低浓度硫酸铵对离子吸附型稀土的浸取动力学研究

Leaching Kinetics of Ion Adsorption Rare Earths Using Low Concentration of Ammonium Sulfate Solution

采用低浓度硫酸铵溶液以柱上淋洗方式在更宽的时间范围内研究了离子吸附型稀土的浸取动力学。以1-2/3η-(1-η)^(2/3)对时间t作图所得的浸取动力学曲线由两段直线组成,证明稀土的浸出过程可以用两个阶段的内扩散控制动力学模型来描述。随着硫酸铵浓度的提高,第一阶段的浸出速率常数急剧上升,而第二阶段的浸出速率常数则先增大而后降低,但两阶段浸出所对应的速率常数差别增大。结合不同粒径颗粒样品和再吸附稀土样品浸出动力学的实验结果认为,两阶段浸出的稀土分别对应于黏土矿物表面与内层的稀土离子,其比例随矿样粒度、形成历史和硫酸铵浓度而变化。

The leaching kinetics of ion adsorption rare earth （IARE） by low concentration of ammonium sulfate solution was investigated by using column elution manner within a longer period. It was found that the leaching kinetics curves plotting 1-2/3η-（1-η）2/3via time show a two stages linear relationship when leaching with low concentration of ammonium sulphate solution, indicating that the leaching process of IARE can be described by a successively two stage of inner diffusion controlled kinetics model. As the concentration of ammonium sulfate solution increased, the difference of the leaching rate constant be- tween the two stages increases. The leaching rate for the first stage increases sharply, and that for the second stage increases first and then decreases. Combined with the leaching kinetics study results of samples with different particle size and re-adsorption rare earth, it is believed that the two stages of leaching processes are respectively corresponded to rare earth ions ad- sorbed on the clay surface and entered into the inner layer of clay mineral particles, their proportion changes with the sample size, leaching agent concentration and the formation history of IARE. Increasing the leaching agent concentration, the share of rare earth ions on the surface which belongs to the first stage of leaching process increase.