Cobalt speciation

Dumond F., Marceau E., and Che M. 2007. A study of cobalt speciation in Co/Al203 catalysts prepared from solutions of cobalt-ethylenediamine complexes. J. Phys. Chem. C 111 4780-89. 

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)... 

Saito MA, Moffett JW. Complexation of cobalt by natural organic ligands in the Sargasso Sea as determined by a new high-sensitivity electrochemical cobalt speciation method suitable for open ocean work. Marine Chem. 2001 75 49-68. 

Saito M. A. and Moffett J. W. (2001b) Cobalt speciation in the equatorial Pacific and Peru upwelling region sources and chemical properties of natural cobalt ligands. Am. Soc. Limnol. Oceanogr. Meet. 

The cobalt speciation and reaction is approximate, but with the right roasting conditions, almost all cobalt can be expected to substantially turn into a sulphate, which would be readily leachable with minimum net acid consumption. However, under the right cobalt conversion conditions, the copper species are only partially sulphated, with some turning into the oxide form. Therefore, in the subsequent atmospheric leach step, a net input of sulphuric acid is required for achieving the highest copper yield. 

In this work ion-exchange and gel-permeation chromatography coupled with membrane filtration, photochemical oxidation of organic metal complexes and CL detection were applied to the study of the speciation of cobalt, copper, iron and vanadium in water from the Dnieper reservoirs and some rivers of Ukraine. The role of various groups of organic matters in the complexation of metals is established. 

Little is known of the oceanic distribution or speciation of cobalt, because very low concentrations (< 200 pM) make its determination difficult. Laboratory studies indicate that cobalt exists in seawater primarily as the cobalt (II) ion and as the carbonate complex. Organic complexes are not considered important. 

Advantages High analysis rate 3-4 elements per hour Applicable to many more metals than voltammetric methods Superior to voltammetry for mercury and arsenic particularly in ultratrace range Disadvantages Nonspecific absorption Spectral interferences Element losses by molecular distillation before atomisation Limited dynamic range Contamination sensitivity Element specific (or one element per run) Not suitable for speciation studies in seawater Prior separation of sea salts from metals required Suspended particulates need prior digestion About three times as expensive as voltammetric equipment Inferior to voltammetry for cobalt and nickel... 

Cobalt. The speciation of radiocobalt has been selected for discussion in this chapter because it exemplifies an element for which much information already exists regarding its stable chemical speciation, yet there are additional species which have become environmentally important as a result of the activities of the nuclear industry Cobalt, the middle member of the first triad of group VIII transition metals in the Periodic Table (iron, cobalt, nickel), is most stable in the divalent state when in simple compounds. Studies of radionuclide releases from nuclear power plants under tropical conditions in India seem to indicate that... 

Leonard, K.S., McCubbin, D. and Harvey, B.R. (1993) A radiochemical procedure for the determination and speciation of radio-cobalt in environmental waters. Sci. Total Environ., 130/131, 237-251. 

Finally, we must somehow resolve the vexing problem of the chemical speciation of trace elements in seawater what is the chemical nature of the various metal chelators whose existence has been demonstrated by electrochemistry Is the chemistry of several metals in surface seawater really controlled by metallophores released by prokaryotes Or are dissolved metals chiefly present as parts of metalloproteins in the process of remineralization How do metal chelators affect the residence times of metals (in particular, scavenged elements such as iron and cobalt) and in turn how do those chelators influence the global carbon cycle via changes in marine primary productivity ... 

Similar demands for speciation of trace elements exist for food analysis. Substantial differences in the biological availability are known for several essential elements and depend on the form in which they are present in the diet. The chemical bases for these differences are known for cobalt, iron, and chromium but not for zinc, copper, and selenium. The importance of speciation in food analysis is best demonstrated by the example of iron. That element, when part of heme compounds, is well absorbed, and there is little influence on the absorption by other factors in the diet. Nonheme iron, on the other hand, is not readily absorbed and, in addition, is subject to many influences from dietary ingredients those influences are poorly understood and probably not completely known (14). 

UCH/GOR] Uchida, E., Goryozono, Y., Naito, M., Aqueous speciation of magnesium, strontium, nickel and cobalt chlorides in hydrothermal solutions at 600°C and 1 kbar, Geochem. J., 30, (1996), 99-109. Cited on page 152. 

For zinc and the first transition series metals manganese, iron, cobalt, and nickel, the free hydrated divalent cation form dominates the dissolved inorganic speciation. The trivalent metal cations Al +, Ga +, Tl +, Fe " ", and Bi + are strongly hydrolyzed (i.e., they form strong complexes with... 

Easy speciation and isotope detection have been identified as playing important roles in optimizing the production of superconducting NbsSn wires by heating a composite of bronze and niobium filaments. Application of TOF-LMMS has provided evidence of the out-diffusion and accumulation of phosphorous, inhibiting Nb3Sn formation when tin diffuses inward. The preferential incorporation of the lower tin isotopes in the NbsSn layer has confirmed the process to be driven by diffusion. The semiconductor industry has used TOF-LMMS to verify the lateral diffusion of dopants, e.g., boron in tantalum and cobalt silicide ruimers only 3 pm wide. Another application is the identification of microscopic residues left on integrated circuits after removal of the photoresist. 

Copper speciation in the concentrate can range from chalcosite (CU2S) to chalcopyrite (Cu2S Fe2S3) as in typical Congo concentrates [3]. The key simplified cobalt and copper sulphating reactions can be approximated as follows ... 

The role of metal speciation in bleomycin uptake and cytotoxicity has been studied extensively. The relatively high amounts of copper in the blood, however,suggest that exogenous or endogenous metals in the blood do not markedly alter the uptake or activity of bleomycin. Nonetheless, a number of other metals can bind to bleomycin including indium and cobalt, and formulating bleomycin with these ex vivo can significantly reduce the cytotoxicity of bleomycin (Lyman et al. 1986). Complexes of this type have been used, however, to examine tumor cell uptake of bleomycin compounds. 

The adsorption of hydrolyzing ions Cr and Co on siUca gel was investigated [78], and speciation of mononucleus hydroxy species in the equiUbrium aqueous phase was also considered to calculate the equilibrium distribution between the soUd phase and bulk solution over the broad range of pH s. Although the different surface complexes of chromium and cobaltic assumed to form on surface sites of silica were not proved by any independent method, the fitting procedure was executed successfully, if only all the possible equilibria were accounted for in the SCMs. 

KotsakisN, Raptopoulou CP, Tangoulis V, Teizis A, Giapintzakis J, Jakusch T (2003) Correlations of synthetic, spectroscopic, structural, and speciation studies in the biologically relevant cobalt(ll) - citrate system the tale of the first aqueous dinuclear cobalt(ll) - citrate complex. Inorg Chem 42 22-31... 

Structure and interfacial speciation of the [Co(H20)6f complexes The sub-tide aqita complex is practically the only Co(II) species present in the nitrate solutions frequently used for motrrtting cobalt on the strrface of a catalytic support. Two different stmctures are the most probable at low and meditrm Co(n) sirrface concentrations (see Figure 7) [7]. 

The stability and solubility constants derived at 25 C for zero ionic strength have been used to create a predominance speciation diagram for cobalt(ll). The... 

Figure 11.61 Predominance diagram for the speciation of the cobalt(ll) ion at 25 °C. The behaviour in the region of -log [H+] > 12 should be treated with caution due to changes in activity coefficients.

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