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Abstract  

The synergistic extraction of uranium(VI) from aqueous nitric acid solution with mixtures of bis(hexylsulfinyl)ethane (BHxSE) and petroleum sulfoxides (PSO) in 1,1,2,2-tetrachloroethane was studied. It has been found that the maximum synergistic extraction effect occurs when the molar ratio of PSO to BHxSE is close to 1. The composition of the complex of synergistic extraction was estimated as UO2(NO3)2 .BHxSE.PSO. The formation constant of the complex was equal to KBP = 4.23±0.03. The effects of extractant, nitric acid, salting-out agent, and complex anion concentrations and temperature on the extraction equilibrium of uranium(VI) were also studied.

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Abstract  

The effect of diluents on the extraction of uranium(VI) with petroleum sulfoxides (PSO) was studied. The decreasing order of extraction ability of PSO is as follows: benzene, toluene, cyclohexane, heptane, kerosene, carbon tetrachloride and chloroform. The effect of temperature on the extraction equilibrium was also investigated and enthalpy of the extraction was obtained. The relationship between the extraction equilibrium constantsK ex and the physical parameters of diluents can be derived.

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Abstract  

The synergic extraction of uranium(VI) from nitric acid solution with a mixture of bis(octylsulfinyl)ethane (BOSE) and petroleum sulfoxides (PSO) in 1,1,2,2- tetrachloroethane has been studied. The composition of the complex of the synergic extraction is UO2(NO3)2·BOSE·PSO. The formation constant of the complex is K PT = 4.44±0.23. The effect of extractant concentration, nitric acid concentration, salting-out agent concentration and temperature on the extraction equilibrium of uranium(VI) is also studied and the enthalpy of the extraction reaction is calculated. It has been found that the maximum synergic extraction effect occurs if the molar ratio of PSO to BOSE is one to one.

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Abstract  

The synergic extraction of uranium(VI) from nitric acid solution with petroleum sulfoxides (PSO) and tri-n-butyl phosphate (TBP) mixture has been studied. It has been found that maximum synergic extraction effect occurs if the molar ratio of PSO to TBP is two to three. The composition of the complex of synergic extraction is UO2(NO3)2·TBP·PSO. The formation constant of the complex isK PT=8.19. The effect of extractant concentration, nitric acid concentration, salting-out agent concentration and temperature on the extraction equilibrium of uranium(VI) was also studied.

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Abstract  

Some popular neutral extractants (PSO-petroleum sulfoxide, DOSO-di-n-octyl sulfoxide, TBP-tributylphosphate etc.) were chosen as synergist to study the synergistic effect on the extraction reaction with HBMPPT (4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione) for U(VI), and the synergistic separation ability of HBMPPT for U(VI) and Th(IV). The synergistic extraction ability shown by the studied systems for U(VI) is as follows: PSO>DOSO>TBP, and the same sequence was also verified for the separation coefficient of U(VI) and Th(IV). The synergistic complexes may be presented as: UO2NO3·BMPPT·S and UO2(BMPPT)2·S for U(VI) (S is PSO, DOSO or TBP).

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Abstract  

The influence of the concentration of nitric, hydrochloric and phosphoric acids, petroleum sulfoxides (PSO), salting-out agent, kind of diluent and temperature on the distribution ratio of U(VI) and Th(IV) has been systematically studied. It is found that the extraction regularity of PSO is similar to that of TBP. The distribution ratio in phosphoric acid is lower, but it increases with the increase of hydrochloric acid concentration and reaches a high value. The U(VI) exhibits the maximum distribution ratio at 3–4 mol/l HNO3. The distribution ratio of U(VI) and Th(IV) increases rapidly in the presence of a salting out agent. The extracted compounds are determined to be UO2(NO3)22PSO and Th(NO3)42PSO. The extraction enthalpies of U(VI) and Th(IV) with PSO were also calculated.

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Abstract  

An expression for rate constant for diffusion controlled reaction of positronium atom /Ps/ with acceptor in condensed phase was obtained, accounting the tunnelling of Ps. The obtained equation is good also for description of the reactions of solvated electron with electroneutral molecules. Owing to the tunnelling transfer existence, the rate constant /k/ is the sum of two terms — the first of them is proportional to the coefficient of relative diffusion of reagents and the second one /characterizing the subbarrier reaction/ does not include the diffusion coefficient. The correlation of the calculated and experimentally obtained rate constants for Ps+O2 reaction in liquids with different diffusion coefficients demonstrates good agreement between theoretical and experimental results. The possibility of electron tunnelling in liquid reaction of excited anthracene quenching with dissolved oxygen is also suggested.

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Abstract  

The extensive use of fossil fuels in energy production causes serious pollution of atmosphere with SO2, CO2, NOx, etc. In Estonia the electricity production is based mainly on the pulverized firing (PF) of low-grade local fuel – Estonian oil shale (EOS) which is characterized by a low calorific value (~9 MJ kg–1) and a high content of mineral matter (65–70%) from which approximately 50% are carbonates. Since 2004, also two boilers based on circulating fluidized bed combustion (CFBC) of EOS are in exploitation. The present study is focused on the comparative investigation of the efficiency of different ashes collected from different technological points of CFB and PF boilers as sorbents for SO2. The influence of experimental temperature on the SO2-binding characteristics of ashes as well as the possibilities of activation of ashes (grinding, hydration) were investigated. It was shown that the SO2-binding capacity of initial ashes at 700C and p(SO2)=190 mm Hg was for CFBC ashes 24–30 mg and for PF ashes 10–23 mg SO2 per 100 mg sample, the best binding capacities belonging to economizer ash (ECOA) and electrostatic precipitator ash from the 1st field (PESPA1f), respectively. However, during initial stage of binding the best results were obtained with air pre-heater ash (PHAA) and ESPA1f (both CFBC ashes). Grinding improved the SO2-binding ability, being the most effective in the case of bottom ash (BA) from CFBC and cyclone ash (PCA) from PF – increase in binding capacity 2 and 2.3 times, respectively. As compared to initial CFBC ashes, the binding characteristics of PF ashes remained lower even after grinding. Hydration and previous calcination improved the binding characteristics only of PF ashes. Hereby, the SO2-binding ability of CFBC ashes is better than of PF ashes and they are more promising sorbents for acidic gases, for example, for sulphur dioxide.

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Journal of Thermal Analysis and Calorimetry
Authors:
Rogério L. Pagano
,
Verônica M. A. Calado
,
Frederico W. Tavares
, and
Evaristo C. Biscaia

, the Particle Swarm Optimization (PSO) [ 1 ] has been extensively applied in parameter estimation. One important detail of these algorithms is that the knowledge of the objective function gradients and the initial parameter guesses are not necessary

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PSO PS1 PS2 PS4 Characterization of nanoparticles and nanocomposites The chemical

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