China.
    Westerstrand, Magnus
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Grahn, Mattias
    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.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Interfacial properties of natural magnetite particles compared with their synthetic analogue2012In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 36-38, no S1, p. 187-194Article in journal (Refereed)
    Abstract [en]

    Understanding of the interactions between iron oxides and flotation reagents is important both for flotation and agglomeration of iron ore. Model systems comprising synthetic iron oxides and pure chemical reagents are commonly applied in experimental work in order to obtain high quality data and to ease the interpretation of the empirical data. Whether the results obtained using model systems are valid for iron ore minerals and commercial reagents is a question seldom addressed in the literature. It is shown in this work that previously reported results obtained from a model system, concerning adsorption of a carboxylate surfactant and sodium metasilicate onto synthetic magnetite nanoparticles, as obtained by in situ ATR-FTIR spectroscopy and contact angle measurements, are applicable to adsorption of flotation reagents on magnetite concentrate. Additionally, the problem of restoring magnetite wetting after flotation is addressed since good wetting of a magnetite concentrate is required to produce iron ore pellets by wet agglomeration. The results from the present work indicate that the wettability of both synthetic magnetite coated with surfactant and magnetite concentrate after flotation can be improved by adsorbing a hydrophilizing agent such as silicate or polyacrylate.

  • 89.
    Raju, G. Bhaskar
    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
    Luleå University of Technology.
    Adsorption of dextrin at mineral/water interface1997In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 193, no 2, p. 215-222Article in journal (Refereed)
    Abstract [en]

    The adsorption mechanism of dextrin on aqueous minerals such as fluorite, apatite, galena, magnetite, γ-alumina, and graphite was studied by adsorption experiments, zeta potential measurements, and FT-IR studies. Depending on the nature of the mineral surface, dextrin was found to interact in three different ways viz. by chemisorption, physisorption, or hydrophobic-hydrophobic interaction. The adsorption density of dextrin was found to be pH dependent. Maximum adsorption of dextrin was obtained around the pH at which the mineral surface is highly hydroxylated. The mechanism of dextrin interaction with the surface metal hydroxy sites, (≡MeOH), was found to proceed via chemical complexation. A linear relationship was observed between the adsorption density of dextrin and the pH of maximum surface hydroxylation. Zeta potential measurements have indicated the possibility of dextrin adsorption by electrostatic interaction under the conditions where mineral surface and dextrin are oppositely charged. Furthermore dextrin was found to adsorb on hydrophobic minerals such as graphite by hydrophobic-hydrophobic interaction. However, the magnitude of adsorption by electrostatic and hydrophobic interaction was found to be very marginal compared to that of chemical complexation.

  • 90.
    Raju, G. Bhaskar
    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
    Luleå University of Technology.
    Complexation mechanism of dextrin with metal hydroxides1998In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 200, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    The complexation of dextrin with metal hydroxides was studied quantitatively by FT-IR and UV-visible reflectance spectroscopic techniques. Though three hydroxyl groups are present in each dextrin molecule, complexation involving only two hydroxyl groups situated at the C-2 and C-3 positions has been studied by many investigators. Involvement of a third hydroxyl group situated at the C-6 position was examined in the present study. Since metal hydroxy sites were found to play a key role in the complexation, precipitates of Ca(OH)2and Pb(OH)2were separately mixed with dextrin solutions at different ratios. Complexes with a stoichiometry of 2:3 (dextrin:metal ion) were identified, indicating the involvement of a third hydroxyl group. However, the ratio of metal ions to hydroxyl groups of dextrin remained as 1:2. Complexation between dextrin and metal hydroxide via a condensation mechanism is proposed.

  • 91.
    Ringqvist, L.
    et al.
    Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Oborn, I.
    Swedish University of Agriculture Sciences, Department of Soil and Environment.
    Poorly humified peat as an adsorbent for metals in wastewater2002In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 36, no 9, p. 2394-2404Article in journal (Refereed)
    Abstract [en]

    Metal adsorption and surface charge determinations were performed previously on well-characterised Sphagnum and Carex peat samples. The aim of this investigation was to determine metal adsorption from complex wastewaters onto these peat samples and compare it to the adsorption onto peat granules, clinoptilolite, glauconite and a flue dust from steel production. A sulphide mine leachate, a landfill leachate and a laundry wastewater were chosen, giving a variation in pH, ionic strength, total organic carbon and concentrations of metals. Metal adsorption was determined in batch and column experiments. The wastewater composition was of great importance for metal removal efficiency, mainly due to the difference in dominating metal species. In the sulphide mine leachate, containing free metal ions, a high metal adsorption was observed onto both peat and inorganic adsorbents. In the landfill leachate the metals formed carbonate and organic complexes and a low metal removal was achieved. Contrary to the leachates, the laundry wastewater contained suspended particles. The high amount of metals removed, 80% of the Cu and 30-60% of the Zn concentration, was probably withdrawn bound to the particle fraction. The highest removal of metal ions was obtained in the sulphide mine leachate with Carex peat, removing 97-99% of the Zn and 85-100% of the Cu content. The Sphagnum peat sample removed 37-77% of the Zn and 80-100% of the Cu content. The differences found between Sphagnum and Carex peat were attributed to the original chemistry of the plant material and the habitat conditions at the time of peat formation. Generally, the combination of glauconite or clinoptilolite with the peat samples in column experiments gave a minor improvement in metal removal.

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  • 92. Roonasi, Payman
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) study of oleate adsorbed on magnetite nano-particle surface2009In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 255, no 11, p. 5891-5895Article in journal (Refereed)
    Abstract [en]

    Magnetite nano-particles were coated with sodium oleate and the spectral behaviour of the coating layer was studied by FTIR spectroscopy after the particles had been heated in air and argon. Magnetite was synthesized by controlled co-precipitation and subsequently coated with sodium oleate. Thermal analysis in combination with mass spectroscopy was carried out to support the FTIR spectroscopic interpretations, but also to monitor the decomposition and surface reaction of oleate adsorbed on the magnetite surface. It was deduced from FTIR and TGA results that the oleate molecules are bonded to iron atoms by a bidentate mononuclear complex and form essentially a single layer with a distance between oleate molecules of ∼36 Å2. It was shown by IR as well as Raman spectroscopy that oleic acid, when heated in air, undergoes decomposition implying that new carbon-oxygen bonds are formed. Heating the iron oxide-oleate system in air also implies oxidation of the double bond at the C:9 position of the alkyl chain and formation of intermediate oxygen-rich molecules. An enthalpy change of ΔH = 49.86 J/g was obtained for oleate desorption/decomposition at ∼350 °C under argon atmosphere and a carbonaceous graphitic species resulted from this decomposition.

  • 93. Roonasi, Payman
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A study on the mechanism of magnetite formation based on iron isotope fractionation2009In: EPD Congress 2009: proceedings of sessions and symposia sponsored by the Extraction and Processing Division (EPD) of The Minerals, Metals & Materials Society (TMS) / [ed] Stanley M. Howard, Warrendale, Pa.: Minerals, Metals & Materials Society, 2009, p. 829-836Conference paper (Refereed)
    Abstract [en]

    Having knowledge of mechanism of magnetite formation is essential in a number of industrial processes including magnetite synthesis and corrosion of iron. In this study, magnetite nano-particle was synthesized via two different ways; coprecipitation of iron (II) and (III) and oxidation of ferrous hydroxide. The samples were characterized using X-ray diffraction (XRD), Mid-Far IR spectroscopy, scanning electron microscopy (SEM), chemical analysis for determination of Fe II/Fe III ratio and ICP-MS for iron isotopic ratio (56Fe/54Fe) measurement. Since fractionation of iron isotopes depends on reaction rate and bonding strength, interpretation of the isotopic data with respect to the possible mechanisms is discussed. No fractionation of iron isotopes was observed for the magnetite synthesized by coprecipitation, whilst magnetite formed from ferrous hydroxide showed higher abundance of '4Fe compared to 56Fe in the beginning of reaction, implying the significance of the following reaction: Fe (OH)2 (solid) < -- > [Fe (OH)]+(aq) + OH-.

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  • 94. Roonasi, Payman
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    An ATR-FTIR study of carbonate sorption onto magnetite2010In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 42, no 6-7, p. 1118-1121Article in journal (Refereed)
    Abstract [en]

    Carbonate is one of the most abundant anions in ground water. It also appears as saturated concentration in the process water at LKAB, a mining company in the northern part of Sweden. Sorption of carbonate on magnetite (the major source of iron ore in this company) may affect the surface chemistry of the iron oxide by forming a carbonate surface instead of an oxide surface. This would affect the interactions between magnetite particles and other species dissolved in the process water. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) has proved to be a useful technique in the study of adsorption/desorption properties of ions in mineral processing and environmental science. Magnetite was synthesized by coprecipitation of Fe II and Fe III in alkaline solution and deposited on a ZnS internal reflection element. Adsorption of carbonate on magnetite, and the effect of pH, Na, Ca, and silicate ions on the amount and speciation of adsorbed carbonate was monitored in situ. Adsorption of carbonate onto magnetite was found to increase with the acidity of the solution from pH 8. 5 to pH 6. 5 and also increased with increasing calcium concentration from 0 to 1. 0 mM. The spectroscopy results were discussed and compared with previous findings in the literature

  • 95. Roonasi, Payman
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    An ATR-FTIR study of sulphate sorption on magnetite: rate of adsorption, surface speciation, and effect of calcium ions2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 333, no 1, p. 27-32Article in journal (Refereed)
    Abstract [en]

    The adsorption of sulphate on magnetite was studied in-situ using ATR-FTIR spectroscopy. Synthetic magnetite particles were deposited on a ZnSe internal reflection element and the spectra of sulphate adsorbed at pH 4-8.5 were recorded. Two different ionic strengths were used viz. 0.01 M and 0.1 M NaCl. The spectra of adsorbed sulphate on magnetite coated ZnSe were compared with the spectra of sulphate solutions at the same pH values and in contact with uncoated ZnSe. The spectrum of adsorbed sulphate at pH 4 showed three maxima at 979, 1044, and 1115 cm-1 indicating a monodentate adsorption in which the Td symmetry of SO42 - is lowered to C3v. At pH 6.5, sulphate adsorbed as an outer-sphere complex with two weak bands appearing at 1102 and 980 cm-1. Moreover, spectra of the adsorbed sulphate at pH 4 were recorded as a function of time and sulphate concentration. The equilibrium absorbance at different concentrations fitted a Langmuir type adsorption isotherm. The Langmuir affinity constant K at pH 4 was determined from the slope and intercept of the Langmuir plot to be K = 1.2344 × 104 M- 1 and the Gibbs free energy of adsorption Δ Gads0 was estimated from this value to be -33.3 kJ/mol. Kinetic analysis indicated that adsorption at pH 4 is fast, whilst the desorption kinetic at the same pH is very slow. In addition, the effect of Ca ions on sulphate adsorption was also studied. It was shown that Ca ions increased the sulphate adsorption on magnetite at pH 8.5.

  • 96. Roonasi, Payman
    et al.
    Yang, Xiaofang
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Competition between sodium oleate and sodium silicate for a silicate/oleate modified magnetite surface studied by in-situ ATR-FTIR Spectroscopy2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 343, no 2, p. 546-552Article in journal (Refereed)
    Abstract [en]

    Attenuated Total Reflection (ATR) IR spectroscopy was utilized to monitor adsorption of sodium oleate and sodium silicate onto synthetic magnetite at pH=8.5, both individually and in a competitive manner. Oleate was adsorbed within a concentration range of 0.01 mM-0.5 mM. It was observed that adsorption of oleate increased linearly with increasing concentration of oleate in solution up to a concentration of 0.1 mM. The infrared spectrum of oleate showed a broad single band at 1535 cm-1 assigned to the asymmetric stretching vibration of carboxylate, implying chemisorption of oleate to the magnetite surface. The kinetics of oleate adsorption followed a pseudo first-order reaction with an apparent rate constant of k1= 0.030 ± 0.002 min-1. Competitve adsorption of silicate and oleate was performed either by adding silicate solution to a magnetite film initially equilibrated with 0.1 mM oleate or adding oleate solution to magnetite treated with silicate solutions in the concentration range 0.1 mM - 5mM. It was shown that silicate, within reasonable time, had only minor effect on the amount of oleate already adsorbed on magnetite. On the other hand, oleate did not efficiently compete with silicate if the latter substance was already adsorbed on the iron oxide.

  • 97. Ruth, Katja Viventsova
    et al.
    Kumpiene, Jurate
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Gunneriusson, Lars
    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.
    Changes in soil organic matter composition and quantity with distance to a nickel smelter: a case study on the Kola Peninsula, NW Russia2005In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 127, no 3-4, p. 216-226Article in journal (Refereed)
    Abstract [en]

    The capacity of soils to absorb contamination depends on a number of factors, such as soil organic matter (SOM) that plays an essential role in adsorption of metal ions, especially in Podzols with their low content of clay minerals. Detailed analysis of SOM can provide information about the potential capacity of a soil to mobilise or immobilise contaminating substances, which in turn can be used to predict potential recovery of the soil ecosystem following heavy metal pollution. The purpose of this study was to learn how an increasing load of heavy metals (Cu and Ni) affects SOM content and structure, and which of the SOM functional groups are responsible for metal retention. The study area is located in the central part of the Kola Peninsula, south of Monchegorsk city and the nickel smelting complex ‘Severonickel’. The amount of total carbon in the soil decreased from 86% to 0.6% as the distance from the smelting complex decreased from 34 to 2 km. Functional groups of the SOM had a larger diversity in less polluted soils than in the soils located closer to the smelting complex. Carboxyl groups had a higher intensity of infra red (IR) bands in soils collected at the distance of 34–27 km than those located closer to the smelter. The most disturbed soil at the site closest to the smelter showed almost no presence of COOH groups. We conducted a laboratory experiment using soils from the least polluted sampling site to assess which SOM functional groups may be responsible for metal retention. Experimental contamination of the soil with the Cu/Ni solution resulted in an overall decrease in the absorbance for all studied functional groups within the measured range, except for COOH. This could be attributed both to changes in the structure of the SOM caused by its reaction with the contaminating substances, and to the leaching of some of the organic compounds from the soil during the experiment. Further studies are needed to better understand which functional groups in the SOM are active in the adsorption processes.

  • 98.
    Shah, Faiz Ullah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rutland, Mark W.
    Surface and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology.
    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. Department of Physics, University of Warwick.
    Interfacial Behavior of Orthoborate Ionic Liquids at Inorganic Oxide Surfaces Probed by NMR, IR and Raman Spectroscopy2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 34, p. 19687-19698Article in journal (Refereed)
    Abstract [en]

    Absorption modes and reactivity of non-halogenated ionic liquids (ILs) at inorganic oxide surfaces of γ-Al2O3, MgO and SiO2 particles were characterized using multinuclear (11B, 31P and 29Si) solid-state magic-angle-spinning NMR, FTIR and Raman spectroscopy. ILs are composed of the trihexyl(tetradecyl)phosphonium cation, [P6,6,6,14]+, and bis(mandelato)borate, [BMB]-, or bis(salicylato)borate, [BScB]-, anions. Spectroscopic measurements were performed on room temperature (298 K) samples and samples exposed to 15 hours of heating at 373 K. The single pulse 11B NMR data of heated [P6,6,6,14][BMB] mixed with the inorganic oxides showed a significant change in spectra of the anion for all three oxides. In contrast, no such spectral changes were detected for heated [P6,6,6,14][BScB] mixed with the inorganic oxides. 31P MAS NMR data for the IL/metal oxide systems revealed interactions between [P6,6,6,14]+ and the surfaces of oxides. A significant intensity of 31P CP-MAS NMR signals indicated a low mobility of cations in these systems. The existence of strongly adhered surface layers of ILs on SiO2 particles was also confirmed by 1H-29Si CP-MAS NMR spectroscopy. FTIR and Raman spectroscopic data revealed strong interactions between the anions and the inorganic surfaces and there is strong correlation with the data obtained from NMR spectroscopy. Although their chemical structures are rather similar, the [BScB]- anion is more stable than the [BMB]- anion at the inorganic oxide surface.

  • 99.
    Wang, Zeng
    et al.
    Luleå University of Technology.
    Larsson, Margareta L.
    Luleå University of Technology.
    Grahn, Mattias
    Luleå University of Technology.
    Holmgren, Allan
    Luleå University of Technology.
    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)
    Abstract [en]

    Thin silicalite-1 films were grown on ATR crystals and used for detection of low amounts of organic molecules in a gas flow by FTIR spectroscopy.

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  • 100.
    Wang, Zheng
    et al.
    Luleå University of Technology.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lidström-Larsson, Margareta
    Luleå University of Technology.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sterte, Johan
    Växjö University, Växjö, Sweden.
    Hedlund, Jonas
    Luleå University of Technology.
    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.

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