Hematite specific surface area

Pigment from Bayer Properties Hematite, specific surface area 17.9 m2/g [374,375],... 

The Fe-B nanocomposite was synthesized by the so-called pillaring technique using layered bentonite clay as the starting material. The detailed procedures were described in our previous study [4]. X-ray diffraction (XRD) analysis revealed that the Fe-B nanocomposite mainly consists of Fc203 (hematite) and Si02 (quartz). The bulk Fe concentration of the Fe-B nanocomposite measured by a JOEL X-ray Reflective Fluorescence spectrometer (Model JSX 3201Z) is 31.8%. The Fe surface atomic concentration of Fe-B nanocomposite determined by an X-ray photoelectron spectrometer (Model PHI5600) is 12.25 (at%). The BET specific surface area is 280 m /g. The particle size determined by a transmission electron microscope (JOEL 2010) is from 20 to 200 nm. 

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. 

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. 

Specific surface area 40 m2 g 1, acidity constants of FeOHg pK., (int) = 7.25, K 2 = 9.75, site density = 4.8 nrrr2, hematite cone = 10 mgle. Ionic strength 0.005. For the calculation the diffuse double layer model shall be used. 

Materials. Synthetic hematite was obtained from J. T. Baker Chemical Company, Phillipsburg, NJ. Particle size analysis using a HIAC instrument (Montclair, CA) indicated the particles to be 80 percent (number) finer than 2 microns. Using nitrogen as the adsorbate, the B.E.T. specific surface area was found to be 9 square meters per gram. The point of zero charge, as obtained from electrophoretic measurements in the presence of indifferent electrolytes, occurred at pH 8.3. 

The specific surface area of a solid is the surface area of a unit mass of material, usually expressed as m g . There is an inverse relationship between surface area and particle size. Massive crystals of hematite from an ore deposit (e. g. specularite) may have a surface area 1 m g". As particle size/crystallinity is governed largely by the chemical environment experienced during crystal growth, the surface area of a synthetic iron oxide depends upon the method of synthesis and that of a natural one, upon the environment in which the oxide formed. 

Dos Santos Alfonso and Stumm (1992) suggested that the rate of reductive dissolution by H2S of the common oxides is a function of the formation rate of the two surface complexes =FeS and =FeSH. The rate (10 mol m min ) followed the order lepidocrocite (20) > magnetite (14) > goethite (5.2) > hematite (1.1), and except for magnetite, it was linearly related to free energy, AG, of the reduction reactions of these oxides (see eq. 9.24). A factor of 75 was found for the reductive dissolution by H2S and Fe sulphide formation between ferrihydrite and goethite which could only be explained to a small extent by the difference in specific surface area (Pyzik Sommer, 1981). 

Maghemite from Nanotek Properties Structure confirmed by XRD (hematite present as an impurity), BET specific surface area 48.5 mVg, particle diameter 26 nm, TEM image and particle size histogram available [1322]. 

Hematite from Alfa Division, Danvers Properties specific surface area 6.5 mVg [670]. 

Acidity constants reported in [1278] are probably based on results from [1335]. Hematite from Alfa Aesar with specific surface area of 6 m-/g was studied in [1278]. 

Hematite from VEB Laborchemie Apolda Properties BET specific surface area 6.8 rnVg [1357]. 

Hematite from Nanostructured and Amorphous Materials, Inc. Properties Purity >99.9%, BET specific surface area 19 m7g, particle size 67 45 nm, spherical [1320]. 

Properties Hematite, BET specific surface area 44 rnVg [1373]. 

Properties >98% hematite [38], contains 0.3 mol% of Cl with respect to Fe, which is not removable by water washing, cubic particles [1394], BET specific surface area 34 m-/g [38], average size 120 nm, uniform particles [38], electron micrograph available [1394]. 

The sample studied in [1403] (heterodispersed hematite) after long aging was coated with hematite using a procedure described in [1401]. The coating-to-core ratio is less than 3 7. BET specific surface area 27.4 m /g [243]. 

Properties Hematite, different shapes obtained dependent on the experimental conditions [1374], BET specific surface area 14 m7g [1424], TEM and SEM images available [1374], IR spectra available [471]. 

The influence of the preparation method on the catalytic properties of lanthanum-doped hematite was studied in this work. It was found that the preparation method strongly affects the properties of the catalysts. The samples showed different particle sizes and specific surface areas as well as different resistance against reduction. The most active catalyst in the ethylbenzene dehydrogenation was obtained by adding the iron and lanthanum nitrate solutions to an ammonium hydroxide solution This solid is also able to produce a low amoimt of coke and has the advantage of being non-active. 

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