No description available.

This dissertation reports the design of a process (patent pending) to remove iron from acid mine drainage (AMD) without the formation of metal hydroxide sludge. The system includes the oxidation of ferrous iron in a packed bed bioreactor, the precipitation of iron within a fluidized bed, the removal of manganese and heavy metals (Cu, Ni, Zn) in a trickling filter at high (>9) pH, with final neutralization in a carbonate bed. The technique avoided the generation of iron oxyhydroxide sludge. In the packed bed bioreactor, maximum substrate oxidation rate (R_,max) was 1500 mg L⁻¹ h⁻¹ at dilution rates of 2 h⁻¹, with oxidation efficiency at 98%. The half-saturation constant (similar to a Ks) was 6 mg L⁻¹. The oxidation rate was affected by dissolved oxygen below 2 mg L⁻¹, with a Monod-type Ko for DO of 0.33 mg L⁻¹. Temperature had a significant effect on oxidation rate, but pH (2.0 to 3.25) and supplemental CO₂ did not affect oxidation rates. Iron hydroxide precipitation was not instantaneous when base was added at a OH/Fe ratio of less than 3. Induction time was found to be a function of pH, sulfate concentration and iron concentration, with a multiple R² of 0.84. Aqueous [Al (III)] and [Mn (II)] did not significantly (α = 0.05) affect induction time over the range of concentrations investigated. When specific loading to the fluidized bed reactor exceeded 0.20 mg Fe m⁻² h⁻¹, dispersed iron particulates formed leading to a turbid effluent. Reactor pH determined the minimum iron concentration in the effluent, with an optimal at pH 3.5. Total iron removals of 98% were achieved in the fluidized bed with effluent [Fe] below 10 mg L⁻¹. Further iron removal occurred within the calcium carbonate bed. Heavy metals were removed both in the fluidized bed reactor as well as in the trickling filter. Oxidation at pH >9 caused manganese to precipitate (96% removal); removals of copper, nickel, and zinc were due primarily to sorption onto oxide surfaces. Removals averaged 97% for copper, 70% for nickel and 94% for zinc. The treatment strategy produced an effluent relatively free of iron (< 3 mg/L), without the formation of iron sludge and may be suitable for AMD seeps, drainage from acidic tailings ponds, active mine effluent, and acidic iron-rich industrial wastewater. / Ph. D.

No description available.

The work in this thesis is concerned with the Green Rusts, which are bluegreen metastable Fe(II) - Fe(III) hydroxy compounds incorporating anions such as SO42-, Cl- or CO3-. These Green Rust compounds (or Fe-GR compounds to distinguish them from the aluminium Green Rusts (Al-GRs) which are isostructural Fe(II) - Al(III) hydroxy compounds) can be produced in a consistent fashion from Fe(II) solutions by the method of induced hydrolysis using Fe(III) gel at pH 7 and under anoxic conditions. A series of sulphate and chloride Fe-GR samples were synthesised, and characterised primarily by the analytical techniques of M8ssbauer spectroscopy, X-Ray diffractometry, infra-red spectroscopy, and vacuum microbalance to measure surface area using the BET N2 adsorption method. For comparison, a few samples of the analogous Al-GR compounds were also synthesised and characterised by the analytical techniques mentioned above. The results in this thesis showed that the systems producing the Fe-GR compounds were of a highly complex nature, and that the amount of precipitate formed depended crucially on the starting conditions. For the 0.1 M FeSO4 system, the GR formed was almost always accompanied by a goethite phase while, for the 0.1 M FeC12 system, pure GR material was only formed at initial Fe(II) - Fe(III) ratios (IFFRs) greater than 6. Any-differences between__the, sulphate and chloride Fe-GRs can. be attributed to the difference in anion-type. X-Ray diffraction in conjunction with electron microscopy and surface area measurements confirm-that the Fe-GRs have a pyroaurite crystal structure, with brucite-like layers formed by a matrix of Fe2+ and Fe 3+ cations and each layer bridged to the other by anions. As far as Messbauer spectroscopy is concerned, the most important diagnostic parameter is the quadrupole splitting (QS) of the Fe(II) doublet measured at 77K for the wet, fresh precipitate (i. e. frozen material). For sul phate Fe-GRs derived from 0.1 M FeSO4 the mean QS is 2.93 ± 0.05 mms-', while for the chloride Fe-GRs derived from 0.1 M FeC12 the mean QS is 2.80 ± 0.05 mms-1. Surface areas for the sulphate Fe-GRs are in the range 40-65 m2. g-1. The products of oxidation and ageing for the Fe-GRs indicate several transformation pathways, especially for the chloride Fe-GRs. Sulphate Fe-GRs converted to goethite on oxidation under both wet and dry conditions, while the chloride Fe-GRs converted to akaganeite on dry oxidation, and to lepidocrocite on wet oxidation. Under both wet and dry anoxic conditions, the chloride Fe-GRs converted to magnetite. In the case of the sulphate Fe-GRs, there was a suggestion that, under the right wet anoxic conditions, the material probably transformed into magnetite. These facts clearly demonstrate that the Fe-GRs are intermediaries in the thermodynamic transformation of Fe in the II oxidation state to Fe in the III oxidation state.

M.Sc. / Sub-Saharan Africa accounts for a large fraction of the world’s infectious diseases, particularly AIDS (Acquired Immunodeficiency Syndrome) and Tuberculosis (TB) and at the same time, iron (Fe) overload is common to several of its regions. Excess Fe aids in the replication of both Human Immunodeficiency Virus (HIV) and Mycobacterium tuberculosis (M.tuberculosis, Lounis, 2001; Georgiou, 2000) and also causes a malfunction of the host’s defense system and may ultimately lead to cell death. Not only does iron assist in pathogen survival but the pathogens themselves have a synergistic relationship where infection of one supports the replication of the other (Toosi, 2001; Bonecini-Almeida et al., 1998). Controlling the replication of these pathogens as well as the iron overload simultaneously becomes a huge task as many pathogenic and host factors needs to be considered at once. Desferrioxamine (DFO), a chelator commonly used to treat clinical conditions of iron overload has been reported to inhibit the multiplication of pathogens and at the same time extract the excess iron.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / The feasibility of extracting iron from iron(III) oxide bearing materials with acetylacetone has been under investigation for many years. This is an alternate, environmentally friendly process for the recovery of iron compared to conventional processes that are energy intensive, have numerous costly process steps and produce large quantities of greenhouse gases. Iron(III) oxide bearing waste materials can be used in this process which reduces its environmental impact as it would not require waste storage. This study investigated the feasibility of reducing the reaction time of the liquid phase extraction of iron from iron ore fines by performing the extraction at elevated pressures and temperatures. It was found that that the extraction under pressure was dependent on temperature, pressure, particle size and solid to liquid ratio. It was found that at high temperatures and long extraction times, an unknown secondary reaction occurs that consumes the desired product, iron(III) acetylacetonate, and inhibits the recovery of these crystals. This results in lower extraction yields. It was found that the side reaction was largely dependent on the temperature of the system and the amount of iron(III) acetylacetonate present. The effects of the side reaction could be limited by lower operating temperatures and reducing the total reaction times. An optimum conversion of iron(III) oxide to iron(III) acetylacetonate of 47.2% was achieved for synthetic iron (III) oxide (> 95 wt% Fe2O3) at a total extraction time of 4 h, 160 °C, 0.025 g:1 mL, operating pressure of 1700 kPa, initial N2 feed pressure of 1010 kPa and 375 rpm stirrer speed. The optimum extraction of iron from iron ore fines (> 93 wt% Fe2O3) to iron(III) acetylacetonate was found to be 20.7% at 4 h, 180 °C, 0.025 g:1 mL and operating pressure of 1900 kPa, initial N2 feed pressure of 1010 kPa and 375 rpm stirrer speed. These are the optimum conditions where the side reaction is limited to improve the recovery and desired reaction conversion capabilities of the process. The operation under pressure yielded lower conversions than that of the atmospheric leaching process developed by Tshofu (acetylacetone water system under reflux). It was also found that it was not possible to reduce the extraction time and achieve comparable extractions when operating at higher temperatures and pressures. The formation of an additional unwanted product would also lead to unnecessary treatment costs in an industrial process. Hence, it was found that pressure leaching as an alternative is not currently viable due to the lower yields and associated high costs. Atmospheric leaching seems to be the most economically feasible option until a better alternative is found. / MT2017

Ho, Ching Man = 可柔韌的白鑄鐵 / 何靜雯. / Thesis submitted in: November 2007. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves ). / Text in English; abstracts in English and Chinese. / Ho, Ching Man = Ke rou ren de bai zhu tie / He Jingwen. / Chapter Chapter 1: --- Introduction --- p.1 / Chapter 1.1 --- Introduction of Composites --- p.1 / Chapter 1.1.1 --- Dispersion-Strengthened composites --- p.2 / Chapter 1.1.2 --- True Particulate Composites --- p.2 / Chapter 1.1.3 --- Fiber-Reinforced Composites --- p.2 / Chapter 1.1.4 --- Laminar Composites --- p.3 / Chapter 1.2 --- Mechanical Properties of Metal Matrix Composites --- p.4 / Chapter 1.2.1 --- Stress-Strain Test --- p.4 / Chapter 1.2.2 --- "Stiffness, Strength and Ductility" --- p.4 / Chapter 1.2.3 --- Hardness --- p.5 / Chapter 1.3 --- Fabrication of Metal Matrix Composites --- p.5 / Chapter 1.3.1 --- Liquid ´ؤ´ؤ State Processing --- p.6 / Chapter 1.3.1.1 --- Infiltration Processes --- p.6 / Chapter 1.3.1.2 --- Dispersion Processes --- p.7 / Chapter 1.3.1.3 --- Spray Processes --- p.7 / Chapter 1.3.1.4 --- In - Situ Processes --- p.8 / Chapter 1.3.2 --- Solid - State Processing --- p.8 / Chapter 1.3.2.1 --- Diffusion Bonding --- p.8 / Chapter 1.3.2.2 --- Deformation Processing --- p.9 / Chapter 1.3.2.3 --- Deposition Techniques --- p.9 / Chapter 1.4 --- Fabrication of Metal Matrix Composites by Spinodal Decomposition --- p.10 / Chapter 1.4.1 --- Phase Transformation --- p.10 / Chapter 1.4.2 --- Nucleation and Growth --- p.12 / Chapter 1.4.2.1 --- Kinetics of Nucleation and Growth --- p.12 / Chapter 1.4.2.2 --- Phase Separation by Nucleation and Growth --- p.14 / Chapter 1.4.3 --- Spinodal Decomposition --- p.14 / Chapter 1.4.3.1 --- Phase Separation by Spinodal Decomposition --- p.14 / Chapter 1.4.3.2 --- The Diffusion Equation for Spinodal Decomposition --- p.15 / Chapter 1.4.4 --- Methods to obtain large undercooling --- p.17 / Chapter 1.5 --- Aim of This Project --- p.18 / Chapter Chapter 2: --- Experimental --- p.26 / Chapter 2.1 --- Preparation of fused silica tube --- p.26 / Chapter 2.2 --- Preparation of Sample --- p.26 / Chapter 2.2.1 --- Weighing and Alloying --- p.26 / Chapter 2.2.2 --- Fluxing --- p.27 / Chapter 2.3 --- Slow Cooling --- p.28 / Chapter 2.4 --- Microstructure Analysis --- p.28 / Chapter 2.4.1 --- Optical Microscope (OM) Analysis --- p.28 / Chapter 2.4.2 --- Sample Preparation for Scanning Electron Microscope (SEM) Analysis --- p.29 / Chapter 2.4.3 --- Sample Preparation for Transmission Electron Microscope (TEM) Analysis --- p.29 / Chapter 2.4.3.1 --- Specimen Requirement --- p.29 / Chapter 2.4.3.2 --- "Cutting, Grinding and Polishing" --- p.30 / Chapter 2.4.3.3 --- Ion Milling --- p.31 / Chapter 2.5 --- Microstructure Characterization by TEM --- p.31 / Chapter 2.5.1 --- Indexing Diffraction Pattern --- p.31 / Chapter 2.5.2 --- Energy Dispersive X-Rav (EDX) Analysis --- p.32 / Chapter 2.6 --- Mechanical Properties --- p.33 / Chapter 2.6.1 --- Hardness Testing --- p.33 / Chapter 2.6.2 --- Compression Testing --- p.33 / Chapter 2.7 --- Characterizations of Non-spinodal Samples --- p.34 / Chapter Chapter 3: --- Study of the Relationship between Microstructures and Undercooling of Fe81C14Si5 --- p.41 / Chapter 3.1 --- Abstract --- p.41 / Chapter 3.2 --- Introduction --- p.42 / Chapter 3.3 --- Experiment --- p.42 / Chapter 3.4 --- Results --- p.44 / Chapter 3.5 --- Discussion --- p.46 / Chapter 3.6 --- Conclusion --- p.46 / Chapter Chapter 4: --- Ductile white cast iron --- p.56 / Chapter 4.1 --- Abstract --- p.56 / Chapter 4.2 --- Introduction --- p.57 / Chapter 4.3 --- Experimental --- p.58 / Chapter 4.4 --- Results --- p.60 / Chapter 4.5 --- Discussions --- p.66

An experimental study of pure iron foil exposed to a hot, dense hydrogen and argon gas mixture in a ballistic compressor yielded evidence of structural and compositional changes of the metal due to the presence of the hydrogen gas. Three iron foils have been compared, one of unexposed pure iron, another of pure iron exposed to a mixture of hydrogen and argon gas, and the third of pure iron exposed to argon alone. Exposure to these high temperature, high pressure gases took place in a ballistic compressor. Line formations were found on the surface of the iron foil exposed to both hydrogen and argon. These appeared as 'V'- or 'W'-shaped configurations, giving the appearance of a serrated edge. Such lines were not found for the other two iron foils. Characteristic peaks of energy dispersive x-ray spectra yield different surface concentrations of oxygen when each iron foil sample is compared. This concentration is much less for iron foil exposed to both hydrogen and argon gases than for the other two samples. Also a larger carbon peak was found for the former sample, when compared to the latter two. A shift in the 200 x-ray diffraction peak by one degree 29 was observed for the sample exposed to hydrogen and argon, and a 'triple' peak was observed for the 310 plane for the same iron sample.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Iron oxyhydroxides are ubiquitous in surface environments, playing a key role in many biogeochemical processes. Their characterization is made challenging by their nanophase nature. Magnetometry serves as a sensitive non-destructive characterization technique that can elucidate intrinsic physical properties, taking advantage of the superparamagnetic behaviour that nanoparticles may exhibit. In this work, synthetic analogues of common iron oxyhydroxide minerals (ferrihydrite, goethite, lepidocrocite, schwertmannite and akaganéite) are characterized using DC and AC magnetometry (cryogenic, room temperature), along with complementary analyses from Mössbauer spectroscopy (cryogenic, room temperature), powder X-ray diffraction and scanning electron microscopy. It was found that all of the iron oxyhydroxide mineral nanoparticles, including lepidocrocite, schwertmannite and akaganéite were superparamagnetic and therefore magnetically ordered at room temperature. Previous estimates of Néel temperatures for these three minerals are relatively low and are understood as misinterpreted magnetic blocking temperatures. This has important implications in environmental geoscience due to this mineral group’s potential as magnetic remanence carriers. Analysis of the data enabled the extraction of the intrinsic physical parameters of the nanoparticles, including magnetic sizes. The study also showed the possible effect on these parameters of crystal-chemical variations, due to elemental structural incorporation, providing a nanoscale mineralogical characterization of these iron oxyhydroxides. The analysis of the intrinsic parameters showed that all of the iron oxyhydroxide mineral nanoparticles considered here have a common magnetic moment formation mechanism associated with a random spatial distribution of iv uncompensated magnetic spins, and with different degrees of structural disorder and compositional stoichiometry variability, which give rise to relatively large intrinsic magnetization values. The elucidation of the magnetic nanostructure also contributes to the study of the surface region of the nanoparticles, which affects the particles’ reactivity in the environment.