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  • 1.
    Agthe, Michael
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Wetterskog, Erik
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Salazar-Alvarez, German
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Bergström, Lennart Magnus
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Dynamic growth modes of ordered arrays and mesocrystals during drop-casting of iron oxide nanocubes2014Inngår i: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 16, nr 8, s. 1443-1450Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The growth modes of self-assembled mesocrystals and ordered arrays from dispersions of iron oxide nanocubes with a mean edge length of 9.6 nm during controlled solvent removal have been investigated with a combination of visible light video microscopy, atomic force microscopy and scanning electron microscopy. Mesocrystals with translational and orientational order of sizes up to 10 μm are formed spontaneously during the final, diffusion-controlled, drop-casting stage when the liquid film is very thin and the particle concentration is high. Convection-driven deposition of ordered nanocube arrays at the edge of the drying droplet is a manifestation of the so called coffee-ring effect. Dendritic growth or fingering of rapidly growing arrays of ordered nanocubes could also be observed in a transition regime as the growth front moves from the initial three-phase contact line towards the centre of the original droplet.

  • 2.
    Aguilar, Wilson
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Study of the Synthesis of ZSM-5 from Inexpensive Raw Materials2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    ZSM-5 is an aluminosilicate with high silica ratio with suitable properties for catalysis, ion exchange, adsorption and membrane applications. ZSM-5 is usually produced industrially from concentrated systems in which there is formation of an amorphous gel phase. Typical syntheses of ZSM-5 require sources of silicon and aluminium, a mineralizer and an organic molecule as so-called templating agent. The silicon and aluminum sources widely used for the synthesis are pure reagent chemicals and in particular quaternary ammonium compounds like tetrapropyl ammonium hydroxides (TPA-OH), are employed as templating agents. Unfortunately, these compounds are rather expensive. Demand for inexpensive sources of aluminosilicates for the synthesis of ZSM-5 has increased during the last two decades. Natural raw materials such as kaolin clay and diatomaceous earth (diatomite) are two potential inexpensive sources of silica and alumina. Moreover, the molecule n-butylamine (NBA) has been reported as a low-cost templating agent to replace the quaternary ammonium compounds. The aim of this work was to show for the first time that leached metakaolinite or diatomite in combination with sodium hydroxide and n-butylamine could be used as inexpensive raw materials for the synthesis of ZSM-5 without using an additional source of silica. After synthesis optimization, both sources of aluminosilicate were found to behave differently during the course of synthesis and led to slightly different products. The chemical composition of the raw materials and the products were determined using inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). Crystallinity was examined by X-ray diffractometry (XRD), the morphology was studied by extreme-high-resolution scanning electron microscopy (XHR-SEM) and the specific surface area was estimated from nitrogen adsorption data by the BET method. The chemical composition of individual crystals was determined by energy dispersive spectrometry (EDS). Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO2/Al2O3 ratios and reduced the amount of impurities. The final ZSM-5 products had a SiO2/Al2O3 ratio in the range 20 – 40. The use of leached diatomite allowed reaching higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of mordenite were formed, which was related to the high calcium content of diatomite. Another considerable advantage of diatomite over kaolin is that diatomite does not require heat treatment at high temperature to convert the kaolin to reactive metakaolin. Further characterization of the system by XHR-SEM and EDS at low voltage was carried out in order to understand the nucleation and early growth of the ZSM-5 zeolite crystals. The observations with unprecedented detail strongly suggest that nucleation and the succeeding growth occurs on the gel surface. The growth rates in the various crystallographic directions already at an early stage are such that the shape of the growing crystals resembles that of the final crystals. However, as the early growth is interface mediated, the growth rate along the gel particles is high and the gel particles will become partially embedded inside the growing crystals at an early stage. The Si and Al nutrients are probably transported along the solid/liquid interface and possibly through the liquid in the form of nanoparticles detaching from the gel. The organic template was initially contained in the liquid. However, it remains unclear at which stage the template becomes incorporated in the solid material. EDS at low voltage was also used to gain compositional information about the sodium/calcium ion exchanged products and extraneous phases when kaolin and Bolivian montmorillonite clay were used for the synthesis of zeolite A by alkali fusion. In order to evaluate the cation exchange capacity (CEC) of the synthesized zeolite, ICP-SFMS and EDS were compared. The EDS method used in this work resulted in (Na,Ca)/Al ratios in equivalent moles very close to 1.0 as expected and was therefore found more reliable than ICP-SFMS to measure cation exchange capacity for zeolite A. To summarize, the present work shows that it was possible to synthesize well-crystallized ZSM-5 zeolite from inexpensive raw materials such as leached metakaolin or leached diatomite, sodium hydroxide and n-butyl amine. Furthermore, the crystallization mechanism evidenced in this system might be more general and also apply for other concentrated systems, e.g. those using TPA as structure-directing. Finally, this work displays that EDS at low voltage can provide valuable local compositional information in the field of zeolite synthesis.

  • 3.
    Aguilar, Wilson
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Cardenas, Edgar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Dendritic growth of NBA-ZSM-5Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Crystallization of ZSM-5 zeolite from a gel using n-butylamine as structure-directing agent was studied. Extreme high-resolution transmission and scanning electron microscopy showed the presence of dendritic features that are present at the crystal surface during most of the reaction time that become smoother towards completion of the crystallization. In addition, a web that likely stems from the gel, comprised of alumina-rich nanoparticles between the dendrites at the surface of the crystals was also identified. When the gel is not in direct contact with the crystal surface, dendrites and the web are not observed, and the crystals grow faster. Thus, the alumina-rich web retards the crystal growth and cause the formation of dendritic features.

  • 4.
    Aguilar, Wilson
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Garcia, Gustavo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Comparison between leached metakaolin and leached diatomaceous earth as raw materials for the synthesis of ZSM-52014Inngår i: SpringerPlus, E-ISSN 2193-1801, Vol. 3, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inexpensive raw materials have been used to prepare ZSM-5 zeolites with SiO2/Al2O3 molar ratios in the range 20 - 40. Kaolin or Bolivian diatomaceous earth was used as aluminosilicate raw materials and sodium hydroxide and n-butylamine were used as mineralizing agents and template. Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO2/Al2O3 ratios and to reduce the amount of iron and other impurities. After mixing the components and aging, hydrothermal treatment was carried out and the products were recovered The results clearly show for the first time that well-crystallized ZSM-5 can be directly prepared from leached metakaolin or leached diatomaceous earth using sodium hydroxide and n-butylamine as mineralizing agents and template under appropriate synthesis conditions. A longer induction time prior to crystallization was observed for reaction mixtures prepared from leached diatomaceous earth, probably due to slower digestion of the fossilized diatom skeletons as compared with that for microporous leached metakaolin. The use of leached diatomaceous earth allowed higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of Mordenite formed, which was related to the high calcium content of diatomaceous earth. Another considerable advantage of diatomaceous earth over kaolin is that diatomaceous earth does not require heat treatment at high temperature for metakaolinization.

  • 5.
    Aguilar-Mamani, Wilson
    et al.
    Department of Chemistry, Faculty of Science and Technology, San Simon University, UMSS, Cochabamba.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Solution-mediated growth of NBA-ZSM-5 crystals retarded by gel entrapment2018Inngår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 487, s. 57-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis of flat tablet-shaped ZSM-5 crystals from a gel using metakaolin as aluminosilicate source and n-butyl amine as structure directing agent was investigated. The evolution inside the solid phase was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetry and mass spectrometry. A kinetic study indicated that the nucleation of the majority crystals occurred concurrently with the formation of the gel upon heating the starting liquid suspension. Microstructural evidences undeniably showed that the gel precipitated on ZSM-5 crystals and mineral impurities originating from kaolin. As a result, crystal growth was retarded by gel entrapment, as indicated by the configuration and morphology of the embedded crystals. The results presented herein are harmonized with a solution-mediated nucleation and growth mechanism. Our observations differ from the autocatalytic model that suggests that the nuclei rest inside the gel until released when the gel is consumed. Our results show instead that it is crystals that formed in an early stage before entrapment inside the gel that rest inside the gel until exposed at the gel surface. These results illustrate the limitation of the classical method used in the field to determine nucleation profiles when the crystals become trapped inside the gel.

  • 6.
    Aguilar-Mamani, Wilson
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Department of Chemistry, Faculty of Science and Technology, San Simon University, Cochabamba, Bolivia.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Internal structure of a gel leading to NBA-ZSM-5 single crystals2018Inngår i: Journal of porous materials, ISSN 1380-2224, E-ISSN 1573-4854, Vol. 25, nr 6, s. 1551-1559Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Porous gel structures are formed during the synthesis of the zeolite ZSM-5 due to the reaction between a source of aluminosilicate, sodium hydroxide, water and a structure directing agent, such as e.g. tetrapropylammonium (TPA) or n-butylamine (NBA). In the present work, the formation of the gel in a heterogeneous system leading to the crystallization of NBA-ZSM-5 zeolite from leached metakaolin was studied extensively. The solid and liquid phases obtained after separation were analyzed by inductively coupled plasma sector field mass spectrometry, dynamic light scattering, extreme high resolution-scanning electron microscopy, energy dispersive spectroscopy, high resolution-transmission electron microscopy, X-ray diffraction and nitrogen gas adsorption. The main gel phase formed after hydrothermal treatment exhibited a sponge-like structure resembling those forming in (Na, TPA)-ZSM-5-based systems. For the first time, the walls of the main gel were shown to be inhomogenous and to possess a biphasic internal structure consisting of a mesoporous skeleton of aluminosilicate nanoparticles embedded in a silicate-rich soluble matrix of soft matter. The data presented in this paper is of primary importance to understand the mechanism by which the gel is consumed and contributes to the growth process of the zeolite crystals.

  • 7.
    Aiello, R.
    et al.
    University of Calabria.
    Artioli, G.
    University of Milan.
    Carotenuto, L.
    MARS Center, Naples.
    Colella, C.
    University of Naples.
    Norby, P.
    University of Oslo.
    Sterte, Johan
    Zeolite synthesis in microgravity2005Inngår i: Topical teams in life & physical sciences: towards new research applications, Noordwijk, Netherlands: ESTEC , 2005, s. 78-85Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    The results of activities performed by the members of the Topical Team on 'Zeolites synthesis in microgravity' are discussed. A method was developed using a two-temperature synthesis procedure to distinguish between the nucleation and growth phase of the crystallization. The experiments have investigated the possibility of suppressing secondary nucleation by imposing a temperature gradient. Optical thickness of the solution has been monitored by interferometry. The Team, on the basis of findings, has elaborated a research program on zeolite film deposition that includes microgravity experimentation.

  • 8.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ojuva, Arto
    Stockholm University, Department of Materials and Environmental Chemistry.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    All-Zeolite Membranes2010Konferansepaper (Fagfellevurdert)
  • 9.
    Akhtar, Farid
    et al.
    Stockholm University, Department of Materials and Environmental Chemistry.
    Ojuva, Arto
    Stockholm University, Department of Materials and Environmental Chemistry.
    Wirawan, Kompiang
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Bergström, Lennart
    Stockholm University, Department of Materials and Environmental Chemistry.
    Hierarchically porous binder-free silicalite-1 discs: a novel support for all-zeolite membranes2011Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, nr 24, s. 8822-8828Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal expansion mismatch between the zeolite film and the support is an important cause for the formation of defects and cracks during the fabrication and use of zeolite membranes. We have studied how silicalite-1 discs with a permeability comparable to commercially available alumina supports can be produced by pulsed current processing (PCP) as a novel substrate for all-zeolite membranes. Hierarchically porous and mechanically strong membrane supports where the surface area and crystallography of the silicalite-1 particles were maintained could be obtained by carefully controlling the thermal treatment during PCP consolidation. In situ X-ray diffraction and dilatometry showed that the coefficient of thermal expansion (CTE) of the silicalite-1 substrate was negative in the temperature range 200-800 degrees C while the commonly used alumina substrate displayed a positive CTE. The critical temperature variation, Delta T, and thicknesses for crack-free supported zeolite films with a negative CTE were estimated using a fracture energy model. Zeolite films with a thickness of 1 mu m can only sustain a relatively modest Delta T of 100 degrees when supported onto alumina substrates while the all-zeolite membranes can support temperature variations above 500 degrees

  • 10.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ojuva, Arto
    Stockholm University, Department of Materials and Environmental Chemistry.
    Wirawan, Kompiang
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    PCP procesing of Zeolite supports for all-zeolite membranes2011Konferansepaper (Fagfellevurdert)
  • 11.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sjöberg, Erik
    Korelskiy, Danil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rayson, Mark
    Department of Chemistry, The University of Surrey, Guildford.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H2 separation performance2015Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 493, s. 206-211Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    raded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H2 separation factor of 12 at 0 °C and a CO2 permeance of 21.3×10-7 mol m-2 s-1 Pa-1 for an equimolar CO2/H2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.

  • 12.
    Andersson, Anna
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    CFD optimization of photochemical UV reactors for VOC degradation2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In 2016 the World Health Organization released a report on Ambient Air Pollution, in this it was stated that one out of every nine deaths all around the world in 2012 were due to air-pollution-related conditions. Urban air pollution involves a broad range of compounds from many diverse sources. Volatile Organic Compounds (VOCs) are some of the important compounds. Almost all VOCs are known to have effect on human health, many of them are carcinogenic. VOCs also contribute to the ground level photochemical smog and the reduction of the stratospheric ozone layer. Therefore, it is important to control the emissions of VOCs from industries and restaurants.

    Today most big scale VOC removal is done by thermal or catalytic incineration. While smaller scale air purification is done by using adsorbing materials such as activated carbon. Both these methods have their drawbacks. A promising technology, which is also environmentally friendly, is UV reactors.

    This thesis is a collaboration with the company Centriair, a company developing and selling UV reactors mainly for odor removal. The UV reactors which are in use today show acceptable performance, with a conversion of 50-60%. However, they have yet to be optimized to get the most out of the reactors. The aim was to try to reach an as high conversion of VOCs as possible in a prototype scale compared to a reference reactor, also in prototype scale. The reactors were simulated using the Computational Fluid Dynamic (CFD) software COMSOL Multiphysics® 5.2a. The simulation was based on earlier lab scale experiments with UV reactors.

    The conclusion from doing this thesis is that the most important challenge with a UV reactor up-scaling and optimization is the dark zones and the bypassing effect given by these. It is very important that the irradiation reaches the whole reactor and that all gas is affected by it. It is also important that the gas is given time to stay by the light sources as long as possible. Two reactors in this thesis had very high conversion results and thus showed potential of being very effective UV reactors. These two reactors showed conversion results of 45% respective 61% higher than the reference reactor used by Centriair today.

  • 13.
    Andersson, Charlotte
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Factors affecting MFI membrane quality2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Zeolites are crystalline aluminosilicates with molecular sieving properties and are widely used in industrial applications such as catalysis, sorption and ion-exchange. Zeolite membranes are highly interesting due to their capability to continuously separate molecules under severe conditions. The MFI zeolite structure has suitable pore diameter for many applications, and its thermal and chemical stability is high. In order to obtain high performance MFI membranes, a thin and defect free film is needed for high flux and high selectivity. In this thesis, parameters affecting quality of zeolite membranes have been investigated. Different MFI-zeolite membranes were prepared using seed crystals and hydrothermal synthesis. Thereafter, membranes were characterized using scanning electron microscopy, single gas permeation measurements, porosimetry and separation experiments. The effect of grain boundaries was investigated by preparing membranes with small crystal size. It was found that a high amount of grain boundaries reduced the quality of the membranes. In another study, the effect of exposure to aqueous solutions was found to increase the amount of non-zeolitic pores in the membrane, and thus it decreased the quality of the membrane. However, no such effect was found for ethanol that was identified as a safe rinsing media. Membranes with different Si/Al ratio were also prepared and evaluated. It was observed that the Si/Al ratio of a MFI membrane influences the performance of the membrane. It was found that an increase of aluminium makes the membrane more polar which leads to an improved adsorption of, and selectivity for polar molecules. The effect of support invasion was also evaluated and the regularity and extension of the support invasion was observed to affect membrane quality. The effect of heating rate during calcination was investigated and no correlation between heating rate and membrane quality was observed. Calcination of membranes was studied in-situ by high temperature synchrotron radiation and a model for crack formation was postulated. In summary, this work has shown that in order to obtain high quality membranes, the amount of grain boundaries, the film thickness and support invasion should be controlled. To obtain the best performance of the membranes the Si/Al ratio should be chosen with respect to the application. Finally, water exposure affects the lifetime of the MFI membranes in certain applications.

  • 14.
    Andersson, Charlotte
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Properties of molecular sieve membranes2004Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Zeolites are crystalline aluminosilicates with molecular sieving properties and are widely used in industry for catalysis, sorption and ion-exchange applications. Zeolite membranes are commercially interesting since this technology may be employed for continuous separation of molecules under severe conditions. MFI zeolite has suitable pore diameter for many applications and relatively high thermal and chemical stability. Zeolite films in membranes must be thin, to obtain a high flux and free from defects for high selectivity. Many parameters are affecting the properties of zeolite films and in this thesis some of them are investigated. MFI zeolite membranes were prepared using seed crystals and hydrothermal synthesis and characterized with scanning electron microscopy, single gas permeation measurements, porosimetry and separation experiments. Membranes grown in one or several steps with seeding in-between the synthesis steps were compared. It was observed that membranes comprised of small crystals and consequently high concentration of grain boundaries had low separation performance. Grain boundaries could also be opened by extensive rinsing, which reduced membrane quality. The influence of the calcination rate on the performance of zeolite membranes of a particular type was also studied. It was demonstrated that the calcination rate does not affect the membrane quality.

  • 15. Andersson, Charlotte
    et al.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Effects of exposure to water and ethanol on silicalite-1 membranes2008Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 313, nr 1-2, s. 120-126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of long exposures to ethanol, water and 0.1 M aqueous solutions of ammonia, sodium hydroxide, tetrapropylammonium hydroxide (TPAOH) and hydrochloric acid on thin TPA-silicalite-1 membranes were studied. Single gas permeation experiments, porosimetry and scanning electron microscopy were used to characterize the membranes. It was found that a short exposure (24 h) will only dissolve synthesis residues and will not affect membrane quality negatively. The only medium that had an effect after 24 h was sodium hydroxide, which almost dissolved the film completely. After exposing TPA-silicalite-1 membranes for 30 days in the various liquids, the membrane quality decreased in the order ethanol < 0.1 M hydrochloric acid < 0.1 M TPAOH < water < 0.1 M ammonia < 0.1 M sodium hydroxide due to dissolution of the silicalite-1 crystals. This study has shown that prolonged exposure to aqueous solutions will lead to dissolution of silicalite-1 crystals causing an increase in micro- and mesopores in the film. The amount and size of the pores will depend on the pH of the aqueous medium. Higher pH gives a higher dissolution and hence more non-zeolitic pores in the silicalite-1 film. Ethanol has no effect on the dissolution of the zeolite film even after 30 days. This finding has an effect in membrane preparation and in several membrane applications such as pervaporation and separation of hydrocarbons isomer mixtures.

  • 16. Andersson, Charlotte
    et al.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Sterte, Johan
    Silicalite-1 membranes with small crystal size2004Inngår i: Recent advances in the science and technology of zeolites and related materials. Part A: proceedings of the 14th International Zeolite Conference, Amsterdam: Elsevier, 2004, s. 626-631Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Silicalite-1 membranes with small crystal size were prepared using a multiseeding method, where the support was repeatedly seeded and exposed to a short hydrothermal treatment up to five times. The film were characterized using SEM, single gas permeation, porosimetry and mixture separation experiment Films with three or four layers were of high quality i.e with minor defects according to the porosimetry experiments but showed poor separation of binary mixtures. This result may be attributed to the small crystal size and/or large amount of grain boundaries in the films.

  • 17.
    Andersson, Joel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Almqvist, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Semi-deterministic chemo-mechanical model of boundary lubrication2012Inngår i: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 156, s. 343-360Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model for tribofilm growth is developed. The model is used in combination with numerical contact mechanics tools to enable evaluation of the combined effects of chemistry and contact mechanics. The model is tuned with experimental data and is thereafter applied to rough surfaces. The growth of the tribofilm is evaluated for 3 different contact cases and short-term tribofilm growth behaviour is analyzed. The results show how tribofilms grow in patches. The model is expected to be used as a tool for analysis of the interaction between rough surfaces.

  • 18. Anthonis, Marc Henry
    et al.
    Bons, Anton-Jan
    Deckman, H. W.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Lai, Wenyih F.
    Peters, J.A.J.
    Crystalline molecular sieve layers and processes for their manufacturePatent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    A process is described for the manufacture of crystalline molecular sieve layers with good para-xylene over meta-xylene selectivity's good para-xylene permeances and selectivities. The process requires impregnation of the support prior to hydrothermal synthesis using the seeded method and may be undertaken with pre-impregnation masking. The crystalline molecular sieve layer has a selectivity (.alpha..sub.x) for para-xylene over meta-xylene of 2 or greater and a permeance (Q.sub.x) for para-xylene of 3.27.times.10.sup.-8 mole(px)/m.sup.2.s.Pa(px) or greater measured at a temperature of .gtoreq.250.degree. C. and an aromatic hydrocarbon partial pressure of .gtoreq.10.times.10.sup.3 Pa.

  • 19.
    Antzutkin, Oleg
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kota, Hanumantha Rao
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ikumapayi, Fatai
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Gunneriusson, Lars
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Johansson, Björn
    New Boliden AB.
    Berggren, Andreas
    New Boliden AB.
    Larsson, Anna-Carin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Bhuiyan, Iftekhar Uddin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsmo, Seija
    LKAB.
    Interactions in multi-component mineral systems2011Konferansepaper (Annet vitenskapelig)
  • 20.
    Antzutkin, Oleg
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kota, Hanumantha Rao
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ikumapayi, Fatai
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Johansson, Björn
    New Boliden AB.
    Berggren, Andreas
    New Boliden AB.
    Larsson, Anna-Carin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holmgren, Allan
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mouzon, Johanne
    Bhuiyan, Iftekhar Uddin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsmo, Seija
    LKAB.
    Interactions in multi-component mineral systems2010Konferansepaper (Annet vitenskapelig)
  • 21.
    Arkhipov, Victor P.
    et al.
    Kazan National Research Technological University.
    Idiyatullin, Zhamil Sh
    Kazan National Research Technological University.
    Potapova, Elisaveta
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Filippov, Andrei
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Micelles and aggregates of oxyethylated isononylphenols and their extraction properties near cloud point2014Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, nr 20, s. 5480-5487Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We used nuclear magnetic resonance (NMR) spectroscopy and dynamic light scattering (DLS) techniques to study the structural and dynamic properties of micellar solutions of nonionic surfactants of a homologous series of oxyethylated isononylphenols - C9H19C6H 4O(C2H4O)nH, where n = 6, 8, 9, 10, or 12 - in a wide range of temperatures, including cloud points. The radii of the micelles and aggregates, as well as their compositions at different concentrations of surfactant, were determined. Using aqueous phenol solutions as a model, we studied the process of cloud point extraction with oxyethylated isononylphenols

  • 22.
    Arkhipov, Victor
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Potapova, Elisaveta
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Filippov, Andrei
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Micelle structure and molecular self-diffusion in isononylphenol ethoxylate–water systems2013Inngår i: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 51, nr 7, s. 424-430Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure and dynamic properties of micellar solutions of nonionic surfactants of a series of isononylphenol ethoxylates, C9H19C6H4O(C2H4O)nH (where n = 6,8,9,10, and 12), were studied by NMR diffusometry, dynamic light scattering, and viscosimetry. The sizes of the micelles were determined for different surfactants and at different surfactant concentrations. The numbers of water molecules bound by a micelle and by one oxyethylene group of the surfactant were estimated

  • 23.
    Arman, S.Y.
    et al.
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Omidvar, H.
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Tabaian, S.H.
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Sajjadnejad, M.
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Fouladvand, Shahpar
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Afshar, Sh.
    Department of Chemistry, Iran University of Science and Technology.
    Evaluation of nanostructured S-doped TiO2 thin films and their photoelectrochemical application as photoanode for corrosion protection of 304 stainless steel2014Inngår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Undoped and S-doped TiO2 thin films were prepared on titanium substrate through a sol–gel method. The photoelectrochemical behavior of S-doped TiO2 thin film (as photoanode) was studied. The effect of Sulfur doping on structural, optical and morphological properties of TiO2 was studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), FT-IR, UV–ViS and FE-SEM. Superiority of the S-doped TiO2 film was shown through taking advantage of linear sweep voltametry measurement, open-circuit potential of 304 stainless steel as well as potetiodynamic polarization technique. Results showed that S-doped TiO2 thin film is an efficient photoanode with long term stability (several hours).

  • 24.
    Axelsson, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Stabilisering av Aluminiumreducerad AOD-slagg.2019Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Slagg har historiskt använts som konstruktionsmaterial i olika applikationer. Alla typer av slagg passar inte på grund av otillräckliga egenskaper. Vid produktion av höglegerat rostfritt stål så är slaggen mycket kalkrik, vilket leder till sönderfall på grund av absorption av vatten. Vissa stålsorter hos Sandvik tillverkas med ett tvåslaggsförfarande där en första reduceringsslagg först används för att sedan ersättas av en raffineringsslagg. Denna rapport behandlar förändringar i slaggsammansättning för att förbättra slaggens egenskaper gällande volymstabilitet efter deponering. I synnerhet så behandlas volymstabilitet av reduceringsslagg och om möjligheterfinns att kombinera bra stålproduktion med volymstabil slagg.Projektet har syftat till att kartlägga hur slaggen fungerar i dagsläget med provtagning nära konverter men även hur förändrade sammansättningar påverkar slaggen som svalnar enligt normal praxis utanför stålverket. Slagger som faller sönder av fasomvandlingar har observerats. Slutligenhar en sammansättning som ser lovande ut ur produktionsperspektiv och stabilitetsperspektivhittats. Slaggen blir då stabil även efter försök att orsaka sönderfall i extrem miljö. Vid produktionmed minskad kalktillsats under reducering kan ungefär två tredjedelar av ingående charger somska reduceras med aluminium hanteras. Med en mindre förändring i AOD processen vid reduceringså skulle ca 6000ton/år kunna skiftas från att sönderfalla till att bli stabil.

  • 25.
    Bayat, Mohammad
    et al.
    Faculty of Chemical Engineering, Research and Technology Centre for Membrane Processes, Iran University of Science and Technology (IUST), Tehran, Iran.
    Nabavi, Mohammad Sadegh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mohammadi, Toraj
    Faculty of Chemical Engineering, Research and Technology Centre for Membrane Processes, Iran University of Science and Technology (IUST), Tehran, Iran.
    An experimental study for finding the best condition for PHI zeolite synthesis using Taguchi method for gas separation2018Inngår i: Chemical papers, ISSN 2585-7290, Vol. 72, nr 5, s. 1139-1149Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Phillipsite zeolite particles and membranes were successfully synthesized at different operational and environmental conditions. Using an L9 orthogonal array of the Taguchi method, effects of experimental condition—synthesis temperature (130–150 °C), synthesis time (2–3 days), number of synthesized layers (1–3), and seeding suspension percentage—for membrane preparation with respect to CO2/CH4 ideal selectivity were investigated. The results showed that the ideal selectivity was improved up to 4.20 from 1.15 by increasing the number of synthesized layers, synthesis temperature, and seed solution concentration and by decreasing synthesis time. Moreover, the best synthesis conditions were defined based on the Taguchi method results and the membrane was synthesized with the highest ideal selectivity which was around 4.40. In addition, it was shown that T zeolite is formed beside PHI zeolite at low temperature even with long synthesis time.

  • 26.
    Bhuiyan, Iftekhar Uddin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Characterization of iron ore green pellets by scanning electron microscopy and X-ray microtomography2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Cryogenic scanning electron microscopy (cryo-SEM), image analysis (IA) of SEM micrographs and X-ray microtomography (XMT) were used to obtain new information about the morphology of iron ore green pellets in this work. Cryo-SEM and freeze fracturing was used to observe entrapped air bubbles and arrangement of particles around the bubbles and in the matrix of wet green pellets. The observations of samples prepared by plunge and unidirectional freezing indicate that unidirectional freezing facilitates the observation of entrapped bubbles with minimum formation of artifacts, whereas plunge freezing enables observation of the degree of water filling at the outer surface of wet pellets with minimum amount of artifacts. It was also observed in the wet pellets that the size of the water domains in the matrix is quite small and the finer grains are mixed with coarser grains resulting in a denser matrix, whereas no fine grains were observed in the vicinity of the air bubbles. Two types of pellets prepared with and without addition of extra flotation reagent prior to balling were studied using IA and XMT. IA of scanning electron micrographs of epoxy impregnated pellets was used to separate bubble porosity from packing porosity and to quantify the former. The individual SEM micrographs acquired by a backscattered electron detector were reconstructed to provide the entire two-dimensional (2D) sections of the pellets. The 2D data obtained by IA were unfolded to three-dimensional (3D) by stereology and relatively good agreement with XMT data was observed. The size and amount of air bubbles could be quantified with both techniques. The addition of extra flotation reagent was found to increase the number of entrapped air bubbles and slightly decrease the median bubble diameter. The additional entrapped air bubbles due to the addition of extra flotation reagent was shown to be responsible for the difference in total porosity observed by mercury porosimetry between the two types of pellets. Mercury intrusion porosimetry (MIP) is shown in this work to produce inappropriate results with regard to the porosity due to bubble entrapment, it only provides values for total porosity and the throat size distribution of the porosity. In summary, this work has shown that cryo-SEM, IA of SEM micrographs and XMT are powerful and very useful methods for characterization of the morphology of iron ore green pellets.

  • 27.
    Bhuiyan, Iftekhar Uddin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Microstructural characterization of iron ore green pellets2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The aim of this thesis work was to develop new methodologies to characterize iron ore green pellets, in wet and dry state. The new characterization methods applied and developed in this work were mainly based on scanning electron microscopy (SEM) to gather both qualitative and quantitative data on different components of the pellets, i.e. mineral particles, water, bentonite and entrapped bubbles.In a first attempt to preserve the structure of wet iron ore green pellets by freezing before investigation by cryogenic SEM, wet pellets were frozen in liquid nitrogen by direct plunging or a new method developed in the present work denoted unidirectional freezing. The former method was found useful to study the degree of water filling at the outer surface of the pellet but led to artifacts in the interior of the pellet. The latter method was developed to confirm that the spherical cavities observed in dry pellets were related to entrapped bubbles in wet pellets. Capillaries were observed at the outer surface of the pellets and fine particles were lacking within a layer of approximately 100 µm from the outer surface and also in the direct vicinity of the air bubbles in the interior of the pellets.More advanced freezing methods were subsequently employed to reveal the artifact free microstructure of bentonite in wet pellets. In order to verify the observations made on a slice of a wet pellet frozen by plunging in liquid ethane, SEM investigations were also carried out on a bentonite suspension and a bentonite-iron ore slurry, which could be cryo-fixed by the most reliable freezing method, i.e. high pressure freezing. All microstructures were comparable and consisted in a voluminous network of well-dispersed clay platelets. This network was found to collapse upon drying. Bentonite was drawn to the contact points between the particles and formed what appeared as bridges, which may impart strength to the dry pellets. A combination of energy dispersive spectroscopy (EDS) and imaging by low-loss backscattered electrons at low voltage evidenced the presence of very finely divided silicate species on the magnetite particles. In order to visualize the three dimensional structure of dispersed bentonite clay with unprecedented resolution, a method based on SEM imaging with a monochromatic and decelerated beam was used for the first time. The recorded images showed very well-dispersed clay platelets forming a fine network of Y shaped contacts, which is quite different from earlier reports of much coarser structures formed as a result of poor sample preparation. Finally, in order to gain quantitative data about the porosity due to bubble entrapment in dry pellets, the entire cross-section of dry epoxy embedded and polished pellets were recorded by SEM. The three-dimensional bubble size distribution was unfolded from 2D SEM data using image processing, image analysis and stereological principles. The same type of pellets was also investigated by X-ray micro-tomography (XMT). The resulting three-dimensional dataset allowed the validation of the unfolding procedure based on stereology. However, the lack of resolution obtained by XMT was shown to lead to slight discrepancies with the SEM data for small bubble sizes. Entrapped air bubbles due to the addition of extra flotation reagent in pellets were shown to be responsible for additional porosity observed by mercury intrusion porosimetry (MIP). In summary, useful characterization methods for iron ore pellets based on SEM have been developed in this work, which opens up new possibilities to for instance study agglomeration processes in more detail.

  • 28.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Forsmo, S.P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Consideration of X-ray microtomography to quantitatively determine the size distribution of bubble cavities in iron ore pellets2013Inngår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 233, s. 312-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray microtomography data of iron ore green pellets of approx. 12 mm in diameter were recorded using a commercial instrument. The reconstructed volume after thresholding represented a unique dataset consisting of a three-dimensional distribution of equiaxed objects corresponding to bubble cavities. This dataset was used to successfully validate a stereological method to determine the size distribution of spherical objects dispersed in a volume. This was achieved by investigating only a few cross-sectional images of this volume and measuring the profiles left by these objects in the cross-sectional images. Excellent agreement was observed between the size distribution of the bubble cavities obtained by directly classifying their size in the reconstructed volume and that estimated by applying the aforementioned stereological method to eight cross-sectional images of the reconstructed volume. Subsequently, we discuss the possibility of calibrating X-ray tomography data quantitatively using the size distribution of the bubble cavities as a figure of merit and the results obtained by applying the stereological method to SEM images as reference data. This was justified by considering the validity of the stereological method demonstrated by tomography, the accurate thresholding made possible by back-scattered electron imaging and the solid reproducibility of the results obtained by SEM. Using different threshold values for binarization of the X-ray microtomography data and comparing the results to those obtained by SEM, we found that X-ray microtomography can be used after proper calibration against SEM data to measure the total porosity of the bubble cavities but can only provide a rough estimate of the median diameter because of the limited resolution achieved in this study.

  • 29.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsmo, S.P.E.
    LKAB.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Quantitative image analysis of bubble cavities in iron ore green pellets2011Inngår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 214, nr 3, s. 306-312Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Scanning electron microscopy and image analysis was used for quantitative analysis of bubble cavities in iron ore green pellets. Two types of pellets prepared with and without addition of flotation reagent prior to balling were studied. The bubble cavity porosity amounted to 2.8% in the pellets prepared without addition of flotation reagent prior to balling. When flotation reagent was added prior to balling, the bubble cavity porosity increased by a factor of 2.4 and the median bubble diameter was decreased slightly. It was also shown that mercury intrusion porosimetry is not suitable for determination of the distribution of bubble cavities. Finally, our data suggested that the difference in total porosity determined by mercury intrusion porosimetry and pycnometry between the two types of pellets was due to the bubble cavities.

  • 30.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsmo, S.P.E.
    LKAB Research and Development.
    Forsberg, Fredrik
    Air bubbles in iron ore green pellets due to flotation reagent: characterization by scanning electron microscopy and X-ray microtomography2011Konferansepaper (Annet vitenskapelig)
  • 31.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Schröppel, Birgit
    Natural and Medical Sciences Institute (NMI), University of Tübingen.
    Kaech, Andres
    Center for Microscopy and Image Analysis, University of Zurich.
    Dobryden, Illia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Forsmo, Seija P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Microstructure of Bentonite in Iron Ore Green Pellets2014Inngår i: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 20, nr 1, s. 33-41Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sodium-activated calcium bentonite is used as a binder in iron ore pellets and is known to increase strength of both wet and dry iron ore green pellets. In this article, the microstructure of bentonite in magnetite pellets is revealed for the first time using scanning electron microscopy. The microstructure of bentonite in wet and dry iron ore pellets, as well as in distilled water, was imaged by various imaging techniques (e.g., imaging at low voltage with monochromatic and decelerated beam or low loss backscattered electrons) and cryogenic methods (i.e., high pressure freezing and plunge freezing in liquid ethane). In wet iron ore green pellets, clay tactoids (stacks of parallel primary clay platelets) were very well dispersed and formed a voluminous network occupying the space available between mineral particles. When the pellet was dried, bentonite was drawn to the contact points between the particles and formed solid bridges, which impart strength to the solid compact.

  • 32.
    Bjorklund, Robert B.
    et al.
    Linköping University.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Arwin, Hans
    Linköping University.
    Vapor adsorption in thin silicalite-1 films studied by spectroscopic ellipsometry1998Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 102, nr 12, s. 2245-2250Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin films of silicalite-1 grown on silicon substrates were studied by spectroscopic ellipsometry. Analysis of spectra using an optical model consisting of a single porous layer on silicon yielded average film thicknesses of 84 and 223 nm for films synthesized for 10 and 30 h. Void fraction for the films was 0.32-0.33. Vapor adsorption from a nitrogen carrier gas at room temperature was monitored by ellipsometry. Isotherms for different adsorbates were obtained by analysis of spectra taken at different vapor concentrations using an optical model where the void volume was filled with both nitrogen and condensed vapors. Quantification of the condensed vapor amount was based on the changes in refractive index when adsorbates replaced nitrogen in the pores. Adsorbate volumes for water, toluene, 1-propanol, and hexane were 0.12, 0.12, 0.15, and 0.17 cm3 liquid g-1 film, respectively.

  • 33.
    Björklund, Robert B.
    et al.
    Linköping University.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Carlsson, Bill
    Vadstena Varmförzinkning AB.
    Ellipsometric study of oxide removal from steel surfaces in hydrochloric acid solutions1999Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, nr 2, s. 494-499Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Iron oxide films formed on three different steel surfaces by thermal oxidation were removed in hydrochloric acid solutions at 20 C. The oxide removal process in flowing solutions was followed in situ by ellipsometry. Two different removal mechanisms were observed in 0.5-2 M HCl, one where undermining of the film resulted in large intact pieces of the oxide leaving the substrate surface at the end of the removal period, and one where the film scaled off the surface in small pieces during the entire removal process. Oxide films which exhibited the undermining mechanism were found to contain about 10% hematite (Fe2O3) and 90% magnetite (Fe3O4). The scaling off mechanism was observed for films which were nearly pure magnetite. Optical models were constructed using data from scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements for the thicknesses and compositions of films after different immersion times in HCl solutions. Spectra calculated from the models agreed well with the experimental spectra.

  • 34.
    Björkvall, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Studie om dynamiken i en pilotrullkrets med rulltrumma2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Luossavaara-Kiirunavaara AB (LKAB) rullar järnmalmslig till råkulor, som sedan bränns till pellets. Råkulorna bildas i rullkretsar som består av rulltrummor och rullsiktar. Under 2017 färdigställdes en pilotskaleanläggning för kulrullning i LKAB:s Agglomeringslaboratorium i Malmberget. Syftet med anläggningen är att prediktera dynamiken i en storskalig rullkrets, under olika betingelser.

    Detta examensarbete är ett första försök att i forskningssyfte studera gensvaret i LKAB:s pilotrullkrets. Syftet var att undersöka om pilotrullkretsen kan prediktera dynamiken och råkulekvalitet i rullning i storskaliga rullkretsar och målet var att fastställa ett effektivt körsätt. Kulrullning är inom LKAB:s kärnkompetens och därför har reagensursprung och karaktär samt dimensionering av rullkretsen lagts med sekretess. Kodnamn används både för sliger och reagens.

    Arbetet inleddes med att skapa ett körschema med målet att så många olika blandningar som möjligt kunde köras i pilotrullkretsen under en normal arbetsdag. Fem olika blandningar kunde köras. Fyra olika tillsatser testades: bentonit, ett flotationsreagens (FLOT), ett organiskt bindemedel (OB) och en ny utvecklingsprodukt (UTV). Första körningen i pilotrullkretsen var med varierande doseringar av bentonit eftersom dess inverkan i kulrullning är välkänt hos LKAB. Försök två och tre, med FLOT respektive OB, kunde jämföras mot tidigare erfarenhet från storskaliga försök. Det fjärde och sista försöket var ett test hur pilotrullkretsen predikterade utvecklingsprodukten UTV. Varje typ av försök utfördes två gånger.

    Pilotrullkretsen predikterade väl både dynamik och råkulekvalitet i alla de tre försöken där erfarenhet från storskaliga körningar var tillgängligt. Den nya, okända, UTV-produkten visade en förbättrad råkulekvalitet, utan att dynamiken i kretsen påverkades negativt. UTV kan därför vara ett intressant alternativ för ett framtida storskaligt försök hos LKAB.

    Det framtagna körschemat fungerade mycket väl. Ett ”grundanalyspaket” har skapats för att underlätta planering och genomförande för framtida pilotrullkretsförsök hos LKAB. Antalet personer som behövs vid rullkretskörningar beror på antalet blandningar och analyser. Vid enklare körningar behövs minst fem personer, utöver försöksledaren. Mer komplexa körningar kan kräva sju personer.

  • 35.
    Bleken, Bjørn Tore L.
    et al.
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Wragg, David Stephen
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Arstad, Bjørnar
    SINTEF Materials and Chemistry, Blindern.
    Gunnæs, Anette Eleonora
    Department of Physics, University of Oslo FERMiO.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Helveg, Stig
    Haldor Topsøe A/S.
    Lundegaard, Lars Fahl
    Haldor Topsøe A/S.
    Beato, Pablo
    Haldor Topsøe A/S.
    Bordiga, Silvia
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Olsbye, Unni
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Svelle, Stian
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Lillerud, Karl Petter
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Unit cell thick nanosheets of zeolite H-ZSM-5: Structure and activity2013Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, nr 9-10, s. 558-566Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    nosheets of zeolite H-ZSM-5 were synthesized and characterized by X-ray diffraction, transmission electron microscopy (TEM), N2- physisorption, FT-IR spectroscopy, 27Al and 29Si MAS NMR spectroscopy in addition to catalytic testing in conversion of methanol to hydrocarbons (MTH). It was found that Rietveld analysis, involving anisotropic broadening parameters, gave average crystallite dimensions in good agreement with TEM images. The selectivities in MTH is intact in the mesoporous nanosheet H-ZSM-5 with the largest difference being a higher C3/C2 ratio compared to regular H-ZSM-5.

  • 36.
    Cai, Juanjaun
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Jiang, Leilei
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Huaming, Wei
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Chongqing, Wang
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Yu, Liang
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Preparation of carbon/cobalt composite from phenolic resin and ZIF-67 for efficient tannic acid adsorption2019Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 287, s. 9-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, a carbon/cobalt composite was prepared and evaluated for adsorption of ecologically harmful tannic acid (TA). The composite was prepared by simply mixing phenolic resin with ZIF-67 and following by carbonization. TEM and SEM images showed that ZIF-67 was etched by phenolic resin and cobalt nanoparticles were formed and evenly distributed in carbon. Macroporous structure was generated between the carbonized phenolic resin and ZIF-67. N2 adsorption-desorption isotherms results exhibited that the composite also had both micro- and meso-pores (average pore size of 5 nm) with a high surface area of 393 m2 g−1. Porous structure and evenly distributed cobalt nanoparticles facilitated the diffusion and adsorption of TA due to the formation of the complex between TA macromolecules and cobalt. The highest observed adsorption amount was as high as 2778 mg g−1, significantly higher than that of the carbon prepared from carbonization of phenolic resin (205 mg g−1) and ZIF-67 (1375 mg g−1). The carbon composite material is easy to recover and reuse due to the magnetic property. The reuse experiment also showed high stability of the composite. All of the results indicated a great potential of the developed carbon composite material in wastewater treatment in the industry.

  • 37.
    Carabante, Ivan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Arsenic (V) adsorption on iron oxide: implications for soil remedeation and water purification2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Addition of iron oxide based adsorbents to arsenic contaminated soils has been proposed as a mean to reduce the mobility of arsenic in the soil. However, the conditions in the soil such as pH value, the presence of phosphate after addition of fertilizer to the soil or the presence of Zn (II) as a co-contaminant may affect the adsorption of arsenate on the iron oxide and may therefore have implications for the mobility of arsenic in the remediated soil.In the present work, a new flow method was developed to study the adsorption of arsenate on synthetic iron oxide with high surface area (ferrihydrite) in situ by means of Attenuated Total Reflection – Fourier Transform Infrared (ATR – FTIR) spectroscopy and the method was used for studying how the adsorption of arsenate was affected by the pH/pD value, the presence of phosphate and Zn (II) in the system. The highest adsorption of arsenate was found at pD 4 and decreased as the pD value increased. The arsenate complexes formed on ferrihydrite appeared to be very stable at pD 4, while the stability decreased as the pD value increased. Arsenate showed a higher adsorption affinity than phosphate on ferrihydrite under the conditions studied. However, phosphate was able to replace about 10 % of pre-adsorbed arsenate on ferrihydrite at pD 4 and about 20 % of the pre-adsorbed arsenate at pD 8.5 in equimolar concentrations of phosphate and arsenate. Phosphate replaced 30 % of pre-adsorbed arsenate at pD 4 and up to 50 % of pre-adsorbed arsenate at pD 8.5 when the concentration of phosphate in the system was 5 times higher than that of arsenate. Batch adsorption experiments indicated an enhancement in the arsenate removal from a ferrihydrite suspension in the presence of Zn (II) at pH 8 in accordance with previous reports. However, no adsorption of arsenate on ferrihydrite in the presence of high concentrations of Zn (II) in the system was observed by infrared spectroscopy. Instead, precipitation of zinc hydroxide carbonate followed by arsenate adsorption on the zinc precipitate was found to be the most likely explanation of these results.Although iron oxides are selective towards arsenate, high specific surface areas are required to achieve sufficiently high adsorption capacity. A method of increasing the specific surface area of coarse hematite particles to obtain a good adsorbent was also developed in the present work. The method comprises an acid treatment to produce iron ions followed by hydrolysis to precipitate an iron oxy-hydroxide coating on the hematite particles. While the arsenate adsorption capacity of the original coarse hematite particles was found to be negligible, the sintered coarse hematite particles showed good potential as an adsorbent for arsenate with an adsorption capacity of about 0.65 mg[As]/g.The method developed for studying adsorption on iron oxides by in situ ATR - FTIR spectroscopy was further developed for studying the adsorption of flotation collectors on iron oxides. Iron ore is often separated from gangue minerals by means of reverse flotation in which a surfactant should selectively adsorb on the gangue mineral rendering it hydrophobic. However, unwanted adsorption of the surfactants on the iron oxide has been reported to affect the production of iron ore pellets. A method was developed to study the adsorption of the surfactant Atrac 1563 on synthetic hematite in situ by means of ATR - FTIR spectroscopy. The adsorption of Atrac 1563 on hematite at pH 8.5 was found to mostly occur via interactions between the polar ester and ethoxy groups of the surfactant and the hematite surface.

  • 38.
    Carabante, Ivan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Study of arsenate adsorption on iron oxide by in situ ATR-FTIR spectroscopy2009Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Stabilization of arsenic contaminated soils by iron oxides has been proposed as a remediation technique to prevent leaching of arsenate into the environment. However, fundamental studies are needed to establish under which conditions the complexes formed are stable. A new method based on ATR-FTIR spectroscopy was adapted to study the adsorption of arsenate species on iron oxides. The measurements required the use of D2O as solvent. The amount of arsenate complexes adsorbed on the iron oxide increased with decreasing pD in the range studied, viz. pD 4-12. Arsenate complexes adsorbed at pD 4 desorbed from the film to some extent as the pD was increased to 8.5 or 12. The stability of arsenate complexes adsorbed on the iron oxide evidently changed with the change in pD, most likely due to the electrostatic repulsion between the negatively charged oxoanion and the more negatively charged iron oxide as the pD increased. From competitive adsorption experiments it was found that arsenate species were more strongly bonded to the iron oxide than phosphate species. Furthermore, it was found that two different phosphate complexes formed on the iron surface at pD 4, one deuterated and the other one de-deuterated. The complexes showed very different stability. The deuterated phosphate complex was desorbed easily from the iron oxide film as arsenate was added to the system whereas the de-deuterated phosphate complex only desorbed slightly from the film upon adding arsenate.This work has increased the fundamental knowledge of the iron oxide/arsenate/phosphate system, which will be of importance for the development of more effective soil remediation techniques.

  • 39. Carabante, Ivan
    et al.
    Grahn, Mattias
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    In situ ATR-FTIR studies on the competitive adsorption of arsenate and phosphate on ferrihydrite2010Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 351, nr 2, s. 523-531Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, in-situ ATR-FTIR spectroscopy was used for the first time to study the competitive adsorption of phosphate and arsenate on ferrihydrite. Deuterium oxide was used as solvent to facilitate the interpretations of recorded infrared spectra.It was found that arsenate and phosphate adsorbed more strongly at lower pD values, showing similarities in the adsorption behavior as a function of pD. However, arsenate complexes were found to be more strongly adsorbed than phosphate complexes in the pD range studied. About five times higher concentration of phosphate in solution was needed to reduce the absorbance due to pre-adsorbed arsenate to the same relative level as for pre-adsorbed phosphate, which was desorbed using a solution containing equal (molar) concentrations in arsenate and phosphate. At pD 4, two phosphate complexes were adsorbed on the iron oxide, one deuterated and one de-deuterated. When phosphate was pre-adsorbed and arsenate subsequently added to the system, the deuterated phosphate complex desorbed rapidly while the de-deuterated phosphate complex was quite stable. At pD 8.5, only the de-deuterated phosphate complex was adsorbed on the iron oxide. Moreover, the arsenate adsorbed was also predominantly de-deuterated as opposite to the arsenate adsorbed at pD 4. During the substitution experiments the configuration of these complexes on the iron oxide surface did not change. To the best of our knowledge, this is the first time this difference in stability of the different phosphate complexes is reported and shows the power of employing in-situ spectroscopy for this kind of studies.

  • 40. Carabante, Ivan
    et al.
    Grahn, Mattias
    Holmgren, Allan
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    The influence of Zn2+ ions on the adsorption of arsenate onto ferrihydrite studied by in situ ATR-FTIR spectroscopy2010Konferansepaper (Annet vitenskapelig)
  • 41.
    Carabante, Ivan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Adsorption of As (V) on iron oxide nanoparticle films studied by in situ ATR-FTIR spectroscopy2009Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 346, nr 1-3, s. 106-113Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stabilization of arsenic contaminated soils by iron oxides has been proposed as a remediation technique to prevent leaching of arsenate into the environment. Fundamental studies are needed to establish under which conditions the complexes formed are stable. In the present work, a powerful technique, viz. ATR-FTIR spectroscopy, is adapted to studies of adsorption of arsenate species on iron oxides. This technique facilitates acquisition of both quantitative and qualitative in situ adsorption data.In the present work, about 800 nm thick films of 6-lineferrihydrite were deposited on ZnSe ATR crystals. Arsenate adsorption on the ferrihydrite film was studied at pD values ranging from 4 to 12 and at an arsenate concentration of 0.03 mM in D2O solution. The amount of adsorbed arsenate decreased with increasing pD as a result of the more negatively charged iron oxide surface at higher pD values. The adsorption and desorption kinetics were also studied. Arsenate showed a higher adsorption rate within the first 70 minutes and a much lower adsorption rate from 70 up to 300 minutes. The low adsorption rate at longer reaction times was partly due to a low desorption rate of already adsorbed carbonate species adsorbed at the surface. The desorption of carbonate species was evidenced by the appearance of negative absorption bands. The desorption of adsorbed arsenate complexes was examined by flushing with D2O at pD 4 and 8.5 and it was found that the complexes were very stable at pD 4 suggesting formation of mostly inner-sphere complexes whereas a fraction of the complexes at pD 8.5 were less stable than at pD 4, possibly due to the formation of outer-sphere complexes.In summary, the ATR technique was shown to provide in situ information about the adsorption rate, desorption rate and the speciation of the complexes formed within a single experiment, which is very difficult to obtain using other techniques.

  • 42.
    Carabante, Ivan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Influence of Zn(II) on the adsorption of arsenate onto ferrihydrite2012Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 46, nr 24, s. 13152-13159Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Addition of iron oxide to arsenic-contaminated soil has been proposed as a means of reducing the mobility of arsenic in the soil. Arsenic and zinc are common coexisting contaminants in soils. The presence of zinc therefore may affect the adsorption properties of arsenic on iron oxide, and may thus affect its mobility in the soil. The influence of Zn(II) on the adsorption of arsenate ions on iron oxide was studied. Batch adsorption experiments indicated that Zn(II) increased the arsenate removal from a solution by ferrihydrite at pH 8. However, ATR-FTIR spectroscopy showed that no adsorption of arsenate on a ferrihydrite film occurred at pD 8 in the presence of Zn(II). Precipitation of zinc hydroxide carbonate followed by arsenate adorption onto the precipitate was found to be a plausible mechanism explaining the arsenate removal from a solution in the presence of Zn(II) at pH/pD 8. The previously suggested mechanisms attributing the enhanced removal of arsenate from solution in the presence of Zn(II) to additional adsorption on iron oxides could not be verified under the experimental conditions studied. It was also shown that at pH/pD 4, the presence of Zn(II) in the system did not significantly affect the adsorption of arsenate on ferrihydrite.

  • 43.
    Carabante, Ivan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    A powerful method for studying the adsorption of As(V) on iron oxides in situ2008Inngår i: Arsenic in the environment - Arsenic from nature to humans: Book of Abstracts, 2008Konferansepaper (Annet vitenskapelig)
  • 44.
    Carabante, Ivan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Fredriksson, Andreas
    Mining Technology R and D, LKAB Kiruna Mine.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Reutilization of porous sintered hematite bodies as effective adsorbents for arsenic(V) removal from water2014Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 53, nr 32, s. 12689-12696Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method was developed to enhance the arsenic adsorption capacity of porous bodies of sintered hematite. The method comprised the formation of a coating of 1 wt % iron oxide nanoparticles on the raw material. The nanoparticles showed two distinct habits: spherical habit, likely ferrihydrite, and acicular habit, likely goethite and/or akaganéite. The specific surface area of the hematite raw material increased from 0.5 to 3.75 m2/g, and the adsorption capacity increased from negligible to 0.65 mg of [As]/g as calculated from equilibrium and breakthrough adsorption data. Equilibrium adsorption data of arsenate on the adsorbent from a solution at pH 5 followed the Langmuir model, while breakthrough adsorption data for a 500 μg/L arsenate solution at pH 5 followed the Thomas model. The adsorbed arsenic could be desorbed using distilled water at pH 12. These results show the potential for the reutilization of waste products comprising coarse hematite bodies as adsorbents.

  • 45.
    Cardenas, Edgar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Synthesis of zeolites from economic raw materials2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Synthesis methods using economic raw materials, such as kaolin and diatomite have been developed for the production of zeolites in the present work. Zeolite Y and ZSM-5 have been synthetized successfully from diatomite and kaolin, respectively. 

    The synthesis of zeolite Y was extensively studied (Paper I) in order to obtain final products with high crystallinity and an appropriate SiO2/Al2O3 ratio to be suitable for application as catalyst. Then, the influence of the alkalinity (in terms of SiO2/Na2O ratio) on the outcome of the synthesis was studied. Thus, an optimum range of alkalinity that satisfies the requirements stated before was found. Additionally, the results also showed that diatomite produce similar products as colloidal silica, which may be expected since both silica sources are highly polymerized forms of silica.

    The synthesized zeolite Y crystals were also ion-exchanged with Lanthanum to obtain a Rare Earth zeolite Y (REY) catalyst (Paper V).  The REY catalyst was shown to be thermally stable up to 800°C as expected for this catalyst. The REY catalyst was also evaluated in the reaction of Catalytic Cracking of cumene. The results of catalytic tests shown that the REY catalyst synthetized from diatomite holds activity towards the catalytic cracking of cumene.

    In addition, studies of synthesis of ZSM-5 zeolite from kaolin have been performed to understand the crystal growth and morphology, crystal size, and aluminum distribution. In particular, the influence of the gel on the morphology of the crystals (Paper II) has been studied. It was observed that when the crystal surface is in contact with the gel phase, dendritic features appear at the crystal surface, that become smoother as the reaction proceeds. On the contrary, when only liquid phase is in contact with crystal surface there is no presence of dendritic features and the growth rate is higher.

    Further studies demonstrated that the ZSM-5 crystals possess a non-homogeneous aluminum distribution, a phenomenon known as Al-zoning.  A thorough characterization at distinct stages of the reaction has been performed (Paper III), on the different reaction mixture phases such as solid part, gel phase and liquid phase. The main finding was that the gel phase consists of a nanoparticle skeleton rich in alumina, filled by a silica rich matrix. In the beginning of crystallization, the silica rich matrix is preferentially consumed to form the crystals, leaving behind the alumina rich nanoparticle skeleton that is consumed later, resulting in the non-homogeneous distribution of aluminum in the crystals.

    Finally, studies of the microstructure of a TPA-ZSM-5 system using fumed silica as silicon source have been performed (paper IV). In this system, three stages of crystallization were observed. Stage I, formation of amorphous gel phase. Stage II formation of XRD amorphous spherical entities denoted as Condensed Agregates (CAs). Stage III, Crystallization of CAs into ZSM-5. This study was focused only in the stage III. Findings showed that ZSM-5 nanocrystals are formed in the core of the CA (beginning of stage III), surrounded by an amorphous shell composed of alumino-silica. As the crystallization proceeds, the amorphous shell crystallizes into ZSM-5 by competitive growth, but the nanocrystals of the core remain intact. Moreover, compositional analysis results showed that the silicon from the liquid phase provided most of the nutrients for growth of the ZSM-5 crystals resulting in polycrystalline ZSM-5 aggregates with an Al rich core - Si rich shell morphology.

  • 46.
    Cardenas, Edgar
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Aguilar, Wilson
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Tai, Cheuk-Wai
    Department of Environmental and Materials Chemistry, Stockholm Unversity.
    Cabrera, Saul
    Chemistry Research Institute, San Andres Mayor University.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Microstructural evolution of condensed aggregates during the crystallization of ZSM-5Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    In the present work, the microstructural evolution of precursors of (TPA, Na)-ZSM-5, previously described as condensed aggregates (CAs) (Ren, 2012), was studied carefully. It was observed that the CAs first comprise a core of nanocrystals and that the core is enveloped by a shell of amorphous gel phase.  During crystallization, the amorphous shell surrounding the core is converted to ZSM-5 crystals that grow to a film surrounding the core. The crystals in the film grow competitively with nutrients provided by the liquid phase surrounding the CAs, while the nanocrystals in the core show little or no signs of growth.

  • 47.
    Cardenas, Edgar
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Aguilar, Wilson
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Zhou, Ming
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Influence of the internal structure of the gel on Al-zoning in NBA-ZSM-5 crystalsInngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The crystallization of ZSM-5 from a gel comprising n-butylamine as structure directing agent was investigated. The samples were characterized by X-ray diffraction, nitrogen gas adsorption, extreme high-resolution transmission and scanning electron microscopy, and energy dispersive spectroscopy. The gel was found to be composed by a silica-rich matrix embedded in a skeleton of alumina-rich nanoparticles. During growth of the crystals, the silica-rich matrix is consumed first, and an increasing fraction of the alumina-rich nanoparticles are utilized later in the growth process. This leads to a non-uniform consumption of the gel walls during crystal growth. Consequently, the Si/Al ratio of the gel is steadily decreasing, which is accompanied by a corresponding decrease in the Si/Al ratio from the center to the outer surface of the crystals, i.e. Al-zoning of the ZSM-5 crystals.

  • 48.
    Cardenas, Edgar
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Cabrera, Saul
    Chemistry Research Institute, San Andres Mayor University.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zeolite Y from diatomaceous earth as catalytic cracking catalystManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A zeolite Y cracking catalyst in the lanthanum form was synthetized from Bolivian diatomite. Characterization was conducted through x-ray diffraction, scanning electron microscopy, nitrogen adsorption and energy dispersive spectroscopy. The catalyst was evaluated in the catalytic cracking of cumene and the results were compared with that of a catalyst prepared from commercial zeolite Y powder. It was shown that the catalytic performance of the catalyst prepared from diatomite was comparable to that for the catalyst prepared from commercial zeolite Y powder.

  • 49.
    Carvalho, Lara
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. IVL – Swedish Environmental Institute, Stockholm, Sweden.
    Ma, Chunyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Öhrman, Olov G. W.
    IVL – Swedish Environmental Institute, Stockholm, Sweden;RISE Energy Technology Center AB, Piteå, Sweden.
    Wetterlund, Elisabeth
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Alkali enhanced biomass gasification with in situ S capture and a novel syngas cleaning: Part 2: Techno-economic analysis2018Inngår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 165, nr Part B, s. 471-482Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous research has shown that alkali addition has operational advantages in entrained flow biomass gasification and allows for capture of up to 90% of the biomass sulfur in the slag phase. The resultant low-sulfur content syngas can create new possibilities for syngas cleaning processes. The aim was to assess the techno-economic performance of biofuel production via gasification of alkali impregnated biomass using a novel gas cleaning systemcomprised of (i) entrained flow catalytic gasification with in situ sulfur removal, (ii) further sulfur removal using a zinc bed, (iii) tar removal using a carbon filter, and (iv) CO2 reductionwith zeolite membranes, in comparison to the expensive acid gas removal system (Rectisol technology). The results show that alkali impregnation increases methanol productionallowing for selling prices similar to biofuel production from non-impregnated biomass. It was concluded that the methanol production using the novel cleaning system is comparable to the Rectisol technology in terms of energy efficiency, while showing an economic advantagederived from a methanol selling price reduction of 2–6 €/MWh. The results showed a high level of robustness to changes related to prices and operation. Methanol selling prices could be further reduced by choosing low sulfur content feedstocks.

  • 50.
    Creaser, D.
    et al.
    Luleå tekniska universitet.
    Andersson, B.
    Chalmers University of Technology.
    Hudgins, R.R.
    University of Waterloo.
    Silveston, P.L.
    University of Waterloo.
    Oxygen partial pressure effects on the oxidative dehydrogenation of propane1999Inngår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 54, nr 20, s. 4365-4370Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of the gas-phase oxygen partial pressure for the oxidative dehydrogenation of propane over a V-Mg-O catalyst was investigated to explore reasons for improved propene yields when dehydrogenation was carried out under periodic operation. Steady-state experiments were performed in which the oxygen partial pressure was varied over a large range at constant propane partial pressures. In addition, the catalyst mass was varied to control the propane conversion so that selectivity and yield could be compared at a constant propane conversion. At the same propane conversion, propene selectivity increased as the partial pressure of oxygen decreased. Thus, propene yields can be improved at steady state by employing low oxygen partial pressures. It is likely that this is the reason for the higher propene yields observed under unsteady-state or periodic operation. It appears that the reaction mechanism must consist of more than one pathway for production of carbon oxides

1234567 1 - 50 of 415
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