Titanium production is a long and complicated process. What we often consider to be the standard method of primary titanium production (the Kroll process), involves many complex steps both before and after to make a useful product from titanium ore. Thus new methods of titanium production, especially electrochemical processes, which can utilize less-processed feedstocks have the potential to be both cheaper and less energy intensive than current titanium production processes. This project is investigating the use of lower-grade titanium ores with the electrochemical MER process for making titanium via a molten salt process. The experimental work carried out has investigated making the MER process feedstock (titanium oxycarbide) with natural titanium ores|such as rutile and ilmenite|and new ways of using the MER electrochemical reactor to \upgrade" titanium ores or the titanium oxycarbide feedstock. It is feasible to use the existing MER electrochemical reactor to both purify the titanium oxycarbide feedstock and produce titanium metal.

Please read the abstract in the section, 00front, of this document (Role and responsibility of the author) / Dissertation (MEng)--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted

The Old Hickory is the largest of a series of Pliocene (?) age heavy mineral sand deposits in Virginia and North Carolina. The high density of heavy minerals allows for selective concentration during transport and deposition. Under the right conditions, placers of considerable size can be formed. The elliptically shaped ore body of the Old Hickory Deposit extends in a North - South direction and is approximately 13 km (8 miles) long and up to 2.5 km (1.5 miles) wide, with an average thickness of 6.5 m (20 feet). The deposit lies along the Fall Zone, where a thin wedge of Cenozoic Coastal Plain sediments unconformably overlies the older rocks of the Piedmont. The principal minerals of economic interest found in the heavy mineral sands at the site are ilmenite (FeTiO₃), leucoxene (Fe<SUB>2-x</SUB>Ti<SUB>3+x</SUB>O<SUB>9+x/2</SUB>) where x is less than or equal to 2, rutile (TiO₂), and zircon (ZrSiO₄). An important focus of this study is the alteration of ilmenite by leaching away of iron, which results in enrichment in titanium. Titanium metal is highly valued for its light weight and high strength. In terms of total economic value, however, the use of titanium dioxide pigments for paint, coated paper, and other products is far more important. As the value of the ore is heavily dependent on the titanium content, the weathering process is a matter of considerable interest to the mineral industry. Analysis of ilmenite grains using reflected light microscopy revealed a wide range of alteration textures. Quantitative analysis and mapping of trace elements showed altered areas with enrichment in Ti and depletion in Fe, Mn, Mg, and Cr. It is believed that the weathering process took place in a reducing environment prior to final deposition according to the reaction: Fe²⁺TiO₃ + 2H⁺ --> Fe²⁺ (aq) + TiO₂ + H₂O Reducing environments are found in water-logged soils such as floodplains and other low-lying areas. Repeated cycles of burial and exhumation during transport would have created conditions ideal for the removal of iron from the ilmenite. / Master of Science

A study has been carried out on the Becher and Summit Processes with the aim of understanding the mechanism and critical parameters required for the production of a range of pure iron oxide pigments, as well as high quality synthetic rutile from reduced ilmenite . The Becher Process currently produces a large quantity of worthless mixed phase iron oxides. However, this study has shown that the range of iron oxides formed are all derived from the transformation of lepidocrocite (y-FeOOH) through the solution phase in iron(II) solutions. The results of a kinetic study of the transformation of lepidocrocite found that the rate exhibited an induction period at low pH, was dependent on temperature and was linearly related to log [H+] and log [Fe2+]. The rate determining step was found to be the formation of suitable product nuclei, following dissolution of the initial oxide at the surface of the crystal lattice. An electrochemical study of these reactions showed that the product formed from the transformation of lepidocrocite was a function of the solution potential and an experimental Eh-pH diagram was constructed to predict the iron oxide phase produced from hydrolysis and transformation reactions. The results from this fundamental study were then applied on both a laboratory and plant scale to produce pure iron oxide phases. A modified Summit Process, involving the removal of metallic iron from the porous reduced ilmenite matrix using FeCl 3, regeneration of iron(III) and the production of pure iron oxide pigments from the waste iron(II) chloride solution, was also investigated in detail. A kinetic study of pure iron dissolution in iron(III) solutions, comparing three electrochemical techniques and a standard solution sampling method, gave consistent rate constants provided allowance was made for the reaction with the proton. The iron dissolution mechanism was found to be iron(III) diffusion controlled, while the dissolution in HC1 was under mixed control. A study using both pure iron and pressed reduced ilmenite discs found that acid consumption could be minimised by the addition of citrate or by the addition of A1 3+ or Fe 2+ , which are believed to block the adsorption of the proton. It was found that iron(III)-citrate complexes inhibited iron(II1) hydrolysis in the reduced ilmenite pores and enhanced the purity of the synthetic rutile product. A study of the oxidation of iron(II) by atmospheric oxygen using copper(II) and activated carbon catalysts found that these catalysts were inefficient for complete iron(III) regeneration. The heating of carbon in the presence of cu2+ was found to enhance the initial rate of iron(II) oxidation, however it is believed that surface oxide redox couples formed on the carbon control the iron(II)/ iron(III) ratio in solution, and prevent complete iron(I1) oxidation. The production of iron oxide pigments under the controlled conditions afforded by the Summit Process, resulted in superior quality pigments than are presently attainable from the Becher Process. However, controlled ageing and crystal growth using waste lepidocrocite from the Becher Process would result in similar quality pigments being produced.

Titania slag is a feedstock to the pigment industry, which in turn provides titania pigment to producers of everyday products like paper, cosmetics and toothpaste. Titania slag is the primary product of the pyrometallurgical process of ilmenite smelting – the other products being iron and CO gas. Titania slag is typically tapped from the furnace into blocks of approximately 20 tons. After cooling these blocks are crushed and milled to size fractions suitable for the processes of the pigment producers. These processes are broadly grouped into two types of technology: the chloride route (during which titania slag is reacted with chlorine and subsequently re oxidised thereby removing the impurities) and the sulphate route (in this process the titania slag is purified after dissolving the slag in sulphuric acid). Due to the nature of these two processes, several specifications are imposed on the quality of the titania slags. The fluidised-bed technology used in the chloride process limits the size distribution of the slag to between 106 µm and 850 µm. Ilmenite smelting industries consequently crush and mill the titania slag to below 850 µm. The fraction below 106 µm is then sold to the sulphate market. Since the coarser chloride grade product is the more valuable product, slag producers continuously strive to improve the ratio between the coarser and finer fractions. This study reports on parameters which influence the particle size distribution of titania slags and therefore the split between the coarser (more valuable) and finer (less valuable) products. Pilot-scale slag ingots were used to identify chemical and process variables which influence the yield of coarser material. The microstructure of as-cast and milled slag was examined, and indicated a role of silicate phases in the crushing behaviour. Industrial-scale slag ingots were used to test whether the roles of tapping rate and water cooling (as identified from the pilot-scale ingots) also applied under industrial conditions. A numerical method was applied to estimate the thermal conductivity of the solidified slag (from measurements on pilot-scale ingots), and to predict the cooling and solidification behaviour of industrial-scale ingots. The study concludes that the chemical composition and cooling conditions of the slag block play central roles in the final particle size distribution of the slag. / Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2009. / Materials Science and Metallurgical Engineering / unrestricted

The Old Hickory mine is a world class placer titanium deposit located at the boundary of the Coastal Plain and the Piedmont in Virginia, astride the Sussex-Dinwiddie county line (77°34' W Long, 36°55'N Lat., Cherry Hill Quad). The Old Hickory deposit, discovered in 1987 by C. R. Berquist, was opened as a commercial mine in 1997, and is presently operated by Iluka Resources. Heavy minerals constitute an average of 8% of the sediment, but locally reach concentrations as rich as 60%. The ore minerals, in order of decreasing concentrations, are ilmenite, rutile, and zircon, which are believed to have been derived from weathering of Piedmont and Blue Ridge sources. After fluvial transport to the coast, the ore minerals were redistributed laterally along the coast by longshore currents, and ultimately concentrated by intense wave action, probably generated by large storms. The ores occur over an area of 8 km x 3 km, with ore minerals being found from the surface to up to depths of 12 meters, and appear to occur in at least two distinct ore horizons. This study examines the general ore mineralogy and differences in the mineralogy, grain sizes, secondary textures, and geochemistry of the ore minerals in the two distinct ore zones. Distinguishable differences between the two zones include a slightly coarser grain size, more angular grains of rutile, and a higher percentage of accessory minerals (epidote, garnet, etc) in the younger zone. Approximately 40% of all the ilmenite grains contain exsolution lamellae of hematite, a residual texture from the time of original ilmenite crystallization. Weathering of these ilmenite grains has preferentially dissolved out the hematite while preserving the original texture; thus the weathering increases the titanium content of the ore by removing some of the iron. The weathering also affects the distribution of minor elements such as aluminum, manganese, and chromium. At Old Hickory, the zircon population can be divided into two main types (thin, elongate rounded pink prisms, and short, thicker white to clear prisms) that may represent either multiple source regions or multiple generations of heavy mineral deposition. The variations in grain size, angularity, and rutile content are likely to be mappable and may prove useful in continuing stratigraphic studies, and in distinguishing separate ore zones. / Master of Science

Synthetically obtained ilmenite (FeO·TiO₂) particles were oxidized under conditions of a non-linear temperature increase over the range 300°-850°C. Short-circuit diffusion in the initial stages of oxidation gave an activation energy of 4.35 ± 0.4 kcal/mole, while above 525°C the activation energy was 50.2 ± 3.0 kcal/mole. The process was shown to be diffusion controlled, with iron the likely mobile species above 525°C, while no mechanism could be singled out for the controlling step in the early stages. The oxidation products in O₂ after 24 hours were shown to be pseudorutile (Fe₂Ti₃O₉) and hematite (Fe₂O₃) in a finely dispersed phase at temperatures below about 800°C, with pseudobrookite (Fe₂TiO₅) and rutile (TiO₂) being stable above this temperature. / Master of Science

The Saint-Urbain and Big Island rutile-bearing ilmenite Fe-Ti oxide deposits are located in the composite 450 km² Saint-Urbain anorthosite (1055-1046 Ma, U-Pb zircon) and in the Lac Allard intrusion (1057-1062 Ma, U-Pb zircon) of the 11,000 km² Havre-Saint Pierre anorthosite suite, respectively, in the Grenville Province of Eastern Canada. Slow cooling rates of 3-4°C/m.y. are estimated for both anorthosites, based on combined U-Pb zircon/rutile/apatite and ⁴⁰Ar/³⁹ Ar biotite/plagioclase geochronology, and resulted from emplacement during the active Ottawan Orogeny. Slow cooling facilitated (1) diffusion of Zr from ilmenite and rutile, producing thin (10-100 microns) zircon rims on these minerals, and (2) formation of sapphirine via sub-so lidus reactions of the type: spinel + orthopyroxene + rutile ± corundum → sapphirine + ilmenite. New chemical and analytical methods were developed to determine the trace element concentrations and Hf isotopic compositions of Ti-based oxides. Rutile is a magmatic phase in the deposits with minimum crystallization temperatures of 781°C to 1016°C, calculated by Zr-in rutile thermometry. Ilmenite present in rutile-free samples has higher Xhem (hematite proportion in ilmenite), higher high field strength element concentrations (Xhem = 30-17; Nb = 16.1-30.5 ppm; Ta 1.28-1.70 ppm), and crystallized at higher temperatures than ilmenite with more fractionated compositions (Xhem = 21-11; Nb = 1.36-3.11 ppm; Ta = <0.18 ppm) from rutile-bearing rocks. The oxide deposits formed by density segregation and accumulation at the bottom of magma reservoirs, in conditions closed to oxygen, from magmas enriched in Fe and Ti. The initial ¹⁷⁶Hf/¹⁷⁷ Hf of rutile and ilmenite (Saint Urbain [SU] = 0.28219-0.28227, Big Island [BI] = 0.28218-0.28222), and the initial Pb isotopic ratios (e.g.²⁰⁶Pb/²⁰⁴ Pb: SU = 17.134-17.164, BI = 17.012-17.036) and ⁸⁷Sr/⁸⁶ Sr (SU = 0.70399-0.70532, BI = 0.70412-0.70427) of plagioclase from the deposits overlap with the initial isotopic ratios of ilmenite and plagioclase from each host anorthosite, which indicates that they have common parent magmas and sources. The parent magmas were derived from a relatively depleted mantle reservoir that appears to be the primary source of all Grenvillian anorthosite massifs and existed for --600 m.y. along the margin of Laurentia during the Proterozoic.

The Saint-Urbain and Big Island rutile-bearing ilmenite Fe-Ti oxide deposits are located in the composite 450 km² Saint-Urbain anorthosite (1055-1046 Ma, U-Pb zircon) and in the Lac Allard intrusion (1057-1062 Ma, U-Pb zircon) of the 11,000 km² Havre-Saint Pierre anorthosite suite, respectively, in the Grenville Province of Eastern Canada. Slow cooling rates of 3-4°C/m.y. are estimated for both anorthosites, based on combined U-Pb zircon/rutile/apatite and ⁴⁰Ar/³⁹ Ar biotite/plagioclase geochronology, and resulted from emplacement during the active Ottawan Orogeny. Slow cooling facilitated (1) diffusion of Zr from ilmenite and rutile, producing thin (10-100 microns) zircon rims on these minerals, and (2) formation of sapphirine via sub-so lidus reactions of the type: spinel + orthopyroxene + rutile ± corundum → sapphirine + ilmenite. New chemical and analytical methods were developed to determine the trace element concentrations and Hf isotopic compositions of Ti-based oxides. Rutile is a magmatic phase in the deposits with minimum crystallization temperatures of 781°C to 1016°C, calculated by Zr-in rutile thermometry. Ilmenite present in rutile-free samples has higher Xhem (hematite proportion in ilmenite), higher high field strength element concentrations (Xhem = 30-17; Nb = 16.1-30.5 ppm; Ta 1.28-1.70 ppm), and crystallized at higher temperatures than ilmenite with more fractionated compositions (Xhem = 21-11; Nb = 1.36-3.11 ppm; Ta = <0.18 ppm) from rutile-bearing rocks. The oxide deposits formed by density segregation and accumulation at the bottom of magma reservoirs, in conditions closed to oxygen, from magmas enriched in Fe and Ti. The initial ¹⁷⁶Hf/¹⁷⁷ Hf of rutile and ilmenite (Saint Urbain [SU] = 0.28219-0.28227, Big Island [BI] = 0.28218-0.28222), and the initial Pb isotopic ratios (e.g.²⁰⁶Pb/²⁰⁴ Pb: SU = 17.134-17.164, BI = 17.012-17.036) and ⁸⁷Sr/⁸⁶ Sr (SU = 0.70399-0.70532, BI = 0.70412-0.70427) of plagioclase from the deposits overlap with the initial isotopic ratios of ilmenite and plagioclase from each host anorthosite, which indicates that they have common parent magmas and sources. The parent magmas were derived from a relatively depleted mantle reservoir that appears to be the primary source of all Grenvillian anorthosite massifs and existed for --600 m.y. along the margin of Laurentia during the Proterozoic.

Thesis (M.Sc.(Metallurgy)--University of Pretoria, 2000. / Summaries in Afrikaans and English. Includes bibliographical references (leaves 108-112).