Evaluating the ability of biosorbents to remove arsenic from water has global significance due to the widespread availability and low cost of biosorbent materials. In this study, the ability of coffee grounds and coconut substrate (two previously unreported biosorbents) to remove arsenic from water was compared against the performance of arsenic removal on rice husk (a recognized and widely tested biosorbent). The three biosorbents were individually screened for their ability to remove arsenite, As (III), and arsenate, As (V), from water. Batch reactors were employed to assess the percent removal, reaction kinetics, adsorption capacity, and desorption of each arsenic species onto/from biosorbents under pH buffered and non‐buffered conditions. The resulting experimental data was statistically interpreted using analysis of variance and ttesting of the means. The experimental results were also fit to existing kinetic and isotherm models to provide kinetic rate constants, the maximum adsorption capacity, and to help interpret the nature of the reactions on the biosorbent surface. While all three biosorbents removed arsenic with similar initial reaction kinetics (pseudo 1st order reaction rate constant for As (III) was 0.13 hr^‐1 for all three biosorbents and for As (V) was 0.17 hr^‐1 for coffee grounds and rice husk and 0.15 hr^‐1 for coconut substrate), the amount of arsenite and arsenate removed was highest for coffee grounds (84 and 91 percent, respectively), followed by rice husk (68 and 72 percent, respectively), and then coconut substrate (26 and 24 percent, respectively). The maximum adsorption capacity of arsenite and arsenate was determined for coffee grounds (0.66 and 0.70 mg/g, respectively) and rice husk (0.55 and 0.66 mg/g, respectively). While desorption was observed for both coffee grounds and rice husk, the total amount of desorption accounted for less than 15 percent of the total retained mass. The results of this thesis work reveal that coffee can be used as an effective biosorbent when compared to rice husk; however, coconut substrate is less effective than rice husk at removing As (III) and As (V).

Alkali Silica Reaction (ASR) is a deleterious, expansive reaction in concrete. Several ASTM methods test potential aggregates for ASR risk. One method uses NaOH digestion, followed by spectroscopic methods, to estimate the amount of reactive silica present in an aggregate. NaOH, however, can digest both crystalline (i.e. quartz) and non-crystalline (e.g. opal), or poorly crystalline silica, potentially yielding falsely high estimates of reactive silica. Studies in soil and plant sciences have used Tiron, an alkaline chelating agent (C6H4S2O8Na2), as a method of digesting opaline silica for spectroscopic analysis. Here we test this approach by analyzing reactive silica in road aggregate. Tiron extraction of reactive silica is more selective, in some cases extracting only ~ 30% of the silica compared to the harsher NaOH extraction: variation is due to differences in aggregate mineralogy, specifically SiO2. In conducting chelation analyses, UV/VIS seems to be a better approach than AA.

Even though the Brazilian ethanol and sugar production system (based on sugarcane industry) have been providing large amounts of bioenergy, the extensive amounts of organic wastes generated cannot be ignored when it comes to sustainability. Using these biomasses to produce biomethane through anaerobic digestion has been proven as a promising way to tackle this issue. This study investigated the biomethane potential of the co-digestion of these biomasses: SF (sugarcane straw : filter cake = 8:2), SFV (sugarcane straw : filter cake : vinasse = 1:4:45), and D (digestate separated from AD of SFV). Three treatments autoclaving (AU), alkaline (AL) treatment using 6% (w/w) NaOH and the combination of these two (AUAL) were then conducted on SF and SFV as pre-treatments; on D as post- treatments. In the biomethane potential tests of untreated material, the highest methane yield was achieved by SFV with 275.28 ± 11 N ml CH4/g VS, followed by SF with 223.25 ± 10 N ml CH4 g-1 VS, substrate D also resulted in a methane potential of 144.69 ± 2 N ml CH4 g-1 VS. As pre-treatments, AL and AUAL both showed increase in methane yield (between 36.0% and 49.1%) and methane production rate. As post-treatments, AU, AL and AUAL showed distinctive results in methane production, with 33.8%, 99.8% and 128.8% increase, respectively. In comparison with pre-treatment, post-treatment showed a better performance in increasing methane production. The following feeding experiments performed in continuous stirred-tank reactors showed that AL treatment led to an average of 248% increase in methane yield. / Sugarcane waste: towards a zero C emission in the Brazilian bioenergy sector

京都大学 / 新制・課程博士 / 博士(農学) / 甲第25327号 / 農博第2593号 / 新制||農||1105(附属図書館) / 学位論文||R6||N5499 / DGAM / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 矢野 浩之, 教授 梅村 研二, 教授 和田 昌久 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

O presente trabalho visou o estudo da modificação química da celulose de linter (obtida de fonte de rápido crescimento e considerada a celulose de maior pureza isolada de fontes vegetais) através da sua derivatização em meio homogêneo, buscando-se a obtenção de materiais com características bem definidas e via um método que apresente boa reprodutibilidade. Dentre os derivados de celulose, os acetatos têm importância industrial significativa. No presente trabalho, acetatos de celulose obtidos no sistema de solvente cloreto de lítio/dimetilacetamida (LiCl/DMAc), com diferentes graus de substituição (GS) foram caracterizados através de 1H NMR, espectroscopia na região do infravermelho, viscosimetria e análises térmicas (DSC e TG). Através de métodos quantitativos aplicados às curvas termogravimétricas pode-se obter parâmetros cinéticos relacionados à decomposição térmica como a energia de ativação (Ea). Os resultados para os acetatos mostraram que conforme o GS aumenta, aumenta o grau de substituição de C2 e C3, e observa-se também aumenta Ea. Acetatos de celulose com diferentes GS foram utilizados para a obtenção de filmes a partir do mesmo sistema de solvente. Visando à obtenção de biocompósitos, filmes de acetatos de celulose com diferentes porcentagens de celulose foram preparados. Nestes filmes, os acetatos são considerados como matriz e a celulose como reforço, se tendo como pressuposto que as cadeias de celulose formarão agregados em solução, os quais serão mantidos nos filmes, atuando então como reforço. Este pressuposto é baseado em resultados de trabalhos anteriores, assim como estudos reológicos feitos no presente trabalho, que mostram que as cadeias de celulose se agregam, mesmo a baixas concentrações. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), cromatografia de exclusão por tamanho (SEC), microscopia eletrônica de varredura (MEV), solvatocromismo, dentre outras. A eliminação dos solventes após a obtenção dos filmes é um fator importante a ser considerado, e os resultados mostraram que o processo escolhido não leva a presença residual dos solventes utilizados. As imagens de MEV indicaram que fibras de celulose nos filmes de biocompósitos no geral não são visíveis em escala microscópica. Este resultado é promissor, pois sugere que as fibras de celulose podem estar presentes em escala nanométrica, já que para alguns filmes a ação como reforço foi observada, através da melhora em algumas propriedades. Ainda, a rugosidade dos filmes de biocompósitos foi alterada com a presença de celulose conforme mostram os resultados de AFM. Os resultados de DMTA indicaram que uma baixa porcentagem de celulose (5% de celulose) no filme de acetato de celulose com GS 0,8, foi suficiente para a ação como reforço ser observada, sugerindo que cadeias de celulose interagiram preferencialmente entre si, gerando estruturas supramoleculares de cadeias agregadas quando ainda no meio solvente (LiCl/DMAc), as quais permaneceram na preparação dos filmes. No entanto, para o filme obtido a partir de um GS maior (GS 1,5), o efeito de reforço da celulose nos filmes de biocompósitos ocorre apenas para a maior proporção de celulose (15% de celulose). Os resultados de ensaio à tração mostraram que dependendo da aplicação, ou seja, a necessidade de filmes mais resistentes à tração e maior rigidez, estes podem ser empregados. Adicionalmente, filmes de celulose e quitosana foram preparados no sistema de solvente NaOHaq./tiouréia. Nestes filmes, considera-se a quitosana como matriz e a celulose como agente de reforço. Acredita-se que as cadeias de celulose prefiram interagir entre si, gerando \"domínios\" de cadeias de celulose. Por este motivo, o termo biocompósito foi empregado também para estes filmes. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), biodegradação, sorção de umidade, microscopia de força atômica (AFM), dentre outras. Os resultados de difração de raios X mostram que o sistema de solvente não altera significativamente a cristalinidade dos filmes, comparativamente aos materiais de partida. As análises térmicas empregadas (TG e DSC) mostraram que a estabilidade térmica é alterada devido a presença dos dois polissacarídeos nos filmes de biocompósitos. O estudo de biodegradação dos filmes de biocompósitos em solo simulado mostrou que a velocidade de biodegradação está relacionada à proporção das regiões não cristalinas, que são mais acessíveis à água e aos microrganismos, isto é, quanto maior o valor de índice de cristalinidade, menor será a velocidade de biodegradação. Importante ressaltar que o comportamento destes filmes em relação à biodegradação está também relacionado com a morfologia apresentada pelos filmes. A análise de AFM mostrou que o aumento da proporção de quitosana nos filmes de biocompósitos leva a maiores valores de rugosidade. Os resultados obtidos para os filmes de quitosana, celulose e biocompósitos (quitosana/celulose), assim como para os filmes de acetato de celulose, celulose e biocompósitos (acetato de celulose/celulose) se mostraram promissores. / This work was aimed at studying the chemical modification of linters cellulose extracted from a source of rapid growth and considered the most pure cellulose from vegetable sources. Derivatization was carried out in a homogeneous medium to obtain materials with well-defined properties via a reproducible method. Here cellulose acetate was obtained with various degrees of substitution (DS) using the lithium chloride/dimethylacetamide system (LiCl/DMAc), being characterized with 1H NMR, infrared spectroscopy, viscometry measurements and thermal analysis (DSC and TG). The thermogravimetric curves were analyzed quantitatively, which allowed the determination of kinetics parameters for the thermal decomposition, including the activation energy (Ea). Ea and the substitution at C2 and C3 increased with increasing DS. Cellulose acetates with distinct DS were obtained in the form of films using the solvents mentioned above. Furthermore, biocomposite films were prepared with different contents of cellulose, in which the acetates were considered as matrices and the cellulose was the loading material. It is assumed that the cellulose chains form aggregates in solution, which will be preserved in the films, thus acting as reinforcement. This hypothesis was based on previous work and confirmed here with rheological data. We show that the cellulose chains are aggregated even at low concentrations. These films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), size exclusion chromatography (SEC), atomic force microscopy (AFM) and scanning electron microscopy. No residual solvent was present after film preparation. The SEM images indicated that the cellulose fibers in the biocomposite films are not visible at the microscopy scale, thus suggesting the presence of cellulose nanofibers. This is promising due to the possible enhancement in the mechanical properties, which was actually observed with a threshold percentage of only 5% of cellulose with DS 0.8. The cellulose chains apparently interacted among each other, generating supramolecular structures with aggregated chains in the LiCl/DMAc solvent. The film roughness investigated with AFM was altered by the presence of cellulose in the composite film. For the film obtained with cellulose acetate with GS 1.5, the effects from cellulose as reinforcement were only observed with higher content of cellulose (15%). According to the stress-strain tests, the films may be employed in applications requiring rigid, mechanically resistant materials. Cellulose/chitosan films were also prepared using NaOHaq./thiourea as solvent, in which chitosan served as the matrix. As in the biocomposite with cellulose acetate, the cellulose chains formed domains. The films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), biodegradation tests, humidity sorption isotherms and AFM. The solvent did not affect the crystallinity of the sample, according to the XRD data. Through thermal analysis, it was inferred that the thermal stability was affected by the presence of chitosan in the biocomposite films. The study of biocomposite film degradation in a simulated soil showed that the rate of biodegradation is associated with the crystalline regions of the sample, which are more accessible to the water and the microorganisms. In other words, the higher the crystallinity the lower the biodegradation rate is. It is worth mentioning that the biodegradability also depends on the film morphology. The analysis of AFM images indicated that the film roughness increased with the content of chitosan. The results obtained with the films made with chitosan, cellulose and biocomposites (chitosan/cellulose), as well as for the films from cellulose acetate and cellulose acetate/cellulose, are promising.

O presente trabalho visou o estudo da modificação química da celulose de linter (obtida de fonte de rápido crescimento e considerada a celulose de maior pureza isolada de fontes vegetais) através da sua derivatização em meio homogêneo, buscando-se a obtenção de materiais com características bem definidas e via um método que apresente boa reprodutibilidade. Dentre os derivados de celulose, os acetatos têm importância industrial significativa. No presente trabalho, acetatos de celulose obtidos no sistema de solvente cloreto de lítio/dimetilacetamida (LiCl/DMAc), com diferentes graus de substituição (GS) foram caracterizados através de 1H NMR, espectroscopia na região do infravermelho, viscosimetria e análises térmicas (DSC e TG). Através de métodos quantitativos aplicados às curvas termogravimétricas pode-se obter parâmetros cinéticos relacionados à decomposição térmica como a energia de ativação (Ea). Os resultados para os acetatos mostraram que conforme o GS aumenta, aumenta o grau de substituição de C2 e C3, e observa-se também aumenta Ea. Acetatos de celulose com diferentes GS foram utilizados para a obtenção de filmes a partir do mesmo sistema de solvente. Visando à obtenção de biocompósitos, filmes de acetatos de celulose com diferentes porcentagens de celulose foram preparados. Nestes filmes, os acetatos são considerados como matriz e a celulose como reforço, se tendo como pressuposto que as cadeias de celulose formarão agregados em solução, os quais serão mantidos nos filmes, atuando então como reforço. Este pressuposto é baseado em resultados de trabalhos anteriores, assim como estudos reológicos feitos no presente trabalho, que mostram que as cadeias de celulose se agregam, mesmo a baixas concentrações. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), cromatografia de exclusão por tamanho (SEC), microscopia eletrônica de varredura (MEV), solvatocromismo, dentre outras. A eliminação dos solventes após a obtenção dos filmes é um fator importante a ser considerado, e os resultados mostraram que o processo escolhido não leva a presença residual dos solventes utilizados. As imagens de MEV indicaram que fibras de celulose nos filmes de biocompósitos no geral não são visíveis em escala microscópica. Este resultado é promissor, pois sugere que as fibras de celulose podem estar presentes em escala nanométrica, já que para alguns filmes a ação como reforço foi observada, através da melhora em algumas propriedades. Ainda, a rugosidade dos filmes de biocompósitos foi alterada com a presença de celulose conforme mostram os resultados de AFM. Os resultados de DMTA indicaram que uma baixa porcentagem de celulose (5% de celulose) no filme de acetato de celulose com GS 0,8, foi suficiente para a ação como reforço ser observada, sugerindo que cadeias de celulose interagiram preferencialmente entre si, gerando estruturas supramoleculares de cadeias agregadas quando ainda no meio solvente (LiCl/DMAc), as quais permaneceram na preparação dos filmes. No entanto, para o filme obtido a partir de um GS maior (GS 1,5), o efeito de reforço da celulose nos filmes de biocompósitos ocorre apenas para a maior proporção de celulose (15% de celulose). Os resultados de ensaio à tração mostraram que dependendo da aplicação, ou seja, a necessidade de filmes mais resistentes à tração e maior rigidez, estes podem ser empregados. Adicionalmente, filmes de celulose e quitosana foram preparados no sistema de solvente NaOHaq./tiouréia. Nestes filmes, considera-se a quitosana como matriz e a celulose como agente de reforço. Acredita-se que as cadeias de celulose prefiram interagir entre si, gerando \"domínios\" de cadeias de celulose. Por este motivo, o termo biocompósito foi empregado também para estes filmes. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), biodegradação, sorção de umidade, microscopia de força atômica (AFM), dentre outras. Os resultados de difração de raios X mostram que o sistema de solvente não altera significativamente a cristalinidade dos filmes, comparativamente aos materiais de partida. As análises térmicas empregadas (TG e DSC) mostraram que a estabilidade térmica é alterada devido a presença dos dois polissacarídeos nos filmes de biocompósitos. O estudo de biodegradação dos filmes de biocompósitos em solo simulado mostrou que a velocidade de biodegradação está relacionada à proporção das regiões não cristalinas, que são mais acessíveis à água e aos microrganismos, isto é, quanto maior o valor de índice de cristalinidade, menor será a velocidade de biodegradação. Importante ressaltar que o comportamento destes filmes em relação à biodegradação está também relacionado com a morfologia apresentada pelos filmes. A análise de AFM mostrou que o aumento da proporção de quitosana nos filmes de biocompósitos leva a maiores valores de rugosidade. Os resultados obtidos para os filmes de quitosana, celulose e biocompósitos (quitosana/celulose), assim como para os filmes de acetato de celulose, celulose e biocompósitos (acetato de celulose/celulose) se mostraram promissores. / This work was aimed at studying the chemical modification of linters cellulose extracted from a source of rapid growth and considered the most pure cellulose from vegetable sources. Derivatization was carried out in a homogeneous medium to obtain materials with well-defined properties via a reproducible method. Here cellulose acetate was obtained with various degrees of substitution (DS) using the lithium chloride/dimethylacetamide system (LiCl/DMAc), being characterized with 1H NMR, infrared spectroscopy, viscometry measurements and thermal analysis (DSC and TG). The thermogravimetric curves were analyzed quantitatively, which allowed the determination of kinetics parameters for the thermal decomposition, including the activation energy (Ea). Ea and the substitution at C2 and C3 increased with increasing DS. Cellulose acetates with distinct DS were obtained in the form of films using the solvents mentioned above. Furthermore, biocomposite films were prepared with different contents of cellulose, in which the acetates were considered as matrices and the cellulose was the loading material. It is assumed that the cellulose chains form aggregates in solution, which will be preserved in the films, thus acting as reinforcement. This hypothesis was based on previous work and confirmed here with rheological data. We show that the cellulose chains are aggregated even at low concentrations. These films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), size exclusion chromatography (SEC), atomic force microscopy (AFM) and scanning electron microscopy. No residual solvent was present after film preparation. The SEM images indicated that the cellulose fibers in the biocomposite films are not visible at the microscopy scale, thus suggesting the presence of cellulose nanofibers. This is promising due to the possible enhancement in the mechanical properties, which was actually observed with a threshold percentage of only 5% of cellulose with DS 0.8. The cellulose chains apparently interacted among each other, generating supramolecular structures with aggregated chains in the LiCl/DMAc solvent. The film roughness investigated with AFM was altered by the presence of cellulose in the composite film. For the film obtained with cellulose acetate with GS 1.5, the effects from cellulose as reinforcement were only observed with higher content of cellulose (15%). According to the stress-strain tests, the films may be employed in applications requiring rigid, mechanically resistant materials. Cellulose/chitosan films were also prepared using NaOHaq./thiourea as solvent, in which chitosan served as the matrix. As in the biocomposite with cellulose acetate, the cellulose chains formed domains. The films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), biodegradation tests, humidity sorption isotherms and AFM. The solvent did not affect the crystallinity of the sample, according to the XRD data. Through thermal analysis, it was inferred that the thermal stability was affected by the presence of chitosan in the biocomposite films. The study of biocomposite film degradation in a simulated soil showed that the rate of biodegradation is associated with the crystalline regions of the sample, which are more accessible to the water and the microorganisms. In other words, the higher the crystallinity the lower the biodegradation rate is. It is worth mentioning that the biodegradability also depends on the film morphology. The analysis of AFM images indicated that the film roughness increased with the content of chitosan. The results obtained with the films made with chitosan, cellulose and biocomposites (chitosan/cellulose), as well as for the films from cellulose acetate and cellulose acetate/cellulose, are promising.

This master's thesis covers an investigation of the reduction behavior of different iron oxides when electrolytically reduced with molten salt electrolysis (MSE). The tested iron oxides were wüstite (FeO), hematite (Fe2O3), magnetite (Fe3O4) and magnetite ore concentrate from the Tapuli deposit in Pajala, Norrbotten, Sweden. The properties of the Tapuli magnetite ore and magnetite ore concentrate were analysed from a mineralogical perspective to evaluate how the raw ore material influences the concentrate and its reduction by the MSE technology. The electrolytic experiments were performed in an Inconel 625 cell body within a pit-furnace. The different iron oxides were tested separately. The reduction samples were constructed of one or three iron oxide briquettes of 20 g each within a molybdenum mesh attached on a molybdenum tray with molybdenum wires. The molten electrolyte was kept at 500°C with an applied voltage of 1.7 or 2.1 V. The used electrolyte was sodium hydroxide (NaOH). The mineralogical examination shows that the Tapuli ore varies in composition between different locations of the deposit with respect to magnetite grain size and skarn composition and grain size. Point analyses with Laser Ablation Single Collector Inductively Coupled Plasma Mass Spectrometry (LA-SC-ICP-MS) on magnetite grains in thin sections from five drill cores fromdifferent parts of the deposit show that the element composition in the magnetite grains vary between the samples. Core-to-rim analyses for Fe, Mg, Mn and Al reveal relatively homogenous grades throughout the grains, with a few exceptions. Phase analysis with XRD shows that reduction has occurred in all tested iron oxides. Without prevention, the reduction products from trials on Fe2O3, Fe3O4 and magnetite ore concentrate show distinct XRD peaks of the by-product NaFeO2. According to XRD, the addition of Na2O seems to have reduced the NaFeO2 formation. Interestingly, no NaFeO2 was formed in the FeO trials. This might be explained by the absence of Fe3+ in FeO. The variation of the current-time curves of the trials is interpreted to depend on the voltage applied, the number of briquettes, briquette decomposition and Na2O addition. Electrolysis in molten NaOH can be used to reduce iron oxides. Despite this, NaOH might not be a suitable electrolyte for this process due to its interaction with Fe2O3 and Fe3O4 resulting information of NaFeO2. Na2O can be used as an additive to prevent formation of NaFeO2 but sharply decreases the current response, thus having an apparent negative effect on the process efficiency. Another preventive measure that can be tested is to calibrate the process voltage to decompose the NaFeO2 but not NaOH. Due to the shown interaction tendency of NaOH, other electrolytes should however be considered for this process. Regarding the Tapuli ore concentrate, more tests are needed to draw conclusions about how the trace elements effects its electrolytic behavior. / Denna masteruppsats avhandlar en undersökning av reduktionsbeteendet hos olika järnoxider vid elektrolytisk reduktion i saltsmälta (molten salt electrolysis (MSE)). Järnoxiderna som har testats är wüstit (FeO), hematit (Fe2O3), magnetit (Fe3O4) och magnetitmalmkoncentrat från malmfyndigheten Tapuli i Pajala, Norrbotten, Sverige. Malmkoncentratets egenskaper har analyserats ur mineralogisk synvinkel för att utvärdera hur den råa malmens mineralogi påverkar koncentratet och dess reduktionsbeteende vid elektrolys i saltsmälta. Elektrolysexperimenten utfördes i cellkropp av Inconel 625 placerad i en gropugn. De olika järnoxiderna testades separat. Reduktionsproverna utgjordes av en eller tre järnoxidbriketter på 20 g inuti ett molybdennät, fastvirade på en molybdenbricka med molybdentråd. Den smälta elektrolyten hölls vid en temperatur av 500°C med en applicerad spänning av 1.7 eller 2.1 V. Elektrolyten som användes var natriumhydroxid (NaOH). Den mineralogiska undersökningen visar att tapulimalmens sammansättning varierar mellan olika delar av fyndigheten med avseende på magnetitens kornstorlek och skarnets sammansättning och kornstorlek. Punktanalyser med Laser Ablation Single Collector Inductively Coupled Plasma Mass Spectrometry (LA-SC-ICP-MS) på magnetitkorn i tunnslip från fem olika borrkärnor visar att elementkoncentrationerna i magnetitkornen varierar mellan proverna. Core-to-rim-analyser på magnetitkornen visar att halterna av Fe, Mg, Mn och Al är tämligen homogena genom hela magnetitkornet med undantag av några få avvikande punkter. Fasanalys med XRD indikerar att reduktion har skett i alla försök. Utan prevention visar reduktionsprodukterna från försöken på Fe2O3, Fe3O4 och magnetitmalmkoncentrat klara indikationer av biprodukten NaFeO2. Enligt XRD verkar tillsats av Na2O ha minskat bildningen av Na2O för Fe2O3, Fe3O4 och Tapuli magnetitmalmkoncentrat. Intressant är att ingen NaFeO2 bildades i försöken med FeO. Förklaringen till detta skulle kunna vara avsaknaden av Fe3+ i FeO. De varierande ström-tidkurvorna från försöken tolkas bero på den applicerade spänningen, antalet briketter, brikettsönderdelning och tillsats av Na2O. Elektrolys i smält NaOH kan användas för att reducera järnoxider. Trots detta kanske NaOH inte är lämplig som elektrolyt i denna process, detta på grund av dess påvisade interaktion med Fe2O3 och Fe3O4 som resulterar i bildning av NaFeO2. Na2O kan tillsättas för att förhindra bildning av NaFeO2 men har en kraftigt negativ effekt på strömstyrkan i processen vilket minskar processens effektivitet. En annan preventiv åtgärd som kan testas är att kalibrera processens spänning så att NaFeO2 sönderdelas men inte NaOH. På grund av den konstaterade interaktionstendensen hos NaOH bör andra elektrolyter tas i beaktande för denna process. Angående magnetitmalmskoncentratet från Tapuli behövs fler tester för att dra slutsatser kring hur spårelementen påverkar dess uppförande vid smältelektrolys.

Le but de ces travaux était d'étudier les mécanismes de gonflement et de dissolution des fibres de cellulose en faisant varier la qualité du solvant (N-methylmorpholine-N-oxide avec différentes quantités d'eau et solutions aqueuses de NaOH à 8%), les conditions de dissolution, comme la tension, et l'origine des fibres (coton, bois, fibres régénérées ou dérivées). Les mécanismes de gonflement et de dissolution ont été étudiés par des observations microscopiques à haute résolution. Une séparation sélective des fractions solubles et insolubles a été réalisée par centrifugation. La distribution de masse molaire, la cristallinité, la composition en sucre, l'allomorphie et la quantité de chaque fraction ont été analysées. A partir de ces résultats, nous avons pu mieux décrire les mécanismes de gonflement et de dissolution des fibres de cellulose et ainsi identifier les principaux paramètres gouvernant la dissolution. Nos résultats montrent que les caractéristiques structurales et moléculaires des fibres de cellulose ainsi que les paramètres de procédés doivent être mieux contrôlés afin d'améliorer la dissolution. (i) Les paramètres de procédés concernent la convection du solvant et la possibilité de mouvements des fibres dans le solvant, (ii) les paramètres structuraux concernent la suppression des parois externes, la déstructuration des parois internes et la suppression sélectives des hémicelluloses, (iii) les paramètres moléculaires concernent la thermodynamique, comme la longueur des chaînes, la cristallinité mais aussi l'amélioration de la mobilité conformationelle des chaînes.

Phosphorus (P) is an essential element for life on our planet. It is central in numerous biochemical processes in terrestrial and aqueous ecosystems including food production; and it is the primary growth-limiting nutrient in some of the world’s biomes. The main source of P for use as agricultural fertilizer is mining of non-renewable mineral phosphate. In terrestrial ecosystems the main source is soil P, where the largest fraction is organic P, composed of many species with widely differing properties. This fraction controls the utilization of P by plants and microorganisms and influences ecosystem development and productivity. However, there is only scarce knowledge about the molecular composition of the organic P pool, about the processes controlling its bioavailability, and about its changes as soils develop. Therefore, the aim of this thesis was to develop robust solution- and solid-state 31P nuclear magnetic resonance spectroscopy (NMR) methods to provide molecular information about speciation of the organic P pool, and to study its dynamics in boreal and tropical soils. By studying humus soils of a groundwater recharge/discharge productivity gradient in a Fennoscandian boreal forest by solution- and solid-state NMR, it was found that P speciation changed with productivity. In particular, the level of orthophosphate diesters decreased with increasing productivity while mono-esters such as inositol phosphates increased. Because the use of solution NMR on conventional NaOH/EDTA extracts of soils was limited due to severe line broadening caused by the presence of paramagnetic metal ions, a new extraction method was developed and validated. Based on the removal of these paramagnetic impurities by sulfide precipitation, a dramatic decrease in NMR linewidths was obtained, allowing for the first time to apply modern multi-dimensional solution NMR techniques to soil extracts. Identification of individual soil P-species, and tracking changes in the organic P pools during soil development provided information for connecting P-speciation to bioavailability and ecosystem properties. Using this NMR approach we studied the transformation of organic P in humus soils along a chronosequence (7800 years) in Northern Sweden. While total P varied little, the composition of the soil P pool changed particularly among young sites, where also the largest shift in the composition of the plant community and of soil microorganisms was observed. Very old soils, such as found Africa, are thought to strongly adsorb P, limiting plant productivity. I used NMR to study the effect of scattered agroforestry trees on P speciation in two semi-arid tropical woodlands with different soil mineralogy (Burkina Faso). While the total P concentration was low, under the tree canopies higher amounts of P and higher diversity of P-species were found, presumably reflecting higher microbial activity. / <p>I delarbete III har titel och författaruppgifter förändrats.</p>

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