Hematite, 856 table

Minerals. Iron-bearing minerals are numerous and are present in most soils and rocks. However only a few minerals are important sources of iron and thus called ores. Table 2 shows the principle iron-bearing minerals. Hematite is the most plentiful iron mineral mined, followed by magnetite, goethite, siderite, ilmenite, and pyrite. Siderite is unimportant in the United States, but is an important source of iron in Europe. Tlmenite is normally mined for titania with iron as a by-product. Pyrite is roasted to recover sulfur in the form of sulfur dioxide, leaving iron oxide as a by-product. 

The specifications for drilling fluid hematite have been set by the API and are Hsted in Table 2 (24). Hematite is used most frequently in high density oil-based muds to minimise the total volume percent soflds (26). The abrasivity of hematite limits its utiUty in water-based muds. 

Table 7.3. Shock-modified powders Crystallite size, strain, and static magnetization data on hematite (after Williamson et al. [86W03]).

The weight of hematite to be blended is found by using Equation 4-324. Taking the appropriate data from Tables 4-154, 4-155, 4-159 and 4-160, and letting X be the unknown weight of hematite per sack of cement, Equation 4-324 is... 

The Unit of Structure.—A spectral photograph of the K-radiation of molybdenum reflected from the face (100) of hematite (planes denoted by primes refer to the axes used by Groth) gave, as shown in Table I, the value 3.682 0.010 A. for d/n. If n is one, this corresponds to a unit of structure with a = 3.70 A., and a = 85° 42. With one Fe2C>3 in this unit, the density calculated from the X-ray data is 5.25, in good agreement with the observed values,1 which range from 5.15 to 5.30. 

The Laue data for corundum (Table IV) are similar to those for hematite. By the arguments previously given the correct space group is seen to be Djjdi and the possible arrangements are accordingly those listed... 

The precursor particles of Pt, Pt02 H20, were tried to be deposited on hematite (a-Fe203) supports (a) polycrystalline ellipsoid (A), (b) monocrystalline ellipsoid (B), (c) monocrystalline pseudocube, and (d) monocrystalline platelet. Also, the precursor particles of Pt were tried to be formed on other supports other than a-Fe203 (a) a-FeOOH, (b) P-FeOOH, (c) Zr02 (A) with rough surfaces, (d) Zr02 (B) with smooth surfaces, and (e) Ti02 (anatase). The mean sizes and yield of the precursor particles are summarized in Table 2 with the specific surface area of the supports. 

Main opaque minerals are chalcopyrite, pyrite, pyrrhotite, sphalerite and bornite (Table 2.22). These minerals commonly occur in massive, banded and disseminated ores and are usually metamorphosed. Hematite occurs in red chert which is composed of fine grained hematite and aluminosilicates (chlorite, stilpnomelane, amphibole, quartz) and carbonates. The massive sulfide ore bodies are overlain by a thin layer of red ferruginous rock in the Okuki (Watanabe et al., 1970). Minor opaque minerals are cobalt minerals (cobaltite, cobalt pentlandite, cobalt mackinawite, carrollite), tetrahedrite-tennantite, native gold, native silver, chalcocite, acanthite, hessite, silver-rich electrum, cubanite, valleriite , and mawsonite or stannoidite (Table 2.22). 

Weighting agents (Table 10-10) are added to increase the density of the cement. They are typically used to combat high bottom-hole pressures. Common additives are powdered iron, ferromat, powdered magnetite, and barite. Hematite ean be used to increase the density of a mixture up to 2200 kg/m (19 Ib/gal). Hematite requires the addition of some water. 

Homopolymers. Polymers such as poly(methacrylamido-4,4,8,8-tetra-methyl-4,8-diaza-6-hydroxynonamethylene dichloride), abbreviated poly(MDTHD), and a triaza analog, abbreviated poly(MTHHDT), have been shown to be effective stabilizers of silica, calcite, and hematite (14,15) as indicated by the data summarized in Table V. 

Copolymers of MDTHD and DMAPMA appeared to be the most effective silica, calcite, and hematite mineral fines stabilizers. Increasing the copolymer MDTHD content had little effect on polymer performance. Similar results were observed for a series of MDTHD -DMAEMA copolymers and a series of DMAEMA CH-C1 salt - DMAEMA copolymers (Table VI). In contrast, increasing the MDTHD content of MDTHD - NNDMAm copolymers from 67% to 90% improved copolymer performance as a silica fines and hematite fines stabilizer. 

Limited silica fines stabilization data indicated that increasing copolymer molecular weight from 100,000 to 1,000,000 daltons had, if anything, a negative effect on silica fines stabilization. At a molecular weight of 1,000,000 daltons, this copolymer appeared to be more effective in stabilizing silica fines than silica/kaolinite, calcite, or hematite fines. However, the results may be due in part to the larger particle size and lower surface area of the silica fines (see Table II). 

The rate law is based on a surface complexation model Liger et al. (1999) developed for the hematite nanoparticles (see Chapter 10, Surface Complexation ). The >FeOH surface sites react by protonation and deprotonation to form >FeOII2h and >FeO-, by complexation with ferrous iron to form >FeOFe+ and >FeOFeOH, and to make a complex >Fe0U020H with uranyl. Table 28.1 shows the reactions and corresponding log K values. The nanoparticles are taken to have a specific surface area of 109 m2 g-1, and a site density of 0.06 per Fe2C>3. 

Measured surface areas (11-point BET analyses) for pure phases such as ferrihydrite, goethite and hematite are in the range as proposed by Cornell Schwertmann (2003) (Table 1). Preliminary XRD analyses showed that temperature impacts the kinetics of phase transformation of ferrihydrite. Data indicated that after seven days, the rate of transformation from ferrihydrite to more crystalline forms, if it was occurring, was too slow to be measured at 25°C (Fig. 1). In contrast to the 25°C experiment, significant, transformations were observed at 50 (Fig. 2) and 75°C (Fig. 3) after 24... 

Fig. 3.4a gives plots of charge resulting from surface protonation vs pH for various oxides. Dots represent experimental data from different authors (Table 3.1a) from titration curves at ionic strength I = 0.1 M (hematite = 0.2 M). It is interesting to note that the data "of different oxides" can be "normalised" i.e., made congruent, if we chose the master variable... 

Surface protonation isotherms. Dots represent experimental data from titration curves at ionic strength I = 0.1 (Hematite, I = 0.2). References are indicated in Table 3.1. The concentration of protonated sites MOH is given in moles nr2. BET surface data were used to calculate the surface concentration. 

The commonest habits for hematite crystals are rhombohedral, platy and rounded (Fig. 4.19). The plates vary in thickness and can be round, hexagonal or of irregular shape. Under hydrothermal conditions, these three morphologies predominate successively as the temperature decreases (Rosier, 1983). The principal forms are given in Table 4.1. Hematite twins on the 001 and the 102 planes. The crystal structure of hematite has a less directional effect on crystal habit than does that of goethite and for this reason, the habit of hematite is readily modified. A variety of morphologies has been synthesized, but in most cases, the crystal faces that enclose the crystals have not been identified. 

The solubility plots for lepidocrocite, ferrihydrite and hematite (Fig. 9.2) and for goethite, ferrihydrite and soil-Fe (Fig. 9.3) show only the total Fe activity. They were obtained in the same way as that for goethite using the appropriate constants from Tables 9.1, 9.2 and 9.4. 

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