Natural ilmenite

Spectra for 22 natural ilmenite samples from different deposits show that ilmenite itself is normally deposited with a composition close to the stoichiometry FeTi03 [108]. The weathering products which occur particularly in beach sands contain Fe ions, but are ill defined and of uncertain composition. The degree of weathering can be measured in any given sample from the MSssbauer spectrum. The spectra of lunar ilmenite at various temperatures is discussed on p. 294. 

The reaction of pure ilmenite does not involve reductive dissolution because the ideal structure contains only Fe(II). However most natural ilmenites represent partial solid solutions with hematite and contain significant amounts of Fe(III). 

This unit was then used for testing conversion of South African coal [49] and petroleum coke [23] using natural ilmenite ores. The low cost of natural ores, such as ilmenite, makes these materials particularly well-suited for solid fuel looping processes, that is, for use in an envirraiment with a high risk of deactivation and carrier loss due to... 

Iron Titanates. Ferrous metatitanate [12168-52-4] FeTiO, mp ca 1470°C, density 472(0), an opaque black soHd having a metallic luster, occurs in nature as the mineral ilmenite. This ore is used extensively as a feedstock for the manufacture of titanium dioxide pigments. Artificial ilmenite may be made by heating a mixture of ferrous oxide and titanium oxide for several hours at 1200°C or by reducing a titanium dioxide/ferric oxide mixture at 450°C. 

Ferrous orthotitanate [12160-20-2] Fe2Ti04, is orthorhombic and opaque. It has been prepared by heating a mixture of ferrous oxide and titanium dioxide. Ferrous dititanate [12160-10-0] FeTi20, is orthorhombic and has been prepared by reducing ilmenite with carbon at 1000°C. The metallic ion formed in the reaction is removed, leaving a composition that is essentially the dititanate. Ferric titanate [1310-39-0] (pseudobrookite), Fe2TiO, is orthorhombic and occurs to a limited state in nature. It has been prepared by heating a mixture of ferric oxide and titanium dioxide in a sealed quartz tube at 1000°C. 

The metallic element titanium (11) is relatively abundant in nature it accounts for 0.56% of the earth s crust. This number may not seem very impressive until you realize that it exceeds the combined abundances of ten familiar elements H, N, C, P, S, Cl, Cr, Ni, Cu, and Zn. The most important ore of titanium is ilmenite. a mineral commonly found as a deposit of black sand along beaches in the United States, Canada, Australia, and Norway. In ilmenite. titanium is chemically combined with iron and oxygen. The presence of iron makes the ore magnetic. 

Titanium dioxide (E171, Cl white 6) is a white, opaque mineral occurring naturally in three main forms rutile, anatase, and brookite. More than 4 million tons of titanium dioxide are produced per year and it is widely used for industrial applications (paints, inks, plastics, textiles) and in small amounts as a food colorant. ° "° Production and properties — Titanium oxide is mainly produced from ilmenite, a titaniferous ore (FeTiOj). Rutile and anatase are relatively pure titanium dioxide (Ti02) forms. Titanium oxide pigment is produced via chloride or sulfate processes via the treatment of the titanium oxide ore with chlorine gas or sulfuric acid, followed by a series of purification steps. High-purity anatase is preferred for utilization in the food industry. It may be coated with small amounts of alumina or silica to improve technological properties. 

In this work, 6 Lac Tio waste rock samples are investigated 3 samples were freshly blasted waste rock and 3 were weathered samples from an old waste rock pile (approximately 25 years old) which underwent significant natural alteration. The ilmenite content varies from approximately 20 to 60 wt% in both... 

Various well-known industrial and municipal waste products particularly those from the base metal industry, contain appreciable amounts of Fe oxides which may make them suitable for remediation purposes. Two examples from industry are the residues from the alumina and the titanium industries. The extraction of either Al or Ti from the natural ores (bauxite and ilmenite/rutile, respectively) leaves behind an alkaline and acidic (sulphuric) residue, respectively, in which Fe oxides are enriched, as indicated by their names Red Mud and Red Gypsum . A sample of Red gypsum is reported to contain ca. 35% of Fe oxide consisting of goethite and hematite, half of which was oxalate soluble (Fauziah et al., 1996). As expected, this material had an appreciable adsorption capacity for phosphate and heavy metals and, if added to soils, could confer these properties on them (Peacock Rimmer, 2000),... 

Titanium occurs in nature in the minerals rutile( Ti02), ilmenite (FeTiOs), geikielite, (MgTiOs) perovskite (CaTiOs) and titanite or sphene (CaTiSi04(0,0H,F)). It also is found in many iron ores. Abundance of titanium in the earth s crust is 0.565%. Titanium has been detected in moon rocks and meteorites. Titanium oxide has been detected in the spectra of M-type stars and interstellar space. 

Titanium is the ninth most abundant element in the earth s crust, and always occurs in combination with oxygen. The more important titanium minerals are shown in Table 12. Of the natural titanium minerals, only ilmenite, leucoxene, and rutile are of economic importance. Leucoxene is a weathering product of ilmenite. 

As in the case of ilmenite, the largest producers are in Australia, the Republic of South Africa and Sierra Leone. There is not enough natural rutile to meet demand, and it is therefore gradually being replaced by the synthetic variety. In 1994 the world wide production of rutile was about 0.5 x 106 t of contained Ti02. Compositions of typical rutile concentrates are given in Table 14. 

Synthetic Rutile. In contrast to ilmenite, only a small number of rutile deposits can be mined economically, and the price of natural rutile is therefore high. Consequently, many different processes have been developed to remove the iron from ilmenite concentrates without changing the grain size of the mineral because this is highly suitable for the subsequent fluidized-bed chlorination process. All industrial processes involve reduction of Fe3+ with carbon or hydrogen, sometimes after preliminary activation of the ilmenite by oxidation. Depending on the reducing conditions, either Fe2 + is formed in an activated ilmenite lattice, or metallic iron is produced. 

Most halloysite appears to be the result of supergene processes and, as noted by Ross and Kerr (1934), leaching by sulphuric acid, produced by the alteration of pyrite, appears to be one of the more common weathering processes. Alunite is commonly associated with halloysite (Ross and Kerr, 1934 Swineford et al., 1954). Sulphuric acid is commonly used to dissolve ilmenite in the manufacture of Ti02 (Willets and Marchett), 1958). It is possible that in nature it serves the same purpose. In the alteration of granitic rocks and pegmatites, feldspar is more likely to alter to halloysite... 

Iron metaniobates(iv) with structures of the natural minerals, ilmenite and pseudo-brookite have been prepared by direct reaction of the oxides under vacuum at 1000—1100°C. The compounds are stable in air up to 500°C, but are oxidized at higher temperatures.326 a-Sr3Fe07 x has been found to be isostructural with Sr3Ti07.327 Synthesis and thermal decomposition of iron(m) normal selenite mono-or tri-hydrate, Fe203,3Se02,xH20 (x = 1 or 3) have been reported.328... 

In natural samples, clinohumite is invariably titanium-rich and often fluorine-bearing (in those cases where fluorine analyzed). There is no apparent systematic composition difference (e.g., Mg/Fe, Ti content) between clinohumites found in massifs and those found in kimberlites and xenoliths. Ulmer and Trommsdorff (1999) argue that titanium-saturated clinohumite has the maximum thermal stability, with titanium-undersatu-rated clinohumite breaking down at lower temperatures in a divariant reaction to form a titanium-saturated clinohumite + olivine + ilmenite + H2O, based on experiments by Weiss (1997) (Figure 9). Because of the dependence of the stability of clinohumite on Ti02, Ulmer and Trommsdorff (1999) argue that the amount of titanoclinohumite in the peridotitic mantle would be controlled by the low Ti02 content... 

Figure 9 Location of the breakdown reaction clinohumite = olivine + ilmenite + fluid after Weiss (1997), as reported in Ulmer and Trommsdorff (1999). Experiments were conducted on three clinohumites of different composition. Abbrevations Xpe = Fe/(Fe + Mg), Xxi = 2Ti/(2Ti + OH), and Xp = F/(F + OH). Shaded areas represent divariant fields over which clinohumite coexists with olivine + ilmenite + fluid because the composition of the clinohumite is changing. Curves bounding shaded area A represent breakdown of a clinohumite with Xpe = 0.04, Xji = 0.28, and Xp = 0. Curve B represents maximum stability limit of natural, F-free clinohumite with Xpe = 0.19, Xji = 0.46, and Xp = 0. Curves bounding shaded area C represent breakdown of a clinohumite with Xpe = 0.03, Xxi = 0.47, and Xp = 0.47. Increasing Xxi, increasing Xp, and decreasing Xpe all tend to stabilize clinohumite to higher temperatures.

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