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  • Author or Editor: Hui-Fang Du x
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Abstract  

The kinetics of oxidation of U(IV) in nitric acid solution by nitrous acid and air oxygen have been studied. The effects of concentrations of U(IV), nitric acid, hydrogen ion and nitrous acid in aqueous solution or oxygen in gas on the oxidation rate have been examined. The oxidation rate increases with increasing temperature and the activation energies are 47 kJ mol–1 for nitrous acid and 91 kJ mol–1 for oxygen. The mechanisms for both oxidation reactions are discussed.

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Abstract  

The kinetics of solvent extraction of U (IV), Th (IV) and U (VI) from nitric acid solution with tributyl phosphate (TBP) in kerosene and cyclohexane have been studied using the single drop technique. The effects of concentrations of U (IV), Th (IV), U (VI), nitric acid, nitrate, TBP and temperature on the extraction rates of U (IV), Th (IV) and U (VI) have been examined. The mechanisms for the three extraction processes are discussed.

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Abstract  

The solvent extraction of U(VI) by p-tert-butylcalix[n]-arene acetate (HnL) (n=4, 6, 8) has been studied. The effects of acidity in aqueous phase and concentration of extractant in organic phase on the distribution ratio were examined. It has been found that the distribution ratio is proportional to [H+]−2 and [HnL](O) and the extracted complex species is UO2Hn −2L. The equilibrium constants of the extraction reactions have been determined. The reaction mechanism is discussed.

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Abstract  

The kinetics of solvent extraction of U(VI) with di(2-ethylhexyl) phosphoric acid (HDEHP) using a microporous hydrophobic hollow fiber membrane extractor has been investigated. The effects of U(VI) and hydrogen ion concentrations in aqueous phase, HDEHP concentration in organic phase, flow velocities of aqueous and organic phase and temperature on extraction rate of U(VI) were examined. The experimental results suggest that the extraction rate of U(VI) is controlled by diffusion.

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Abstract  

The kinetics of stripping of thorium(IV) and uranium(IV) from tributylphosphate (TBP)-kerosene with dilute nitic acid solution has been studied using the Lewis cell technique. The effects of concentrations of Th(IV), U(IV), nitric acid, TBP, temperature and stirring speed on the stripping rate have been examined. The result show that the stripping rates of Th(IV) and U(IV) are all controlled by diffusion process.

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