We report on the surface properties of a photoresponsive surfactant that incorporates the light-sensitive azobenzene group into its tail. Cis-trans photo-isomerization of this group alters the ability of the surfactant to pack into adsorbed monolayers at an air-water interface or into aggregates in solution, causing a significant variation in bulk and surface properties upon changes in the illumination conditions. NMR studies indicate that a solution left in the dark for an extended period of time contains trans isomer almost exclusively, while samples exposed to light of fixed wavelength eventually reach a photostationary equilibrium with significant amounts of both isomers present. Dynamic surface tension studies performed on this system under different illumination conditions (dark, UV light, visible light) show profoundly different approaches to equilibrium. At concentrations well above the CMC, the same equilibrium tension is reached in all three cases, presumably corresponding to a surface saturated with the trans (more surface active) isomer. The dark sample shows a simple, single-step relaxation in surface tension after creation of a fresh interface, while the UV and visible samples exhibit a more rapid initial decrease in tension, followed by a plateau of nearly constant tension, and end with a final relaxation to equilibrium. It is hypothesized that this behavior of the UV and visible samples is caused by competitive adsorption between the cis and trans isomers present in these mixtures. Presumably the cis surfactant reaches the interface more quickly, leading to a cis-dominated interface having a tension value corresponding to the intermediate plateau, but is ultimately displaced by the trans isomer. Diffusional time scale arguments which consider the extremes of possible micellar dissolution rates are used to analyze the relaxation data of the dark sample, and the results indicate that micellar dissolution in these samples is slow. / Singapore-MIT Alliance (SMA)

Les fluides spéciaux (mélanges d’hydrocarbures utilisés comme solvants pour applications diverses) sont produits à partir de l’hydrodésaromatisation des charges pétrolières (naphta et distillats moyens) initialement riches en aromatiques. Leur mise en marché respecte une exigence environnementale (moins de 100 ppm en aromatique) parfois difficile à atteindre compte tenu de la composition initiale de la charge. Par conséquent, à partir de l’identification des molécules réfractaires à l’hydrogénation, un choix de molécules modèles réparti selon trois familles, les monoaromatiques (toluène, indane, tétraline, cyclohexylbenzène, nonylbenzène), les diaromatiques (naphtalène, biphényle) et les triaromatiques (phénanthrène), a permis d’étudier leur réactivité dans les conditions opératoires d’hydrogénation.A partir d’une approche expérimentale couplée à la modélisation cinétique, les schémas réactionnels et une échelle de réactivité ont été établis pour ces molécules modèles. Leur transformation conduit majoritairement du produit totalement hydrogénés. Les monoaromatiques sont les plus réactifs alors que les triaromatiques sont les moins réactifs. Néanmoins, en mélange, le pouvoir inhibiteur d’une molécule sur l’hydrogénation des autres aromatique augmente avec son aromaticité. Le phénanthrène est alors la molécule la plus inhibitrice. Les polyaromatiques engendrent alors une accumulation de monoaromatiques rendant difficile l’hydrogénation totale des charges pétrolières. Ceci est dû à des effets de compétition à l’adsorption à la surface du catalyseur entre les aromatiques qui ont été chiffrés en déterminant à partir d’un modèle suivant le formalisme de Langmuir-Hinshelwood. / Special fluids (hydrocarbon mixture used as solvents for various applications) are produced from deep hydrodearomatization of petroleum distillates (naphta and middle distillates) with high aromatic contents. Their commercialization follows a stringent environmental regulation (less than 100 ppm of aromatics) that is not always reachable due to the initial feedstock composition. Therefore, from the refractory molecules identification for hydrogenation, a selection of three families of model molecules, monoaromatics (toluene, indane, tetralin, cyclohexylbenzene, and nonylbenzene), diaromatics (naphthalene, biphenyl) and triaromatics (phenanthrene) allowed to study their reactivity in the hydrogenation operating conditions.By an experimental approach coupled with kinetic modeling, reaction schemes and a reactivity scale were established for these model molecules. Their transformation leads to the major formation of the saturated product. Monoaromatics are the most reactive while triaromatics are the less reactive. However, in mixture, the inhibiting strength of a molecule on the other aromatic hydrogenation increases with their aromaticity. Therefore, phenanthrene is the strongest inhibitor. Polyaromatics provoke an accumulation of monoaromatics generating a challenging petroleum distillates total hydrogenation. This is due to competitive adsorption effects at the catalyst surface between aromatics that was quantified from a model following the Langmuir-Hinshelwood formalism.

In order to optimize the synthesis of metal nanoparticle-polymer systems, there are certain processes which must be understood. Perhaps the most important one is the selective interfacial interaction between the block copolymer and the growing metal nanoparticles. To investigate this interaction, four different approaches were taken. The first approach looked at the strength of interaction between the competing blocks of the copolymer and the metal nanoparticles surface. The second approach looked at the effect of polymer architecture on the metal nanoclusters. The third approach looked at the polymer composition and solvent effects on the phase behavior of the metal nanocluster-block copolymer nanocomposite. Finally, the influence of the metal precursor on the rate of the decomposition was examined. It was found that adsorbed layers of PS on the cobalt nanoparticles are completely displaced by PMMA when the solvent is a common good solvent. An adsorbed layer of only PMMA is also obtained through competitive adsorption from a common good solvent. However, in a selective solvent that is poor for PS, sequential adsorption leads to the formation of mixed layers. In homopolymer solutions, the cluster size reaches a minimum at a finite chain MW. In the case of diblock copolymers, the only parameter (for a fixed copolymer concentration) controlling the cluster size in suspensions of di-block copolymers is the molecular weight of one block, in this case PMMA, and is indifferent to other parameters including the molecular weight of the other block (PS) or the solvent quality. It was also found that the spatial distribution of the metal clusters synthesized in-situ coincided with the morphology dictated by thermodynamically-driven microdomain structure of the block copolymer. Moreover, the overall final morphology of the nanocomposite is locked into place while in solution, and fast solvent evaporation does not cause this morphology to change. Finally, results showed that the rate of nanocomposite synthesis occurred faster in the PS suspensions compared to PMMA, indicating that chemical bonds between PMMA and the cobalt nanoclusters slowed the thermal decomposition of the metal precursor. So the PMMA chains provided sites for nucleation, but did not necessarily aid particle growth.

The Canadian mining industry is a multi-billion-dollar effort and one of Canada’s largest industrial sectors, creating jobs and security across the country. Certain practices employed within the industry have led to great developments, while increasing productivity and reducing costs. One such practice is the use of nitrogen-based explosives, which have serious environmental repercussions, namely the introduction of large quantities of ammonia into the ecosystem through means of complex blends of wastewaters also containing various metals. These explosive impacted mining wastewaters (EIMWW), must be treated before being introduced into natural waterways as ammonia pose several threats to the environment including the depletion of dissolved oxygen as well as acute toxicity for fish. Newterra, a provider of modular treatment solutions for water, wastewater and groundwater, requested an assessment of the feasibility of a brine-based ion exchange (IE) system for the removal of ammonia from EIMWW, that would be simple to operate and could be deployed in remote areas. The following thesis consists of an evaluation of several IE materials, to determine the feasibility of an IE system for the treatment of real EIMWW. Potassium and calcium were determined to be the problematic ions present in the EIMWW, potentially leading to competitive adsorption issues. This was accomplished by comparing batch IE isotherms for five different IE materials; one natural zeolite (clinoptilolite), one modified clinoptilolite (Resintech SIR-600), and three synthetic resins (Purolite SSTC60, Amberlite IR120 Na and Bojie BC121 H) using both a synthetic single-solute ammonia wastewater and real EIMWW with a total ammonia nitrogen (TAN) concentration of 3.87 meq TAN/L (~70 mg/L). The three synthetic resins produced the largest reductions in capacities from the effects of competition and featured the following exchange capacities when treating EIMWW: 0.24±0.03, 0.25±0.01 and 0.22±0.001 meq TAN/g for the Purolite, Amberlite and Bojie resins respectively. These were respective reductions of 87±0.96, 86±0.80 and 87±0.03 % compared to their single-solute TAN solution capacities. The two zeolites featured higher multi-component exchange capacities; 0.32±0.04 meq TAN/g for the clinoptilolite and 0.42±0.01 meq TAN/g for the SIR-600. Furthermore, calcium was found to pose minimal competitive effects and potassium was responsible for the most capacity reduction. Batch regeneration experiments with the clinoptilolite and SIR-600 were undertaken to evaluate the long-term performance of both materials. These consisted of IE isotherms with the EIMWW followed by material regeneration with various regenerants including a 2.5 % KCl/2.5 % NaCl, a 5 % KCl, and a 2.5, 5 and 10 % NaCl solution. Ultimately, the 5 % and 10 % NaCl solutions were the only regenerants to result in an increase of capacity with the 10 % solution featuring higher capacities for both materials. After four exchange/regeneration cycles using a 10 % NaCl brine, the clinoptilolite produced the following capacities: 0.16±0.01 meq Ca2+/g, 0.39±0.06 meq K+/g and 0.34±0.02 meq TAN/g. For the same conditions the Resintech SIR-600 resulted in the following capacities: 0.12±0.01 meq Ca2+/g, 0.52±0.01 meq K+/g and 0.46±0.00 meq TAN/g. Based on the higher TAN exchange performance, column studies were performed with the Resintech SIR-600 to validate the material’s performance using a more realistic mode of operation similar to real world applications. This was accomplished by comparing the capacities of the material using both a single solute TAN wastewater as well as the EIMWW and a breakthrough concentration criterion of 0.55 meq TAN/L (~10 mg/L). The EIMWW featured breakthrough after only 50 bed volumes, comparatively to the synthetic TAN solution where breakthrough occurred after 274 bed volumes, indicating that competition played a significant role in the performance of the system.

Pour ajuster la rhéologie des matériaux cimentaires et modifier leurs principales propriétés d'écoulement, l'utilisation des polymères organiques est nécessaire. L'objectif de cette thèse est de définir un cadre général physique permettant de caractériser qualitativement les conséquences de l'introduction d'un ou plusieurs polymères dans une pâte de ciment. De façon à s'affranchir des spécificités chimiques de chaque molécule, nous prenons le parti d'adopter une approche physique générale dans laquelle un polymère est défini par sa localisation (en solution ou à la surface d'un grain) et par sa taille caractéristique (en solution ou à la surface d'un grain). Nous sélectionnons des polymères couvrant la gamme de molécules disponibles lors de la formulation d'un matériau cimentaire : super-plastifiants, agents de viscosité, retardateurs de prise, floculants. Dans un premier temps, nous étudions le comportement des polymères dans le fluide interstitiel d'une pâte de ciment. Nous mesurons leurs rayons hydrodynamiques en solution et leur influence sur la viscosité du fluide interstitiel d'une pâte de ciment. Nous montrons qu'au premier ordre, la conformation, en régime dilué, de la majorité des polymères étudiés ici et tirés de la littérature, peut être décrite par la même courbe maitresse en fonction de la masse molaire. Nous identifions la fraction volumique des polymères en solution comme le paramètre principal qui est à même de capturer la physique dominante et commune à la majorité des polymères étudiés ici et régissant leur comportement macroscopique en solution. Nous étudions ensuite le comportement des polymères dans une pâte de ciment. Nous mesurons leur adsorption à la surface des particules de ciment et nous analysons les résultats obtenus dans deux régimes asymptotiques de la littérature: le régime d'adsorption à faible taux de couverture de surface et le régime d'adsorption à la saturation qui nous donnent respectivement des informations sur l'affinité intrinsèque du trio polymère/surface/solvant et sur la conformation des polymères adsorbés à la saturation. Nous discutons alors les valeurs d'affinité et d'adsorption à la saturation mesurées à la lueur des paramètres et des structures moléculaires de nos polymères. Dans une troisième partie, nous rappelons les origines physiques microscopiques du comportement rhéologique d'une pâte de ciment. Nous identifions, dans le cas où les polymères n'introduisent pas de nouvelles forces dans le système deux paramètres principaux, la distance inter-particulaire et la viscosité du fluide interstitiel, qui peuvent être ajustés par l'ajout de polymères et entrainer des changements majeurs dans la rhéologie d'une pâte de ciment standard. Dans une dernière partie, nous étudions la compétition d'adsorption entre polymères à la surface des particules de ciment. Nous proposons tout d'abord un protocole expérimental basé sur des mesures de diffraction dynamique de la lumière nous permettant de distinguer les adsorptions respectives de deux polymères sur une même surface. Nous illustrons ensuite la compétition d'adsorption et l'utilisation potentielle qui peut être faite de cette technique en étudiant successivement les compétitions d'adsorption entre un super-plastifiant et trois autres espèces adsorbantes : des ions sulfates, un retardateur de prise et un agent de viscosité. Nous montrons que, selon le taux de couverture de surface, cette compétition peut être plus au moins marquée et ses conséquences rhéologiques plus au moins drastiques. L'approche physique proposée ici consistant à ignorer autant que possible les spécificités chimiques des macromolécules étudiées atteint, à plusieurs occasions, ses limites. Lorsque c'est le cas, nous regroupons à la fin des parties concernées les discussions et analyses des situations où l'introduction d'un polymère dévie de la réponse générique au premier ordre obtenue pour l‘ensemble des autres macromolécules étudiées / To fulfil the rheological requirements of cementitious materials, mix designer engineers use various polymers. Theses admixtures either stay in the suspending fluid modifying its viscosity or adsorb at the surface of cement particles modifying their surface properties and their interactions. In this work, we propose a general physical frame allowing for the description of the consequences of the addition of one or various polymers on the rheology of cement paste. We identify two main parameters affecting the rheology of cement paste, which can be modified by chemical admixtures. These parameters are the inter-particle distance and the viscosity of the suspending fluid. Our solution viscosity and hydrodynamic radii measurements in synthetic cement pore solution suggest that the volume fraction of polymers is the main parameter enhancing the viscosity of the suspending fluid. By means of rheological and adsorption measurements, we study the effects of polymers on the inter-particle distance and the rheological behavior of the suspension. Finally, we study the competitive adsorption between polymers at the surface of cement particles. We propose a technique based on dynamic light scattering measurements allowing for the measurement of the respective adsorption of two polymers at the surface of cement particles. We then study the competitive adsorption between a super-plasticizer and sulfate ions, retarder or viscosity enhancing admixtures

Foam fractionation is an adsorptive bubble separation technology that has shown potential as a replacement to the more costly and non-sustainable traditional downstream processing methods such as solvent extraction and chromatography for biological systems. However biological systems mostly tend to be a mixture of surface active species that complicates the foam fractionation separation. In this thesis a detailed experimental study on the application of foam fractionation to separate a well-defined surfactant-protein mixture was performed with emphasis on the competitive adsorption behaviour and transport processes of surfactant-protein mixtures in a foam fractionation process. Surface tension and nuclear magnetic resonance (NMR) measurements showed that nonionic surfactant Triton X−100 maximum surface pressure, surface affinity and diffusivity were a factor of 2.05, 67.0 and 19.6 respectively greater than that of BSA. Thus Triton X−100 dominated the surface adsorption at an air-water surface by diffusing to the surface and adsorbing at the surface faster than BSA. This competitive adsorption behaviour was observed in foam fractionation experiments performed for Triton X−100/BSA mixtures for different feed concentration ratios and air flow rates. The recovery and enrichment of Triton X−100 were found to increase and decrease respectively with increasing air flow rate for all foam fractionation experiments as expected for a single component system. However the recovery and enrichment of BSA were both found to increase with increasing air flow rate for high feed concentrations of Triton X−100.Bubble size measurements of the foamate produced from foam fractionation experiments showed that at steady state conditions the bubbles rising from the liquid pool were stabilised by BSA. However at the top of the column the recovery of Triton X−100 in the foamate (75% to 100%) was always greater than the recovery of BSA (13% to 76%) for all foam fractionation experiments. In addition, for high feed concentrations of both components and at low air flow rates, the enrichment of BSA remained at almost unity for most experiments and only increased when the recovery of Triton X−100 reached 100%. Thus it was concluded that Triton X-100 displaced the adsorbed BSA from the surface. The foam drainage properties of Triton X−100/BSA mixtures were characterised using two methods; forced foam drainage and from pressure profiles of steady state foam fractionation experiments (pressure method). The drainage data from the forced foam drainage was found not to be compatible with experimental foam fractionation results, by indicating that stable foam was not produced during the foam fractionation experiments. However stable foam was repeatedly produced during foam fractionation experiments. The drainage data from the pressure method was found to be in close agreement to experimental foam fractionation experiments. The work in this thesis takes a significant step beyond the literature experimental foam fractionation studies for multicomponent systems. In addition to investigating the effect of foam fractionation process parameters on the separation of mixed systems, the results from the characterisation studies of surface adsorption and foam properties provided insight and deeper understanding of the competitive adsorption behaviour of surfactants and proteins in a foam fractionation process.

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A large number of organic contaminants are commonly found in industrial and municipal wastewaters. Aromatic compounds, such as phenol, aniline and their derivatives, are contaminants of high priority and usually coexist in waste streams from industries of, for example, aromatic amine compounds and ammonolysis of phenols. Thus, for proper unit design to remove contaminant mixtures by adsorption, multi-component adsorption models are necessary. The present work was aimed at examining the applicability of Ideal Adsorbed Solution Theory (IAST), a prevailing thermodynamic model, and its derivative i.e. Segregated IAST (SIAST) and Real Adsorbed Solution Theory (RAST) to multi-solute adsorption from the aqueous phase, specifically, bi-solute adsorption of phenols, anilines and nitrobenzene onto a hyper-crosslinked polystyrene resin, MN200. Based on the experimental bi-solute adsorption isotherms, we have successfully developed methods for modeling with RAST incorporated with Wilson equation, Nonrandom two-liquid (NRTL) model, and an empirical four-parameter equation developed in this work. It turns out that our proposed four-parameter equation can fit the activity coefficients, γ_(i ), better than the other two equations and thus enhanced the accuracy of RAST in predicting bi-solute adsorption equilibrium. Besides successfully developing methods for properly designing binary-solute batch experiments and accurately modeling with RAST, two empirical linear relationships have been developed for the adsorption of a number of infinite dilute solutes in the presence of a major contaminant (either 4-methylphenol or nitrobenzene). Results show that polyparameter linear free energy relationships have a great potential in predicting adsorbed phase activity coefficients of solutes when the adsorbed amounts are dominated by the major contaminant and the adsorbed mixture resembles infinite dilute solution. Activity coefficients under such conditions were represented by〖 γ〗_i^∞ and were successfully extrapolated to γ_(i )at non-infinite conditions by γ_(i )models i.e. Wilson equation. To the best of our knowledge, this is the first systematic study predicting adsorbed phase activity coefficients for bi-solute adsorption. In addition, our tri- and tetra-solute adsorption data showed that the predominating solute, NB in this case, solely contributed to the competitive effect while the dilute solutes tend not to interact with each other. This indicates that for each solute, the competitive effects can be independently considered and a multi-component system with n components but only one component dominating can be treated as (n-1) bi-solute systems separately. This will significantly simplify the calculation for modeling multi-component adsorption while it is also close to many real systems where there is one major contaminant or a large amount of NOM in present. Our findings have proved a major step forward to accurately modeling multi-solute adsorption for proper unit design of adsorption processes. / Civil Engineering

The adsorption behavior of silicic acid and arsenite alone and competitively on goethite over a broad pH range (3-11) at environmentally relevant concentrations was investigated utilizing pH adsorption data and zeta potential measurements. Both addition scenarios (Si before As(III) and As(III) before Si) were examined. The results of the adsorption experiments and zeta potential measurements were then used to model the single ion and competitive ion adsorption on goethite with the CD-MUSIC model implemented in the FITEQL 4.0 computer program. Silicic acid adsorption was reduced by the presence of arsenite for all but one of the adsorption scenarios examined, while in contrast silicic acid had little effect upon arsenite adsorption. However, the presence of silicic acid, regardless of the addition scenario, dramatically increased the arsenite equilibrium solution concentration over the entire pH range investigated. The CD-MUSIC model was able to predict the single ion adsorption behavior of silicic acid and arsenite on goethite. The modeled zeta potential data provided further evidence of the CD-MUSIC model's ability to describe the single anion adsorption on goethite. Our model was also able to collectively describe adsorption and zeta potential data for the low Si-arsenite adsorption scenario quite well however, our model under-predicted silicic acid adsorption for the high Si-arsenite competitive scenario. / Master of Science