The Leveäniemi iron oxide apatite (IOA) deposit, mined by LKAB, is located in Norrbotten, northern Sweden. The deposit has a partially more complex mineralogy than the neighbouring and more famous IOA deposits of Kiirunavaara and Malmberget. The Leveäniemi deposit contains comparatively more ore containing both magnetite and hematite but also maghemite and with slightly different trace element chemistry of the iron oxide minerals. Hematite is currently not considered a valuable mineral in the Svappavaara mineral processing and in the magnetite concentrate titanium and vanadium are considered to be penalty elements. Ore samples were collected from selected drill cores and from these polished thin sections were prepared that were investigated by optical microscopy, EPMA, and FE-SEM-EDS. Investigations focused on iron oxide mineralogy and mineral chemistry with special consideration to titanium and vanadium as those elements are considered deleterious in subsequent blast furnace or direct reduction processes. Investigations revealed that magnetite is the predominant mineral with secondary hematite being the second most abundant iron oxide mineral. In the investigated samples vanadium concentration in magnetite ranges from 0.12 to 0.32% V2O3 with higher concentrations in the southern part of the deposit. No such conclusions regarding spatial distribution could be done for titanium. Furthermore, the investigations indicated that alteration from primary magnetite to secondary hematite does not significantly affect the trace element chemistry of the minerals. Titanium in iron oxides occurs as either inclusions or lamellae of titanium oxide minerals. Vanadium in iron oxides occur as a substitution element and does not occur in stochiometric vanadium minerals. It is considered unfeasible to lower the content of these deleterious elements by physical separation methods. / Leveäniemi är en järnoxid-apatitfyndighet (IOA) i Norrbotten som bryts av LKAB. Fyndigheten har en delvis mer komplex mineralogi än de närliggande och mer kända IOA-fyndigheterna Kiirunavaara och Malmberget. Leveäniemifyndigheten innehåller jämförelsevis mer malm innehållande både magnetit och hematit men även maghemit samt med något annorlunda spårämneskemi i järnoxidmineralen. Hematit anses inte i nuläget vara ett värdemineral i Svappavaaras malmförädling och i magnetitekoncentratet anses titan och vanadin utgöra straffelement. Malmprov togs från utvalda borrkärnor och från dessa tillverkades polerade tunnslip som undersöktes med optisk mikroskopering, EPMA och FE-SEM-EDS. Undersökningarna var fokuserade på järnoxidernas mineralogi och mineralkemi med speciellt fokus på titan och vanadin då grundämnena anses vara skadliga i efterföljande masugns- eller direktreduktionsprocesser. Undersökningarna visade att magnetit är det dominerade mineralet med sekundär hematit som det näst vanligaste förekommande järnoxidsmineralet. I de undersökta proven varierade vanadinhalten från 0,12% till 0,32% V2O3 med högre halter i fyndigheten södra delar. Inga liknande slutsatser angående rumsliga fördelningen av titan kunde göras. Vidare så indikerade undersökningarna att omvandling från primär magnetit till sekundär hematit inte nämnvärt påverkar spårämneskemin i mineralen. Titan i järnoxider förekommer antingen som inneslutning eller lameller av titanoxidsmineral. Vanadin i järnoxider förekommer som ett substitutionselement och förekommer inte som stökiometriska vanadinmineral. Det anses inte vara tekniskt eller ekonomiskt möjligt att sänka halterna av dessa skadliga grundämnen med hjälp av fysiska separationsmetoder.

Carbon dioxide (CO2) is formed when fossil fuels such as oil, gas and coal are burned in power producing plants. CO2 is naturally found in the atmosphere as part of the carbon cycle, however it becomes a primary greenhouse gas when human activities disturb this natural balanced cycle by increasing levels in the atmosphere. In light of this fact, greenhouse gas mitigation strategies have garnered a lot of attention. Carbon capture, utilization and sequestration (CCUS) has emerged as a possible strategy to limit CO2 emissions into the atmosphere. The technology involves capturing CO2 at the point sources, using it for other markets or transporting to geological formations for safe storage. This thesis aims to understand and probe the chemistry of the reactions between CO2 and iron-bearing sediments to ensure secure storage for millennia. The dissertation work presented here focused on trapping CO2 as a carbonate mineral as a permanent and secure method of CO2 storage. The research also explored the use of iron-bearing minerals found in the geological subsurface as candidates for trapping CO2 and sulfide gas mixtures as siderite (FeCO3) and iron sulfides. Carbon dioxide sequestration via the use of sulfide reductants of the iron oxyhydroxide polymorphs lepidocrocite, goethite and akaganeite with supercritical CO2 (scCO2) was investigated using in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The exposure of the different iron oxyhydroxides to aqueous sulfide in contact with scCO2 at ~70-100 ˚C resulted in the partial transformation of the minerals to siderite (FeCO3). The order of mineral reactivity with regard to siderite formation in the scCO2/sulfide environment was goethite < lepidocrocite ≤ akaganéite. Overall, the results suggested that the carbonation of lepidocrocite and akaganéite with a CO2 waste stream containing ~1-5% H2S would sequester both the carbon and sulfide efficiently. Hence, it might be possible to develop a process that could be associated with large CO2 point sources in locations without suitable sedimentary strata for subsurface sequestration. This thesis also investigates the effect of salinity on the reactions between a ferric-bearing oxide phase, aqueous sulfide, and scCO2. ATR-FTIR was again used as an in situ probe to follow product formation in the reaction environment. X-ray diffraction along with Rietveld refinement was used to determine the relative proportion of solid product phases. ATR-FTIR results showed the evolution of siderite (FeCO3) in solutions containing NaCl(aq) concentrations that varied from 0.10 to 4.0 M. The yield of siderite was greatest under solution ionic strength conditions associated with NaCl(aq) concentrations of 0.1-1 M (siderite yield 40% of solid product) and lowest at the highest ionic strength achieved with 4 M NaCl(aq) (20% of solid product). Based partly on thermochemical calculations, it is suggested that a decrease in the concentration of aqueous HCO3- and a corresponding increase in co-ion formation, (i.e., NaHCO3) with increasing NaCl(aq) concentration resulted in the decreasing yield of siderite product. At all the ionic strength conditions used in this study, the most abundant solid phase product present after reaction was hematite (Fe2O3) and pyrite (FeS2). The former product likely formed via dissolution/reprecipitation reactions, whereas the reductive dissolution of ferric iron by the aqueous sulfide likely preceded the formation of pyrite. These in situ experiments allowed the ability to follow the reaction chemistry between the iron oxyhr(oxide), aqueous sulfide and CO2 under conditions relevant to subsurface conditions. Furthermore, very important results from these small-scale experiments show this process can be a potentially superior and operable method for mitigating CO2 emissions. / Chemistry

Mn oxides have high redox potentials and are known to be very reactive, rendering many contaminants susceptible to degradation via oxidation. Although Mn oxides typically occur as mixtures with other metal oxides (e.g., Fe, Al, and Si oxides) and natural organic matter (NOM) in soils and aquatic environments, most studies to date have studied the reactivity of Mn oxides as a single oxide system. This study, for the first time, examined the effect of representative metal oxides (Al2O3, SiO2, TiO2, and Fe oxides) and NOM or NOM-model compounds (Aldrich humic acid (AHA), Leonardite humic acid (LHA), pyromellitic acid (PA) and alginate) on the oxidative reactivity of MnO2, as quantified by the oxidation kinetics of triclosan (a widely used phenolic antibacterial agent) as a probe compound. The study also examined the effect of soluble metal ions released from the oxide surfaces on MnO2 reactivity. In binary oxide mixtures, Al2O3 decreased the reactivity of MnO2 as a result of both heteroaggregation and complexation of soluble Al ions with MnO2. At pH 5, the surface charge of MnO2 is negative while that of Al2O3 is positive resulting in intensive heteroaggregation between the two oxides. Up to 3.15 mM of soluble Al ions were detected in the supernatant of 10 g/L of Al2O3 at pH 5.0 whereas the soluble Al concentration was 0.76 mM in the mixed Al2O3 + MnO2 system at the same pH. The lower amount of soluble Al in the latter system is the result of Al ion adsorption by MnO2. The experiments with the addition of 0.001 to 0.1 mM Al3+ to MnO2 suspension indicated the triclosan oxidation rate constant decreased from 0.24 to 0.03 h-1 due to surface complexation. Fe oxides which are also negatively charged at pH 5 inhibited the reactivity of MnO2 through heteroaggregation. The concentration of soluble Fe(III) ions ( 4 mg-TOC/L or [alginate/PA] > 10 mg/L, a lower extent of heteroaggregation was also observed due to the negatively charged surfaces for all oxides. Similar effects on aggregation and MnO2 reactivity as discussed above were observed for ternary MnO2‒Al2O3‒NOM systems. HAs, particularly at high concentrations (2.0 to 12.5 mg-C/L), alleviated the effect of soluble Al ions on MnO2 reactivity as a result of the formation of soluble Al-HA complexes. Alginate and PA, however, did not form soluble complexes with Al ions so they did not affect the effect of Al ions on MnO2 reactivity. Despite the above observations, the amount of Al ions dissolved in MnO2+Al2O3+NOM mixtures was too low, as a result of NOMs adsorption on the surface to passivate oxide dissolution, to have a major impact on MnO2 reactivity. In conclusion, this study provided, for the first time, a systematical understanding of the redox activity of MnO2 in complex model systems. With this new knowledge, the gap between single oxide systems and complex environmental systems is much narrower so that it is possible to have a more accurate prediction of the fate of contaminants in the environment. / Civil Engineering

The growth of Fe₃O₄ and FeOOH crystals was investigated. Growth modifiers were used to alter the formation of iron oxides from ferrous hydroxide precipitates. Multifunctional carboxylic acids were found to have a strong influence on morphology of FeOOH. Dicarboxylic acids, containing two and seven carbons, changed the characteristics of α-FeOOH. These changes included alteration of the isoelectic point of the particulates and changes in particle size and shape. EDTA was found to alter the phase of FeOOH formation, favoring the synthesis of γ-FeOOH over α-FeOOH at temperatures below 50°C. The effects of multifunctional carboxylic acids were dependent upon the time of addition, and the presence of other growth modifiers. The changes in FeOOH formation were postulated to occur due to interaction between the acid molecules and Green Rust II, a common intermediate in iron oxide growth. The growth of Fe₃O₄ was found to be sensitive to solution pH, and the form of the iron starting materials. Examination of reaction intermediates by x-ray diffraction showed that other Crystalline phases formed prior to the production of Fe₃O₄. Different intermediate phases occurred depending on the amount of hydroxide in the reaction, and differences in Fe³⁺ starting materials. The production of different intermediate phases affected the morphology of Fe₃O₄. Early precipitation of Fe₃O₄ led to small particles, while formation of crystalline Fe(OH)₂ led to large crystals. Formation of a mixture of Green Rust II and Fe(OH)₂ early in the oxidation process led to formation of multiple nuclei, and produced smaller average particles with a wide particle size distribution. Fe₃O₄ particles prepared from α-FeOOH seed crystals were spherical, while Fe₃O₄ particles prepared from FeSO₄ alone were octahedral crystals. / Ph. D.

This dissertation explores the development and optimization of Metal-Organic Frameworks (MOFs) and Nanoparticle Organic Hybrid Materials (NOHMs) for efficient CO₂ capture and investigates enhanced sorbent regeneration using a non-thermal transfer. Chapter 2 introduces the versatility and challenges of MOFs, including their structural adaptability and issues with hydrostability, highlighting the need for water-resistant modifications or coatings to maintain functionality in humid conditions. Chapter 3 and 4 focus on advancements in MOF design for CO₂ capture and the synthesis of encapsulated MOFs with enhanced durability against moisture, using HKUST-1 integrated with hydrophobic polymer PTMSP as an example to demonstrate its potential despite challenges in optimizing CO₂ sorption efficiency when exposed to water. Chapter 5 explores NOHMs, particularly ionically tethered polyethylenimine (NIPEI), for creating air-filter-like fiber mat systems with significant CO sorption capabilities, even under low CO₂ concentrations and humid conditions, suggesting further material and design optimization for industrial applications. Chapter 6 presents a modeling study on gas transport behaviors within NOHM-polymer interfaces, utilizing Molecular Dynamics (MD) simulations to enhance our understanding of CO₂ sorption dynamics, pointing towards the importance of ion diffusion rates and the distribution of gas molecules for improved capture efficiency. Chapter 7 delves into CO₂ desorption techniques, comparing microwave radiation to conventional thermal heating, showing the efficiency and energy-saving benefits of microwave regeneration, especially when incorporating Fe₃O₄ magnetite into NOHMs. This chapter also stresses the necessity of innovative reactor designs to ensure uniform heating and address technical challenges like nanoscale temperature measurement and uneven heat distribution. Chapter 8 extends the discussion to future research directions, emphasizing the potential of NOHMs for CO₂ capture and conversion, the exploration of their electrochemical performance, and the need for understanding CO₂ transport mechanisms for enhanced conversion efficiency. It calls for comprehensive evaluations of sorbents in terms of stability, kinetics, capacity, selectivity, and cost-effectiveness, alongside advancements in microwave regeneration technology to overcome current limitations in sorbent heating efficiency. Overall, this dissertation underscores the ongoing need for innovative solutions to improve CO₂ capture technologies, highlighting the promise of MOFs and NOHMs in addressing climate change challenges through scalable carbon capture, utilization, and storage (CCUS) applications.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2005. / 199 leaves single sided printed, preliminary pages i-vii and numbered pages 1-191. Includes bibliography, list of figures and tables. Digitized using a Hp Scanjet 8250 Scanner to pdf format (OCR). / ENGLISH ABSTRACT: This study provided scientific proof of the precipitation of iron and other metal species in the HAL circuit at the Mineral Separation Plant of Namakwa Sands. Iron and aluminium hydroxides were the most abundant precipitate complexes that formed in the HAL circuit. Sulphates formed bridges with the iron complexes. It was found that precipitation of iron in the HAL circuit was a function of the pH, ferric ion concentration and temperature of the process water. Experimental work provided abundant evidence that the precipitated iron hydroxide and other species adsorb to the surfaces of zircon and rutile mineral particles due to opposite zeta potentials of the mineral particles and iron hydroxide. These adsorbed species altered the electrostatic potential of the mineral surfaces, which reduced the electrostatic separation efficiency of these minerals. It was determined that an improvement of 7% could be expected if the precipitation and attachment of iron could be minimised. Based on the experimental results, conceptual processes were developed and iterative simulations were set up to determine the optimum solution that would maximise the removal of dissolved iron. This solution would ensure clean mineral surfaces free of any adsorbed precipitates. This process circuit was constructed in May to August 2004 at a total capital cost of R4.8m and removed 99.97% of the total dissolved iron prior to caustic addition. Prime zircon recoveries were increased by 3-7%. / AFRIKAANSE OPSOMMING: Hierdie studie het wetenskaplike bewyse gelewer dat yster en ander spesies neerslae vorm in die HAL proses van die Mineraal Skeidings Aanleg van Namakwa Sands. Yster- en aluminium hidroksiede was die vernaamste neerslag komplekse wat gevorm het in die HAL proses. Sulfaat spesies het verbindings gevorm met die yster komplekse. Die neerslag van yster was ‘n funksie van pH, ferric ioon konsentrasie en temperatuur van die proses water. Eksperimentele werk het genoegsame bewyse gelewer dat die yster hidroksied neerslag en ander spesies adsorbeer op die oppervlaktes van sirkoon en rutiel minerale weens teenoorgestelde zeta potensiale van die mineraal partikels en yster hidroksiede. Hierdie geadsorbeerde spesies het die elektrostatiese potentiaal van die mineraal oppervlaktes verander wat sodoende die elektrostatiese skeidingsvermoë van hierdie minerale verminder het. ‘n Verbetering van 7% in elektrostatiese skeiding van sirkoon en rutiel minerale kan verwag word indien die neerslag en adsorbsie van yster minimiseer word. Konseptuele prosesse, gebasseer op die eksperimentele resultate, is ontwikkel. Itteratiewe simulasies is opgestel om die optimum proses te bepaal wat sodoende die maksimum verwydering van die opgeloste yster sou verseker. Hierdie oplossing sou skoon mineraal oppervlaktes, vry van enige geadsorbeerde neerslae, verseker. Hierdie prosesaanleg was opgerig in Mei tot Augustus 2004 teen ‘n kapitaalkoste van R4.8m en dit het 99.97% van die totale opgeloste yster verwyder voordat natrium hidroksied bygevoeg is. Primêre sirkoon opbrengste het sodoende toegeneem met 3-7%.

published_or_final_version / abstract / Earth Sciences / Doctoral / Doctor of Philosophy

Nanoenergetic composite materials have been synthesized by a sol-gel chemical process where the addition of a weak base molecule induces the gelation of a hydrated metal salt solution. A proposed proton scavenging mechanism, where a weak base molecule extracts a proton from the coordination sphere of the hydrated iron (III) complex in the gelation process to form iron (III) oxide/hydroxide, FeIIIxOyHz, has been confirmed for the weak base propylene oxide (PO), a 1,2 epoxide, as well as for the weak bases tetrahydrofuran (THF), a 1,4 epoxide, and pyridine, a heterocyclic nitrogen-containing compound. THF follows a similar mechanism as PO; the epoxide extracts a proton from the coordination sphere of the hydrated iron complex forming a protonated epoxide which then undergoes irreversible ring-opening after reaction with a nucleophile in solution. Pyridine also extracts a proton from the hydrated metal complex, however, the stable six-membered molecule has low associated ring strain and does not endure ring-opening. Fe2O3/Al energetic systems were synthesized from the epoxides PO, trimethylene oxide (TMO) and 3,3 dimethyl oxetane (DMO). Surface area analysis of the synthesized matrices shows a direct correlation between the surface area of the iron (III) oxide matrix and the quantified exothermic heat of reaction of the nano-scaled aluminum-containing energetic material due to the magnitude of the interfacial surface area contact between the iron (III) oxide matrix and the aluminum particles. The Fe2O3(PO)/Al systems possess the highest heat of reaction values due to the oxide interfacial surface area available for contact with the aluminum particles. Also, reactions containing nano-scale aluminum react differently than those containing micron-scale aluminum. RuO2/Al energetic systems behave differently dependent on the atmosphere the sample is heated. Heating the RuO2/Al samples in an inert atmosphere results in the complete reduction of the ruthenium oxide matrix to Ru(0) before reaction with the aluminum particles, resulting in the exothermic formation of RuxAly intermetallics, with the stoichiometry dependent on the initial Ru:Al concentration. However, heating the samples in an oxygen-rich atmosphere results in an exothermic reaction between RuO2 and Al.

Despite significant developments in imaging modalities and therapeutics, cancer mortality rates remain unchanged. Detecting cancer before it has spread to other organs improves patient outcome dramatically. Therefore, greater emphasis must be placed on developing novel technology for early cancer detection and disease monitoring. Nanometer-sized materials have unique optoelectronic and magnetic properties. In particular, semiconductor quantum dots (QD) are a new class of fluorophores that are bright, photostable, and can be simultaneously excited to emit different wavelengths of light. Magnetic iron oxide nanoparticles are another class of unique nanomaterials that exhibit superparamagnetism and are strongly magnetized only in the presence of a magnetic field. In this dissertation, we describe the integration of semiconductor QDs and magnetic iron oxide nanoparticles and potential applications for (i) early detection of cancer biomarkers through routine screening, and (ii) disease monitoring through the capture and analysis of rare circulating tumor cells. First, we describe the development of integrated magneto-optical beads that can be optically encoded and magnetically separable for isolating low amounts of biomolecules from solution. Second, we demonstrate improved detection sensitivity by combining immunomagnetic beads and highly luminescent nanoparticles in a sandwich assay. Next, we describe integration of magnetic and QD nanotechnology for the selective capture and molecular profiling of rare cells. We demonstrate the ability to spectroscopically determine relative molecular levels of markers to identify invasive cells. As disease monitoring requires the analysis of patient blood samples, we have also studied nanoparticle-cell interactions using QDs to determine nanoparticle behavior in whole blood as a function of surface coatings. We observed that anionic nanoparticles with carboxylic acid groups (-COOH) were strongly associated with leukocytes, but interestingly this association was cell specific. Hydroxyl-modified QDs (QD-OH) suppressed binding and uptake by leukocytes as efficiently as PEG-modified QDs. The integration of nanotechnologies represents a new and exciting approach that has the potential to push the limits of detection sensitivity and permit isolation and profiling of multiple biomarkers from large sample volumes.

Development of nanostructures as MR contrast agent will significantly improve the field of disease diagnostics. Contrast agents such as iron oxide nanoparticles are less toxic compared to more commonly used gadolinium based agents. A subclass of iron based nano particles are super paramagnetic iron oxide nano particles, (SPIOs) which are widely studied MR contrast agents useful in both imaging and drug delivery applications. In this work, SPIOs were synthesized and characterized and used for cellular tracking and multi modal labeling. A new solvent exchange method was utilized to coat different core size iron oxide nano particles. SPIOs were characterized for in-vivo imaging using MR and they had a very uniform size distribution which was determine using dynamic light scattering (DLS) and transmission electron microscopy. Furthermore, blood circulation half-life of 16nm SPIOs were determined through tail vein injection. SPIOs have many applications among which is the in vivo tracking of stem cells which is critical for determination of stem cells fate after injection. Magnetic Resonance (MR) as a non-invasive method can provide significant information about the fate of the cells as well as determination of the success rate of therapeutic cellular deliveries. Mesenchymal stem cells can be loaded with super paramagnetic iron oxide nano particles (SPIOs) and have their movements followed once planted in vivo. We present our findings on the effect of SPIO concentration and stem cell density on the MR signal and transverse relaxation time. Our preliminary results indicated that SPIOs do not cause mesenchymal stem cell cytotoxicity and do not affect proliferation ability up to 200 μg/ml concentration. The release of the nanoparticles was investigated 24 hours post internalization and the result showed that SPIOs will stay inside the cell. We also found that the contrast increases in a concentration dependent manner. Our results suggest that using MR with low concentration of SPIOs is a novel and promising method for tracking of mesenchymal stem cells. In this work SPIOs were also labeled with 64Cu to investigate their potential for multi modal positron emission tomography (PET) MR imaging. Dual modality PET MR SPIO contrast agent can be synthesized to image diseases such as cancer and atherosclerosis. The advantage is the non-invasive and early detection of disease at molecular lever before it has spread to late stages or in case of the atherosclerosis before the plaque has blocked the vessel. To develop a multi modal contrast agent, a positron emitter, 64Cu (half-life of 12.701 ± 0.002 hours), was used in labeling and synthesis was performed all in one step with the addition of 64Cu chelator, 14-PE DTPA followed by radiolabeling for both 6.5nm SPIO and 17nm SPIO. After labeling and purification with the desalting column, the amount of dissociated 64Cu in the solution was determined using radio thin layer chromotagraphy (TLC) and the particle was shown to have minimum amount of fee 64Cu. Serum stability of labeled SPIO was determined in vitro by incubating 64Cu-labeled SPIOs in mouse serum at 37 °C for 24 hr with constant shaking. Radio TLC result then revealed that 64Cu stays bounded to the SPIO after 24 hours in mouse serum. This means that 64Cu labeled SPIO has a great potential as a dual modality contrast agents and further in-vivo studies are required to verify the findings.