• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.2
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• pp.85-90
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• 2018

For the recovering rare earths in the spent nickel-metal hydride batteries, 10 M NaOH is added to the solution leached with sulfuric acid. The rare earth powders were precipitated at rate of 98 % at the condition of pH 2.0 or less. The recovered rare earth complex precipitate increased the leaching rate to nitric acid by heat treatment at $800^{\circ}C$ for 4 hours. Subsequently secondary precipitation was performed by adding oxalic acid to the solution in which the rare earth complex precipitate was dissolved. The re-precipitated rare earth powders were converted into oxide form through heat treatment at $800^{\circ}C$ for 4 hours with purity of 99.5 %.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.361-365
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• 2007

The precipitation reaction of some rare earth chlorides ($Ce/Nd/GdCl_3$) in a LiCl-KCl molten salt has been carried out by reaction with oxygen. Identification of rare earth precipitates by reaction with oxygen and effects of oxygen sparging time (max. 420 min) and molten salt temperature ($450{\sim}750^{\circ}C$) on conversion were investigated. In this study, regardless of the oxygen sparging time and the molten salt temperature, oxychlorides (REOCl) for $NdCl_3$ and $GdCl_3$, and an oxide ($REO_2$) for $CeCl_3$ are formed as a precipitate, which are identical with the estimation results of Gibbs free energy of reaction (${\Delta}G_r$). The conversion of rare-earth chlorides into insoluble precipitates was described by using a conversion ratio. The conversion ratio increased exponentially with the oxygen sparging time and finally showed asymptotic value, over 0.999 at $750^{\circ}C$ of the molten salt temperature and over 300 min of sparging time conditions. The conversion ratios were increased with the molten salt temperature. In case of $CeCl_3$, when the sparging time exceed 60 min, the values of the conversion ratio were nearly constant over 0.999 in all experimental temperature conditions.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.65-70
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• 2010

The distillation rate on LiCl-KCl eutectic salt under different vacuums from 0.5-50 mmHg was first investigated by using both a non-isothermal and a isothermal thermogravimetric (TG) analysis. Based on the non-isothermal TG data, distillation rate equations as a function of the temperature could be derived. Calculated flux by these model flux equations was in agreement with the distillation rate obtained from isothermal TG analysis. A distillation rate of $10^{-4}-10^{-5}$ mole $cm^{-2}sec^{-1}$ is obtainable at temperatures less than 1300K and vacuums of 0.5-50 mmHg. About a 99% salt distillation efficiency was obtained after an hour at a temperature above 1150 K under 50 mmHg in a small scale distillation test system. An increase in the vaporizing surface area is relatively effective for removing residual salt in the remaining particles, when compared to that for the vaporizing time. Over 99.95% of total distillation efficiency was obtained for a 1-h distillation operation by increasing the inner surface area from $4.52cm^2$ to $12.56cm^2$.