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  • 1.
    Abolhasani, Hasanali
    et al.
    Department of Materials and Polymer Engineering, Faculty of Engineering, Hakim Sabzevari University, Sabzevar 9617976487, Iran.
    Farzi, Gholamali
    Department of Materials and Polymer Engineering, Faculty of Engineering, Hakim Sabzevari University, Sabzevar 9617976487, Iran.
    Davoodi, Ali
    Materials and Metallurgical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad 917751111, Iran.
    Vakili-Azghandi, Mojtaba
    Department of Materials Engineering, Faculty of Engineering, University of Gonabad, Gonabad, 96919-57678, Iran.
    Das, Oisik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Neisiany, Rasoul Esmaeely
    Department of Materials and Polymer Engineering, Faculty of Engineering, Hakim Sabzevari University, Sabzevar 9617976487, Iran.
    Development of self-healable acrylic water-based environmental-friendly coating as an alternative to chromates coatings2023Ingår i: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 176, artikel-id 107402Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, different coating systems, including solvent-based epoxy and water-based acrylic resins, were evaluated for their potential as an alternative to chromate coatings in order to avoid Cr(VI) toxic hazards. The resins were used as either pigment-free coatings or were formulated with 20-wt% zinc/aluminum pigments. The coatings were subsequently applied on galvanized ST12 steel plates and their corrosion resistance was investigated by electrochemical impedance spectroscopy (EIS) evaluations. The effect of the binder and pigment type on the impact resistance of two different polymeric coatings was also evaluated. The results of impact tests revealed completely peeled film from the substrate for epoxy coatings. However, under the same experimental conditions, very few small cracks were created in water-based acrylic coatings for both pigmented and pigment-free cases. In addition, some other parameters such as drying time and coating cost were taken into account to select a good alternative to chromate coatings. The results of this work can facilitate the introduction of an inexpensive environmentally friendly acrylic coating as a promising self-healing alternative to chromate coating.

  • 2.
    Abrahamsson, Filip
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Leaching of Pyrrhotite from Nickel Concentrate2017Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Icke-oxidativ syralakning av magnetkis från Kevitsas Ni-koncentrat har studerats samt metoder för tillvaratagande av biprodukter. Genom en selektiv upplösning av magnetkis (Fe1-xS, 0<x<0.25) kan värdefulla metaller som Ni och Co anrikas i det slutliga koncentratet. Samtidigt som mängden Fe och S som skickas till smältverken minskar, vilket också innebär att mindre biprodukter i form av slagg och SO2 erhålls vid den pyrometallurgiska smältningen av Ni-koncentratet. En experimentell design plan genomfördes för att studera lakningen där syrakoncentrationen varierades från 38.8% till 57.8%H2SO4 och temperatur från 60 till 100°C. Bäst resultat erhölls vid de lägre parameterinställningarna. Lakning vid 60°C med en initial syrakoncentration på 38.8%H2SO4 visade sig vara tillräcklig för att selektivt lösa upp merparten av all magnetkis och lämna kvar en anrikad produkt. Via QUEMSCAN bekräftades att merparten av all magnetkis hade löst upp sig och att huvudsakligt Ni-mineral fortfarande var pentlandit. Kemiska analyser visade att mer än 95% av Ni, Co och Cu stannade kvar i fasta godset.

       Den tillämpade lakningsmetoden genererar biprodukter i form av stora mängder Fe2+ i lösning och H2S i gasform. För att tillvarata Fe2+ har kristallisering av laklösning som järn(ii) sulfat (FeSO4∙nH2O) studerats genom kylning. De kristalliserade kristallerna avvattnades till monohydrat, FeSO∙1H2O, genom avvattning i stark svavelsyra (80%H2SO4). XRD bekräftade FeSO∙1H2O som huvudfas i slutliga kristallerna och kemisk analys visade på ca 30%Fe med huvudsakliga orenheter i form av 1.5% Mg, 0.4%Ca och 0.2% Ni.

       Möjligheten till att laka i återcirkulerad lösning efter kristallisering har undersökts. Lakning i återcirkulerad lösning visade inga negativa effekter då liknande halter och utbyten erhölls till det fasta godset.

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  • 3.
    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 nanocubes2014Ingår i: CrystEngComm, E-ISSN 1466-8033, Vol. 16, nr 8, s. 1443-1450Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    Aguilar, Wilson
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Study of the Synthesis of ZSM-5 from Inexpensive Raw Materials2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

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  • 5.
    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-5Ingår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093Artikel i tidskrift (Övrigt vetenskapligt)
    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.

  • 6.
    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-52014Ingår i: SpringerPlus, E-ISSN 2193-1801, Vol. 3, nr 1Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    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 entrapment2018Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 487, s. 57-64Artikel i tidskrift (Refereegranskat)
    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.

  • 8.
    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 crystals2018Ingår i: Journal of porous materials, ISSN 1380-2224, E-ISSN 1573-4854, Vol. 25, nr 6, s. 1551-1559Artikel i tidskrift (Refereegranskat)
    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.

  • 9.
    Ahmed, Mukhtiar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Fluorine-Free Ionic Liquid Based Electrolytes: Synthesis and Structural Characterization2022Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Since their introduction by Sony in 1990, lithium-ion batteries (LIBs) have acquired a sizable market share. They have the best energy densities, a high open circuit voltage, a low self-discharge rate, no memory effect, and a slow loss of charge when not in use. These properties make them the most popular rechargeable batteries for portable gadgets, electric vehicles and aerospace applications.  They do, however, pose major safety issues since the electrolytes are made up of fluorinated salts dissolved in volatile organic solvents, the former being meta-stable at ambient temperature and the latter being flammable a with high vapour pressure. Thus, there is an urge to develop thermally and electrochemically stable non-fluorinated electrolytes to improve the safety and performance of batteries. Electrolytes based on ionic liquids (ILs) in general offer a range of suitable advantages including low volatility and high thermal and electrochemical stabilities,and can additionally be made fluorine-free. In general, their physicochemical properties are determined by the interactions between the cations and anions, which are controlled by the chemical functionalities present, with vast freedom in structural design to reduce these interactions and enhance also the ion mobilities. 

    In this study, favoring from of “structural design” three different families of fluorine-free ionic liquids-based electrolytes are designed and created. These families of ILs comprising n- tetrabutylphosphonium, imidazolium, pyridinium based cations and pyridine, pyrazine and ether functionalized salicylate-based anions. The structures and purity of these new ILs are characterized by using multinuclear NMR, FTIR and mass spectrometry. Several features and properties of the novel electrolytes are investigated; thermogravimetric analysis, differential scanning calorimetry, ionic conductivity and electrochemical stability. These studies are further complemented by using PFG NMR diffusometry to understand the possible interaction mechanisms between the oppositely charged ions within the electrolytes, and especially, the influence of Li+ addition in the IL-based electrolytes. 

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  • 10.
    Ahmed, Naeem
    et al.
    Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor, Malaysia.
    Shahid, Muhammad
    Department of Biological Sciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor, Malaysia.
    Siow, Kim S
    Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor, Malaysia.
    Razip Wee, M F Mohd
    Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor, Malaysia.
    Haron, Farah Farhanah
    Pest and Disease Management Programme, Horticulture Research Centre, Malaysian Agricultural Research and Development Institute, Serdang 43400, Selangor, Malaysia.
    Patra, Anuttam
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Fazry, Shazrul
    Department of Food Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor, Malaysia.
    Germination and growth improvement of papaya utilizing oxygen (O2) plasma treatment2022Ingår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 55, nr 25, artikel-id 255205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In general, cold plasma treatment improves crop germination and growth. The purpose of this research is to examine the impact of low-pressure O2 plasma treatment on the germination and growth kinetics of papaya seeds. Seeds were treated for 40 s at a discharge power of 80 W using O2 as a monomer. Physical and chemical changes were studied to understand the mechanism of germination and growth improvement. Furthermore, changes in phytohormones and antioxidant activity that were beneficial to germination were also examined. O2 plasma treatment improved wettability, surface etching, and oxidation, and affected other molecular-level changes leading to a 16% germination improvement in papaya.

  • 11.
    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 microgravity2005Ingår i: Topical teams in life & physical sciences: towards new research applications, Noordwijk, Netherlands: ESTEC , 2005, s. 78-85Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    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.

  • 12.
    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 Membranes2010Konferensbidrag (Refereegranskat)
  • 13.
    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 membranes2011Ingår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, nr 24, s. 8822-8828Artikel i tidskrift (Refereegranskat)
    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

  • 14.
    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 membranes2011Konferensbidrag (Refereegranskat)
  • 15.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden.
    Sjöberg, Erik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Korelskiy, Danil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rayson, Mark
    Department of Chemistry, The University of Surrey, Guildford, Surrey GU2 7XH, UK.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden.
    Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H2 separation performance2015Ingår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 493, s. 206-211Artikel i tidskrift (Refereegranskat)
    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.

  • 16.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dobryden, Illia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Almqvist, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Apparent Elastic Modulus of Polyethylene and its Nanocomposites Measured at Different Scales2023Ingår i: ICCM 2023 - Proceedings of the 2023 23rd International Conference on Composite Materials / [ed] Brian G. Falzon; Conor McCarthy, Queen's University Belfast , 2023Konferensbidrag (Refereegranskat)
  • 17.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pupure, Liva
    Riga Technical University, Kalnciema Iela 6, Rīga, LV-1048, Latvia.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Analysis of long-term performance of wood polymer composites with added multifunctionality2022Ingår i: 80th International Scientific Conference of the University of Latvia - Advanced Composites and Applications: Book of Abstracts, Riga: University of Latvia , 2022, s. 9-Konferensbidrag (Övrigt vetenskapligt)
  • 18.
    Altaee, Mohammed J.
    et al.
    Environmental Research and Studies Centre, University of Babylon, Hilla, Iraq.
    Altayee, Sarmed A. S.
    Department of Chemical Engineering, College of Engineering, University of Babylon, Hilla 51001, Iraq.
    Kadhim, Majid M. A.
    Department of Civil Engineering, College of Engineering, University of Babylon, Hilla 51001, Iraq.
    Jawdhari, Akram
    Department of Civil Engineering, Queen’s University, Kingston, Canada.
    Majdi, Ali
    Building and Construction Techniques Engineering, Al-Mustaqbal University College, 51001, Babylon, Iraq.
    Chabuk, Ali
    Department of Environment Engineering, College of Engineering, University of Babylon, Hilla 51001, Iraq.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Evaluation of Existing Bond-Slip Relations for CFRP-Steel Joints and New Model for Linear and Nonlinear Adhesives2022Ingår i: Advances in Civil Engineering / Hindawi, ISSN 1687-8086, E-ISSN 1687-8094, Vol. 2022, artikel-id 3673438Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Existing bond-slip (τ-s) relations for fibre-reinforced polymer (FRP)-steel joints employ different shapes and mathematical expressions, inferring that their predictions of failure load and mode, and other interface properties, might be inconsistent or inaccurate. In this study, predictions of four widely used τ-s relations are evaluated using a large experimental database of 78 double-lap FRP-steel specimens. To facilitate the evaluation process, a robust finite element (FE) model is developed for each test, implementing data from either of the existing τ-s relations to define the FRP-steel interface. Comparisons between test and FE results indicated that the existing τ-s models were unable of predicting the ultimate load (Pu) and effective bond length (Leff) of FRP-steel joints, or the relation between Pu and bond length and that between Leff and FRP modulus (Ef). A new τ-s model is developed based on an inverse FE simulation, comparison with experimental results, and regression analysis. It considers the effects of Ef, the type of FRP reinforcement (sheet or plate), and applies to both linear and nonlinear adhesives. The model predictions were validated by comparing with results from small bond tests and large FRP-strengthened steel beams tested under bending, yielding excellent results for Pu, failure mode, and all other interfacial properties.

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  • 19.
    Amari, Abdelfattah
    et al.
    Department of Chemical Engineering, College of Engineering, King Khalid University, Abha, Saudi Arabia; Research Laboratory of Processes, Energetics, Environment and Electrical Systems, National School of Engineers of Gabes, Gabes University, Gabes, Tunisia.
    Noreen, Ayesha
    Department of Social Environmental Sciences, Faculty of Language History and Geography, Ankara University, Ankara, Turkey.
    Osman, Haitham
    Department of Chemical Engineering, College of Engineering, King Khalid University, Abha, Saudi Arabia.
    Sammen, Saad Sh.
    Department of Civil Engineering, College of Engineering, University of Diyala, Diyala, Iraq.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Salman, Hayder Mahmood
    Department of Computer Science, Al-Turath University College Al Mansour, Baghdad, Iraq.
    Investigation of the viable role of oil sludge-derived activated carbon for oily wastewater remediation2023Ingår i: Frontiers in Environmental Science, E-ISSN 2296-665X, Vol. 11, artikel-id 1138308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A wide range of studies has been carried out to describe the equilibrium data of adsorption for the surface adsorption process. However, no extensive investigation has been carried out to evaluate the oil sludge based activated carbon surface adsorption. Therefore, the possibility of carbon active production using different oil sludges and consequently the adsorption mechanism of these kind of adsorbents is still unknown. In this study, a novel low-cost approach was introduced to synthesize the activated carbon using oil sludge applying a two-step process including carbonization and chemical activation. In this way, four different types of oil sludges were characterized and then applied to synthesize different carbon actives and their performance were investigated as an adsorbent. The results showed that all synthesized activated carbons, with about 6% ash and pH = 7 and the specific surface area of 110 m2/gr, have the ability to treatment of oily wastewater; which can be referred to the high carbon content (>80%). The iodine number and the efficiency of prepared activated carbon were obtained as 406.8 mg/g and 94%, respectively. The adsorption process was also studied at different process conditions such as temperature (308–338 K), pH value (3–9) and adsorbent amount (50–200 mg/L) to find the optimum condition for wastewater treatment. The results show that the pH value has an optimum in the adsorption rate (the maximum adsorption was measured at pH = 5) and the adsorption capacity can be reduced by increasing the temperature or decreasing the adsorbent amount. Moreover, three different adsorption isotherm models were applied, i.e., Langmuir, Temkin, and Freundlich isotherms; which the Langmuir equation was more suitable than others investigated isotherm models with R2 ≈ 0.999.

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  • 20.
    Amin, Muhammad
    et al.
    Interdisciplinary Research Center for Hydrogen Technologies and Carbon Management (IRC-HTCM), King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia.
    Shah, Hamad Hussain
    Department of Engineering, University of Sannio, Benevento, Italy.
    Naveed, Abdul Basit
    Department of Chemistry, University of Louisville, Louisville, KY, United States.
    Iqbal, Amjad
    Faculty of Materials Engineering, Silesian University of Technology, Gliwice, Poland.
    Gamil, Yaser
    Department of Civil Engineering, School of Engineering, Monash University Malaysia, Subang Jaya, Selangor, Malaysia.
    Najeh, Taoufik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Life cycle assessment of iron-biomass supported catalyst for Fischer Tropsch synthesis2024Ingår i: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 12, artikel-id 1374739Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The iron-based biomass-supported catalyst has been used for Fischer-Tropsch synthesis (FTS). However, there is no study regarding the life cycle assessment (LCA) of biomass-supported iron catalysts published in the literature. This study discusses a biomass-supported iron catalyst’s LCA for the conversion of syngas into a liquid fuel product. The waste biomass is one of the source of activated carbon (AC), and it has been used as a support for the catalyst. The FTS reactions are carried out in the fixed-bed reactor at low or high temperatures. The use of promoters in the preparation of catalysts usually enhances C5+ production. In this study, the collection of precise data from on-site laboratory conditions is of utmost importance to ensure the credibility and validity of the study’s outcomes. The environmental impact assessment modeling was carried out using the OpenLCA 1.10.3 software. The LCA results reveals that the synthesis process of iron-based biomass supported catalyst yields a total impact score in terms of global warming potential (GWP) of 1.235E + 01 kg CO2 equivalent. Within this process, the AC stage contributes 52% to the overall GWP, while the preparation stage for the catalyst precursor contributes 48%. The comprehensive evaluation of the iron-based biomass supported catalyst’s impact score in terms of human toxicity reveals a total score of 1.98E−02 kg 1,4-dichlorobenzene (1,4-DB) equivalent.

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  • 21.
    Amjad, Um-e-Salma
    et al.
    Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan.
    Tajjamal, Arshia
    Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan.
    Ul-Hamid, Anwar
    Core Research Facilities, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia.
    Faisal, Abrar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan.
    Zaidi, Syed Ammar Hussain
    Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan.
    Sherin, Lubna
    Department of Chemistry, COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan.
    Mir, Amna
    Department of Physics, COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan.
    Mustafa, Maria
    Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan.
    Ahmad, Nabeel
    Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan.
    Hussain, Murid
    Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan.
    Park, Young-Kwon
    School of Environmental Engineering, University of Seoul, Seoul 02504, Republic of Korea.
    Catalytic cracking of polystyrene pyrolysis oil: Effect of Nb2O5 and NiO/Nb2O5 catalyst on the liquid product composition2022Ingår i: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 141, s. 240-250Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The catalytic cracking of polystyrene pyrolysis oil was investigated over a Nb2O5 and a NiO/Nb2O5 catalyst in a fixed bed reactor. First, the pyrolysis of two different polystyrene feedstock (polystyrene foam and polystyrene pellet) was carried out in a semi-batch reactor, and the resulting polystyrene pellets pyrolysis oil was selected for catalytic cracking reaction because of its high liquid yield (85%). Catalytic cracking experiments were then performed at different temperatures (350–500 °C) using Nb2O5 or NiO/Nb2O5 catalyst. Gas chromatography–mass spectrometry analysis of liquid product obtained from the catalytic cracking process showed that the dimers in the pyrolysis oil were converted to monomers during the catalytic cracking process. The catalytic cracking results also showed that the NiO/Nb2O5 catalyst (having slightly higher acidic sites) had slightly higher activity for monomer conversion than the Nb2O5 catalyst (having less acidic sites). X-ray diffraction, transmission electron microscopy, pyridine Fourier transform infrared spectroscopy, NH3 Temperature Programmed Desorption and X-ray photoelectron spectroscopy were used to characterize the catalyst. The highest catalytic cracking activity was observed at 400 °C with the Nb2O5 catalyst with 4% toluene, 6% ethylbenzene, approximately 50% styrene, 13% α-methyl styrene, and only 6% of dimers in the liquid oil. The increase in temperature positively affected the yield of gases during catalytic cracking process.

  • 22.
    Andersson, Anna
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    CFD optimization of photochemical UV reactors for VOC degradation2017Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

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  • 23.
    Andersson, Charlotte
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Factors affecting MFI membrane quality2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

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  • 24.
    Andersson, Charlotte
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Properties of molecular sieve membranes2004Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

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  • 25. 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 membranes2008Ingår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 313, nr 1-2, s. 120-126Artikel i tidskrift (Refereegranskat)
    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.

  • 26. 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 size2004Ingår 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. 626-631Konferensbidrag (Refereegranskat)
    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.

  • 27.
    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 lubrication2012Ingår i: Faraday discussions, ISSN 1359-6640, E-ISSN 1364-5498, Vol. 156, s. 343-360Artikel i tidskrift (Refereegranskat)
    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.

  • 28.
    Andersson, Sofia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Influence of metal ions on lignin-based carbon fiber quality2017Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Carbon fiber is a lightweight, versatile material with many current and potential applications. To be able to expand the market for carbon fiber composites in other areas than special applications the production costs must be reduced. One way of accomplishing this could be to use a less expensive raw material where lignin is a good example as it can be provided at lower cost, is renewable and abundantly available compared to commercially used raw materials today.

    So far, the mechanical properties of lignin-based carbon fibers are inferior relative to commercial carbon fibers. For lignin-based carbon fibers to enter the commercial market more research is necessary to gain knowledge of the conversion of lignin to carbon fiber. The LightFibre project investigates the possibilities to produce carbon fibers based on a mixture of softwood kraft lignin and cellulose. The kraft lignin is isolated from black liquor in the kraft/sulfate process with the LignoBoost process. This master thesis project was conducted within in the LightFibre project and evaluated whether metal ions generally present in kraft lignin had an influence on the final carbon fiber quality in terms of mechanical properties and morphology. The mechanical properties were determined with tensile testing, the morphology by scanning electron microscopy (SEM) and the relative abundance of studied elements with electron dispersive spectroscopy (EDS).

    The influence of the chosen metal ions was tested by impregnation of dry-jet wet spun prefibers based on 70 wt.% softwood kraft lignin and 30 wt.% dissolving pulp cellulose. The fibers were impregnated in room temperature with solutions containing Na2SO4, K2SO4, MgSO4, FeSO4 and Al2(SO4)3 salts where the cations were the focus in these trials. The concentrations used for impregnation were 0.2 and 1M of the cations.

    The obtained mechanical properties of the carbon fibers of the samples impregnated with different metal ions did not deviate significantly from the reference which had a tensile strength of 870 MPa and tensile modulus of 68 GPa. The analysis of morphology with SEM showed no defects or damage of any of the fibers. Therefore, it was concluded that the impregnated metal ions: K+, Na+, Al3+, Mg2+ and Fe2+ at the obtained levels in the fibers cause no effects on the fibers during the stabilization and carbonization that affects the mechanical performance of final carbon fiber.  The amount of potassium in one of the samples was estimated to 0.1 wt.%.

    From the results of this study it may be suggested that the general recommendation of <0.1 wt.% ash in lignin can be exceeded, for dry-jet wet-spun kraft lignin/cellulose-based carbon fibers.

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  • 29. 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 manufacture2000Patent (Övrig (populärvetenskap, 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.

  • 30.
    Antonopoulou, Io
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Development of biocatalytic processes for selective antioxidant production2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Feruloyl esterases (FAEs, EC 3.1.1.73) represent a subclass of carboxylic acid esterases that under normal conditions catalyze the hydrolysis of the ester bond between hydroxycinnamic acids (ferulic acid, sinapic acid, caffeic acid, p-coumaric acid) and sugar residues in plant cell walls. Based on their specificity towards monoferulates and diferulates, substitutions on the phenolic ring and on their amino acid sequence identity, they have been classified into four types (A-D) while phylogenetic analysis has resulted in classification into thirteen subfamilies (SF1-13). Under low water content, these enzymes are able to catalyze the esterification of hydroxycinnamic acids or the transesterification of their esters (donor) with alcohols or sugars (acceptor) resulting in compounds with modified lipophilicity, having a great potential for use in the tailor-made modification of natural antioxidants for cosmetic, cosmeceutical and pharmaceutical industries. The work described in this thesis focused on the selection,characterization and application of FAEs for the synthesis of bioactive esters with antioxidant activity in non-conventional media. The basis of the current classification systems was investigated in relation with the enzymes’ synthetic and hydrolytic abilities while the developed processes were evaluated for their efficiency and sustainability.

    Paper I was dedicated to the screening and evaluation of the synthetic abilities of 28 fungal FAEs using acceptors of different lipophilicity at fixed conditions in detergentless microemulsions. It was revealed that FAEs classified in phylogenetic subfamilies related to acetyl xylan esterases (SF5 and 6) showed increased transesterification rates and selectivity. In general, FAEs showed preference on more hydrophilic alcohol acceptors and in descending order to glycerol > 1-butanol > prenol. Homology modeling and small molecule docking simulations were employed as tools for the identification of a potential relationship between the predicted surface and active site properties of selected FAEs and the transesterification selectivity.

    Papers II- IV focused on the characterization of eight promising FAEs and the optimization of reaction conditions for the synthesis of two bioactive esters (prenyl ferulate and L-arabinose ferulate) in detergentless microemulsions. The effect of the medium composition, the donor and acceptor concentration, the enzyme load, the pH, the temperature and the agitation on the transesterification yield and selectivity were investigated. It was observed that the acceptor concentration and enzyme load were crucial parameters for selectivity. Fae125 (Type A, SF5) iiexhibited highest prenyl ferulate yield (81.1%) and selectivity (4.685) converting 98.5% of VFA to products after optimization at 60 mM VFA, 1.5 M prenol, 0.04 mg FAE mL-1, 40oC, 24 h, 53.4:43.4:3.2 v/v/v n-hexane: t-butanol: 100 mM MOPS-NaOH pH 8.0. On the other hand, FaeA1 (Type A, SF5) showed highest L-arabinose ferulate yield (52.2 %) and selectivity (1.120) at 80 mM VFA, 55 mM L-arabinose, 0.02 mg FAE mL-1, 50oC, 8 h, 19.8: 74.7: 5.5 v/v/v n-hexane: t-butanol: 100 mM MOPS-NaOH pH 8.0.

    In paper V, the effect of reaction media on the enzyme stability and transesterification yield and selectivity was studied in different solvents for the synthesis of two bioactive esters: prenyl ferulate and L-arabinose ferulate. The best performing enzyme (Fae125) was used in the optimization of reaction conditions in the best solvent (n-hexane) via response surface methodology. Both bioconversions were best described by a two-factor interaction model while optimal conditions were determined as the ones resulting in highest yield and selectivity.Highest prenyl ferulate yield (87.5%) and selectivity (7.616) were observed at 18.56 mM prenol mM-1VFA, 0.04 mg FAE mL-1, 24.5 oC, 24.5 h, 91.8: 8.2 v/v n-hexane: 100 mM sodium acetate pH 4.7. Highest L-arabinose ferulate yield (56.2%) and selectivity (1.284) were observed at 2.96 mM L-arabinose mM-1VFA, 0.02 mg FAE mL-1, 38.9 oC, 12 h, 90.5: 5.0: 4.5 v/v/v n-hexane: dimethyl sulfoxide: 100 mM sodium acetate pH 4.7. The enzyme could be reused for six consecutive reaction cycles maintaining 66.6% of its initial synthetic activity. The developed bioconversions showed exceptional biocatalyst productivities (> 300 g product g-1FAE) and the waste production was within the range of pharmaceutical processes.

    Paper VI focused on the investigation of the basis of the type A classification of a well-studied FAE from Aspergillus niger(AnFaeA) by comparing its activity towards methyl and arabinose hydroxycinnamic acid esters. For this purpose, L-arabinose ferulateand caffeate were synthesized enzymatically. kcat/Kmratios revealed that AnFaeA hydrolyzed arabinose ferulate 1600 times and arabinose caffeate 6.5 times more efficiently than methyl esters. This study demonstrated that short alkyl chain hydroxycinnamate esters which are used nowadays for FAE classification can lead to activity misclassification, while L-arabinose esters could potentially substitute synthetic esters in classification describing more adequately the enzyme specificitiesin the natural environment.

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  • 31.
    Antonopoulou, Io
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Use of feruloyl esterases for chemoenzymatic synthesis of bioactive compounds2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Feruloyl esterases (FAEs, EC 3.1.1.73) represent a subclass of carboxylic acid esterases that under normal conditions catalyze the hydrolysis of the ester bond between hydroxycinnamic acids (ferulic acid, sinapic acid, caffeic acid, p-coumaric acid) and arabinose residues in plant cell walls. Based on their specificity towards monoferulates and diferulates, substitutions on the phenolic ring and on their amino acid sequence identity, they have been classified into four types (A-D). The use of FAEs as accessory enzymes for the degradation of lignocellulosic biomass and their synergism with other hemicellulases has been studied for application in many industries, such as the food, the biofuel and the paper pulp industry. In the recent years, the use of FAEs as biosynthetic tools has been underlined. Under low water content, these enzymes are able to catalyze the esterification of hydroxycinnamic acids or the transesterification of their esters resulting in compounds with altered lipophilicity, revealing a great potential for tailor-made modification of natural antioxidants for use in cosmetic, cosmeceutical and pharmaceutical industries.

    The first part of the thesis is focused on the optimization of reaction conditions for the synthesis of two bioactive esters: prenyl ferulate and L-arabinose ferulate using 5 FAEs (FaeA1, FaeA2, FaeB1, FaeB2 and MtFae1a) from Myceliophthora thermophila in detergentless microemulsions. Reaction conditions were optimized investigating parameters such as the medium composition, the substrate concentration, the enzyme load, the pH, the temperature and the agitation. Regarding the synthesis of prenyl ferulate, FaeB2 offered the highest transesterification yield (71.5±0.2%) after 24 h of incubation at 30oC using 60 mM vinyl ferulate (VFA), 1 M prenol and 0.02 mg FAE/mL in a mixture comprising of 53.4: 43.4: 3.2 v/v/v n-hexane: t-butanol: 100 mM MOPS-NaOH pH 6.0. At these conditions, the competitive hydrolysis was 4-7 fold minimized. Regarding the synthesis of L-arabinose ferulate, FaeA1 offered highest transesterification yield (35.9±2.96%) after 8 h of incubation at 50oC using 80 mM VFA, 55 mM L-arabinose and 0.02 mg FAE/mL in a mixture of 19.8: 74.7: 5.5 v/v/v n-hexane: t-butanol: 100 mM MOPS-NaOH pH 8.0. It was revealed that the type B FAEs from M. thermophila show higher preference to more lipophilic acceptors like prenol, while the type A FaeA1 was more efficient in the synthesis of the more hydrophilic L-arabinose ferulate.

    The second part of the thesis is focused on the investigation of the basis of the type A classification of a well-studied FAE from Aspergillus niger (AnFaeA) by comparing its activity towards methyl and arabinose hydroxycinnamate esters. For this purpose, L-arabinose ferulate and caffeate were synthesized enzymatically. kcat/Km ratios revealed that AnFaeA hydrolyzed arabinose ferulate 1600 times and arabinose caffeate 6.5 times more efficiently than methyl esters. This study demonstrated that short alkyl chain hydroxycinnamate esters which are used nowadays for FAE classification can lead to activity misclassification, while L-arabinose esters could potentially substitute synthetic esters in classification.

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  • 32.
    Antonopoulou, Io
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Dilokpimol, Adiphol
    Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University.
    Iancu, Laura
    Dupont Industrial Biosciences.
    Mäkelä, Miia R.
    Department of Microbiology, University of Helsink.
    Varriale, Simona
    Department of Chemical Sciences, University of Naples “Federico II”.
    Cerullo, Gabriella
    Department of Chemical Sciences, University of Naples “Federico II”.
    Hüttner, Silvia
    Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology.
    Uthoff, Stefan
    Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster.
    Jütten, Peter
    Taros Chemicals GmbH & Co KG.
    Piechot, Alexander
    Taros Chemicals GmbH & Co KG.
    Steinbüchel, Alexander
    nstitut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster.
    Olsson, Lisbeth
    Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology.
    Faraco, Vincenza
    Department of Chemical Sciences, University of Naples “Federico II”.
    Hildén, Kristiina
    Department of Microbiology, University of Helsinki.
    de Vries, Ronald
    Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    The Synthetic Potential of Fungal Feruloyl Esterases: A Correlation with Current Classification Systems and Predicted Structural Properties2018Ingår i: Catalysts, E-ISSN 2073-4344, Vol. 8, nr 6, artikel-id 242Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Twenty-eight fungal feruloyl esterases (FAEs) were evaluated for their synthetic abilities in a ternary system of n-hexane: t-butanol: 100 mM MOPS-NaOH pH 6.0 forming detergentless microemulsions. Five main derivatives were synthesized, namely prenyl ferulate, prenyl caffeate, butyl ferulate, glyceryl ferulate, and l-arabinose ferulate, offering, in general, higher yields when more hydrophilic alcohol substitutions were used. Acetyl xylan esterase-related FAEs belonging to phylogenetic subfamilies (SF) 5 and 6 showed increased synthetic yields among tested enzymes. In particular, it was shown that FAEs belonging to SF6 generally transesterified aliphatic alcohols more efficiently while SF5 members preferred bulkier l-arabinose. Predicted surface properties and structural characteristics were correlated with the synthetic potential of selected tannase-related, acetyl-xylan-related, and lipase-related FAEs (SF1-2, -6, -7 members) based on homology modeling and small molecular docking simulations.

  • 33.
    Antonopoulou, Io
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hunt, Cameron
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Cerullo, Gabriella
    Department of Chemical Sciences, University of Naples "Federico II".
    Varriale, Simona
    Department of Chemical Sciences, University of Naples “Federico II”.
    Gerogianni, Alexandra
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Faraco, Vincenza
    Department of Chemical Sciences, University of Naples "Federico II".
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Tailoring the specificity of the type C feruloyl esterase FoFaeC from Fusarium oxysporum towards methyl sinapate by rational redesign based on small molecule docking simulations2018Ingår i: PLOS ONE, E-ISSN 1932-6203, Vol. 13, nr 5, artikel-id e0198127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The type C feruloyl esterase FoFaeC from Fusarium oxysporum is a newly discovered enzyme with high potential for use in the hydrolysis of lignocellulosic biomass but it shows low activity towards sinapates. In this work, small molecule docking simulations were employed in order to identify important residues for the binding of the four model methyl esters of hydroxycinnamic acids, methyl ferulate/caffeate/sinapate/p-coumarate, to the predicted structure of FoFaeC. Subsequently rational redesign was applied to the enzyme’ active site in order to improve its specificity towards methyl sinapate. A double mutation (F230H/T202V) was considered to provide hydrophobic environment for stabilization of the methoxy substitution on sinapate and a larger binding pocket. Five mutant clones and the wild type were produced in Pichia pastoris and biochemically characterized. All clones showed improved activity, substrate affinity, catalytic efficiency and turnover rate compared to the wild type against methyl sinapate, with clone P13 showing a 5-fold improvement in catalytic efficiency. Although the affinity of all mutant clones was improved against the four model substrates, the catalytic efficiency and turnover rate decreased for the substrates containing a hydroxyl substitution.

  • 34.
    Antonopoulou, Io
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Spanopoulos, Athanasios
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str, Zografou Campus, Athens, Greece.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Single cell oil and ethanol production by the oleaginous yeast Trichosporon fermentans utilizing dried sweet sorghum stalks2020Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, s. 1609-1617Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ability of the oleaginous yeast Trichosporon fermentans to efficiently produce lipids when cultivated in dried sweet sorghum was evaluated. First, lipid production was evaluated in synthetic media mimicking the composition of sweet sorghum stalks and optimized based on the nitrogen source and C: N ratio. Under optimum conditions, the lipid production reached 3.66 g/L with 21.91% w/w lipid content by using a mixture of sucrose, glucose and fructose and peptone at C: N ratio 160. Cultivation on pre-saccharified sweet sorghum stalks offered 1.97 g/L, while it was found that sweet sorghum stalks can support yeast growth and lipid production without the need for external nitrogen source addition. At an attempt to increase the carbon source concentration for optimizing lipid production, the Crabtree effect was observed in T. fermentans. To this end, the yeast was evaluated for its potential to produce ethanol under anaerobic conditions in synthetic media and sweet sorghum. The ethanol concentration at 100 g/L glucose was 40.31 g/L, while utilizing sweet sorghum by adding a distinct saccharification step and external nitrogen source offered ethanol concentration equal to 23.5 g/L. To the authors’ knowledge, this is the first time that the Crabtree effect is observed in T. fermentans.

  • 35.
    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 systems2011Konferensbidrag (Övrigt vetenskapligt)
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  • 36.
    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 systems2010Konferensbidrag (Övrigt vetenskapligt)
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  • 37.
    Anukam, Anthony Ike
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Nyamukamba, Pardon
    Technology Station: Clothing and Textiles, Cape Peninsula University of Technology, Symphony Way, Bellville, South Africa.
    The Chemistry of Human Excreta Relevant to Biogas Production: A Review2022Ingår i: Anaerobic Biodigesters for Human Waste Treatment / [ed] Mukesh Kumar Meghvansi, A. K. Goel, Springer, 2022, s. 29-38Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    As obnoxious as it may sound, studies involving human excreta are of great importance to sanitation, one of the most effective ways by which public health can be improved. The composition of human excreta is highly variable and contains all that enters into the toilet including water, urine, anal cleansing materials, lipids, proteins, polysaccharides, chemical elements, and undigested food residues as well as municipal wastes. A great deal of past and present research has focused on efficient utilization of this waste product of the human digestive system, particularly in biological processes, such as anaerobic digestion, where the waste is used as substrate to produce value-added products like biogas. However, there is very limited data on the chemistry of human excreta and its direct impact on anaerobic digestion process efficiency. This review therefore aims to illustrate the significance of the chemistry of human excreta relevant to biogas production and discuss key criteria and values that will help advance research and development of anaerobic digestion systems using human excreta as a treatment technology.

  • 38.
    Argyropoulos, Dimitris D. S.
    et al.
    Departments of Chemistry and Forest Biomaterials, North Carolina State University, 431 Dan Allen Drive, Raleigh, North Carolina 27695, USA.
    Crestini, Claudia
    Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, 30170 Venezia-Mestre, Italy.
    Dahlstrand, Christian
    Ren Fuel K2B AB, Rapsgatan 25, SE-754 50 Uppsala, Sweden.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Division of Bioeconomy and Health, RISE Research Institutes of Sweden, Lindholmspiren 7 A, SE-41756 Göteborg, Sweden.
    Gioia, Claudio
    Department of physics, University of Trento, Via Sommarive 14, 38123 Trento, Italy.
    Jedvert, Kerstin
    Division of Materials and Production, RISE Research Institutes of Sweden, Lindholmspiren 7 A, SE-41756 Göteborg, Sweden.
    Henriksson, Gunnar
    Wallenberg Wood Science Center (WWSC), KTH, Royal Institute of Technology, 100 44 Stockholm, Sweden.
    Hulteberg, Christian
    Department of Chemical Engineering, Faculty of Engineering, Lund University, 221 00 Lund, Sweden.
    Lawoko, Martin
    Wallenberg Wood Science Center (WWSC), KTH, Royal Institute of Technology, 100 44 Stockholm, Sweden.
    Pierrou, Clara
    RenFuel Materials AB, Rapsgatan 25, SE-754 50 Uppsala, Sweden.
    Samec, Joseph S. M.
    Ren Fuel K2B AB, Rapsgatan 25, SE-754 50 Uppsala, Sweden; RenFuel Materials AB, Rapsgatan 25, SE-754 50 Uppsala, Sweden; Department of Organic Chemistry, Stockholm University, Svante Arhenius väg 16 C, 10691 Stockholm, Sweden; Department of Chemistry, Faculty of Science, Chulalongkorn University, Pathumwan, 10330 Bangkok, Thailand.
    Subbotina, Elena
    Center for Green Chemistry and Green Engineering, Yale University, 370 Prospect St, New Haven, CT 06511, USA.
    Wallmo, Henrik
    Valmet AB, Regnbågsgatan 6, 41755 Göteborg, Sweden.
    Wimby, Martin
    Valmet AB, Regnbågsgatan 6, 41755, Göteborg, Sweden.
    Kraft Lignin: A Valuable, Sustainable Resource, Opportunities and Challenges2023Ingår i: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 16, nr 23, artikel-id e202300492Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Kraft lignin, a by-product from the production of pulp, is currently incinerated in the recovery boiler during the chemical recovery cycle, generating valuable bioenergy and recycling inorganic chemicals to the pulping process operation. Removing lignin from the black liquor or its gasification lowers the recovery boiler load enabling increased pulp production. During the past ten years, lignin separation technologies have emerged and the interest of the research community to valorize this underutilized resource has been invigorated. The aim of this Review is to give (1) a dedicated overview of the kraft process with a focus on the lignin, (2) an overview of applications that are being developed, and (3) a techno-economic and life cycle asseeements of value chains from black liquor to different products. Overall, it is anticipated that this effort will inspire further work for developing and using kraft lignin as a commodity raw material for new applications undeniably promoting pivotal global sustainability concerns.

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  • 39.
    Arkhipov, Victor P.
    et al.
    Department of Physics, Kazan National Research Technological University, Kazan 420015, Russian Federation.
    Arkhipov, Ruslan
    Institute of Physics, Kazan Federal University, Kazan 420008, Russian Federation.
    Filippov, Andrei
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rhamnolipid Biosurfactant: Use for the Removal of Phenol from Aqueous Solutions by Micellar Solubilization2023Ingår i: ACS Omega, E-ISSN 2470-1343, Vol. 8, nr 33, s. 30646-30654Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Selective measurements of the self-diffusion coefficients of molecules of the biological surfactant rhamnolipid (RL) in individual aqueous solutions and in solutions with phenol as a solubilizate were carried out by nuclear magnetic resonance (NMR) diffusometry. Based on the obtained results, the solubilization characteristics of RLs were calculated. They are the fraction of solubilized phenol molecules, the phenol micelle-water distribution coefficient, the molar solubilization coefficient, the hydrodynamic radii of RL monomers and micelles, the aggregation numbers of micelles, and the solubilization capacity of micelles. Fraction of the solubilized phenol molecules increases and approaches 80-90% with increasing RL concentration. The solubilization capacity of the micelles increases from several units to 102 with an increase in both the concentration of RLs and the concentration of phenol in solution.

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  • 40.
    Arkhipov, Victor P.
    et al.
    Department of Physics, Kazan National Research Technological University, Kazan, Russian Federation.
    Arkhipov, Ruslan V.
    Institute of Physics, Kazan Federal University, Kazan, Russian Federation.
    Filippov, Andrei
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    The efficiency of micellar solubilization of naphthalene from aqueous solutions using rhamnolipid as a biological surfactant according to NMR diffusometry2024Ingår i: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458XArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.The micellar solubilization of naphthalene from its saturated aqueous solutions using the biosurfactant rhamnolipid was studied. Using the NMR diffusion method, selective measurements of the self-diffusion coefficients of molecules of all components of the solution—naphthalene, rhamnolipid, and water—were carried out at various rhamnolipid concentrations from 0.06 to 100 g/L. Based on the results of diffusometry, the distribution of naphthalene molecules between the states free in solution and states bound by micelles was found. With an increase in the concentration of rhamnolipids, the proportion of bound naphthalene molecules increases from 50% at CRL = 2 g/L to 100% at CRL ≥ 50 g/L. The micelle-water partition coefficient Km and the molar solubilization ratio MSR were calculated.

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  • 41.
    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 point2014Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, nr 20, s. 5480-5487Artikel i tidskrift (Refereegranskat)
    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

  • 42.
    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 systems2013Ingår i: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 51, nr 7, s. 424-430Artikel i tidskrift (Refereegranskat)
    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

  • 43.
    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 steel2014Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 251, s. 162-169Artikel i tidskrift (Refereegranskat)
    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).

  • 44.
    Axelsson, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Stabilisering av Aluminiumreducerad AOD-slagg.2019Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

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  • 45.
    Bajracharya, Suman
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bian, Bin
    Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, USA; Water Desalination and Reuse Center, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
    Jimenez-Sandoval, Rodrigo
    Water Desalination and Reuse Center, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia; Environmental Science and Engineering Program, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Katuri, Krishna P.
    Water Desalination and Reuse Center, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
    Saikaly, Pascal E.
    Water Desalination and Reuse Center, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia; Environmental Science and Engineering Program, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
    Nature inspired catalysts: A review on electroactive microorganism-based catalysts for electrochemical applications2024Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 488, artikel-id 144215Artikel, forskningsöversikt (Refereegranskat)
  • 46.
    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 separation2018Ingår i: Chemical papers, ISSN 2585-7290, Vol. 72, nr 5, s. 1139-1149Artikel i tidskrift (Refereegranskat)
    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.

  • 47.
    Bazar, July Ann
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hrůzová, Kateřina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sand, Anders
    Boliden Mineral AB, SE-936 81 Boliden, Sweden.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Organosolv Lignin Particles as a Partial Replacement of Xanthate Collector in a Copper Sulfide Ore Flotation: Scale-up StudyManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The transition to a sustainable, green economy indeed requires more access to strategic/critical metals for renewable energy technologies while simultaneously reducing reliance on fossil fuels and their byproducts. In mineral processing, various research for an environment-friendly flotation reagents have been ongoing for many years. In this paper, the potential of organosolv lignin particles (OLP) as a biobased reagent that can improve the grade and recovery of Cu was demonstrated using real sulfide ore. The main advantage of this process is that it requires low dosage of OLP in the tested condition and set-up. The initial laboratory batch flotation tests showed that potassium amyl xanthate (PAX) can be partially replaced with OLP by 50% and in the absence of depressant, lime. These results were further verified in semi-pilot flotation tests that showed an increase in recovery by 8% in the rougher stage and comparable grade in the final cleaner stage when using the OLP-PAX mixture with respect to PAX at full dosage. In general, this paper presents the progress towards validating the viability of OLP as a biobased flotation reagent suitable for industrial-scale applications.

  • 48.
    Bazar, July Ann
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hrůzová, Kateřina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sand, Anders
    Boliden Mineral AB, SE-936 81 Boliden, Sweden.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Organosolv Lignin Particles as a Partial Replacement of Xanthate Collector in a Copper Sulfide Ore Flotation: Scale-up StudyManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The transition to a sustainable, green economy indeed requires more access to strategic/critical metals for renewable energy technologies while simultaneously reducing reliance on fossil fuels and their byproducts. In mineral processing, various research for an environment-friendly flotation reagents have been ongoing for many years. In this paper, the potential of organosolv lignin particles (OLP) as a biobased reagent that can improve the grade and recovery of Cu was demonstrated using real sulfide ore. The main advantage of this process is that it requires low dosage of OLP in the tested condition and set-up. The initial laboratory batch flotation tests showed that potassium amyl xanthate (PAX) can be partially replaced with OLP by 50% and in the absence of depressant, lime. These results were further verified in semi-pilot flotation tests that showed an increase in recovery by 8% in the rougher stage and comparable grade in the final cleaner stage when using the OLP-PAX mixture with respect to PAX at full dosage. In general, this paper presents the progress towards validating the viability of OLP as a biobased flotation reagent suitable for industrial-scale applications.

  • 49.
    Bertilsson, Olle
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Study of leaching behavior of tin in Zinc-clinker and Mixed Oxide2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Due to the increasing usage of Sn in different electronics, such as solders and in touchscreens, together with Boliden Rönnskärs increased intake of electronic waste as a secondaryraw material, a Zn-containing product called Zn-clinker has increasing amounts of Sn. TheZn-clinker is shipped to Boliden Zn-smelter in Odda, where the Zn-clinker is mixed in withcalcine (roasted concentrate) and leached in several steps. Since Zn-clinker is a product froma halogen removal in a clinker-furnace, the feed material (Mixed Oxide), for this furnace, wasalso investigated since there are plans to replace clinkering with soda-washing in the future.Most of the Sn ends up in the leaching residue which then is deposited in the mountaincaverns close by the Boliden Odda smelter. Boliden is studying the possibility to recoverPb/Ag and Sn content from the leaching residue and create a valuable by-product. Bystudying how the leaching of Sn behaves, together with a characterization of the materials, thefollowing question should be answered: “During which sulphuric acid leaching conditions, ofZn-clinker and Mixed Oxide, is the leaching of Sn minimized?”

    The leaching results for Zn-clinker showed that 8-10% Sn will leach out, despite changingtemperature, redox potential, time and pH. A characterization of the material with SEM-EDSand XRD-analysis was also conducted to see if Sn could be identified in any phases in thematerials. The studies provided enough evidence that Zn2SnO4 could be concluded to be themain phase in the leaching residue for Zn-clinker, a form that would not leach underconditions presented in this project. However, 8-10% of the Sn will come together with Feand when Fe leach out, so does Sn.

    The leaching results for Mixed Oxide pointed towards that different phases from them foundin Zn-clinker was present. Sn losses varied between 10-20% but raised to 47% whentemperature was changed to 80 °C during leaching. The SEM-EDS analysis showed that theidentified Sn-phases contained more Sn than in Zn-clinker and together with the leachingresults, a conclusion that Sn would mainly be found as SnO2 or SnO in the Mixed Oxide, butthere is still uncertainty about the distributions of these forms.

    Unfortunately half of the As leached out during the soda-washing for Mixed Oxide, creating aleachate with Cl, F and As that need to be taken care of. This could be challenging andpresenting a costly side-project for the route different from the Zn-clinker route used today.Another observation was that PbCO3 formed during the soda-washing, a phase that willconsume more sulphuric acid during leaching.

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  • 50.
    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, sammanläggning (Övrigt vetenskapligt)
    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.

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