Cobalt emission spectroscopy

Bromo-2-pyridyla2o)-5-diethylamiQophenol (5-Br-PADAP) is a very sensitive reagent for certain metals and methods for cobalt have been developed (23). Nitroso-naphthol is an effective precipitant for cobalt(III) and is used in its gravimetric determination (24,25). Atomic absorption spectroscopy (26,27), x-ray fluorescence, polarography, and atomic emission spectroscopy are specific and sensitive methods for trace level cobalt analysis (see... 

The nuclear decay of radioactive atoms embedded in a host is known to lead to various chemical and physical after effects such as redox processes, bond rupture, and the formation of metastable states [46], A very successful way of investigating such after effects in solid material exploits the Mossbauer effect and has been termed Mossbauer Emission Spectroscopy (MES) or Mossbauer source experiments [47, 48]. For instance, the electron capture (EC) decay of Co to Fe, denoted Co(EC) Fe, in cobalt- or iron-containing compormds has been widely explored. In such MES experiments, the compormd tmder study is usually labeled with Co and then used as the Mossbauer source versus a single-line absorber material such as K4[Fe(CN)6]. The recorded spectrum yields information on the chemical state of the nucleogenic Fe at ca. 10 s, which is approximately the lifetime of the 14.4 keV metastable nuclear state of Fe after nuclear decay. 

The catalysts were characterized by inductively coupled plasma emission spectroscopy (ICP-ES Perkin Elmer Optima 3300RL) to determine cobalt content, x-ray diffraction (XRD Bruker A-500) with crystallite size determination using the Rietveld method, and temperature-programmed reduction (Zeton Altamira AMI-200) using 30 ml/min 10% H2/Ar and a ramp rate of 10°C/min. Surface area... 

Carbon deposition from CO on a cobalt catalyst at low pressures is known to be a structure-sensitive process. CO is adsorbed molecularly on the low index surfaces (Co (0001)), but its dissociation occurs on the Co (1012), Co (1120), and polycrystalline surfaces.5762 Deposition of carbon on Co (1012) and the probable formation of Co3C have been established by Auger emission spectroscopy (AES) and low-energy electron diffraction (LEED) techniques.66... 

J. van de Loosdrecht, P. J. van Berge, M. W. J. Craje and A. M. van der Kraan, The application of Mossbauer emission spectroscopy to industrial cobalt based Fischer-Tropsch catalysts, Hyperfine Interact., 2002, 139/140, 3-18. 

Mossbauer Measurements. Co-Mo catalysts cannot be studied directly in absorption experiments since neither cobalt nor molybdenum has suitable Mossbauer isotopes. However, by doping with 57Co the catalysts can be studied by carrying out Mossbauer emission spectroscopy (MES) experiments. In this case information about the cobalt atoms is obtained by studying the 57Fe atoms produced by the decay of 57Co. The possibilities and limitations on the use of the MES technique for the study of Co-Mo catalysts have recently been discussed (8., 25.). 

P. J. Galley, J. A. Horner and G. M. Hieftje, Automated simplex optimisation for monochromatic imaging inductively coupled plasma atomic emission spectroscopy, Spectrochim. Acta, Part B, 50(1), 1995, 87-107. 170. L. M. Cabezon, M. Caballero, J. M. Diaz, R. Cela and J. A. Perez-Bustamante, Multielemental separation and determination of some heavy metals (copper, cobalt, cadmium and nickel) in tap water and high salinity media by CGA (colloidal gas aphron)-coflotation, Analusis, 19(4), 1991, 123-127. 

Table IV. Comparison of Results for Determination of Lead, Cobalt, and Nickel by Atomic Absorption (A) and Emission Spectroscopy (B)...

Emission spectroscopy with arc and spark excitation has been used since the 1930s for many industrial analyses. In metaUurgy, for example, the presence in iron and steel of the elements nickel, chromium, sihcon, manganese, molybdenum, copper, aluminum, arsenic, tin, cobalt, vanadium, lead, titanium, phosphoms, and bismuth have been determined on a routine basis. Modem instruments can also measure oxygen, nitrogen, and carbon in metals, which used to require separate measurements with dedicated high-temperature... 

Emission spectroscopy of the corrosion product showed that small amounts of aluminum (4%), sodium (3%), cobalt (2%), chromium (0.35%), boron (0.25%), and iron (0.05%) were ptesenL The remaining 90% of the material analyzed was nonmetallic. 

The detection and determination of traces of cobalt is of concern in such diverse areas as soflds, plants, fertilizers (qv), stainless and other steels for nuclear energy equipment (see Steel), high purity fissile materials (U, Th), refractory metals (Ta, Nb, Mo, and W), and semiconductors (qv). Useful techniques are spectrophotometry, polarography, emission spectrography, flame photometry, x-ray fluorescence, activation analysis, tracers, and mass spectrography, chromatography, and ion exchange (19) (see Analytical TffiTHODS Spectroscopy, optical Trace and residue analysis). 

The most direct information on the state of cobalt has come from Mossbauer spectroscopy, applied in the emission mode. As explained in Chapter 5, such experiments are done with catalysts that contain the radioactive isotope 57Co as the source and a moving single-line absorber. Great advantages of this method are that the Co-Mo catalyst can be investigated under in situ conditions and the spectrum of cobalt can be correlated to the activity of the catalyst. One needs to be careful, however, because the Mossbauer spectrum one obtains is strictly speaking not that of cobalt, but that of its decay product, iron. The safest way to go is therefore to compare the spectra of the Co-Mo catalysts with those of model compounds for which the state of cobalt is known. This was the approach taken... 

Figure 27. Distribution of cobalt among the various species of an activated HDS catalyst, as determined by emission Mossbauer spectroscopy. The catalyst, prepared by impregnation of ammonium heptamolybdate and 57Co nitrate, was as similar as possible to the commercial one used for obtaining the results presented in the previous figures (3wt% as CoO, 13 wt% as M0O3 on -/-alumina). All precautions were taken to avoid possible errors due to noninstantaneous charge compensation in the sequence of nuclear events in 57Co decay (this has to be taken into account in the nonconducting M0S2 matrix) [155, 156].

Kamnev, A.A., Antonyuk, L.P., Smirnova, V.E., Serebrennikova, O.B., Kulikov, L.A., Perfiliev, Y.D. Trace cobalt speciation in bacteria and at enzymic active sites using emission Mossbauer spectroscopy. Anal. Bioanal. Chem. 372, 431 35 (2002)... 

One of the important applications of MBssbauer spectroscopy is in the determination of bonding of the MBssbauer nuclide. Since the cobalt MBssbauer s ctrun can only be observed in the emission mode, the radioactive isotope must be inserted into the... 

Chemical vapor deposition (CVD) was applied to produce homogeneous thin films of pure and doped spinel cobalt oxide with similar morphology on the surface of planar and monolithic supports. The planar substrates were used to investigate the thermal stability and the redox properties of the spinel using temperature-programmed methods monitored by emission-FTIR spectroscopy, while the monolithic substrates were used to test the catalytic performance of the deposited films toward the deep oxidation of methane and to evaluate its durability. The high performance of cobalt oxide to oxidize methane in diluted streams was demonstrated at 500 °C. Furthermore, controlled doping of cobalt oxide layers with suitable cations was demonstrated for nickel as an example, which resulted in substantial increase of electric conductivity. 

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