The objective of this work was the development of an efficient adsorbent for irreversible immobilization of heavy metals in contaminated soils. The adsorbent was prepared by pillaring montmorillonite with silica followed by the grafting of a chelate ligand onto its surface. Its structure was studied by the Brunauer, Emmett, and Teller Method adsorption of N2, Dynamic Light Scattering, and Scanning Electron Microscopy. The adsorption capacity of the organoclay was measured by its mixing with contaminated kaolin soil samples and by analysis of heavy metal contents in leachate. The adsorbent was efficient in immobilization of heavy metals in both neutral aqueous and acidic media. In addition, the adsorbent was efficient in environmental samples reducing the concentration of iron in all samples in aqueous and acidic media. As a result, the adsorbent can be used for reduction of heavy metal leaching from contaminated sites.

In the Swedish concept for final disposal of spent nuclear fuel, referred to as KBS-3, a three-layered protection system is used. The system consists of a copper canister holding the spent nuclear fuel deposited 500 meters in a repository built in groundwater saturated granitic rock. The copper canisters are placed in deposition holes, buffered and backfilled by bentonite clay. One of the challenges associated with this system is the long-term exposure of the engineered barriers i.e. the canister including the spent fuel and the cast iron insert as well as the bentonite buffer to ionizing radiation. The possible effects of radiation on the materials in the engineered barriers have been studied not only by the Swedish Nuclear Fuel and Waste Co (SKB), but also by academia nationally and internationally. In this work, literature studies have been carried out to investigate whether all possible/potential effects of ionizing radiation from the spent nuclear fuel on the engineered barriers have been considered by SKB. Apart from a general summary of the relevant issues in chapter one, regions within the KBS-3 design where enhanced radiation may occur have been identified and the related radiation induced processes have been summarized in chapter two. These issues include effects of water-radiolysis on the spent fuel, the cast-iron insert and other ferrous materials, the copper shell and the bentonite buffer. Three types of possible damages have been identified: the microstructural defects in the ferrous materials by direct radiation, the radiation-induced microstructural alterations of the spent fuel and the bentonite and radiation-induced oxidation i.e. dissolution of the fuel and corrosion of the ferrous metals and the copper. The relevant SKB documents have been identified (in chapter 3) to be the SR-Site main report, the underlying Process reports and reports of FUD-programs. Apart from these documents, other SKB technical reports and open literature are used as basis for assessing whether all the issues mentioned in chapter two of this study have been considered by SKB.  According to the assessment, most of the significant issues mentioned in chapter two have been mentioned and discussed in the identified SKB documents. In the main safety assessment, i.e. the SR-Site project, the significance of most of the radiation processes has been based on dose levels expected at the different regions within the KBS-3 design. Irrespective of the assessments in SR-Site though, the current understanding of the relevant issues and plans for future research efforts summarized in FUD-programs reflect the research developments. However, the recent developments in understanding of radiation-induced effects on montmorillonite and the corrosion of copper in argon atmosphere need to be given due importance in coming FUD-programs. A separate investigation of radiation effects on FSW-joints may contribute to removal of the remaining uncertainties. In addition, mechanism involved in radiation-induced fuel dissolution and copper corrosion may require more research efforts than those planned. / Det svenska konceptet för slutförvar av använt kärnbränsle, KBS-3, består av tre barriärer som är tänkt att skydda omgivningen mot joniserande strålning från använt kärnbränsle. Systemet består av specialtillverkade kopparkapslar som innehåller det använda kärnbränslet. Kapslarna förvaras i deponeringshål 500 meter ner i berggrunden och är inneslutna i bentonitlera. En av frågeställningarna associerade med djupt geologiskt förvar av kärnbränsle är hur de konstruerade barriärna, alltså kopparhöljen som omsluter gjutjärninsatsen och det använda kärnbränslet samt bentonitleran, kan påverkas av joniserande strålning från det använda kärnbränslet. Möjliga strålningseffekter på de skyddande barriärna har studerats nationellt och internationellt. Syftet med denna studie var att utvärdera huruvida SKB har i sina säkerhetsanalyser av slutförvaret tagit tillräcklig hänsyn till effekter av joniserande strålning på de konstruerade barriärna. Studien består av tre kapitel där kapitel 1 utgör en generell sammanfattning av frågeställningar kopplade till KBS-3 barriärer. I kapitel 2 har områden i och omkring de konstruerade barriärna där joniserande strålning från använt kärnbränsle kan förekomma identifierats och möjliga strålningsinducerade processer i dessa områden sammanfattats. Tre typer av möjliga strålningsinducerade skador har identifierats: 1) strålningsinducerade mikrostrukturella defekter i metaller som förekommer i systemet, 2) strålningsinducerade mikrostrukturella förändringar i använt kärnbränsle och i bentonitleran samt 3) strålningsinducerad oxidation, dvs. upplösning av det använda kärnbränslet och korrosion av metaller som förekommer i systemet. SKB-dokumenten som identifierats (i kapital 3) som relevanta för utvärderingen i denna studie är följande: Säkerhetsanalysen (SR-Site), tekniska rapporter som ligger till grund för SR-Site och FUD-programmen. Enligt bedömningen i denna studie har SKB tagit hänsyn till de flesta relevanta frågeställningarna kopplade till strålningsinducerade effekterna på de konstruerade barriärna. I SR-Site har de flesta bedömningar relaterade till och om signifikansen hos de strålningsinducerade processerna baserats på doser och dosrater som förväntas förekomma i och omkring de konstruerade barriärna. Oavsett bedömningarna i SR-Site har dock de mest relevanta frågeställningarna tagits upp i FUD-programmen och framtida forskningsinsatser i enlighet med det som av SKB har uttryckts som behov av en utökad processförståelse. Dessa frågeställningar reflekterar väl de mest signifikanta utvecklingarna som rapporterats i öppna vetenskapliga studier om strålningsinducerade processer som kan förekomma i ett djupt geologiskt förvar för använt kärnbränsle. De senaste rapporterade observationerna om strålningseffekter på montmorillonit och kopperkorrosion i argonatmosfär måste dock tas upp och diskuteras i de kommande FUD-programmen. Separata studier av strålningseffekter på koppardelar som har behandlats med FSW-teknik rekommenderas. För att uppnå en bättre och djupare förståelse för de förekommande mekanismerna i strålningsinducerad upplösning av använt kärnbränsle krävs sannolikt mera forskningsinsatser än de planerade.

In this work 23Na MAS NMR was validated as a successful quantitative method for studies of exchanging sodium in bentonites useful, in particular, for studies of ion-exchange kinetics. Na-enriched bentonites equilibrated in a re-circulated process water at iron-oxide pelletizing plants may acquire properties of Ca-bentonites after already 20 minutes of the equilibration time, since >50 % of sodium ions will be exchanged by calcium ions during first minutes of bentonite placed in contact with the process water. It was shown that all sodium activated bentonites used in this study exchange >50% of sodium in Na+/Ca2+ and ca 20 % of sodium in binary Na+/Mg2+ systems with the same bentonite/solution ratio and same concentrations of these ions in aqueous solutions as in the process water at a pelletizing plant. In total, approximately 50 % of the exchangeable sodium in original bentonites was exchanged after equilibrating of bentonites in the process water already after 20 minutes. Experimental Na+/Ca2+ exchange curves for ‘model’ Ca2+(aq) solutions and for process water are very similar as Ca2+ is the dominant constituent in the process water. Since bivalent ions (Ca2+ and Mg2+) that present in the process water readily replace Na+ ions, Na-bentonite transforms into Ca- or Mg- bentonite, which have worse rheological, swelling and, therefore, binding properties. This ion-exchange process can influence the binder performance in the pelletizing process. Taking into account that fluorapatite is one of the components present in a blend of minerals processed, possible interactions between orthophosphate (the principal anionic component of apatites) and bentonites in aqueous suspensions are considered. It was found that sorption of orthophosphate on Ca-montmorillonite follows a different pattern from sorption of orthophosphate on aluminum oxides and kaolinite. While there is a small amount of sorption below pH 7, which may involve inner-sphere complexation and precipitation of AlPO4 to Al-OH edge sites on the montmorillonite crystals, most sorption of orthophosphate occurs at higher pH. Both macroscopic sorption measurements and solid-state 31P MAS NMR suggest that above pH 7 there is precipitation of proton depleted calcium phosphate phases. Based on both 31P chemical shifts and 31P chemical shift anisotropies it was concluded that the principal precipitated phased are most likely ‘brushite-like’ phases. Very short spin-lattice T2(31P) relaxation times (≤100 μs) for the orthophosphate/bentonite systems can possibly be explained by the presence of paramagnetic Fe in bentonites. Since there are insufficient concentrations of soluble Fe species in the supernatant solution that may give rise to the observed effects, it is likely that orthophosphate is precipitated as thin layers on the surfaces of montmorillonite crystals, where phosphorus may interact with Fe atoms present in the crystal lattice. PO4-tetrahedra in sorbed species can be also distorted giving rise to a larger 31P CSA than for pure ‘apatite-like phases’. 29Si MAS and 1H-29Si CP/MAS NMR experiments on bentonite samples also performed in this work provide information about impurities of quartz in bentonites, a level of substitution of aluminum by iron atoms in the structure of montmorillonite and about the degree of hydration of montmorillonite. 29Si NMR experiments on bentonite incubated with waterglass in aqueous suspensions at concentrations of sodium silicates as in the process water demonstrated that one can follow the process of polymerization of waterglass in solutions and also detect sodium silicates polymerized on surfaces of bentonites already after 1 hour of incubation. Polymerized waterglass sorbed on bentonite surfaces may also alter rheological, swelling and, therefore, binding properties of sodium-activated bentonites used in pelletization of iron-oxide ores.

Carbon capture, utilization and storage (CCUS) in confined saline aquifers in sedimentary formations has the potential to reduce the impact of fossil fuel combustion on climate change by storing CO2 in geologic formations in perpetuity. At PT conditions relevant to CCUS, CO2 is less dense than the pre-existing brine in the formation, and the more buoyant CO2 will migrate to the top of the formation where it will be in contact with cap rock. A typical cap rock is clay-rich shale, and interactions between shales and CO2 are poorly understood at PT conditions appropriate for CCUS in saline formations. In this study, the interaction of CO2 with clay minerals in the cap rock overlying a saline formation has been examined, using Na-rich montmorillonite as an analog for clay-rich shale. Attenuated Total Reflectance -- Fourier Transform Infrared Spectroscopy (ATR -FTIR) was used to identify potential crystallographic sites (AlAlOH, AlMgOH and interlayer space) where CO2 could interact with montmorillonite at 35"C and 50"C and from 0-1200 psi.  Analysis of the data indicates that CO2 that is preferentially incorporated into the interlayer space, with dehydrated montmorillonite capable of incorporating more CO2 than hydrated montmorillonite. No evidence of chemical interactions between CO2 and montmorillonite were identified, and no spectroscopic evidence for carbonate mineral formation was observed.  Further work is needed to determine if reservoir seal quality is more likely to be degraded or enhanced by CO2 - montmorillonite interactions. / Master of Science

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An integrated program has been developed to explore the reactivity of 2:1 phyllosilicates (biotite and the clays montmorillonite, hectorite, and nontronite) with respect to acid dissolution using in situ atomic force microscopy (AFM). Three techniques are described which make it possible to fix these minerals and other small particles to a suitable substrate for examination in the fluid cell of the atomic force microscope. A suite of macros has also been developed for the Image SXM image analysis environment which make possible the accurate and consistent measurement of the dimensions of clay particles in a series of AFM images, so that dissolution rates can be measured during a fluid cell experiment. Particles of biotite and montmorillonite were dissolved, and their dissolution rates normalized to their reactive surface area, which corresponds to the area of their edge surfaces (A_e). The A_e-normalized rates for these minerals between pH 1-2 are all ~10E^-8 mol/m²*s, and compare very well to other A_e-normalized dissolution rates in the literature. Differences between the A_e-normalized rates for biotite and the BET-normalized rates (derived from solution chemical studies) found in the literature can be easily explained in terms of the proportion of edge surface area and the formation of leached layers. However, the differences between the A_e-normalized montmorillonite rates and the literature values cannot be explained the same way. Rather, it is demonstrated that rates derived from solution studies of montmorillonite dissolution have been affected by the colloidal behavior of the mineral particles. Finally, the dissolution behavior of hectorite (a trioctahedral smectite) and nontronite ( a dioctahedral smectite) were compared. Based on the differential reactivity of their crystal faces, a model of their surface atomic structures is formulated using Hartman-Perdock crystal growth theory, which explains the observed data if it is assumed that the rate-determining step of the dissolution mechanism is the breaking of connecting bonds between the octahedral and tetrahedral sheets of the mineral structure. / Ph. D.

With advantages of high cation exchange capacity, swelling-shrinking property and large specific surface area, monmtorillonite is chosen as a carrier and modified with Fe3+ saturation for estrogen decontamination. 17β-Estradiol (βE2) has highest estrogenic activity among estrogens and is selected as representative compound. Rapid βE2 transformation in the presence of Fe3+ - saturated montmorillonite in aqueous system was observed and βE2 oligomers were the major βE2 transformation products. About 98% of βE2 were transformed into oligomers which are >107 times less water-soluble than βE2 and therefore are much less bioavailable and mobile. Fe3+ -saturated montmorillonite catalysis achieved highest βE2 removal efficiency at neutral solution pH and higher temperature. Common cations did not have impact on the reaction efficiency. Dissolved organic matter slightly reduced βE2 removal efficiency. Regardless of wastewater source, ~40% βE2 removal efficiency was achieved for wastewater effluents when they were exposed to same dosage of Fe3+ -saturated montmorillonite as that for simple water systems which achieved ~83% removal efficiency. For real wastewater that contained higher organic matter, higher dosage of Fe3+ -saturated montmorillonite would be needed to create available reaction sites for βE2. This thesis also reports that Fe3+ -saturated montmorillonite effectively deactivate wastewater microorganisms. Microbial deactivation rate was 92±0.6% when secondary wastewater effluent was mixed with Fe3+ -saturated montmorillonite at 35 mg/mL for 30 min, and further increased to 97±0.6% after 4-h exposure. Freeze-drying Fe3+ -saturated montmorillonite iii after each usage resulted in 82±0.5% microbial deactivation efficiency even after fourth consecutive use. For convenient application, Fe3+ -saturated montmorillonite was further impregnated into filter paper through wet-end addition and formed uniformly impregnated paper. Scanning electron microscopy (SEM) imaging showed Fe3+ -saturated montmorillonite was evenly dispersed over cellulose fiber surface. When filtering 50 mL and 200 mL water spiked with live Escherichia coli (E. coli) cells at 3.67×108 CFU/mL, Fe3+ -saturated montmorillonite impregnated paper with 50% mineral weight loading deactivated E. coli with 99% and 77%, respectively. Dielectrophoresis and impedance analysis of filtrate confirmed that the deactivated E. coli passing through Fe3+ -saturated montmorillonite paper did not have trapping response due to higher membrane permeability and conductivity. The results demonstrate feasibility of using Fe3+ -saturated montmorillonite impregnated paper for convenient point-of-use drinking water disinfection. / Ph. D.

Nanocomposites have been receiving a lot the attention in the last decade from both industry and academia, since a small amount of nanofiller can significantly improve the materials properties. In the field of thermoplastics, polypropylene (PP) is one of the most used materials , due its easy processability, good balance of mechanical properties, and low cost. However, PP has certain shortcomings such as poor gas barrier and low thermal stability which limit its application. In order to be classified as nanocomposite the material needs to have at least one phase with one dimension less than 100nm. The properties achieved by nanocomposites will depend on the type of polymer, type of dispersed phase (filler), surface interaction between filler and polymer, and the production method. Nanofillers present many shapes and sizes, but they can be grouped in nanoparticles, nanotubes and nanoplates. Montmorillonite (MMT) is a clay that has been extensively studied to produce PP nanocomposites, due to its availability, high aspect ratio, high modulus and high cation exchange capacity, characteristics that result in composite with improved properties. Three different morphologies can be observed in PP/MMT nanocomposites: agglomerates (similar to the conventional composites); intercalated; or exfoliated. Among these morphologies, exfoliation is the most desirable and the hardest to be achieved in PP/MMT nanocomposites. Several methods have been used to produce PP nanocomposites. They can be grouped in three main groups: solution blending; melt processing; and in situ polymerization. In order to produce an exfoliated nanocomposite, some methods have assisted the exfoliation using supercritical fluids. Supercritical carbon dioxide is by far the most explored one. Polypropylene is a semi-crystalline polymer and its properties rely on amount of its crystallinity, which is related to its stereochemical configurations. Isotactic PP and syndiotactic PP result in a semi-crystalline polymer while atactic results in an amorphous polymer. Two catalyst systems can be used to produce isotactic PP: Metallocene and Ziegler-Natta (ZN). This research study was carried out in order to develop an appropriated process to produce PP/MMT nanocomposites with a high level of exfoliation using in situ polymerization assisted by supercritical propylene. The main idea is to use supercritical propylene to treat the montmorillonite before polymerization. In this process, the small molecules of propylene diffuse inside the clay galleries under supercritical conditions (high pressure and temperature) until reaching complete saturation. Once this saturation is reached the mixture of polypropylene and clay is catastrophically decompressed and fed into an autoclave reactor. The propylene polymerization reaction is them catalyzed by ZN catalyst. The pressure of the mixture of propylene-montmorillonite from the supercritical condition to the reactor autoclave decreased significantly, allowing propylene to expand and exfoliate the clay as it was fed in the reactor. Propylene in supercritical conditions was used in this works because it is the monomer for the subsequently polymerization and because its good properties at supercritical conditions. In order to evaluate the results the following methods were used: transmission electron microscopy (TEM) to investigate the nanoscale sample morphology and evaluate the clay exfoliation, X-ray diffraction (XRD) to determine interlamellar distance, d001, of the clay, differential scanning calorimetry (DSC) to determine the amount of crystallization of polymer and composite, thermogravimetric analysis (TGA) to determine composite clay content, scanning electron microscopy (SEM) to evaluate the morphology, and clay swelling test to evaluate the compatibility among various pairs clays-solvent. The first part of this work evaluated the interaction and swelling effects of different pairs of clay-solvent with or without sonication. This was necessary in order to choose the best clay to carry out the study. Four solvents with different polarity (chlorobenzene, toluene, cyclohexane and hexane) and eight clays (seven organically modified and one unmodified) were evaluated with or without sonication. Closite 15A and 93A presented the best results with different solvents and they were selected for further experiments. The experiments also showed that sonication improves the swelling of the clay. Initial screening of the polymerization reaction was carried out using two conditions: feeding supercritical propylene without clay and adding clay without the addition of supercritical fluid. The addition of supercritical propylene did not modify the morphology and properties of PP in comparison to the normal polymerization. The addition of Cloisite 15A or Cloisite 93A (pre-treated with toluene, not with supercritical propylene) produced nanocomposites. Although Cloisite 15A showed better results on the swelling tests, Cloisite 93A presented much better polymerization yield, therefore it was selected for further investigation using treatment with supercritical propylene. Cloisite93A was submitted to a treatment under four different supercritical propylene conditions (temperature and pressure) for thirty minutes. Each mixture was subsequently fed to the reactor through a catastrophic expansion inside an autoclave reactor running a propylene polymerization reaction. The results from XRD and TEM show a significant improvement on the exfoliation when treating the clay under supercritical propylene conditions followed by in situ polymerization, as compared to the in situ polymerization without treating the clay with supercritical propylene. In conclusion, the utilization of supercritical propylene has improved the dispersion of the clay at the nanoscale during the preparation of these nanocomposites by in situ polymerization.