Med den ökande trenden av process slutning inom massabruken, så har det indikerats att återvinningen av tvättvätska från de olika tvättsteg troligen resulterar i negativa effekter. Närvaron av olika komponenter kan påverka upplösningen av lignin genom att främja dess återdeponering på massan, och därmed påverka senare steg inom bruket. Denna studie fokuserade på effekten av tvättvätskes sammansättningen, pH och magnesiumjoners innehållet på ligninåterfästningen till fibrerna under brunmassatvätt. Projektets syfte var att finna nya relevanta insikter för dagens verksamheter. För den experimentella proceduren blandades massa- och vätskaprover erhållna från ett barrveds-sulfatmassabruk, relevanta lösningsmodifikationer genomfördes, och dessa placerades i ett vattenbad vid 90 °C. Därefter tvättades och separerades den resulterande blandningen. Kappatal och ISO-ljusstyrka användes för massakaraktärisering, samt UV-VISspektroskopi för tvättvätskor. En ytterligare procedur med alkalisk urlakning utfördes på massan för att identifiera den relativt svaga liginbindningen. Resultaten indikerade att högre ligninhalt och konduktivitet, lägre pH och högre MgSO4 koncentration i tvättvätskor ökar lignininnehållet i massan. Under proceduren identifierades en möjlig konkurrens mellan borttagningen av lignin från fibrerna och återfällningen. Genom att uföra studier på olika bruksvätskor, så påverkades flera variabler systemet samtidigt, vilket förhindrade identifikationen av den dominerande variabeln som potentiellt kunde justeras för att minska återdeponeringen. Det observerades dock att en tillsatts av NaOH i tvättvätskor kunde reducera lignininnehållet i massan, medans däremot en ökning av MgSO4 kunde ha negativa effekter. / With the growing tendency of process closure within pulp mills, recycling liquors into different washing stages was observed to result in likely negative effects. The presence of different components may affect lignin dissolution, by promoting its redeposition onto pulp therefore affecting later stages in the mill. The present study focused on the effect of washing liquor composition, pH, and magnesium ions content on lignin reattachment to fibres during brown stock washing. This project’s motivation was to provide new insights relevant for today’s operations. For the experimental procedure, pulp and liquor samples obtained from a softwood kraft pulp mill were mixed, relevant solution modifications were performed, and these were set inside a water bath at 90 °C. Then, the resulting mixture was washed and separated. Kappa number and ISO brightness were employed for pulp characterization, and UV-VIS spectroscopy for washing liquors. An additional procedure of alkaline leaching was performed on pulp to identify relatively weak lignin attachment. Obtained results indicated that higher lignin content and conductivity, lower pH and higher MgSO4 concentration in washing liquors increase the lignin content in pulp. A competition between lignin removal from fibres and reattachment was identified to be possibly occurring during the procedure. By performing studies on different mill liquors, multiple variables affected the system simultaneously, which hinders the identification of the dominant variable to be potentially adjusted for reducing the redeposition. However, it was seen that adding NaOH in washing liquors could reduce lignin content in the pulp, whereas an increase in MgSO4 could present negative effects.

The acidification has been a known problem in Sweden for several decades. Sulphurous compounds, spread from the British Isles and the European continent led to a decrease in the pH-value of the rain that fell over Sweden. Since the acidification was discovered in the 1960s, active measures against the sulphurous deposition have been undertaken. The sulphurous deposition has decreased by 90 %, and the problem was for some time considered under control, until recently when a new era of the acidification may have started. Due to the increased demand of renewable energy, and Sweden’s potential to use biomass instead of fossil fuels, whole tree harvesting has been more utilized. Studies indicate that the forest soils are depleted in base cations in a faster rate when whole tree harvesting is performed compared to regular stem harvesting. Mass balance calculations and simulations indicate that an increased bio uptake of base cations due to whole tree harvesting leads to an increased biological acidification. However, although many studies agree that the impact of the whole tree harvest on the base cation supply of the soils is significant, long running Swedish experiments indicate that the difference between whole tree harvesting and regular stem harvesting diminishes over time. After a 40 year period, the difference in base cation supply between whole tree harvested soils and stem harvested soils are small. The reason for this could be different processes that reallocate base cations from different pools, which are not usually studied. The aim has been to investigate and evaluate different chemical extraction methods (Aqua Regia, HCl, EDTA, BaCl2, NH4OAc and water) capability to extract the base cations calcium, potassium, magnesium and sodium from four different Swedish forest soils and what this means for our understanding of how much base cations a soil contains. The extractions indicated that there is a statistical significant difference between the methods ability to extract base cations. Generally Aqua Regia was the most potent method, followed by HCl, EDTA, BaCl2, NH4OAc and water in decreasing order of effectiveness to extract the base cations. Linear correlations were found between EDTA, BaCl2 and NH4OAc. The internationally widely used method NH4OAc was considered to be at risk of underestimating the amount of base cations in the soil. / Försurningsproblematiken har länge varit ett känt problem i Sverige. Svavelhaltiga föroreningar som spreds från de brittiska öarna och den europeiska kontinenten ledde till att pH-värdet i regnet som föll över Sverige sjönk. Sedan upptäckten på 60-talet har aktiva åtgärder vidtagits mot utsläppen vilket har lett till en minskning av de försurande föroreningarna med 90 %. På grund av den stora utsläppsreduktionen som skett ansågs försurningsproblematiken vara under kontroll, tills nyligen då en ny etapp av för- surningen kan ha påbörjats. På grund av den ökande efterfrågan av förnyelsebar energi, i kombination med Sveriges stora skogstillgångar, har helträdsskörd av träd blivit alltmer nyttjad. Studier visar att markens baskatjonförråd utarmas i större utsträckning av helträdsskörd, då även grenar, rötter och toppar tas om hand jämfört med vanlig stamskörd då endast stammen tas med från skogen. Massbalanssimuleringar antyder att ett ökat bioupptag av baskatjoner på grund av helträdsskörd leder till en ökad biologisk försurning. Trots att många studier är överens om helträdsskördens inverkan på markens innehåll av baskatjoner visar lång- liggande försök i Sverige att skillnaderna mellan uttag av hela träd och stamved minskar med tiden. Efter en period på 40 år återstår endast små skillnader mellan avverknings- metoderna. Orsakerna till varför mätningarna och massbalansberäkningarna och simuleringarna inte stämmer överens kan vara många, t.ex. att det finns processer som kan omfördela baskatjoner från de som vanligtvis studeras. Syftet har varit att undersöka och utvärdera olika kemiska extraktionsmetoders (Aqua Regia, HCl, EDTA, BaCl2, NH4OAc och vatten) förmåga att extrahera baskatjonerna kalcium, kalium, magnesium och natrium från fyra olika skogsjordar i Sverige och vad resultaten betyder för vår uppfattning av mängden baskatjoner i marken. Extraktionerna visade att en statistiskt signifikant skillnad fanns mellan metodernas förmåga att extrahera de olika baskatjonerna. Generellt var Aqua Regia den metod som extraherade den största mängden baskatjoner, HCl, EDTA, BaCl2, NH4OAc och vatten följde i fallande ordning efter förmåga att extrahera baskatjonerna. Linjära korrelationer mellan EDTA, BaCl2 och NH4OAc upptäcktes. Den internationellt ofta använda metodiken för att extrahera baskatjoner, NH4OAc, ansågs riskera att underskatta mängden baskatjoner i marken.

År 2012 publicerades en sammanfattande syntesrapport från Energimyndigheten (2012). Rapporten fann bevis på att grotuttaget låg på ca 14 TWh/år. Rapporten visar också att Sveriges skogar kan hantera upp till 24 TWh/ år utan att orsaka allvarliga konsekvenser på omgivningen eller nästkommande generationer av träd. Studien beräknade grotens potentiella uttag utifrån insamlade analyser av markkemi, tekniska verktyg och uppskattningar. Dagens rapporter angående ämnet estimerar potentialen till ungefär densamma med en liten höjning till ca 27-30 TWh/år. Detta har satts i relation till hur olika hyggeslagrings tekniker påverkar det möjliga uttaget av grot tillsammans med hur kemin i marken påverkar trädens tillväxt och omgivningen. Grotuttaget gick ner till ca 8-9 TWh/år från år 2012 till 2019, från 14 TWh/år. Eftersom skogsägarna i Sydsverige är privatbrukare och behöver gå runt ekonomiskt för att kunna fortsätta sina verksamheter leder detta till att grotuttaget följer kostnadseffektiviteten av grot i sverige. I framtiden uppskattas det att grotuttaget kan öka drastiskt. Beroende på hur utvecklingen sker kan det verkliga uttaget skilja stort med många påverkande faktorer som t.ex. kostnadseffektivitet och utveckling av andra energikällor. / In 2012 a synthesis report was published by ”Energimyndigheten (2012)”. The report states that forest residues used as bioenergy represents around 14 TWh/year. The report also shows that Swedish forests can manage an outtake of up to 24 TWh/year without suffering from serious consequences, -on the plantation grounds or for, the next coming generation of trees. The study calculated the potential residue of forest outtake from collected analysis of soil chemistry, technical tools and estimations. Recent reports on forest residue outlet estimates a potential of about the same as 2012 with a slight rise to approximately 27-30 TWh/year. This has been put into relation of how different logging storage techniques affect the trees growth, the plantation grounds and the surroundings. The forest residue outlet went down to between 8-9 TWh/year from 2012-2019. This is because the main part of the forests in southern Sweden belongs to private owners and who experienced a decreasing economy to sell their residue. That leads to a problem, where the actual forest residue outlet is heavily dependent on the cost efficiency of forest residues. In the future it is estimated that the forest residue outlet can increase drastically. Depending on how the development proceed, the future outlet of forest residues may differ greatly depending on the future cost efficiency and how other energy sources develop and progress.

Íons polihalogenados de Si, X3Si+ (X = F, Cl), são fragmentos facilmente gerados em espectrometria de massas por ionização eletrônica de compostos de silício polihalogenados. Estes cátions possuem um elevado caráter eletrofílico e desempenham um papel importante como intermediários em processos de corrosão auxiliados por plasma utilizados na fabricação de dispositivos em microeletrônica. Esta dissertação apresenta um estudo sobre a reatividade dos íons +SiCl3, em fase gasosa, perante uma série de substratos neutros simples como água, alcoóis, amônia, aminas e algumas bases doadoras de elétrons π. As reações íon-molécula em fase gasosa foram caracterizadas do ponto de vista experimental por espectrometria de massas de ressonância ciclotrônica de íons por transformada de Fourier (FTICR) a pressões da ordem de 10-8 Torr. As reações foram acompanhadas em função do tempo de reação na cela do espectrômetro, o que permitiu a elucidação de uma série de reações sequenciais. O perfil de energia das reações e as estruturas dos íons silicênios formados nestas reações foram também caracterizados por métodos de química computacional, usando métodos ab initio e métodos baseados na teoria do funcional da densidade, a fim de elucidar o mecanismo das reações. Observou-se que o cátion +SiCl3 reage rapidamente em fase gasosa com os diversos substratos neutros através de processos semelhantes a reações de solvólise que resultam na adição do neutro seguida de eliminação de HCl. Em vários dos casos, foi possível observar a solvólise total do cátion com substituição dos três átomos de cloro. Os cálculos revelam que estas reações se processam inicialmente pela adição do eletrófilo aos centros ricos em densidade eletrônica dos substratos neutros e que estes adutos são mais estáveis que os reagentes isolados. O estado de transição destas reações envolve uma migração 1,3 de um hidrogênio e a energia calculada para o estado de transição é consideravelmente menor que a energia dos reagentes, fato este comum para reações rápidas íon/molécula em fase gasosa. Os cálculos para a espécie correspondente +CCl3 revelam que este tipo de reação não é favorável para os cátions metílicos substituídos e experimentalmente reações semelhantes não são observadas para +CCl3. No caso dos íons ClnSi(OH)3-n+ (n=1, 2 e 3), oriundos das reações de hidrólise do íon +SiCl3, observou-se reações secundárias de condensação com SiCl4 que levam a formação de espécies iônicas com ligações tipo siloxanas (-Si-O-Si-). Os cálculos teóricos sugerem que estas reações se processam inicialmente através de um intermediário tipo clorônio, R1-Cl+-R2 seguida de uma transferência formal de um átomo de Cl e rearranjo para uma estrutura tipo siloxana. / Polyhalogenated silicenium ions, X3Si+ (X = F, Cl), are common fragment ions in the mass spectra of polyhalogenated silanes obtained by electron ionization. These ions are powerful electrophiles and are believed to play a role in plasma enhanced corrosion processes and plasma enhanced chemical vapour deposition processes. In this dissertation, we present some new results on the gas-phase reactivity of the +SiCl3 ion with a number of simple n electron donor bases such as water, alcohols, ammonia, amines and some π electron donor bases. Ion-molecule reactions were characterized experimentally by Fourier transform ion cyclotron resonance mass spectrometry (FTICR) at pressures in the 10-8 Torr range. Reactions were followed as a function of trapping time of the ions in the cell of the spectrometer and this allowed for the identification of subsequent reactions of the primary product ions. The energy diagram and structure of the different silicenium ions were also characterized by computational chemistry using both ab initio and density functional theory methods in order to understand the mechanism of these reactions. +SiCl3 reacts rapidly in gas phase with various neutral substrates through processes similar to solvolysis in which the neutral substrate adds onto the silicenium ion followed by elimination of HCl. In some cases, complete solvolysis is observed with substitution of all three chlorine atoms. The calculations show that reactions proceed by initial addition of the electrophile onto the electron center of the neutral substrates giving rise to stable adducts. The transition state for these reactions involve a 1,3 hydrogen migration and the calculated energy for these transition states is less than the energy of the isolated reactants, a fact that is common to fast gas-phase ion-molecule reactions. Similar calculations for +CCl3 reveal similar solvolysis reactions to be energetically unfavourable, and in fact these reactions are not observed experimentally. Secondary reactions have been observed for the product ions ClnSi(OH)3-n+ (n = 1, 2 and 3), obtained from successive hydrolysis of +SiCl3, with the parent SiCl4 neutral. These secondary condensation reactions yield ionic species containing a siloxane type linkage (-Si-O-Si-). The theoretical calculations suggest that is that these secondary condensation reactions initially proceed via chloronium ion intermediate, R1-Cl+-R2 , followed by formal Cl transfer and rearrangement to a siloxane type structure.

Nous explorons les propriétés structurales de nanoparticules cœur-coquille, avec un cœur de ferrite MFe2O4 (M = Mn et Co) ou de ferrite mixte Mn-Zn. Ces nanoparticules sont obtenues par co-précipitation hydrothermique et sont dispersées en milieu acide par un traitement de surface empirique au nitrate ferrique, protégeant les nanograins contre une dissociation chimique par une fine couche superficielle de maghémite. La fraction volumique du cœur, de la coquille et l’épaisseur de la couche superficielle sont déterminées par dosage chimique. Nous suivons les changements structurels des nanocristaux de MnFe2O4 et CoFe2O4, pendant la durée du traitement de surface, tandis que ceux des nanoparticules de ferrite mixte Mn-Zn sont étudiés en fonction de leur teneur en zinc. Diffraction de rayons-x et de neutrons sont utilisées pour déterminer les paramètres de structure, en particulier la diffusion de cations dans les interstices de la ferrite spinelle. Pour un haut degré de fiabilité, des raffinements de Rietveld sont réalisés. Les distances inter-atomiques, l’état d’oxydation moyen et le degré d’inversion sont déterminés par spectroscopie d’absorption des rayons-x. Morphologie, cristallinité et taille des nanoparticules de ferrite mixte Mn-Zn sont étudiées par TEM/HRTEM et par diffraction des électrons. Dans les nanoparticules MnFe2O4 et de ferrite mixte Mn-Zn, on constate la présence de cations Mn3+ en environnement octaédrique, responsables de déformations anisotropes (effet Jahn-Teller). Le degré d’inversion obtenu ici diffère de celui du bulk en raison de la réduction à l’échelle nanométrique et de l'augmentation du rapport surface/volume pendant le processus de synthèse. / Structural properties of core-shell ferrite nanoparticles MFe2O4 (M = Mn and Co) and Mn-Zn ferrite nanoparticles are here investigated. The nanoparticles are synthesized by hydrothermal co-precipitation and are dispersed in acid medium thanks to an empirical surface treatment by ferric nitrate, which prevents the chemical dissociation by a thin maghemite layer incorporated at the surface of the nano-grains. Chemical titrations allow us to calculate volume fractions of core and shell, as well as the surface-layer thickness. Structural changes induced by the surface treatment are followed as a function of treatment duration in MnFe2O4 and CoFe2O4 nanocrystals. Whereas structural changes in Mn-Zn ferrite nanoparticles are investigated as a function of zinc content. X-ray and Neutron diffractions are used to determine the structural parameters, in particular cationic distribution in the spinel ferrite sites. Precise structural information with high degree of reliability is obtained by Rietveld refinements. To investigate the local structure of these materials, X-ray Absorption Spectroscopy measurements are performed, allowing determining interatomic distances, mean oxidation state and inversion degree. Morphology, crystallinity and size of mixed-ferrite nanoparticles are investigated by TEM/HRTEM and electron diffraction. In Mn-Zn ferrite nanoparticles, the presence of Mn3+ in octahedral environment is responsible for anisotropic distortions, known as Jahn-Teller effect. The inversion degree obtained in this work diverges from the bulk values due to the reduction to nanoscale and to the increase of the surface/volume ratio, associated to the synthesis process.

Íons polihalogenados de Si, X3Si+ (X = F, Cl), são fragmentos facilmente gerados em espectrometria de massas por ionização eletrônica de compostos de silício polihalogenados. Estes cátions possuem um elevado caráter eletrofílico e desempenham um papel importante como intermediários em processos de corrosão auxiliados por plasma utilizados na fabricação de dispositivos em microeletrônica. Esta dissertação apresenta um estudo sobre a reatividade dos íons +SiCl3, em fase gasosa, perante uma série de substratos neutros simples como água, alcoóis, amônia, aminas e algumas bases doadoras de elétrons π. As reações íon-molécula em fase gasosa foram caracterizadas do ponto de vista experimental por espectrometria de massas de ressonância ciclotrônica de íons por transformada de Fourier (FTICR) a pressões da ordem de 10-8 Torr. As reações foram acompanhadas em função do tempo de reação na cela do espectrômetro, o que permitiu a elucidação de uma série de reações sequenciais. O perfil de energia das reações e as estruturas dos íons silicênios formados nestas reações foram também caracterizados por métodos de química computacional, usando métodos ab initio e métodos baseados na teoria do funcional da densidade, a fim de elucidar o mecanismo das reações. Observou-se que o cátion +SiCl3 reage rapidamente em fase gasosa com os diversos substratos neutros através de processos semelhantes a reações de solvólise que resultam na adição do neutro seguida de eliminação de HCl. Em vários dos casos, foi possível observar a solvólise total do cátion com substituição dos três átomos de cloro. Os cálculos revelam que estas reações se processam inicialmente pela adição do eletrófilo aos centros ricos em densidade eletrônica dos substratos neutros e que estes adutos são mais estáveis que os reagentes isolados. O estado de transição destas reações envolve uma migração 1,3 de um hidrogênio e a energia calculada para o estado de transição é consideravelmente menor que a energia dos reagentes, fato este comum para reações rápidas íon/molécula em fase gasosa. Os cálculos para a espécie correspondente +CCl3 revelam que este tipo de reação não é favorável para os cátions metílicos substituídos e experimentalmente reações semelhantes não são observadas para +CCl3. No caso dos íons ClnSi(OH)3-n+ (n=1, 2 e 3), oriundos das reações de hidrólise do íon +SiCl3, observou-se reações secundárias de condensação com SiCl4 que levam a formação de espécies iônicas com ligações tipo siloxanas (-Si-O-Si-). Os cálculos teóricos sugerem que estas reações se processam inicialmente através de um intermediário tipo clorônio, R1-Cl+-R2 seguida de uma transferência formal de um átomo de Cl e rearranjo para uma estrutura tipo siloxana. / Polyhalogenated silicenium ions, X3Si+ (X = F, Cl), are common fragment ions in the mass spectra of polyhalogenated silanes obtained by electron ionization. These ions are powerful electrophiles and are believed to play a role in plasma enhanced corrosion processes and plasma enhanced chemical vapour deposition processes. In this dissertation, we present some new results on the gas-phase reactivity of the +SiCl3 ion with a number of simple n electron donor bases such as water, alcohols, ammonia, amines and some π electron donor bases. Ion-molecule reactions were characterized experimentally by Fourier transform ion cyclotron resonance mass spectrometry (FTICR) at pressures in the 10-8 Torr range. Reactions were followed as a function of trapping time of the ions in the cell of the spectrometer and this allowed for the identification of subsequent reactions of the primary product ions. The energy diagram and structure of the different silicenium ions were also characterized by computational chemistry using both ab initio and density functional theory methods in order to understand the mechanism of these reactions. +SiCl3 reacts rapidly in gas phase with various neutral substrates through processes similar to solvolysis in which the neutral substrate adds onto the silicenium ion followed by elimination of HCl. In some cases, complete solvolysis is observed with substitution of all three chlorine atoms. The calculations show that reactions proceed by initial addition of the electrophile onto the electron center of the neutral substrates giving rise to stable adducts. The transition state for these reactions involve a 1,3 hydrogen migration and the calculated energy for these transition states is less than the energy of the isolated reactants, a fact that is common to fast gas-phase ion-molecule reactions. Similar calculations for +CCl3 reveal similar solvolysis reactions to be energetically unfavourable, and in fact these reactions are not observed experimentally. Secondary reactions have been observed for the product ions ClnSi(OH)3-n+ (n = 1, 2 and 3), obtained from successive hydrolysis of +SiCl3, with the parent SiCl4 neutral. These secondary condensation reactions yield ionic species containing a siloxane type linkage (-Si-O-Si-). The theoretical calculations suggest that is that these secondary condensation reactions initially proceed via chloronium ion intermediate, R1-Cl+-R2 , followed by formal Cl transfer and rearrangement to a siloxane type structure.

Ce travail s'inscrit dans le cadre de recherche des propriétés superficielles des solides divisés. Nous avons étudiés les hétérogénéités morphologiques et énergétiques superficielles des kaolinites en couplant deux approches l'adsorption d'argon basse pression et la microscopie à force atomique pour l'analyse 3D des particules. Les solides utilisés sont des phyllosilicates 1:1 : deux kaolinites de référence de la Clay Mineral Society Kga1 et Kga2, une kaolinite industrielle (High Gloss), une kaolinite de Decazeville. Après purification, les échantillons ont été échangés avec des cations monovalents Li+, Na+, K+, Cs+. La modélisation des isothermes dérivées par la méthode DIS montrent que la nature des cations influencent les phénomènes d'adsorption sur les faces basales et latérales. Sur les faces basales, des cations sont présents en très faible quantité, soit fortement associé à la surface (substitutions héterovalentes), soit physisorbés sur la surface sous forme d'espèces neutres. Sur les faces latérales, les cations échangeables sont associés aux surfaces en provoquant des points de nanorugosité. Le film d'argon adsorbé est hétérogène ou les particules d'argon s'organisent autours des microreliefs générés par les cations. De ce fait, l'estimation de la lamellarité de la kaolinite par adsorption d'argon doit être effectué en présence des cations monovalents de petite taille (Li+, Na+). Cette étude a montré que la microscopie à force atomique est une bonne méthode pour la détermination des propriétés morphologiques des minéraux dans le cas des échantillons homogènes et par analyse d'un grand nombre des particules.

Les smectites en suspension aqueuse sont des argiles gonflantes largement utilisées dans l'industrie pour leurs capacités d'adsorption, d'étanchéité, de transport ou de liant. Ces propriétés sont inégales en fonction des caractéristiques minéralogiques et physico-chimiques des suspensions. Ce travail a pour but de comprendre l'action de la charge interfoliaire sur les structures construites par le système eau argile en fonction de la concentration pour des smectites homoioniques ou mixte. Son originalité est de coupler des méthodes minéralogiques, physico-chimiques et une large gamme d'essais rhéométriques.<br />Deux populations de smectites (Na+ et Ca2+) sont étudiées séparément puis en mélange. A faible concentration (inférieure à 60 g/l), les suspensions sodiques sont très visqueuses car les feuillets dispersés forment des réseaux. Les feuillets de smectite calcique sont associés en flocs aisément déformables rendant les suspensions peu visqueuses et rhéofluidifiantes. En mélange, les deux populations interagissent faiblement, lorsque le cortège d'échange d'équilibre est atteint (20 % de sodium), les viscosités sont minimales.<br />A plus forte concentration (60 à 100 g/l), les courbes d'écoulement permettent de différencier un domaine de déformation viscoélastique, un domaine d'écoulement hétérogène (bandes de cisaillement) et un domaine d'écoulement homogène. L'étude de la thixotropie révèle l'existence de deux cinétiques de déstructuration/restructuration.<br />L'étude de 12 bentonites brutes permet de monter que la rhéomètrie est un bon moyen de différenciation entre les bentonites sodique naturelle (Herschel-Bulkley), calcique naturelle (Newton) ou calcique activée (Bingham).

From the Proceedings of the 1972 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 5-6, 1972, Prescott, Arizona / The need for increased control of seepage from both natural and artificial small ponds and lakes has become more apparent with the increased frequency of their construction and use on the farm, ranch, and in recreational urban use. Seepage control methods are also becoming more numerous. Unfortunately, comparisons as to effectiveness, longevity and costs are not readily available. This paper investigates some control techniques being used in this region and evaluated them according to the above criteria. Emphasis was on the use of available physiochemical methods other than rubber membranes and concrete liners. Examples of the types of controls in use include plastic, soil compaction aids, hydrophobic chemicals and monovalent cation applications, such as sodium chloride. Some examples of the use of these methods in Arizona are shown and the results of some field comparison tests conducted using 8 x 8 square foot double -ringed infiltrometers presented. Recommendations are made of additional research that should be undertaken to improve the technology of the control of seepage losses.

Electrodialysis performance strongly depends on the boundary layer near ion exchange membranes. The thickness of the boundary layer has not been clearly evaluated due to its substantial fluctuation around the spacer geometry. In this study, the boundary layer thickness was defined with three statistical parameters: the mean, standard deviation, and correlation coefficient between the two boundary layers facing across the spacer. The relationship between the current and potential under conditions of the competitive transport between mono- and di-valent cations was used to estimate the statistical parameters. An uncertainty model was developed for the steady-state ionic transport in a two-dimensional cell pair. Faster ionic separations were achieved with smaller means, greater standard deviations, and more positive correlation coefficients. With the increasing flow velocity from 1.06 to 4.24 cm/s in the bench-scale electrodialyzer, the best fit values for the mean thickness reduced from 40 to less than 10 μm, and the standard deviation was in the same order of magnitude as the mean. For the partitioning of mono- and di-valent cations, a CMV membrane was examined in various KCl and CaCl₂ mixtures. The equivalent fraction correlation and separation factor responded sensitively to the composition of the mixture; however, the selectivity coefficient was consistent over the range of aqueous-phase ionic contents between 5 and 100 mN and the range of equivalent fractions of each cation between 0.2 and 0.8. It was shown that small analytic errors in measuring the concentration of the mono-valent cation are amplified when estimating the selectivity coefficient. To minimize the effects of such error propagation, a novel method employing the least square fitting was proposed to determine the selectivity coefficient. Each of thermodynamic factors, such as the aqueous- and membrane-phase activity coefficients, water activity, and standard state, was found to affect the magnitude of the selectivity coefficient. The overlimiting current, occurring beyond the electroneutral limit, has not been clearly explained because of the difficulty in solving the singularly perturbed Nernst-Planck-Poisson equations. The steady-state Nernst-Planck-Poisson equations were converted into the Painlevé equation of the second kind (P[subscript II] equation). The converted model domain is explicitly divided into the space charge and electroneutral regions. Given this property, two mathematical formulae were proposed for the limiting current and the width of the space charge region. The Airy solution of the P[subscript II] equation described the ionic transport in the space charge region. By using a hybrid numerical scheme including the fixed point iteration and Newton Raphson methods, the P[subscript II] equation was successfully solved for the ionic transport in the space charge and electroneutral regions as well as their transition zone. Above the limiting current, the sum of the ionic charge in the aqueous-phase electric double layer and in the space charge region remains stationary. Thus, growth of the space charge region involves shrinkage of the aqueous-phase electric double layer. Based on this observation, a repetitive mechanism of expansion and shrinkage of the aqueous-phase electric double layer was suggested to explain additional current above the limiting current. / text