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  • 151.
    Astorsdotter, Jennifer
    KTH, School of Chemical Science and Engineering (CHE).
    Dewatering Cellulose Nanofibril Suspensions through Centrifugation2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cellulose nanofibrils (CNF) is a renewable material with unique strength properties. A difficulty in CNF production is that CNF suspensions contain large amounts of water. If CNF suspension volume can be decreased by dewatering facilitated by centrifugation, then transportation costs and storage costs can be reduced. The aim of this thesis is to investigate the impact various parameters have on CNF centrifugation dewatering and identify optimal conditions for maximal water removal.

    A laboratory study was conducted using four materials; 2.0 w% enzymatically treated CNF (CNF1), 1.9 w% carboxymethylated CNF (CNF2) and two commercial samples (1.9 w% CNFA and 1.8 w% CNFB). The main method was analytical centrifugation up to 2330 g. Parameters tested were initial concentration before centrifugation, temperature, NaCl addition, pH, and applied solid compressive pressure (g-force and surface weight). In addition to centrifugation experiments the four materials were characterized with laser diffraction, UV-vis absorption, Dynamic light scattering, and dry weight measurements.

    Analysis of the experimental data collected show that increase in initial concentration give a higher final concentration, but less water is removed. Furthermore, temperature changes have no effect on separation of CNF and water. At an applied solid compressive pressure of 3 kPa and initial concentration at 1.5 w% the concentrations 5.5 w%, 1.5 w%, 4.0 w%, and 4.3 w% can be reach for CNF1, CNF2, CNFA, and CNFB respectively. After extrapolation of polynomial functions fitted to experimental data an applied solid compressive pressure of 22 kPa and initial concentration at 1:5 w%, the concentrations 9.1 w%, 1.5 w%, 6.9 w%, and 7.9 w% are predicted for CNF1, CNF2, CNFA, and CNFB respectively. The thickening of CNF suspensions achieved and predicted in this thesis implies possibilities for large amounts of water removal, e.g. the water content in a CNF1 suspension is reduced from 65.7 litres/kg CNF to 10.0 litres/kg CNF at the solid compressive pressure 22 kPa. The concentrations at 22 kPa are determined by extrapolation from experimental data <3 kPa solid compressive pressure. The carboxymethylated CNF2 can not be dewatered unless it is diluted or if salt or pH is adjusted. This is directly correlated to the electrostatic forces in the suspension and the Debye length. Addition of salt or lowered pH also eliminate any concentration gradients in diluted and centrifuged CNF2 suspensions.

  • 152.
    Atapour, Masoud
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Wei, Zheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Chaudhary, Himanshu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Lendel, Christofer
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Odnevall Wallinder, Inger
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Hedberg, Yolanda
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Metal release from stainless steel 316L in whey protein - And simulated milk solutions under static and stirring conditions2019In: Food Control, ISSN 0956-7135, E-ISSN 1873-7129, Vol. 101, p. 163-172Article in journal (Refereed)
    Abstract [en]

    Stainless steel is an important transport and processing contact material for bovine milk and dairy products. Release (migration) of metals, ions, complexes or wear debris/particles, and metal-induced protein aggregation in such environments are hence important to consider both from a corrosion and food safety perspective. This study aims on investigating the release of iron (Fe), chromium (Cr), and nickel (Ni) from AISI 316L stainless steel in contact with whey protein solutions relevant for protein drinks, and on how the whey proteins are influenced by stirring with a magnetic stir bar and metal release. Mechanistic insight is gained by parallel investigations of metal release from two reference non-protein containing solutions, a metal-complexing (citrate-containing) simulated milk solution (SMS) and a low complexing phosphate buffered saline solution (PBS). All immersion exposures were conducted at pH 6.8 for 0.5, 4, 24 and 48 hat room temperature at static and stirring conditions. All solutions and samples were investigated using different chemical, spectroscopic, microscopic, and electrochemical methods. Significantly higher amounts of Fe, Cr, and Ni were released into the whey protein solution (80 g/L) as compared to SMS and PBS. Strong enrichment of Cr in the surface oxide and reduction of the surface oxide thickness were associated with a higher amount of Ni release in the metal-complexing solutions (SMS and whey protein) compared with PBS. Stirring conditions resulted in higher amounts of metal release, enrichment of Cr in the surface oxide, and clear signs of wear of the 316L surface in all solutions compared to static conditions. The wear mechanism in the whey protein solution was different as compared to corresponding processes in SMS and PBS, involving an etching-like process and larger-sized wear debris. Electrochemical measurements at static conditions confirmed observed differences between the solutions, with the lowest corrosion resistance observed for coupons exposed in the whey protein solution, followed by SMS and PBS. Released metals in solution from the 316L coupons in contact with the whey protein solution resulted in enhanced rates of protein aggregation and precipitation of protein aggregates from solution. Further studies should be made to investigate other relevant test conditions and assess toxicological risks.

  • 153.
    Atari Jabarzadeh, Sevil
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Prevention of Biofilm Formation on Silicone Rubber Materials for Outdoor High Voltage Insulators2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Microbial colonization on the surface of silicone rubber high voltage outdoor insulators often results in the formation of highly hydrated biofilm that influence the surface properties, such as surface hydrophobicity. The loss of hydrophobicity might lead to dry band formation, and, in the worst cases, flashover and failure of the insulator.

    In this work, the biocidal effects of various antimicrobial compounds in silicone rubber materials were determined. These materials were evaluated according to an ISO standard for the antimicrobial activity against the growth of aggressive fungal strains, and microorganisms that have been found colonizing the surfaces of outdoor insulators in several areas in the world. Several compounds suppressed microbial growth on the surfaces of the materials without compromising the material properties of the silicone rubber. A commercial biocide and thymol were very effective against fungal growth, and sodium benzoate could suppress the fungal growth to some extent. Thymol could also inhibit algal growth. However, methods for preservation of the antimicrobial agents in the bulk of the material need to be further developed to prevent the loss of the compounds during manufacturing. Biofilm formation affected the surface hydrophobicity and complete removal of the biofilm was not achieved through cleaning. Surface analysis confirmed that traces of microorganisms were still present after cleaning.

    Further, surface modification of the silicone rubber was carried out to study how the texture and roughness of the surface affect biofilm formation. Silicone rubber surfaces with regular geometrical patterns were evaluated to determine the influence of the surface texture on the extent of microbial growth in comparison with plane silicone rubber surfaces. Silicone rubber nanocomposite surfaces, prepared using a spray-deposition method that applied hydrophilic and hydrophobic nanoparticles to obtain hierarchical structures, were studied to determine the effects of the surface roughness and improved hydrophobicity on the microbial attachment. Microenvironment chambers were used for the determination of microbial growth on different modified surfaces under conditions that mimic those of the insulators in their outdoor environments. Different parts of the insulators were represented by placing the samples vertically and inclined. The microbial growth on the surfaces of the textured samples was evenly distributed throughout the surfaces because of the uniform distribution of the water between the gaps of the regular structures on the surfaces. Microbial growth was not observed on the inclined and vertical nanocomposite surfaces due to the higher surface roughness and improved surface hydrophobicity, whereas non-coated samples were colonized by microorganisms.

  • 154.
    Atarijabarzadeh, Sevil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Biofilm formation on silicone materials containing various antimicrobial agents2010Conference paper (Refereed)
    Abstract [en]

    The colonisation of microorganisms and subsequent biofilm formation on the surface of polymeric high voltage insulators affect the surface properties and can lead to failure of the insulators.  In this study, silicone materials were prepared with different antimicrobial agents. The materials were analysed for the changes in the physical, chemical, surface and mechanical properties before and after biological growth test.

     

    Microorganisms used for the biological tests were fungi defined in the international standard test ISO 846 for electrical applications (Aspergillus niger van Tieghem, Penicillium funiculosum Thom, Paecilomyces variotii Bainier, Chaetomium globosum Kunze: Fries, Aspergillus terreus Thom, Aureobasidium pullulans (de Bary) Arnaud & Penicillium ochrochloron Biourge) and algae isolated from insulators in Sri Lanka and Tanzania (Chlorella vulgaris var. Autotrophica + various bacterial strains). Fungi growth test was performed by inoculation of the fungi on the surface of the materials and incubation in an oven at 28°C and 98% humidity for a specific period. Algae growth test was performed by inoculation on the material surface and subsequent incubation in room temperature under a constant fluorescent lamps for a specific period.

     

    The results indicated that some of the samples could prevent the biofilm formation on the surface of the materials while the microbial growth was unaffected on the pure silicone rubber.

  • 155.
    Atarijabarzadeh, Sevil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Biofilm formation on silicone nanocomposites containing different antimicrobial agents2010Conference paper (Refereed)
    Abstract [en]

    In this study three types of clay/silicon nanocomposites were prepared. Clay was modified with two different antimicrobial agents (p-aminobenzoic acid and partially aminated poly(vinylbenzyl chloride) and used for preparation of the nanocomposites, which aimed to show antimicrobial properties and also easy dispersion of the clay into the polymeric matrix. Reference nanocomposites were made through the modification of the clay with a siloxane surfactant to make an easy dispersion of the clay into the silicone rubber. Nanocomposites were studied for resistancy against biological attack according to the international standard tests. Growth test results indicated that some of the nanocomposites can inhibit biological growth more than pristine nanocomposites. Modified clay was studied with x-ray diffraction technique. Materials were also studied with scanning electron microscopy before and after biological growth to analyse the biofilm formation on the surface.

  • 156.
    Atasoy, Merve
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Eyice, Ozge
    Queen Mary Univ London, Sch Biol & Chem Sci, London E1 4NS, England..
    Schnurer, Anna
    Swedish Univ Agr Sci, Dept Mol Sci, Bioctr, SE-75007 Uppsala, Sweden..
    Cetecioglu, Zeynep
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Volatile fatty acids production via mixed culture fermentation: Revealing the link between pH, inoculum type and bacterial composition2019In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 292, article id 121889Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to investigate the effects of operational parameters, inoculum type and bacterial community on mixed culture fermentation to produce one dominant acid type in the mixture of volatile fatty acids (VFA). The study was performed using three different inocula (large&small granular and slurry) with glucose under various initial pH. The VFA production efficiency reached to 0,97 (gCOD/gSCOD) by granular sludge. VFA composition was changed by initial pH: in neutral conditions, acetic acid; in acidic conditions, acetic and butyric acids, in alkali conditions butyric acid were dominated, respectively. The VFA production was positively affected by the high relative abundance of Firmicutes. On the contrary, a negative correlation was seen between VFA production and the relative abundance of Chloroflexi. The results revealed the physical sludge structure of inoculum was the key factor for production efficiency, whereas, pH was the most important parameter to affect VFA composition.

  • 157. Athavale, Rohini
    et al.
    Dinkel, Christian
    Wehrli, Bernhard
    Bakker, Eric
    Crespo, Gaston A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Brand, Andreas
    Robust Solid-Contact Ion Selective Electrodes for High-Resolution In Situ Measurements in Fresh Water Systems2017In: ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS, ISSN 2328-8930, Vol. 4, no 7, p. 286-291Article in journal (Refereed)
    Abstract [en]

    Biogeochemical processes are often confined to very narrow zones in aquatic systems. Therefore, highly resolved in situ measurements are required to study these processes. Potentiometric solid -contact ion selective electrodes (SC-ISEs) are promising tools for such measurements. SCISEs show good performance in analyses under controlled experimental conditions. Very few sensor designs, however, can sustain the challenges of natural water matrices and external environmental conditions during in situ applications. We fabricated ammonium and pH selective SC-ISEs with functionalized multiwalled carbon nanotubes (f-MWCNT) as a solid contact. Their functionality was tested in the laboratory and applied in situ for vertical profiling in a eutrophic lake. Sensors were insensitive to strong redox changes, high sulfide concentrations, and bright daylight conditions during the application in the lake. In addition, sensors are easily fabricated and exhibit short response times (<10 s). The proposed design of SC-ISEs based on f-MWCNTs is quite suitable for high-resolution in situ profiling of ionic species in fresh water lakes.

  • 158. Atlas, Salima
    et al.
    Raihane, Mustapha
    Hult, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Lahcini, Mohammed
    Ameduri, Bruno
    Radical copolymerization of acrylonitrile with 2,2,2-trifluoroethyl acrylate for dielectric materials: Structure and characterization2013In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 51, no 18, p. 3856-3866Article, review/survey (Refereed)
    Abstract [en]

    Radical copolymerization based on acrylonitrile (AN) and 2,2,2-Trifluoroethyl acrylate (ATRIF) initited by AIBN was investigated in acetonitrile solution. The resulting poly(AN-co-ATRIF) copolymers were characterized by 1 H, 13 C, and 19 F NMR and IR spectroscopy, and size exclusion chromatography (SEC). Their compositions were assessed by 1 H NMR. The kinetics of radical copolymerization of AN with ATRIF was investigated from sereval experiments achieved at 70 degrees C from initial [AN](0)/[ATRIF](0) molar ratios ranging between 20/80 and 80/20 and was enabled to determine the reactivity ratios of both comonomers. From the monomer-polymer copolymerization curve, the Fineman-Ross and Kelen-Tudos laws enabled to assess the reactivity ratios (r(AN) = r(1) = 1.25 +/- 0.04 and r(ATRIF) = r(2) = 0.93 +/- 0.05 at 70 degrees C) while the revised patterns scheme led to r(12) = r(AN) = 1.03, and r(21) = r(ATRIF) = 0.78 at 70 degrees C. In all cases, rAN x rATRIF product was close to unity, which indicates that poly(AN-co-ATRIF) copolymers exhibit a random structure. This was also confirmed by the Igarashi's and Pyun's laws which revealed the presence of AN-ATRIF, AN-AN, and ATRIF-ATRIF dyads. The Q and e values for ATRIF were also assessed (Q(2) = 0.62 and e(2) = 0.93). The glass transition temperature values, Tg, of these copolymers increased from 17 to 61 degrees C as the molar percentage of ATRIF decreased from 77 to 16% in the copolymer. Thermogravimetry analysis of poly(AN-co-ATRIF) copolymers showed a good thermal stability compared to that of poly(ATRIF) homopolymer due to incorporation of AN comonomer.

  • 159.
    Austrell, Per-Erik
    et al.
    Division of Structural Mechanics, Lund Institute of Technology.
    Kari, LeifKTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Constitutive Models for Rubber IV: proceedings of the 4th European Conference for Constitutive Models for Rubber, ECCMR 2005, Stockholm, Sweden, 27-29 June 20052005Collection (editor) (Refereed)
    Abstract [en]

    The unique properties of elastomeric materials are taken advantage of in many engineering applications. Elastomeric units are used as couplings or mountings between stiff parts. Examples are shock absorbers, vibration insulators, flexible joints, seals and suspensions etc.

     

    However, the complicated nature of the material behavior makes it difficult to accurately predict the performance of these units, using for example finite element modelling. It is therefore necessary that the constitutive model accurately capture relevant aspects of the mechanical behavior.

     

    The latest development concerning constitutive modelling of rubber is collected in these proceedings. It is the fourth ECCMR-European Conference on Constitutive Modelling in a series on this subject.

     

    Topics included in this volume are, Hyperelastic models, Strength, fracture & fatigue, Dynamic properties & the Fletcher-Gent effect, Micro-mechanical & statistical approaches, Stress softening, Viscoelasticity, Filler reinforcement, and Tyres, fiber & cord reinforced rubber.

  • 160.
    Auvinen, Sonja
    et al.
    VTT.
    Tingelöf, Thomas
    VTT.
    Ihonen, Jari
    VTT.
    Siivinen, Jarmo
    VTT.
    Johanson, Max
    Åbo Akademi.
    Cost effective in-situ characterization of coatings for PEFCbipolar plates demonstrated with PVD deposited CrN2011In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, no 5, p. B550-B556Article in journal (Refereed)
    Abstract [en]

    The corrosion and contact resistances of coated and uncoated stainless steel grades were studied. The coatings studied were PVD CrN and arc discharge deposited Au. The samples were aged in long steady-state experiments using a multisinglecell device. MEAs and exhaust water were analyzed for accumulated iron after measurements. Iron accumulation was measured from MEAs, exhaust water and gas outlet pipes from the cells. The interfacial contact resistances were measured before and after the fuel cell experiments. Low contact resistance was achieved with all coated samples. The main accumulation site of dissolved iron was found to be the MEA and GDLs. A large variation in the corrosion results due to differences in the coating quality was observed. Some coatings with low interfacial contact resistance were found to be prone to corrosion. The CrN coating was also tested in a stack, and it performed well. It was concluded that the multisinglecell is a useful tool for screening different coatings reliably and cost-effectively.

  • 161.
    Avalos, Arturo Salazar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Superiorly Plasticized PVC/PBSA Blends through Crotonic and Acrylic Acid Functionalization of PVC2017In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 9, no 3, article id 84Article in journal (Refereed)
    Abstract [en]

    Superior plasticization efficiency was achieved by a grafting from functionalization of the PVC backbone. This was deduced to a synergistic effect of internal plasticization and improved intermolecular interactions between PVC and an oligomeric poly(butylene succinate-co-adipate) ( PBSA) plasticizer. A mild grafting process for functionalization of the PVC chain by crotonic acid ( CA) or acrylic acid ( AA) was used. The formation of PVC-g-CA and PVC-g-AA was confirmed by FTIR and H-1 NMR. Grafting with the seemingly similar monomers, CA and AA, resulted in different macromolecular structures. AA is easily homopolymerized and long hydrophilic poly( acrylic acid) grafts are formed resulting in branched materials. Crotonic acid does not easily homopolymerize; instead, single crotonic acid units are located along the PVC chain, leading to basically linear PVC chains with pendant crotonic acid groups. The elongation of PVC-g-CA and PVC-g-AA in comparison to pure PVC were greatly increased from 6% to 128% and 167%, respectively, by the grafting reactions. Blending 20% ( w/w) PBSA with PVC, PVC-AA or PVC-CA further increased the elongation at break to 150%, 240% and 320%, respectively, clearly showing a significant synergistic effect in the blends with functionalized PVC. This is a clearly promising milestone towards environmentally friendly flexible PVC materials.

  • 162. Axegard, Peter
    et al.
    Bergnor, Elisabeth
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ekholm, Ulrika
    Bleaching of softwood kraft pulps with H2O2, O3, and ClO21996In: TAPPI Journal, ISSN 0734-1415, Vol. 79, no 1, p. 113-119Article in journal (Refereed)
    Abstract [en]

    Ozone or chlorine dioxide bleaching prior to hydrogen peroxide bleaching greatly improves the performance of the hydrogen peroxide stage. The efficiency is further improved by a chelating treatment immediately after the ozone or chlorine dioxide stage. With an optimal metal ion profile, laboratory bleached (OAZQP) softwood kraft pulps can reach brightness levels above 90% ISO, with 5-10% lower pulp strength properties and bleaching costs comparable to ECF bleaching. It also is possible to obtain full brightness with only hydrogen peroxide provided the metal ion profile is optimal, e.g., by using multiple QP treatments. The chemical consumptions, expressed as oxidation equivalents per decreased kappa number are the same as for sequences including ozone or chlorine dioxide. Ozone and chlorine dioxide are comparable as far as delignification and brightness efficiency go.

  • 163. Axegård, Peter
    et al.
    Bergnor, Elisabeth
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ekholm, Ulrika
    The role of metal ions in TCF-bleaching of softwood kraft pulps.: Vol.31994In: Proceedings Tappi Pulping conf., 1994, p. 1161-1167Conference paper (Refereed)
  • 164. Axelsson, Patrik
    et al.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Teder, Ants
    Bleachability of Alkaline Birch Pulps.2000In: Proceedings 6th European Workshop on Lignocellulosics and Pulp., 2000Conference paper (Refereed)
  • 165. Axelsson, Patrik
    et al.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Teder, Ants
    Influence of alkali profile in the kraft cook on the bleachability of birch.2001In: : Book:Vol I, 2001, p. 41-44Conference paper (Refereed)
  • 166.
    Azhar, Shoaib
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Lindström, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Extraction of hemicelluloses from fiberized spruce wood2015In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 117, p. 19-24Article in journal (Refereed)
    Abstract [en]

    A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90◦C/120min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses. 

  • 167.
    Aziz, Baroz
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Nordström, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Fischer, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    (2/1) p-Aminobenzoic acid-Acetone SolvateManuscript (Other academic)
  • 168.
    Azwar, Edwin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Agro-Waste Derived Additives for Polylactide and Tapioca Starch2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Development of materials from renewable resources is one of the big challenges facing our world. In this thesis agro-industrial waste derivatives were developed and evaluated as additives for two common renewable polymer matrices, polylactide (PLA) and starch. Two waste products, wood flour (WF) and rice bran (RB) were evaluated in different forms. Milled WF and RB were either used directly to prepare PLA and starch biocomposites or they were liquefied by acid catalyzed hydrolysis to low molecular weight products. The complex polyol mixtures from liquefaction were tested directly as PLA and starch additives or utilized as monomers for synthesis of esters. The synthesized esters were evaluated as plasticizers for PLA and starch. The effect of different additives on tensile properties, miscibility, surface chemistry and morphology were evaluated by Instron, DSC, FTIR, FTIR imaging and SEM. In the case of polylactide films the influence of additives on hydrolytic degradation rate and process was evaluated by following the weight loss, surface changes, compositional changes and/or water-soluble migrants and degradation products by FTIR, SEM, pyrolysis-GC-MS and ESI-MS. The most marked difference in mechanical properties was observed in the case of PLA modified with liquefied wood flour derived ester plasticizer (PWF). Addition of 10 and 30 weight-% plasticizer increased the strain at break from a few percent for pure PLA to over 100 and 300%, respectively. The liquefied rice bran based ester, however, did not form miscible blends with PLA and it did not function as plasticizer. In some cases the impact of additives on the following degradation process was significant. Depending on the used additive, they could either concentrate in the matrix during the hydrolysis of polylactide or they were rapidly released to the surrounding water. In some cases clear hydrolysis catalyzing effects were observed. Liquefied rice bran in combination with mineral fillers and/or traditional plasticizers seemed to have the best potential as starch plasticizer.

  • 169.
    Babiker, Dina
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Ahlstrand, Matilda
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Experimental Study of Mineral Carbonation of Wollastonite for Increased CO2 Uptake2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The cement and concrete industry stand for approximately 8% of the global CO2 emissions. The demand of concrete and cement is expected to increase rapidly with the growing world population and increased urbanization. This makes it of the utmost importance for the industry to try to mitigate its emissions. One way to reduce the industry’s environmental impact is by mineral carbonation curing through which CO2 can be sequestered in the concrete. This investigation studied the CO2 uptake of wollastonite (CaSiO3) which can be used for mineral carbonation. The CO2 uptake of different brands of wollastonite powders for different temperatures, pressures and water to solid ratios were tested through carbonation, and the samples were then analyzed through XRD, SEM and particle size analysis. The results showed large differences in CO2 uptake between the brands of wollastonite powders. They also indicate that lower temperatures lead to higher CO2 uptake but also possibly slow down the reaction rate and that higher CO2 pressures seem to increase CO2 uptake though the effect is small.

    There was significant variation of the effects of the water to solid ratios on CO2 uptake between the tested brands. The morphology of the powders also seemed to be of little relevance as an amorphous and crystalline powder were the two best performing powders, similarly particle size is not indicated by the result to have a large effect on CO2 uptake, though further studies are required to fully determine the effect of the morphology and particle size.

  • 170.
    Backman, Anna
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Lange, Jakob
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Transport properties of uniaxially oriented aliphatic polyketone2004In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 42, no 6, p. 947-955Article in journal (Refereed)
    Abstract [en]

    The oxygen, carbon dioxide, and water-transport properties of a uniaxially oriented aliphatic polyketone were determined. The polyketone was drawn to 5-10 times its original length. The transport properties were related to changes in crystallinity estimated by differential scanning calorimetry and density measurements and by changes in the molecular and crystal orientation assessed by, respectively, infrared and X-ray spectroscopy. The film structures were characterized by confocal scanning laser microscopy and scanning electron microscopy. Stress-strain tests on the drawn specimens enabled the impacts of orientation on the transport and mechanical properties to be compared. A draw-induced increase in crystallinity and molecular orientation yielded permeabilities at a draw ratio of 10 that were 30-40% of the original value, and the percentage decrease was basically independent of the type of gas/vapor molecule. Also, the diffusivities of oxygen and carbon dioxide decreased by an order of magnitude. The fact that the amorphous permeability was peaking at a draw ratio of about 5 was a consequence of a peak in amorphous solubility, which was very high for oxygen and absent for water. It was suggested that the peak in solubility was mainly caused by the destruction of the polymer hydrogen-bond network during drawing and crystal reorientation. The impact of structural reorganization within the polymer and presence of surface valleys seemed to have less impact on the mechanical properties than on the transport properties. This suggested that transport data are more sensitive than mechanical data in probing material defects and changes in molecular packing and morphology.

  • 171.
    Backström, Eva
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Trash to Treasure: Microwave-Assisted Conversion of Polyethylene to Functional Chemicals2017In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 56, no 50, p. 14814-14821Article in journal (Refereed)
    Abstract [en]

    An effective microwave-assisted process for recycling low-density polyethylene (LDPE) waste into value-added chemicals was developed. To achieve fast and effective oxidative degradation aimed at production of dicarboxylic acids, nitric acid was utilized as an oxidizing agent. Different conditions were evaluated, where recycling time and concentration of oxidizing agent were varied and the end products were characterized by FTIR, NMR, and HPLC. After just 1 h of microwave irradiation at 180 degrees C in relatively dilute nitric acid solution (0.1 g/mL), LDPE powder was totally degraded. This transformation led to few well-defined water-soluble products, mainly succinic, glutaric, and adipic acids, as well as smaller amounts of longer dicarboxylic acids, acetic acid, and propionic acid. The length of the obtained dicarboxylic acids could to some extent be tuned by adjusting the reaction time, temperature, and amount of oxidizing agent. Finally, the developed process was verified by recycling LDPE freezer bags as model LDPE waste. The freezer bags were converted mainly into dicarboxylic acids with a yield of 71%, and the carbon efficiency of the process was 37%. The developed method can, thus, contribute to a circular economy and offers new possibilities to increase the value of plastic waste.

  • 172.
    Badal Tejedor, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. RISE Research Institutes of Sweden, Sweden.
    Nordgren, Niklas
    Schuleit, Michael
    Millqvist-Fureby, Anna
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    AFM Colloidal Probe Measurements Implicate Capillary Condensation in Punch-Particle Surface Interactions during Tableting2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 46, p. 13180-13188Article in journal (Refereed)
    Abstract [en]

    Adhesion of the powders to the punches is a common issue during tableting. This phenomenon is known as sticking and affects the quality of the manufactured tablets. Defective tablets increase the cost of the manufacturing process. Thus, the ability to predict the tableting performance of the formulation blend before the process is scaled-up is important. The adhesive propensity of the powder to the tableting tools is mostly governed by the surface surface adhesive interactions. Atomic force microscopy (AFM) colloidal probe is a surface characterization technique that allows the measurement of the adhesive interactions between two materials of interest. In this study, AFM steel colloidal probe measurements were performed on ibuprofen, MCC (microcrystalline cellulose), alpha-lactose monohydrate, and spray-dried lactose particles as an approach to modeling the punch particle surface interactions during tableting. The excipients (lactose and MCC) showed constant, small, attractive, and adhesive forces toward the steel surface after a repeated number of contacts. In comparison, ibuprofen displayed a much larger attractive and adhesive interaction increasing over time both in magnitude and in jump-in/jump-out separation distance. The type of interaction acting on the excipient steel interface can be related to a van der Waals force, which is relatively weak and short-ranged. By contrast, the ibuprofen steel interaction is described by a capillary force profile. Even though ibuprofen is not highly hydrophilic, the relatively smooth surfaces of the crystals allow "contact flooding" upon contact with the steel probe. Capillary forces increase because of the "harvesting" of moisture due to the fast condensation kinetics leaving a residual condensate that contributes to increase the interaction force after each consecutive contact. Local asperity contacts on the more hydrophilic surface of the excipients prevent the flooding of the contact zone, and there is no such adhesive effect under the same ambient conditions. The markedly different behavior detected by force measurements clearly shows the sticky and nonsticky propensity of the materials and allows a mechanistic description.

  • 173. Badia, J. D.
    et al.
    Kittikorn, Thorsak
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Santonja-Blasco, L.
    Martizez-Felipe, A.
    Ribes-Greus, A.
    Ek, Monica
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Water absorption and hydrothermal performance of PHBV/sisal biocomposites2014In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 108, p. 166-174Article in journal (Refereed)
    Abstract [en]

    The performance of biocomposites of poly(hydroxybutyrate-co-valerate) (PHBV) and sisal fibre subjected to hydrothermal tests at different temperatures above the glass transition of PHBV (T-H = 26, 36 and 46 degrees C) was evaluated in this study. The influences of both the fibre content and presence of coupling agent were focused. The water absorption capability and water diffusion rate were considered for a statistical factorial analysis. Afterwards, the physico-chemical properties of water-saturated biocomposites were assessed by Fourier-Transform Infrared Analysis, Size Exclusion Chromatography, Differential Scanning Calorimetry and Scanning Electron Microscopy. It was found that the water diffusion rate increased with both temperature and percentage of fibre, whereas the amount of absorbed water was only influenced by fibre content. The use of coupling agent was only relevant at the initial stages of the hydrothermal test, giving an increase in the diffusion rate. Although the chemical structure and thermal properties of water-saturated biocomposites remained practically intact, the physical performance was considerably affected, due to the swelling of fibres, which internally blew-up the PHBV matrix, provoking cracks and fibre detachment.

  • 174. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, A.
    Material valorisation of amorphous polylactide. Influence of thermo-mechanical degradation on the morphology, segmental dynamics, thermal and mechanical performance2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 4, p. 670-678Article in journal (Refereed)
    Abstract [en]

    This paper reports the effects of multiple mechanical recycling on the structure and properties of amorphous polylactide (PIA). The influence of the thermo-mechanical degradation induced by means of five successive injection cycles was initially addressed in terms of macroscopic mechanical properties and surface modification. A deeper inspection on the structure and morphology of PLA was associated to the thermal properties and viscoelastic behaviour. Although FT-IR analysis did not show significant changes in functional groups, a remarkable reduction in molar mass was found by viscometry. PIA remained amorphous throughout the reprocessing cycles, but the occurrence of a cold-crystallization during DSC and DMTA measurements, which enthalpy increased with each reprocessing step, suggested chain scission due to thermo-mechanical degradation. The effect of chain shortening on the glass-rubber relaxation studied by DMTA showed an increase in free volume affecting the segmental dynamics of PLA, particularly after the application of the second reprocessing step, in connection to the overall loss of performance showed by the remaining properties.

  • 175. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, A
    The role of crystalline, mobile amorphous and rigid amorphous fractions on the performance of recycled poly (ethylene terephthalate) (PET)2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 1, p. 98-107Article in journal (Refereed)
    Abstract [en]

    The action of thermo-mechanical degradation induced by mechanical recycling of poly(ethylene terephthalate) was simulated by successive injection moulding cycles. Degradation reactions provoked chain scissions and a reduction in molar mass mainly driven by the reduction of diethyleneglycol to ethylene glycol units in the flexible domain of the PET backbone, and the formation ofeOH terminated species with shorter chain length. The consequent microstructural changes were quantified taking into account a three-fraction model involving crystalline, mobile amorphous (MAF) and rigid amorphous fractions (RAF). A remarkable increase of RAF, to a detriment of MAF was observed, while the percentage of crystalline fraction remained nearly constant. A deeper analysis of the melting behaviour, the segmental dynamics around the glass-rubber relaxation, and the macroscopic mechanical performance, showed the role of each fraction leading to a loss of thermal, viscoelastic and mechanical features, particularly remarkable after the first processing cycle.

  • 176. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, Amparo
    Characterization of Induced Thermo-mechanical Degradation on Poly (ethylene terephthalate)2011Conference paper (Refereed)
  • 177. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, Amparo
    STUDY OF THERMO-MECHANICAL AND THERMO-OXIDATIVE DEGRADATION OF POLYLACTIDE BYMALDI-TOF MS. A STATISTICAL DESIGN OF EXPERIMENTS TO OPTIMIZE THE SAMPLE PREPARATIONPROCEDURES2011Conference paper (Refereed)
  • 178.
    Bagheri, Banafsheh
    KTH, School of Chemical Science and Engineering (CHE).
    En jämförelse av sjöarna Fysingen och Vallentunasjön2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 179.
    Bainetas Rosendahl, Andreas
    KTH, School of Chemical Science and Engineering (CHE).
    En undersökning av fluktuationer av BOD7 i industriavloppet hos Coca-Cola Enterprises anläggning i Sverige2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Stockholm Vatten introduced in januari 2014 a fee on biochemical oxygen demand (BOD) that is being releaed by industrial processes. Untreated BOD could have an oxygen depleting effect on recipients and thus affect aquatic life if the reciever is a lake or a stream.

    The goal with this research thesis is to investigate the fluctuating patterns of specifically BOD7 in the industrial sewage of Coca-Cola Enterprises Sweden (CCES). Additionally to find possible BOD7 sources and investigate where, how and why these fluctuating patterns occur. Another objective for this research thesis is to discuss the correlation of chemical oxygen demand (COD) and BOD.

    A large part of this research thesis consisted of analyzing data from the databases of CCES and Eurofins. Eurofins is an external company that analyzes samples taken from the industrial waste of CCES. During the research thesis samples were taken from the industrial waste and sent for analysis of BOD7 and CODcr.

    After rebuilding at CCES production plant the dates which were looked at were 2015-01-01 to 2016-05-31. The analysis consisted of looking at what dates sampling was done of BOD7 and CODcr and correlating these with events happening in the production facility during these dates. The temporary events that were looked at were if discarding or dumping of beverage happened, what products were manufactured and how many changeovers took place during the sampling dates.

    The results indicated that a high number of changeovers would generally give a high BOD7. Discarding and dumping of products would also give a high BOD7, which can be confirmed by the sampling of the industrial waste. The discarded beverage would also have the alternative of sending the it away to another company, SITA, that would use it to make biofuel. This however did not show any economic advantage regarding savings on the fee for BOD7 since CCES have to pay SITA for the transport of the discarded beverage.

    The analysis of the existing data from Eurofins confirmed a positive correlation of BOD7 and CODcr. CODcr measure the chemical oxidizable material which means that in addition to measuring the organic oxidizable material it also measures the inorganic oxidizable material. This results in that CODcr will almost always be larger than the BOD7.

  • 180.
    Baldassarre, Venezia
    KTH, School of Chemical Science and Engineering (CHE).
    Fischer-Tropsch Synthesis on ZrO2-promoted Co/Al2O3 Catalysts: Effect of Catalyst Support Preparation Methods2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Alumina is considered to be an effective catalyst support in the Fischer-Tropsch synthesis, owing to its favourable mechanical properties. However, if cobalt is deposited over alumina, the formation of active phase-support species decreases the catalyst reducibility and can be detrimental to the reaction performance. Recently, according to some reports, zirconia has attracted attention as a cobalt catalyst promoter for improving reducibility, activity and C5+ selectivity.

    This experimental work is aimed at studying the influence of zirconia promotion on cobalt-based catalysts. Two different support preparation methods were investigated: the pH-controlled precipitation of the zirconia promoter over a gamma alumina carrier from a one-phase and from a microemulsion solution. Two microemulsion systems were used: the water-in-oil and the oil-in-water techniques. The zirconia loading target over alumina was 20 wt% for all the promoted carriers. The cobalt active phase was deposited via the incipient wetness impregnation, reaching a concentration of 12 wt% over all the catalysts, including on a non-promoted one. Moreover, a further support was prepared using the oil-in-water microemulsion technique and impregnated with 15 wt% Co.

    X-ray diffraction, N2 adsorption and H2 chemisorption characterisations revealed comparable catalyst porosities and cobalt dispersions. Furthermore, TPR analyses showed that reducibility is not influenced by the addition of zirconia.

    The catalyst activation treatment was performed under pure hydrogen at 1 atm, 350 °C for 16 h. The syngas flow, passing through a fixed bed reactor, was first set to 250 NmL/min and then decreased until 30%, 40% and 50% CO conversion values were reached. The catalytic test results revealed an increase in activity and enhancement of C5+ selectivity for the catalyst prepared by pH-controlled precipitation of zirconia from the ordinary solution, relative to the non-promoted one. On the other hand, the “microemulsion” catalysts showed a significant decrease in turnover frequency compared to the Co/Al2O3 catalyst performance. Selectivity to C5+ and CH4 were respectively enhanced and reduced by promoting the catalyst with zirconia, for each conversion step. Olefin-to-paraffin content ratio in the fraction of C2, C3 and C4, along with the deactivation trend, were also analysed and discussed.

  • 181.
    Barre, Ahmed
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Varför har Fysingen en mycket hög ekologisk status, trots dess näringsrika omgivning?2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 182.
    Barrientos, Javier
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Deactivation of cobalt and nickel catalysts in Fischer-Tropsch synthesis and methanation2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

                A potential route for converting different carbon sources (coal, natural gas and biomass) into synthetic fuels is the transformation of these raw materials into synthesis gas (CO and H2), followed by a catalytic step which converts this gas into the desired fuels. The present thesis has focused on two catalytic steps: Fischer-Tropsch synthesis (FTS) and methanation. The Fischer-Tropsch synthesis serves to convert synthesis gas into liquid hydrocarbon-based fuels. Methanation serves instead to produce synthetic natural gas (SNG). Cobalt catalysts have been used in FTS while nickel catalysts have been used in methanation.

                The catalyst lifetime is a parameter of critical importance both in FTS and methanation. The aim of this thesis was to investigate the deactivation causes of the cobalt and nickel catalysts in their respective reactions.

                The resistance to carbonyl-induced sintering of nickel catalysts supported on different carriers (γ-Al2O3, SiO2, TiO2 and α-Al2O3) was studied. TiO2-supported nickel catalysts exhibited lower sintering rates than the other catalysts. The effect of the catalyst pellet size was also evaluated on γ-Al2O3-supported nickel catalysts. The use of large catalyst pellets gave considerably lower sintering rates. The resistance to carbon formation on the above-mentioned supported nickel catalysts was also evaluated. Once again, TiO2-supported nickel catalysts exhibited the lowest carbon formation rates. Finally, the effect of operating conditions on carbon formation and deactivation was studied using Ni/TiO2 catalysts. The use of higher H2/CO ratios and higher pressures reduced the carbon formation rate. Increasing the temperature from 280 °C to 340 °C favored carbon deposition. The addition of steam also reduced the carbon formation rate but accelerated catalyst deactivation.

                The decline in activity of cobalt catalysts with increasing sulfur concentration was also assessed by ex situ poisoning of a cobalt catalyst. A deactivation model was proposed to predict the decline in activity as function of the sulfur coverage and the sulfur-to-cobalt active site ratio. The results also indicate that sulfur decreases the selectivity to long-chain hydrocarbons and olefins.

  • 183.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    González, N.
    Lualdi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    The effect of catalyst pellet size on nickel carbonyl-induced particle sintering under low temperature CO methanation2016In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 514, p. 91-102Article in journal (Refereed)
    Abstract [en]

    Abstract The present work aims to evaluate the effect of catalyst pellet size on deactivation due to nickel carbonyl-induced particle sintering. For that purpose, a γ-Al2O3-supported nickel catalyst was prepared and tested under low temperature and high CO partial pressure. A total of four different pellet sizes were employed in the present study. It was found that the deactivation rate decreases with increasing pellet size. A very severe deactivation was observed when using small pellets. Large pellets exhibited instead a more stable performance. This difference in catalyst stability was explained by X-ray diffraction analyses which revealed that the growth of the nickel particles was very severe when using small pellets. An evaluation of heat and mass transfer phenomena in these four pellets was also conducted. It was found that, under the present low temperature reaction conditions, the temperature at the catalyst external surface can greatly differ from that in the bulk gas when using sufficiently large pellets. It was also shown that, for large pellets, the major part of the interior of the catalyst is exposed to negligible CO partial pressures and high temperatures, fact that can reduce the potential for nickel carbonyl formation.

  • 184.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Montes, V.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Further insights into the effect of sulfur on the activity and selectivity of cobalt-based Fischer–Tropsch catalysts2016In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 275, p. 119-126Article in journal (Refereed)
    Abstract [en]

     A sulfur poisoning study was performed by ex situ poisoning of a platinum-promoted cobalt/alumina catalyst with different sulfur amounts. The poisoned catalyst samples were tested at relevant Fischer–Tropsch reaction conditions and at the same CO conversion in order to evaluate the effect of sulfur on catalyst activity and product selectivity. It was found that the activity and the selectivity to long-chain hydrocarbons decrease with increasing sulfur content. Moreover, it was found that sulfur has no significant effect on the CO2 selectivity. It was also shown that sulfur significantly enhances olefin hydrogenation. Finally, a deactivation model relating the catalyst activity and the sulfur to cobalt active site ratio was proposed and used to describe the experimental results.

  • 185.
    Bastardo Zambrano, Luis Alejandro
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Chitosan-SDS association probed by Small-Angle Neutron ScatteringManuscript (preprint) (Other (popular science, discussion, etc.))
  • 186. Bebelis, S.
    et al.
    Bouzek, K.
    Cornell, Ann
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ferreira, M. G. S.
    Kelsall, G. H.
    Lapicque, F.
    Ponce de León, C.
    Rodrigo, M. A.
    Walsh, F. C.
    Highlights during the development of electrochemical engineering2013In: Chemical engineering research & design, ISSN 0263-8762, E-ISSN 1744-3563, Vol. 91, no 10, p. 1998-2020Article in journal (Refereed)
    Abstract [en]

    Over the last century, electrochemical engineering has contributed significantly to societal progress by enabling development of industrial processes for manufacturing chemicals, such as chlorine and the Nylon precursor adiponitrile, as well as a wide range of metals including aluminium and zinc. In 2011, ca. 17 M tonne Cu p.a. was electro-refined to 99.99%+ purity required by electrical and electronic engineering applications, such as for electrodepositing with exquisite resolution multi-layer inter-connections in microprocessors. Surface engineering is widely practised industrially e.g. to protect steels against corrosion e.g. by electroplating nickel or using more recent novel self-healing coatings. Complex shapes of hard alloys that are difficult to machine can be fabricated by selective dissolution in electrochemical machining processes. Electric fields can be used to drive desalination of brackish water for urban supplies and irrigation by electrodialysis with ion-permeable membranes; such fields can also be used in electrokinetic soil remediation processes. Rising concerns about the consequences of CO2 emissions has led to the rapidly increasing development and deployment of renewable energy systems, the intermittency of which can be mitigated by energy storage in e.g. redox flow batteries for stationary storage and novel lithium batteries with increased specific energies for powering electric vehicles, or when economically viable, in electrolyser-fuel cells. The interface between electrochemical technology and biotechnology is also developing rapidly, with applications such as microbial fuel cells.Some of these applications are reviewed, the challenges assessed and current trends elucidated in the very active area of Chemical Engineering bordering with material science and electrochemistry.

  • 187.
    Becker, Sebastian
    KTH, School of Chemical Science and Engineering (CHE).
    Inverkan av olika joner och jonconcentrationer på porstorleksfördelningen i trämassa-fibrer2011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The basic ingredient of paper is the individual wood fibers. The property of the fibers depends on a variety of factors e.g., method of pulp production and processing. The final sheet quality depends in part on how the fibers interface between each other and therefore factors that affect the fiber size are of interest.

    The flexibility of the fibers depends in part on the pore water i.e., the fiber swelling. The sheet becomes less flexible at low water content which gives a loss in strength. Thus it becomes desirable to increase the water uptake.

    The experimental investigation described in this report consists of exposing the wood fibers to different ions and ionic strength and then measure the pore size by thermoporosimetry where a DSC (Differential Scanning Calorimeter) is used. DSC measures the freezing point of water in the pores of the wood fibers. As the freezing point varies with the pore size the size distribution can be determined.

    The results show that there are complications with thermoporosimetry measurements at different ion concentrations. The strength of the ionic solutions will contribute to a fictitious pore volume, which makes analysis difficult to interpret.

  • 188. Beckham, Gregg T.
    et al.
    Bomble, Yannick J.
    Matthews, James F.
    Taylor, Courtney B.
    Resch, Michael G.
    Yarbrough, John M.
    Decker, Steve R.
    Bu, Lintao
    Zhao, Xiongce
    McCabe, Clare
    Wohlert, Jakob
    Bergenstråhle, Malin
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Brady, John W.
    Adney, William S.
    Himmel, Michael E.
    Crowley, Michael F.
    The O-Glycosylated Linker from the Trichoderma reesei Family 7 Cellulase Is a Flexible, Disordered Protein2010In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 99, no 11, p. 3773-3781Article in journal (Refereed)
    Abstract [en]

    Fungi and bacteria secrete glycoprotein cocktails to deconstruct cellulose Cellulose degrading enzymes (cellulases) are often modular with catalytic domains for cellulose hydrolysis and carbohydrate binding modules connected by linkers rich in serine and threonine with O-glycosylation Few studies have probed the role that the linker and O-glycans play in catalysis Since different expression and growth conditions produce different glycosylation patterns that affect enzyme activity the structure function relationships that glycosylation imparts to linkers are relevant for understanding cellulase mechanisms Here the linker of the Trichoderma reesei Family 7 cellobiohydrolase (Cel7A) is examined by simulation Our results suggest that the Cel7A linker is an intrinsically disordered protein with and without glycosylation Contrary to the predominant view the O-glycosylation does not change the stiffness of the linker as measured by the relative fluctuations in the end to end distance rather it provides a 16 A extension thus expanding the operating range of Cel7A We explain observations from previous biochemical experiments in the light of results obtained here and compare the Cel7A linker with linkers from other cellulases with sequence based tools to predict disorder This preliminary screen indicates that linkers from Family 7 enzymes from other genera and other cellulases within T reesei may not be as disordered warranting further study

  • 189. Bedo, Daniel
    et al.
    Imre, Balazs
    KTH, School of Biotechnology (BIO), Glycoscience. Hungarian Academy of Sciences, Hungary; Budapest University of Technology and Economics, Hungary.
    Domjan, Attila
    Schoen, Peter
    Vancso, G. Julius
    Pukanszky, Bela
    Coupling of poly(lactic acid) with a polyurethane elastomer by reactive processing2017In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 97, p. 409-417Article in journal (Refereed)
    Abstract [en]

    A segmented polyurethane elastomer (PU) was synthesized in poly(lactic acid) (PLA) melt by reactive processing. The isocyanate component was anticipated to react with the end-groups of PLA resulting in the formation of block-copolymers. The stoichiometry of the functional groups was optimized in the preliminary experiments. Two different processing methods were compared in the further experiments: conventional mixing of PU with PLA (PLA/PU), and reactive blending (PLA-b-PU). The comparison of the structure and properties of compatibilized reactive blends and conventional physical blends clearly shows the benefits of reactive processing. Coupling resulted in a finer dispersion of the particles in the matrix leading to better mechanical properties in the reactive blend. The successful synthesis of PEA-b-PU block copolymers was confirmed by NMR spectroscopy. The isocyanate component was found to react only with the hydroxyl end-groups of PLA, while the formation of amide and acylurea groups was not detected on the carboxyl end.

  • 190.
    Beheshti, Reza
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Sustainable Aluminum and Iron Production2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Aluminium recycling requires 95% less energy than primary production with no loss of quality. The Black Dross (BD) produced during secondary aluminium production contains high amounts of water-soluble compounds, therefore it is considered as a toxic waste. In the present work, salt removal from BD by thermal treatment has been investigated in laboratory scale. The optimum conditions for treatment were established, i.e., temperature, gas flow rate, holding time, rotation rate, and sample size. The overall degree of chloride removal was established to increase as a function of time and temperature. Even Pretreated Black Dross (PBD) was evaluated as a possible raw material for the production of a calcium aluminate-based ladle-fluxing agent to be used in the steel industry. The effects of different process parameters on the properties of the produced flux were experimentally investigated, i.e. CaO/Al2O3 ratio, temperature, holding time, and cooling media. The utilization of PBD as the alumina source during the production of a calcium aluminate fluxing agent shows promising results. The iron/steel industry is responsible for 9% of anthropogenic energy and process CO2 emissions. It is believed that the only way to a long-term reduction of the CO2 emissions from the iron/steel industry is commercialization of alternative processes such as Direct Reduction (DR) of iron oxide. Detailed knowledge of the kinetics of the reduction reactions is, however, a prerequisite for the design and optimization of the DR process. To obtain a better understanding of the reduction kinetics, a model was developed step-by-step, from a single pellet to a fixed bed with many pellets. The equations were solved using the commercial software COMSOL Multiphysics®. The final model considers the reaction rate and mass transfer inside the pellet, as well as the mass transfers and heat transfer in the fixed bed. All the models were verified against experimental results, and where found to describe the results in a satisfying way.

  • 191.
    Behrouz Akrami, Shahab
    KTH, School of Chemical Science and Engineering (CHE).
    Källor i Haninge
 ‐ vattenkvalitet och 
tillgänglighet2013Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report about springs in Haninge Municipality, which is located to the south of Stockholm, is a diploma work at KTH. The survey was made in collaboration with Haninge Municipality and Källakademin (Swedish Academy of Springs). The work was carried out by two students, one who specialized in the present condition of the springs (this report) and one who focused on their history and tradition. The primary aim of this research is to give Haninge Municipality and its residents better knowledge of the springs that exist in the municipality, especially with regard to their water quality and location.

    The municipality strives to inform the public about springs and to provide the springs with signs. The information about the existence of the springs and the locations of them has been obtained from various databases, primarily SGU (Geological Survey of Sweden), the Swedish Forest Agency and the Stockholm county administration and also through private contacts.

    After the localization of the springs, seven of them were chosen for sampling. The chosen springs were visited and sampled. The water was analyzed with respect to the following parameters: temperature, pH, conductivity, alkalinity, chemical oxygen demand (CODMn), chloride, colour, taste, smell and transparency. The first three of these parameters were determined in the field. In addition to these parameters, the concentration of metal ions and the total phosphorous content were also determined. The metals that were analysed include cadmium, calcium, potassium, magnesium, sodium and copper.

    The results gave the following information: Four springs, Källbacken, Gubbkärret, Mellanbergskällan and Sandemar are suitable for restoration and they have very good water quality from chemical-physical point of view. These four springs have different characteristics and there are minor problems conserning restoration but they, need further sampling and examination.

    Three springs, Lillsjön, Nytorp and Trefaldighetskällan at Utö have inferior quality and would require greater efforts to restore.

  • 192.
    Beldowski, Piotr
    et al.
    UTP Univ Sci & Technol, Inst Math & Phys, Al Kaliskiego 7, PL-85796 Bydgoszcz, Poland..
    Weber, Piotr
    Gdansk Univ Technol, Atom & Opt Phys Div, Dept Atom Mol & Opt Phys, Fac Appl Phys & Math, Narutowicza 11-12, PL-80233 Gdansk, Poland..
    Dédinaité, Andra
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Box 5607, SE-11486 Stockholm, Sweden..
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Box 5607, SE-11486 Stockholm, Sweden..
    Gadomski, Adam
    UTP Univ Sci & Technol, Inst Math & Phys, Al Kaliskiego 7, PL-85796 Bydgoszcz, Poland..
    Physical crosslinking of hyaluronic acid in the presence of phospholipids in an aqueous nano-environment2018In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, no 44, p. 8997-9004Article in journal (Refereed)
    Abstract [en]

    Hyaluronic acid and phospholipids are two components in the synovial joint cavity that contribute to joint lubrication synergistically. Molecular dynamics simulations were performed and hydrogen bonds in hyaluronic acid were analyzed to identify specific sites that are responsible for its physical cross-linking. Two molecular masses of hyaluronic acid, 10 kDa and 160 kDa, were considered. We use molecular dynamics simulations and the small world network approach to investigate dynamic couplings using a distance map applied to oxygen atoms in a chain of hyaluronic acid in the presence of phospholipids and water. The distance characterizing the coupling can be defined in various ways to bring out the most evident differences between various scenarios of the polymer chain conformation We show herein a physical distance understood as H-bond length and classes of these distances which are defined in a coarse-grained picture of the molecule. Simulation results indicate that addition of phospholipids has little influence on hyaluronic acid crosslinking. However, longer chains and addition of lipids promote appreciably long lasting (resilient) networks that may be of importance in biological systems. Specific sites for hydrogen bonding of phospholipids to hyaluronic acid have also been identified.

  • 193.
    Bellais, Michel
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Liliedahl, Truls
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Influence of different shrinkage models and fuel geometry on heat transfer during rapid pyrolysis of solid biofuels2002In: Proceedings of the Finnish-Swedish FlameDays: Adapting Combustion Technology to New Fuels and Fuel Mixtures,september 2002, Vaasa, Finland: The Finnish and Swedish National Committees of The International Flame Research Foundation, IFRF, 2002Conference paper (Refereed)
  • 194.
    Bellais, Michel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Svenson, J.
    Pettersson, J. B. C.
    Omrane, Alaa
    KTH.
    Ossler, F.
    Aldén, M.
    Fast drying of large wood particles under pyrolysing conditions: experimental study and modellingIn: Fuel, ISSN 0016-2361, E-ISSN 1873-7153Article in journal (Other academic)
  • 195.
    Bellander, Hampus
    KTH, School of Chemical Science and Engineering (CHE).
    Evaluation of a hygroscopic condenser2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In Sweden the industries releases about 50 TWh / year of low temperature waste heat[1], often in the form of humid air flows. Today, conventional flue gas condensation is only exploiting a minor part of the energy from these flows. It is a well-established and profit­able way of improving the efficiency of district heating plants and other boilers for wet fuels. How­ever, the condensation is only applicable when the dew point of the flue gas is above the temperature demand for the heating net. The paper industry gives a good illustration of the limitations for conventional condensation: several MW of wet air streams with dew points of 60-65 ̊ C are released but cannot be recovered since the tempe­ra­ture demand is 70-80 ̊ C for the heating net. Different technologies for more advanced waste heat recovery are developing and this report is evaluating a demonstration plant for “hygro­scopic condenser”, which uses a hygroscopic solution that allows condensation above the dew point. The hygro­scopic solution is potassium formate, which enables condensation to start about 20 ̊ C above the dew point and is sufficiently non-toxic and non-corrosive.

    The objective of this work is to evaluate both the equipment and the process during some initial tests at the paper mill at Holmen, Braviken. The aim is also to suggest improvements of the process, the components and the additional equipment for future continuous operation. 

    The equipment consists of two main parts:  a hygroscopic absorption stage and a regene­ration stage. The major part of the humid air is led into an absorption column where vapor is absorbed by the formate solution and rises its temperature. This recovered waste heat is transferred to the heating net by a plate heat exchanger. The regeneration unit is used to maintain the hygroscopic concentrations by evaporation of vapor from the formate solution (amount of absorbed vapor = amount of evaporated vapor). The regene­rator is driven by process steam from the existing 3.5 bar net. The evaporated vapor is led to a conventional condenser where the regeneration energy can be recovered and the condensate is bled off.  The recovered heat from the process (hygroscopic absorber + regeneration condenser) is used in the heating net at Holmen, Braviken (VVG-net).   

    The initial tests have been made during 15 hours of initial operation, when the equipment has delivered about 3 MWh in total. The tests show a good temperature performance since the dew point of the humid air has been lowered from about 60oC to 47oC. The reco­vered heat was used for heating from 65oC to about 80oC. During the initial tests the capacity has not yet reached the design values. As an example the delivered heat was measured to 280 kW where­of 46kW from absorbed vapor, 129 kW from the sensible heat in the incoming humid air and 105 kW from the regeneration. The bottle-neck parts of the equipment have been localized and will be overseen during the summer of 2011 and the process is planned to be in use during the autumn with an output capacity of 500kW. The coefficient of performance (COP) is calculated to just below 2 during normal operation but was about 2.7 in the test runs due to the high portion of sensible heat.

    [1]Förekomst av industriellt spillvärme vid låga temperaturer,  Ingrid Nyström, Per-Åke Franck, Industriell Energianalys AB, 2002-04-15

  • 196.
    Belonoshko, Anatoly B.
    et al.
    KTH, Superseded Departments, Physics.
    Rosengren, Anders
    KTH, Superseded Departments, Physics.
    Dong, Qian
    KTH, Superseded Departments, Materials Science and Engineering.
    Hultquist, Gunnar
    KTH, Superseded Departments, Materials Science and Engineering.
    Leygraf, Christofer
    KTH, Superseded Departments, Materials Science and Engineering.
    First-principles study of hydrogen diffusion in α-Al 2O3 and liquid alumina2004In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 69, no 2, p. 243021-243026Article in journal (Refereed)
    Abstract [en]

    We have studied the energetics and mobility of neutral hydrogen in alumina Al2O3 using ab initio density-functional calculations. The mobility of hydrogen was studied in corundum (α-Al2O 3) as well as in liquid alumina. Using both static as well as molecular-dynamics calculations, and applying classical transition state theory, we derive the temperature-dependent diffusivity of hydrogen in α-Al 2O3 as D(T)=(21.7 × 10-8 m 2/s)exp(-1.24 eV/kT). The corresponding diffusivity of hydrogen in liquid/amorphous alumina, derived directly from ab initio molecular dynamics calculations, is D(T)=(8.71 × 10-7 m2/s)exp(-0.91 eV/kT). The computed diffusivity compares very well to experimental data. We conclude that diffusion of neutral hydrogen through the bulk of alumina is a good approximation of the mechanism for hydrogen mobility in corrosion scales. The representation of grain-boundary structures by amorphous alumina is, probably, realistic at higher temperatures.

  • 197.
    Benamira, M.
    et al.
    ENSCP, Paris.
    Albin, V.
    ENSCP, Paris.
    Ringuedé, A.
    ENSCP, Paris.
    Vannier, R-N.
    UMR 8181 CNRS.
    Bodén, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Cassir, M.
    ENSCP, Paris.
    Structural and Electrical Properties of Gadolinia-doped Ceria Mixed with Alkali Earth Carbonates for SOFC Applications2007In: SOLID OXIDE FUEL CELLS 10 (SOFC-X), PTS 1 AND 2 / [ed] Eguchi, K; Singhai, SC; Yokokawa, H; Mizusaki, H, 2007, p. 2261-2268Conference paper (Refereed)
    Abstract [en]

    The properties of composite materials based on mixtures of gadolinium-doped ceria (GDC) and Li(2)CO(3)-K(2)CO(3) are analyzed as potential SOFC electrolytes. In a temperature range higher than 500 degrees C, their ionic conductivity is significantly higher than for single GDC. Discontinuities were found in the conductivity Arrhenius diagram (sigma vs. 1/T) around the melting point of the carbonate mixture (490 degrees C), showing, at least partially, the contribution of molten carbonates. At this stage, precise mechanisms are still under analysis.

  • 198.
    Benamira, M.
    et al.
    Chimie ParisTech.
    Ringuede, A.
    Chimie ParisTech.
    Hildebrandt, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Vannier, R-N
    UMR 8181 CNRS.
    Cassir, M.
    Chimie ParisTech.
    Gadolinia-doped ceria mixed with alkali carbonates for SOFC applications: II - An electrochemical insight2012In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, no 24, p. 19371-19379Article in journal (Refereed)
    Abstract [en]

    Composite materials based on gadolinia-doped ceria (GDC) and alkali carbonates (Li2CO3-K2CO3 or Li2CO3-Na2CO3) are potential electrolytes for low temperature solid oxide fuel cell applications (LTSOFC). This paper completes a first one dedicated to the thermal, structural and morphological study of such compounds; it is fully focussed on their electrical/electrochemical properties in different conditions, temperature, composition and gaseous atmosphere (oxidative or reductive). The influence of the gaseous composition on the Arrhenius conductivity plots is evidenced, in particular under hydrogen atmosphere. Finally, electrical conductivity determined by impedance spectroscopy is presented as a function of time to highlight the stability of such composites over 6000 h. First results on single cells showed performance at 600 degrees C of 60 mW cm(-2).

  • 199.
    Benavente, Martha
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Adsorption of Metallic Ions onto Chitosan: Equilibrium and Kinetic Studies2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Equilibrium isotherms and the adsorption kinetics of heavy metals onto chitosan were studied experimentally. Chitosan, a biopolymer produced from crustacean shells, has applications in various areas, particularly in drinking water and wastewater treatment due to its ability to remove metallic ions from solutions. The adsorption capacity of chitosan depends on a number of parameters: deacetylation degree, molecular weight, particle size and crystallinity. The purpose of this work was to study the adsorption of copper, zinc, mercury, and arsenic on chitosan produced from shrimp shells at a laboratory level.

    The experimental work involved the determination of the adsorption isotherms for each metallic ion in a batch system. The resulting isotherms were fitted using the Langmuir model and the parameters of the equation were determined. Kinetic studies of adsorption for different metallic ions at different concentrations and with different particle sizes were performed in batch and column systems. Simplified models such as pseudo-first-order, pseudo-second-order, and intra-particle diffusion equations were used to determine the rate-controlling step. Some preliminary studies were carried out to address the application of chitosan as an adsorbent in the removal of heavy metals or other metallic ions from natural water and wastewater. The regeneration of chitosan was also studied.

    The results showed that the adsorption capacity depends strongly on pH and on the species of metallic ions in the solution. The optimum pH value for the metallic cation adsorption was between 4 and 6, whereas for arsenic adsorption it was about 3. When the pH is not controlled, the adsorption capacity is independent of the initial pH with the solution reaching a final pH of about 7. It was also found that the Langmuir equation described very well the experimental adsorption data for each metallic ion. The adsorption capacity for the metals on chitosan follows the sequence Hg>Cu>Zn>As.

    The study of the adsorption kinetics of these metallic ions shows that the particle size has a significant influence on the metal uptake rate for copper; but that it has only a slight influence on the adsorption rate of zinc and mercury in the range studied. Arsenic adsorption exhibited an interesting behaviour which depends strongly on the pH of the solution; the uptake increased at short adsorption times and then decreased at long times. The analysis of kinetic models showed that the pseudo-second-order adsorption mechanism is predominant, and the overall rate of the metallic ion adsorption process is therefore controlled by adsorption reactions and not by mass transfer for the range of particle sizes examined in this study.

    With regard to the regeneration of chitosan, it was found that sodium hydroxide is a good agent for zinc and arsenic desorption, whereas ammonium sulphate and sodium chloride were the most suitable for copper and mercury desorption, respectively. The ability of chitosan to remove arsenic from natural water, and copper and zinc from mining waste water was verified. The use of these results for designing purposes is a subject for future work.

  • 200.
    Benavente, Martha
    et al.
    Department of Chemical Engineering, National University of Engineering, Managua, Nicaragua.
    Arévalo, Marcos
    Department of Chemical Engineering, National University of Engineering, Managua, Nicaragua.
    Martinez, Joaquin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Speciation and Removal of Arsenic in column packed with chitosan2006In: Water Practice & Technology, ISSN 1751-231X, Vol. 1, no 4, p. 2006-89Article in journal (Refereed)
    Abstract [en]

    The arsenic speciation and arsenic removal in chitosan packed column were studied. Arsenic removal experiments were carried out with an arsenic standard solution (1.0 mg/l) and drilled well water samples from Limon Mine Community at different pH, water flowrate, and volume of adsorbent material. The simulation of arsenic speciation was carried out at a pH range from 0 to 12, a temperature of 25ºC, a pE equal to 4, and a total arsenic concentration of 1.34 x 10-5 mol kg-1. According to speciation calculations arsenic is found mainly in oxidized form in the conditions of Limon Mine’s drilled well waters, dihydrogen arsenate ion (H2AsO4-), and hydrogen arsenate ion (HAsO42-) being the major species. The experiments showed that arsenic adsorption depends mainly on the pH as well as the activity of functional groups that compose the chitosan structure. At pH 3 and volume of adsorbent material of 337.8 cm3 an adsorption of 94% was obtained from arsenic standard solution, and the arsenic present in the Limon Community’s water was almost totally removed at pH 3 and 7. The use of the results for designing purposes demands the breakthrough curves for chitosan to be determined.

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