Kim, Chul-Joo
(Korea Institute of Geoscience and Mineral Resources)
,
Yoon, Ho-Sung
(Korea Institute of Geoscience and Mineral Resources)
,
Chung, Kyung Woo
(Korea Institute of Geoscience and Mineral Resources)
,
Lee, Jin-Young
(Korea Institute of Geoscience and Mineral Resources)
,
Kim, Sung-Don
(Korea Institute of Geoscience and Mineral Resources)
,
Shin, Shun Myung
(Korea Institute of Geoscience and Mineral Resources)
,
Kim, Hyung-Seop
(Department of Environmental and Chemical Engineering, Seonam University)
,
Cho, Jong-Tae
(Department of Environmental and Chemical Engineering, Seonam University)
,
Kim, Ji-Hye
(Department of Environmental and Chemical Engineering, Seonam University)
,
Lee, Eun-Ji
(Department of Environmental and Chemical Engineering, Seonam University)
,
Lee, Se-Il
(Department of Environmental and Chemical Engineering, Seonam University)
,
Yoo, Seung-Joon
(Department of Environmental and Chemical Engineering, Seonam University)
A leaching kinetics was conducted for the purpose of recovery of praseodymium in sulfuric acid ($H_2SO_4$) from REE slag concentrated by the smelting reduction process in an arc furnace as a reactant. The concentration of $H_2SO_4$ was fixed at an excess ratio under the conditi...
A leaching kinetics was conducted for the purpose of recovery of praseodymium in sulfuric acid ($H_2SO_4$) from REE slag concentrated by the smelting reduction process in an arc furnace as a reactant. The concentration of $H_2SO_4$ was fixed at an excess ratio under the condition of slurry density of 1.500 g slag/L, 0.3 mol $H_2SO_4$, and the effect of temperatures was investigated under the condition of 30 to $80^{\circ}C$. As a result, praseodymium oxide ($Pr_6O_{11}$) existing in the slag was completely converted into praseodymium sulfate ($Pr_2(SO_4)_3{\cdot}8H_2O$) after the leaching of 5 h. On the basis of the shrinking core model with a shape of sphere, the first leaching reaction was determined by chemical reaction mechanism. Generally, the solubility of pure REEs decreases with the increase of leaching temperatures in sulfuric acid, but REE slag was oppositely increased with increasing temperatures. It occurs because the ash layer included in the slag is affected as a resistance against the leaching. By using the Arrhenius expression, the apparent activation energy of the first chemical reaction was determined to be $9.195kJmol^{-1}$. In the second stage, the leaching rate is determined by the ash layer diffusion mechanism. The apparent activation energy of the second ash layer diffusion was determined to be $19.106kJmol^{-1}$. These relative low activation energy values were obtained by the existence of unreacted ash layer in the REE slag.
A leaching kinetics was conducted for the purpose of recovery of praseodymium in sulfuric acid ($H_2SO_4$) from REE slag concentrated by the smelting reduction process in an arc furnace as a reactant. The concentration of $H_2SO_4$ was fixed at an excess ratio under the condition of slurry density of 1.500 g slag/L, 0.3 mol $H_2SO_4$, and the effect of temperatures was investigated under the condition of 30 to $80^{\circ}C$. As a result, praseodymium oxide ($Pr_6O_{11}$) existing in the slag was completely converted into praseodymium sulfate ($Pr_2(SO_4)_3{\cdot}8H_2O$) after the leaching of 5 h. On the basis of the shrinking core model with a shape of sphere, the first leaching reaction was determined by chemical reaction mechanism. Generally, the solubility of pure REEs decreases with the increase of leaching temperatures in sulfuric acid, but REE slag was oppositely increased with increasing temperatures. It occurs because the ash layer included in the slag is affected as a resistance against the leaching. By using the Arrhenius expression, the apparent activation energy of the first chemical reaction was determined to be $9.195kJmol^{-1}$. In the second stage, the leaching rate is determined by the ash layer diffusion mechanism. The apparent activation energy of the second ash layer diffusion was determined to be $19.106kJmol^{-1}$. These relative low activation energy values were obtained by the existence of unreacted ash layer in the REE slag.
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제안 방법
concentrations was investigated. A leaching experiment was conducted at two different H2SO4 concentrations of a stoichiometric ratio (3 mol H2SO4/mol Pr6O11) and an excess ratio (4 mol H2SO4/mol Pr6O11). As the results, Pr(OH)3 precipitate was not produced at all the two conditions as the shown in Fig.
The crystal structure and crystallinity of the REE slag were analyzed under the following analytical conditions (CuKα source, scanning speed 1°/min, 40 kV, 40 mA, 0°≤2θ≤90° scanning range) by X-ray diffraction spectroscopy (D8 ADVANCE, BRUKER AXS).
This study was also conducted to recover REE metals from lowgrade monazite-type REE raw material and selected praseodymium as a research objective among the components in REE slag because praseodymium cost increased as highest growth rate of price from 14 US$/kg to now 175 US$/kg recently [4].
성능/효과
(3) Optimum condition for the recovery of praseodymium from the REE slag was given to the condition of slurry density of 1.500 g/L, 0.3 mol/L H2SO4, temperature of 80 ℃, leaching time of 5 h. The leaching yield was proportional to the leaching temperature under the condition of excess H2SO4 over the stoichiometric ratio.
In conclusion, the leaching rate and yield are proportional to the leaching temperature in the case of low-grade raw materials with unreacted ash layers.
In the experiment it was assumed that there was no change of concentration during the leaching reaction because the H2SO4 was excessively added than the stoichiometric ratio necessary in the reaction. This experiment was fixed at the condition of 0.
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