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  • Author or Editor: M. Abdel-Hamid x
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Abstract  

The spectrophotometric determination of pure U(IV) or U(VI) ions in solution with Arsenazo I is greatly dependant on the pH of the solutions. The experimental conditions for the differential estimation of the different oxidation states of U ions, in the same sample, using Arsenazo I have been identified and implemented. The results showed that the applied method is rather rapid and accurate.

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Abstract  

Polyvalent ions are very sensitive to gamma irradiation in aqueous solutions. The present work is a part of a more comprehensive study dealing with the stabilization of certain oxidation states of some polyvalent ions during their gamma irradiation in aqueous systems. Sulphite ions, being well known reducing agents has been used for stabilizing Fe(II) ions in aqueous solutions during gamma radiolysis. Fe(II) ions in solution are known to be readily oxidized by gamma radiations in such a way that a 10–3N solution decays completely in about 2 hours at a dose rate 310 Gy/hr. In presence of an excess of sulphite ions it was found that Fe(II) ions were stabilized for extended time periods depending on the amount of sulphite ions used. The conditions of stabilization and its limits in the studied case has been identified.

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Abstract  

The various aspects of valency stabilization of polyvalent ions during -radiolysis have been further investigated. Ce(IV) ions, which are normally reduced in their aqueous solution, were found to be stabilized for increasing periods of time when they were irradiated in the presence of increasing amounts of bromate ions. It was found that the addition of about fifteen times excess of bromate ions to a 10–3 N Ce(IV) solution stabilized the cerium ions in the tetravalent state for about 120 hours during irradiation at a dose rate of 336 Gy/h. Increasing the amount of bromate used resulted in a subsequent increase in the protection time. It has been also noted that while bromate ions protected Ce(IV) in solution, the latter ions showed a clear protective effect on the bromate used, i.e., there is a mutual protective effect. The probable mechanisms, conditions and limitations of the protection process have been discussed. Based on the data obtained in the present work, it has been suggested that the protection of Ce(IV) ions by bromate ions in aqueous solutions during -radiolysis is very probably due to the preferential interaction of bromate with the reducing radiolysis products of water which are capable of reducing Ce(IV) to Ce(III).

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Abstract  

The distribution coefficient of sulphide, sulphite, sulphate and thiosulphate anions between different concentrations of aqueous alkali metal chloride solutions and the anion exchanger Dowex 1X8 is studied. The obtained distribution deportment of these anions is explained in the light of water-water, anion-cation and ion-ion interactions as well as the different tendencies of the alkali ions to hydration. Based on the separation factors encountered between adjacent anions, a chromatographic method is adopted for isolation of the sulphur anions by gradient elution. This method is further compared with the chromatographic procedures so far reported for separation of the investigated anions.

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Abstract  

The thermal decomposition of some Ni(II)-carboxylate-imidazole complexes in a nitrogen atmosphere was studied non-isothermally. From the non-isothermal thermoanalytical data, it was found that these complexes decompose through a stepwise release of imidazole molecules and/or CO ones forming unstable intermediates which produce metal oxide or the metal as a final decomposition product. TG in conjunction with DTG were used to evaluate the kinetic and thermodynamic parameters of the decomposition reaction. The kinetic studies were performed employing a computer-oriented kinetic analysis of each set of W-T data obtained under constant heating rate. The diffusion processes are the decisive mechanisms for the decomposition. The values of ΔE, A, ΔH, ΔS and ΔG for activation were calculated for the complexes and correlated to variation in their structure.

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Abstract  

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.

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Abstract  

The kinetics of the exchange of sulphate and chloride ions on the strongly basic anion exchanger Dowex 1X8, of different particle diameters is investigated. The diffusion coefficient values are calculated by two diferent methods, discussed in the light of the processes governing the exchange reactions encountered, and found to be mainly controlled by particle diffusion. The distribution behaviour of sulphate, sulphite, thiosulphate and sulphide between aqueous KCl solutions of different concentrations and a number of selected anion exchange resins is studied. The data are explained on the premises of the different interactions involved in both aqueous and resineous phases. The effect of the alkali metal chloride molarities in the aqueous phase (LiCl, NaCl and KCl) on the exchange behaviour of the different S-anions is also investigated. The results are interpreted in the light of the water—water interaction and the competition for hydration between the alkali metal cations and the exchanged S-anions.

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Abstract  

Different Nd-zeolites were prepared from the original NaX and NaY zeolites by ion exchange. The hydrated and thermally activated (at 550 °C) samples obtained were irradiated with -rays of 1.5 and 10.0 Mrad. The unirradiated and irradiated samples were characterized mainly by X-ray diffraction and tested for catalytic activity in cumene cracking. The X-ray diffraction patterns indicated a slight decrease of crystallinity after irradiation. However, the irradiated samples exhibited higher catalytic activities than unirradiated ones. -Irradiated hydrated zeolites were found to possess comparable activities, whereas the irradiated dehydrated samples were more active. Higher irradiation doses resulted in more active dehydrated zeolites than those irradiated with a lower dose. The observed higher activity was attributed to the formation of tricoordinate aluminium atoms in the zeolite structure, leading to increase of the number of acidic sites and consequently to a catalytic activity.

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