The transformation of VOHPO40.5H2O (VPO) precursor doped with cobalt or iron for n-butane oxidation to maleic anhydride was
investigated by thermogravimetric analysis under air and nitrogen, with and without n-butane in the flow. While almost no
effect was observed in nitrogen or air, a strong influence of the doping was observed when n-butane was added to the nitrogen
or air. This resulted in a delay of the decomposition of the precursor and a further reoxidation of the VPO catalyst, particularly
for doping with cobalt at low percentage (1%). This shows that doping can change the oxidation state of vanadium phosphorus
oxide catalysts, which can explain differences in their catalytic performances and the favourable effect of doping by cobalt.
A series of complexes has been prepared with the halides of cobalt(II), nickel(II), copper(II) and 2-,3-,4-ethylpyridine. The compounds were essentially all octahedral with the exception of those formed between 2-ethylpyridine and the cobalt(II) halides. The stereochemical configurations were deduced using spectral and magnetic properties. The decomposition of the complexes was studied by thermogravimetry and differential thermal analysis.
Trace amounts of transition elements (Fe, Co, Ni and Cu) in zirconium fluoride and NBS SRM's were determined by substoichiometric radioactivation analysis. The contents of impurities in sublimed sample were less than those of high-purity material and of reagent grade. The detection limits of these elements in zirconium fluoride were 10 ng/g for iron, 0.01 ng/g for cobalt, 1 ng/g for nickel and 0.1 ng/g for copper. The analytical results for iron, cobalt, nickel and copper in NBS SRM's were in good agreement with certified values.
Authors:H. Aly, M. El-Dessouky, M. Raieh, and S. Mohamed
Synergic extraction of trivalent iron and cobalt with thenoyltriflouroacetone (HTTA) and the synergic bases (B) benzylamine
(BA), dibenzylamine (DBA) and tribenzylamine (TBA) was studied. The extracted adducts proved to have the general formula M(TTA)3·B for all the amines investigated. The formation constants of the mixed-ligand complexes decrease in the order DBA>TBA>BA.
While equilibrium constant β3,1 for the Co(TTA)3·DBA complex is higher than the corresponding iron adduct, β3,1 for the iron adducts with BA and TBA are higher than those for cobalt.
The oxidation of a fine cobalt powder mixed with solid corrodents was investigated in the air. NaCl, Na2SO4, CaCl2, mixture of NaCl with Na2SO4, mixture of NaCl with MgO, and mixtures of Na2SO4 with V2O5, MoO3 and Fe2O3, respectively, were chosen as corrodents. Thermoanalytical diagrams were recorded within the temperature range from 20 to
1200C. It was stated that none of the corrodents induced the cobalt oxidation to start at a lower temperature. NaCl and mixture
of NaCl with Na2SO4 accelerated the oxidation slightly but addition of MgO stopped this effect.
Authors:P. Dimotakis, H. Papaefthymiou, and M. Soupioni
The oscillatory phenomenon during isothermal annealing of neutron irradiated crystalline cobaltic complexes is shown to extend for heating times up to 120 h without significant damping of amplitude and frequency of the oscillations. A mechanistic approach based on the Volterra-Lotka model is attempted involving defects and dissipative structure according to non-equilibrium thermodynamics.
This work reports a study on the synergistic extraction of cobalt(II), spiked with60Co from hydrochloric acid solutions by mixtures of trioctylamine (TOA) and neutral organophosphorous donors into carbon tetrachloride.
Synergistic coefficients and adduct formation constants have been evaluated from distribution measurements and correlated
with the basic character of donors.
The determination of leachability of radioisotopes of cesium and cobalt from preloaded zeolites in distilled water, base solution and acid solution has been studied. For the experiment, we used natural and chemically treated zeolites. The zeolites before leaching were calcined at different temperatures.
The inorganic sorbent potassium cobalt(II) hexacyanoferrate(II) was tested for removal of radiocesium from alkaline salt solutions that are typical of intermediate level radioactive wastes generated at spent fuel reprocessing plants in India. Excellent results were obtained both in batch equilibration and column operation.
No-carrier-added radionuclides of arsenic and selenium were produced in 16O irradiated cobalt target matrix. The initial products, formed by 59Co(16O,xn)70-73Br reaction, decayed promptly to arsenic and selenium radionuclides, which were subsequently separated by liquid-liquid extraction (LLX) using di-(2-ethylhexyl) phosphoric acid (HDEHP) and trioctylamine (TOA) as liquid ion exchangers.