The high temperature reduction of ilmenite by various reducing agents is investigated. The experiments were performed in a microgravimetric reactor system. The starting materials and products were characterized using X-ray diffraction (XRD) with a Cu Kα source, high-resolution scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and wavelength-dispersive X-ray (WDX) analyses, mercury porosimetry and Mossbauer spectrometry. The fundamentals of ilmenite reduction by hydrogen and carbon monoxide are compared and analyzed both experimentally and through theoretical modeling. Both processes involve the diffusion of Fe product away from the reaction front through the TiO₂ phase, followed by the nucleation and growth of a separate Fe phase. The main differences between CO and H₂ reduction of ilmenite are that the rate of H₂ reduction of ilmenite is much faster than that by CO and TiO₂ can be further reduced to lower oxides of titanium at temperature higher than 876°C. A technique for the synthesis of lunar ilmenite simulants has been developed. The simulant sample have been successfully prepared with desired physical and chemical properties. The significance of this work is that it is possible to generate the kinetics data even without having access to real lunar ilmenite which is precious and difficult to obtain at the present time. The results of ilmenite reduction by a mixture of H₂ and CO indicate that the mechanism is similar to the reduction of ilmenite by H₂ or CO alone. However, the overall process is more complex because of the reaction between H₂ and CO₂ generated from the CO reduction of ilmenite. MgTiO₃, an important impurity in lunar ilmenite, has some effect on the reduction kinetics and mechanism. This depends on the reduction temperature and conversion. In samples containing MgTiO₃ impurity, in addition to the expected Fe and TiO₂ product phases, an unreduced core enriched in MgTiO₃ is observed. The movement of MgTiO₃ towards the core is a significant factor affecting the reduction rate.

306 p. illus appendices on 1 reel (neg.) / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1970

Based in part on thesis-Massachusetts Institute of Technology. / "O.N.R. contract N5ori-078596." Bibliography: p.34.

The petrogenesis of magmatic Fe-Ti oxide ores associated with massif-type andesine anorthosites is investigated through detailed studies of the world-class Tellnes ilmenite deposit (SW Norway), the Grader layered intrusion (Quebec, Canada) and Fe-Ti ores from the Suwalki anorthosite (NE Poland). Extensive sampling in the field and in drill-cores reveals significant petrographical and compositional variations within a single ore body and between deposits from different anorthosite complexes. The composition of phases from bulk XRF analyses on mineral separates and from in situ LA-ICP-MS, Sr isotopic composition of plagioclase, bulk rocks major and trace element contents and the spatial variation of these data are used to understand controlling factors on ore composition. Phase diagrams and experimental data on ferrobasalts as well as comparisons with the well-documented Bjerkreim-Sokndal layered intrusion (SW Norway) are systematically used to further refine our understanding on the genesis of Fe-Ti ores. More than 100 samples from drill-cores in the Tellnes ilmenite deposit, part of the late-Proterozoic (930-920 Ma) Rogaland Anorthosite Province (SW Norway), reveal significant petrographical and compositional variations within the ore body. Four zones are defined, based on variations in modal proportions and cumulus mineral assemblages: the Lower and Upper Central Zones and the Lower and Upper Marginal Zones. Plagioclase and whole-rock compositions discriminate the zones and display patterns interpreted as a result of mixing of either plagioclase-ilmenite or plagioclase-ilmenite-orthopyroxene-olivine cumulates with a melt of ferrodioritic (jotunitic) composition. Its content decreases from 80 to 20 % from the margins to the central part of the ore body. Phase diagrams for a jotunitic parental magma reproduce the crystallization sequence at 5 kbar. Uniform Sr isotope ratios do not support magma mixing. The cryptic layering of the ore body precludes injection as a crystal mush but favours in situ crystallization from an evolving magma in a sill-like magma chamber. The present trough-shape and mineral orientations result from deformation during gravity-induced subsidence and by up-doming of the anorthosite. Major and trace element XRF and in situ LA-ICP-MS analyses of ilmenite in the Tellnes ilmenite deposit further constrain the two-stage fractional crystallization model of a ferrodioritic Fe-Ti-P rich melt. Stage 1 is characterized by ilmenite-plagioclase cumulates, and stage 2 by ilmenite-plagioclase-orthopyroxene-olivine cumulates. The concentration of V and Cr in ilmenite, corrected for the trapped liquid effect, (1) defines the cotectic proportion of ilmenite to be 17.5 wt.% during stage 1, and (2) implies an increase of during stage 2, most likely related to a shift in fO2. The proportion of 17.5 wt.% is lower than the modal proportion of ilmenite (ca. 50 wt.%) in the ore body, implying accumulation of ilmenite and flotation of plagioclase. The fraction of residual liquid left after crystallization of Tellnes cumulates is estimated at 0.6 and the flotation of plagioclase at 26 wt.% of the initial melt mass. The MgO content of ilmenite (1.4-4.4 wt.%) is much lower than the expected cumulus composition. It shows extensive postcumulus re-equilibration with trapped liquid and ferromagnesian silicates, correlated with distance to the host anorthosite. The Zr content of ilmenite, provided by in situ analyses, is low and uncorrelated with stratigraphy or Cr content. The data demonstrate that zircon coronas observed around ilmenite formed by subsolidus exsolution of ZrO2 from ilmenite. The U-Pb zircon age of 920 ± 3 Ma probably records this exsolution process. The Grader layered intrusion belongs to the Havre-Saint-Pierre anorthosite in the Grenville Province (Quebec, Canada). This intrusion has a basin-like morphology and contains significant resources of Fe-Ti-P in ilmenite and apatite. Outcropping lithologies are massive oxide alternating with anorthosite layers, banded ilmenite-apatite-plagioclase rocks and layered oxide apatite (gabbro-) norites. Several drill cores provide evidence for stratigraphic variations of mineral and bulk cumulate compositions controlled by fractional crystallization and importantly the successive appearance of liquidus phases: plagioclase and ilmenite followed by apatite, then orthopyroxene together with magnetite, and finally clinopyroxene. This atypical sequence of crystallization results in the formation of plagioclase-ilmenite-apatite cumulates or nelsonites in plagioclase-free layers. Fine-grained ferrodiorites which cross-cut the coarse cumulates are shown to be in equilibrium with the noritic rocks. The high TiO2 and P2O5 contents of these liquids explain the early saturation of ilmenite and apatite before Fe-Mg silicates, which implies that nelsonites actually represent cumulates rather than Fe-Ti-P-rich immiscible melts. The location of the most evolved mineral and bulk cumulates compositions at several tens of meters below the top of the intrusion, forming a sandwich horizon, suggests crystallization both from the base and top of the intrusion. The concentrations of V and Cr in ilmenite display a single fractionation path for the different cumulus assemblages and define the cotectic proportion of ilmenite to 21 wt.%. This corresponds to bulk cotectic cumulates with ca. 8 wt.% TiO2, which is significantly lower than what is commonly observed in the explored portion of the Grader intrusion. The proposed mechanism of ilmenite-enrichment is lateral removal of plagioclase due to its buoyancy in the dense ferrodiorite. This plagioclase has probably accumulated in other portions of the intrusion or has not been distinguished from the host anorthosite. Fe-Ti deposits in the Proterozoic Suwalki massif-type anorthosite (NE Poland), recognized through geophysical exploration, have been sampled in deep cores reaching 2800 m depth. Bulk cumulate analyses and liquidus phases composition of 70 Fe-Ti ores support their cumulate origin. The sequence of crystallization is: plagioclase, orthopyroxene, Ti-magnetite and ilmenite (64:36 on average), apatite and clinopyroxene. Fe-Ti-rich cumulates are commonly layered and display continuous relation with the host anorthosite. They do not represent well-defined intrusions such as the major Fe-Ti Tellnes and Lac Tio deposits. Fe-Ti oxides microtextures show conspicuous subsolidus re-equilibration, particularly external granule exsolution of pleonaste from Ti-magnetite. The composition of associated fine-grained ferrodiorites reveals relatively low Ti content and similar Mg# compared to jotunitic rocks associated with hemo-ilmenite ores in the Rogaland Anorthosite Province. Geochemical characteristics of these plausible parental magmas can account for the high Ti-magnetite/ilmenite ratio in cumulates. The diapiric emplacement of anorthositic plutons clearly influences the crystallization of Fe-Ti ores and is responsible for crystal sorting controlled by the density contrast of liquidus phases. Polybaric crystallization is evidenced by the high and variable Al2O3 content of orthopyroxene and by the occurrence of olivine corona around orthopyroxene interpreted from phases diagram to result from adiabatic decompression. The comparatively low V content in Ti-magnetite results from highly oxidized crystallization conditions. It thus emerges that principal controlling factors on the formation of Fe-Ti ore and on their characteristics are parental magma composition, sequence of crystallization, crystal sorting, crystallization of trapped liquid, oxygen fugacity and postcumulus re-equilibration. Indeed, fine-grained rocks of Fe-Ti-P-rich ferrodioritic (jotunitic) composition, interpreted as parental melt composition, are responsible for atypical sequence of crystallization with ilmenite as an early liquidus mineral and apatite saturation for high fraction of residual liquid. The trace element content of ilmenite, particularly V and Cr, has been used to calculate cotectic proportion of ilmenite during fractional crystallization of ferrodiorites. These proportions are usually lower than those observed in Fe-Ti ores, which implies ilmenite sorting. This occurs by plagioclase flotation due to its buoyancy in the dense ferrodiorite. This plagioclase may have accumulated in other portions of the intrusion or has not been distinguished from the host anorthosite. Extensive postcumulus re-equilibration with trapped liquid and ferromagnesian silicates strongly modifies the primary liquidus composition of Fe-Ti oxides. The data also demonstrate that zircon coronas commonly observed around ilmenite in Fe-Ti ores formed by subsolidus exsolution of ZrO2 from ilmenite. The basin-like morphology of most Fe-Ti ores hosting intrusions results from the deformation during gravity-induced subsidence and by up-doming of the anorthosite. As immiscibility of a Fe-Ti-P-rich melt and magma mixing have not been evidenced in the studied Fe-Ti ores, early ilmenite saturation accompanied by ilmenite sorting due to plagioclase buoyancy are thus the only mechanisms responsible for the formation of Fe-Ti deposits in Proterozoic massif-type anorthosites.

A study has been conducted on the aeration of reduced ilmenite with emphasis on increasing the aeration speed and understanding the mechanism of the aeration based on laboratory scale experiments. These issues were highlighted by comparing the currently operating Becher process which incorporates the use of an ammonium chloride catalyst in the aeration process.The speed of production of synthetic rutile from the Becher process is currently dictated by the time the reduced ilmenite remains in the aeration tank. As these times can vary greatly for no obvious reason, experiments were conducted to find which parameters could be changed to increase the speed of leaching. It was found that by increasing the oxygen content to 100 per cent the aeration time was reduced by at least half.By replacing ammonium chloride with various other amine compounds as the catalyst it was found there was a relationship between pK[subscript]a and aeration time. It was also found that the more sterically hindered the amine group, the slower the leaching. The use of ethylenediammonium chloride has shown that, when used at two thirds of the ammonium chloride concentration, aeration can be completed an hour (17%) faster than with the ammonium chloride catalyst. Furthermore, when ethylenediammonium chloride was used with a 100 per cent oxygen gas flow the aeration time was reduced by two thirds.Other compounds that did not contain amine groups were also investigated as catalysts in reduced ilmenite aerations. Of those tested only a citric acid / trisodium citrate mixture managed to aerate the reduced ilmenite substantially faster than the standard ammonium chloride catalyst. Other compounds with similar structure to the citrate ion failed to aid the aeration at all.

No description available.

Thesis (Ph. D.)--Murdoch University, 1990. / Thesis submitted to the School of Mathematical and Physical Sciences. Includes bibliographical references (p. 309-322).

Thesis (M. Eng.)(Mining)--University of Pretoria, 2003. / Includes bibliographical references.

The kinetics of dissolution of ilmenite, containing haematite, in aqueous solutions of sulphuric acid have been studied. Iron was found to leach from the mineral complex at a faster rate than titanium. The rates of solution of both iron and titanium increased, up to certain limiting values, upon abrading the mineral during leaching and were found to be related to the hydrogen ion activity of the leaching solution by a first order dependency. The results have been interpreted in terms of preferential and possibly diffusion-controlled leaching of the haematite with ilmenite being removed both by slow leaching and tearing out from the specimen surface. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

No description available.