Goethite spectrum

In order to explain the similarity between the SAL-goethite spectrum and the aqueous SAL-Fe(III) spectrum, a chelate structure similar to that drawn above must be assumed to form during SAL adsorption on goethite. 

Fig. 7.1 Infrared spectra of iron oxides in the range 400 to 4000 cm (ca. 1 mg in 300 mg KBr). a) Wave number range 1000-4000 cm b) wave number range 400-1000 cm The insert in the goethite spectrum shows that the two OH bending vibrations shift to higher wave...

Fig. 8.31 Left) In the Mossbauer spectrum taken in the Columbia Hills at a rock called Clovis the mineral goethite (GT) (a-FeOOH) could be identified. GT is a clear mineralogical evidence for aqueous processes on Mars. Right) The rock Clovis is made out of rather soft material as indicated by the electric drill-current when drilling the - - I cm deep hole seen in the picture. Drill fines are of brownish color. The pattern to the right of the drill hole was made by bmshing the dust off the surface by using the RAT...

Figure 3. CIR-FTIR spectra of goethite (ct-FeOOH) at 100 g/L solid concentration suspended in water at pH 6.5 (a) spectrum of suspension, (b) spectrum of supernatant, (c) difference spectrum a-b. Reproduced with permission from Ref. 37. Copyright 1986 American Chemical Society.

Figure 10. MES spectrum for a synthetic brown (hematite and goethite)...

Figure 11 shows the differences between synthetic hematite and one from burning an ochre and between a synthetic goethite and a typical yellow ochre (in which the iron is chiefly goethite in character). Note the extra peak or peaks in the center of the hematite spectrum in the natural material. 

Fig. 3-1. Band assignment for the diffuse reflectance spectrum of a goethite. Note that one band eould not be assigned. EPT electron pair transition OMCT oxygen-metal charge transfer. From Seheinost et al., 1999 with permission.

This method produces ca. 9 g goethite with a surface area of ca. 20 m / g. The crystals are acicular and consist of several domains along the needle (a-)axis. An electron micrograph is shown in Fig. 5-2 a, an X-ray diffractogram in Fig. 5-6 and an IR spectrum in Fig. 5-7. The crystals are bounded mainly by 101 faces (Fig. 5-3). 

The method produces ca. 5-6 g goethite of low crystallinity and a surface area of about 80 m /g. The crystals resemble goethites from various natural environments. An X-ray diffractogram is shown in Fig. 5-9, an EM photo in Fig. 5-10 and a Mossbauer spectrum in Fig. 5-11. An X-ray... 

Method 6 produces about 8 g of hematite which consists of grainy-look-ing ellipsoidal (spindle-type) crystals (Fig. 10-5 d) and has a surface area of ca. 80-90 m /g. Again, as seen from the X-ray pattern the sample is reasonably pure and well crystallized (Fig. 10-2) but contains adsorbed oxalate and a trace of goethite (see IR spectrum in Fig. 10-3). 

Bocqnet S (1996) Snperparamagnetism and the Mossbaner spectrum of goethite a comment on a recent proposal by Coey et al. J Phys Condensed Matter 8 111-113 Bodker F, Hansen MF, Bender Koch C, Lefmann K, Morap S (2000) Magnetic properties of hematite nanoparticles. Phys Rev B 61 6826-6838... 

Figure 5. Normalized -weighted As-EXAFS spectra (a) and Fourier transforms (FTs) (b) of As(V) sorption on goethite (total reaction time = 1032 hours) after I hour and 24 hours desorption ofAs(V) by 6 mM phosphate. The spectrum ofscorodite is plotted for comparison. Solid lines are experimental data dotted lines are least-squares fits. Peak positions in FTs are not corrected for phase-shift effects, and are therefore approximately 0.5 A shorter than the true distance. Reprinted from O Reilly et al. (2001) with permission.

Figure 5. Evidence for surface species (right) in the normalized, background-subtracted, k3-weighted EXAFS spectra (left) of selenate and selenite ions reacted with goethite. The EXAFS spectra of selenate or selenite ions in aqueous solution are shown as dashed curves, with vertical arrows denoting contributions from Fe(III) in the selenite spectrum. Reactive surface OH groups on goethite are...

Properties XRD pattern, Mossbauer spectrum available [1318]. PZC/IEP of hematite-goethite composite is presented in Table 3.468. 

Properties Goethite, needles, 213 nm long and 44 nm wide, TEM and HR TEM images, IR spectrum, TGA and DTA results available [1600]. Properties of particles obtained at different reagent concentrations and temperatures are also described in [1600], but IEP is only available for one recipe. 

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