Radiolysis of aqueous solutions of ethylenediaminetetraaceta tocobalt(II) and (III)

The radiolysis of ethylenediaminetetraacetatocobalt (II) and (III) has been studied, both in the presence and absence of oxygen, Radiolytic degradation of the metal chelate was observed. Based on the experimental data, a radiolytic degradation mechanism of the chelates is proposed and discussed.     

Radiolysis of aqueous solutions of ethylenediaminetetraacetatocerium(III)

The effect of γ-rays on acidic and alkaline solutions of ethylenediaminetetraacetatocerium(III) has been studied both in the presence and absence of oxygen. A mechanism is proposed, in which the radiolytic degradation of the complex is due only to OH, while the radiolytic oxidation of Ce(III) EDTA to Ce(IV) by γ-rays occurs via the formation of hydrogen peroxide.     

Radiolysis of aqueous solutions of cobalt/II/ and cobalt/III/ 2,2′-bis-[aminoethyl]ether-tetraacetate complexes

Radiolysis of aqueous solutions of di- and trivalent cobalt with 2,2-bis/aminoethyl/ether-tetraacetic acid /BAETA/ was investigated, both in absence and in presence of oxygen. A radiolytic mechanism has been proposed where it has been shown that the degradation of the chelation is due to OH only.     

Hydrated cobalt(II) and nickel(II) ammine diphosphates isolated from aqueous solutions

Hydrated amorphous cobalt and nickel(II) ammine diphosphates were prepared.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9, 2004, pp. 1421–1424.Original Russian Text Copyright © 2004 by Voitenko, Zhilyak, Kopilevich.     

Heteropolynuclear cobalt(II) and nickel(II) ethylenediaminetetraacetates in aqueous solutions of aminoethanoic acid

Complexation in the Co(II)?Ni(II)?aminoethanoic acid (HGly)?EDTA (H₄Edta) system was studied at different molar ratios of components by absorption spectrophotometry. The mathematical modeling of A = f(pH) curves was used to establish that bi-, tri-, and tetranuclear heteroligand complexes like [(CoGly)Edta(NiGly)]^2?, [(CoGly₂)Edta(NiGly₂)]^4?, [(CoGly₂)Edta(NiGly₂)₂]^4?, [(CoGly₂)₂Edta(NiGly₂)]^4?, and [(CoGly₂)₂Edta(NiGly₂)₂]^4?, whose accumulation fraction attained 80?100% at optimal pH values, were formed depending on the ratio of reagents and the acidity of a medium. The formation equilibrium and total stability constants of these complexes were calculated, and a hypothesis about their structure was made.     

Oxidation of cobalt(II) with air oxygen in aqueous ethylenediamine solutions

Oxidation of aqueous Co(NO₃)₂–ethylenediamine (En) solutions with air oxygen was investigated at 20 °C and pH 5.2–7.0, with and without mechanical stirring, by measuring the Co^II concentration, pH and redox potential on an Au electrode. In most cases, the oxidation rate was proportional to the concentration of CoEn ²⁺ _n (n = 2, 3) complexes, and the influence of the solution pH on the rate of reaction was accounted for by the pH dependence of the Co^II complex distribution. It was found that sulphate inhibits and bromide accelerates the oxidation process. Possible oxidation routes are discussed. The oxidation process is limited to some extent by O₂ transport from the air to the bulk solution.     

Radiolysis of aqueous solutions of thiamine

The results of the radiolysis of aqueous solutions of thiamine (vitamin B₁) are presented. The yields for decomposition of thiamine and the product of radiolytic products were determined. The G values decrease as the dose increases. Some radiolytic products were identified. Decomposition of thiamine was slightly dependent on the presence of oxygen and on the pH of the solution. At pH 4.4 with a concentration of 2.5 × 10⁻⁴ mol L⁻¹ of thiamine in an oxygen free aqueous solution, the G⁰ value for decomposition is 5.0.     

Interaction of nickel(II) and cobalt(II) salts with chitosan hydrochloride and acetate in aqueous solutions

Fundamental aspects of the complexation of cobalt(II) and nickel(II) ions with chitosan hydrochloride in water and chitosan in an aqueous solution of acetic acid were studied. The relation between the numbers of chitosan moles and metal ions involved in the interaction was found. The optimal conditions for synthesis of complexes were determined and their chemical composition and spectral properties were analyzed. The possible reaction mechanisms were discussed.     

Radiolysis of U(VI)-arsenazo-1 complex in aqueous solutions

The effect of absorbed dose on the decolouration of U(VI)-arsenazo-1 complex solutions has been investigated at pH 8.3. G-values were determined as a function of complex concentration as well as of OH, e _aq ^– scavengers. Using competition kinetics, rate constants were determined and the degradation mechanism discussed.     

Extraction of cobalt(II) from aqueous thiocyanate solutions by tri-n-octylamine

The distribution of cobalt(II) between acidic thiocyanate solutions and tri-n-octylainine dissolved in various diluents has been measured for several cobalt(II) loadings and amine concentrations. Diluents investigated included n-hexane, cyclohexane, benzene, xylene, carbon tetrachloride, chloroform, chlorobenzene, o-dichlorobenzene and nitrobenzene. In all cases, the species extracted is bis(tri-n-octylammonium) tetrathiocyanatocobaltate(II). The ability of each diluent to extract cobalt(II) from acidic thiocyanate solutions is approximately correlated with the dielectric constant of the pure diluent, i.e., the smaller the dielectric constant, the larger the distribution ratio, with the exceptions of nitrobenzene and chloroform.     

Spectral and magnetic studies on normal cobalt(II) planar and cobalt(III) octahedral, spin-crossover cobalt(III) octahedral and planar-tetrahedral cobalt(II) carbodithioates

Five cobalt(II) complexes, a normal complex Co(4-PPipzcdt)₂ (4-PPipzcdt = 4-phenylpiperazine-1-carbodithioate), and four zwitterionic complexes, Co(4-PPipzcdtH)₂X₂ and Co(4-MPipzcdtH)₂X₂ (X = Cl, Br; 4-PPipzcdtH = 4-phenylpiperazine-1-carbodithioic acid, 4-MPipzcdtH = 4-methylpiperazine-1-carbodithioic acid), have been synthesized. Normal cobalt(III) complexes of the type Co(4-MPipzcdt)₃ and Co₂ {2-MPipz(cdt)₂}₃ (2-MPipz(cdt)₂ = 2-methylpiperazine-1,4-dicarbodithioate) and two zwitterionic cobalt(III) complexes of the type Co(4-MPipzcdtH)₃X₃ (X = Cl, Br) have also been obtained. In addition to the room temperature IR and electronic spectra and magnetic susceptibility studies, all the complexes, except the normal Co(4-MPipzcdt)₃ and Co(4-PPipzcdt)₂ and zwitterionic Co(4-MPipzcdtH)₃Cl₃, have been investigated by variable-temperature magnetic susceptibility measurements. The results of the variable-temperature magnetic susceptibility studies suggest that two cobalt(II) carbodithioates exhibit a square planar-tetrahedral equilibrium, while two cobalt(III) octahedral carbodithioates show a spin-crossover phenomenon.     

The structural organization of oligonuclear cobalt(II,III) and cobalt(III) carboxylates

The review deals with the topology of homonuclear carboxylate complexes of cobalt(II, III) and cobalt(III) whose structures are built from the monocarboxylate anions RCOO^– (R is a radical containing no electron-donating substituents), water, and its deprotonated forms.     

Complexation of cobalt(II) with histidinato(pentaammine)cobalt(III) in aqueous medium. A kinetic and mechanistic study

Summary The kinetics of formation and dissociation of the binuclear complex of Co^II with histidinato(pentaammine)Co^III have been studied at 10.0°Ct°C25°C and I = 0.3 mol dm^–3 (ClO _inf4 ^sup– ). The formation of the binuclear complex, [(NH₃)₅Co^IIILCo^II]⁴⁺ (L = histidinate), in the 5.7–6.8 pH range involves the reaction of Co(OH₂) _inf6 ^sup2+ with the deprotonated, (NH₃)₅CoL²⁺, and monoprotonated, (NH₃)₅CoLH₃₊, forms of the complex. The rate and activation parameters for the formation are consistent with an I _d mechanism. The binuclear species undergoes dissociation to yield the parent Co^III substrate and Co(OH₂) _inf6 ^sup2+ via spontaneous and acid-catalysed paths. Comparison of spontaneous dissociation rate of the binuclear complex with other related systems indicated the chelate nature of the binuclear species.     

Radiolysis of aqueous solutions of nitrilotriacetic acid

The radiolysis of nitrilotriacetic acid (NTA) in neutral or alkaline solution, was studied in the presence and in the absence of dissolved oxygen. The radolytic yields of decomposition of NTA and formation of iminodiacetic acid(IDA) were determined; G(-NTA) was found to be equal to G(IDA). The formation of hydrogen peroxide and carbonyl compounds was also followed. The radiolysis was found to be initiated by hydrogen abstraction by both H and OH radicals with the formation of a dehydrogenated radical intermediate which ultimately stabilizes to give products. The radiolytic mechanism under different conditions has been discussed. From competition kinetic studies with sodium formate in neutral solution, the rate constant, k(OH + NTA), was found to be 3.0 x 10⁸ dm³ mol⁻¹s⁻¹.     

Thermodynamics of complexation of lead(II) and cobalt(II) with N-(carboxymethyl)aspartic acid in aqueous solutions

The enthalpies of complexation of lead(II) and cobalt(II) with N-(carboxymethyl)aspartic acid (H₃Y) were determined calorimetrically at 298.15 K within a wide ionic strength range (KNO₃). The thermodynamic characteristics of formation of the CoY₂- and PbY_2? complexes were calculated at non-zero and zero ionic strengthes. The explanation of the obtained values is given.     

Radiolysis of aqueous solutions of gadolinium nitrate

The specific effect due to Gd³⁺ ion on the radiolysis of aqueous nitrate solutions was determined by measurement of H₂, H₂O₂ and NO ₂ ^– radiolytic yields produced by gamma-irradiation of aerated and deaerated solutions of gadolinium, sodium and calcium nitrates in the concentration range of 10^–5 to 0.3M. Important O₂ consumption in aerated and O₂ evolution in deaerated Gd(NO₃)₂ solutions was found by radiolysis in comparison with the inert cations nitrates. In the former the Gd³⁺ ion generates an O₂ transporter producing an increase in the H₂O₂ yield and a decrease in the NO ₂ ^– yield, while in the latter it enhances the H₂ and NO ₂ ^– production with respect to the same nitrate concentration of the Na⁺ solutions.