Separation of Rare Earth Elements by Gel Particles of Alginic Acid as a Natural Polymer

1.一种天然聚合物(海藻酸)的凝胶颗粒可以收集稀土离子，如La、Nd、Sm、Dy和Yb。凝胶收集的稀土用稀盐酸溶液完全洗脱。测定了各稀土元素在凝胶和液相之间的分配比。对平衡数据进行了分析，计算了分配平衡常数、分离因子和稀土结合容量。当溶液中有乳酸作为络合剂时，随着策略酸浓度和溶液pH值的增加，分离因子增大。对于重稀土的分离因子，本体系可与25ﾟ℃下以乙二胺四乙酸乙酯为淋洗剂的离子交换树脂体系或以四叔丁基苯为萃取剂的溶剂萃取体系相比较。此外，凝胶颗粒的结合能力与合成的离子交换树脂相当。用间歇操作的搅拌罐测量了凝胶颗粒对稀土的吸收速率，结果表明，凝胶颗粒对稀土的总吸收速率是由稀土离子与海藻酸的离子交换反应控制的。然后对数据进行分析，确定动力学方程中的反应速率常数。柱实验表明，用乳酸溶液可以完全分离钕(ND)和Yb(Yb)的二元混合物。通过降低溶液的流速和提高溶液的pH值，改善了Nd-Yb混合物的分离效果。实验数据与根据提出的速率表达式预测的理论穿透曲线吻合较好。

1. The gel particles of a naturally occurring polymer (alginic acid) could collect rare-earth ions such as lanthanum, neodymium, samarium, dysprosium and ytterbium. The rare earths collected by gels were completely eluted with the dilute HCI solution.2. The distribution ratios of the individual rare earths between the gel and liquid phases were measured. The equilibrium data were analyzed to evaluate the distribution equilibrium constants, the separation factors and the rare earth-binding capacity. When lactic acid is present as a complexing agent in the solutions, the separation factors were enhanced by an increase in the tactic acid concentration and the pH of the solution. As regards the separation factor for heavy rare earths, the present system may be compared favorably with the ion-exchange resin system with HEDTA eluent at 25 ﾟC or the solvent extraction system with TBP. Furthermore, the binding capacity of gel particles stands comparison with that of synthetic ion-exchange resins.3. The rates of the uptake of rare earths by the gel particles were measured using an agitated vessel operated batchwise, and it was concluded that the overall uptake rate is controlled by the ion-exchange reaction of rare-earth ions with the alginic acid. The data were then analyzed to determine the reaction rate constant in the kinetic equation.4. Column experiments showed that the complete separation of the binary mixture of neodymium(Nd) and ytterbium(Yb) can be achieved with lactic acid solutions. The separation of the Nd-Yb mixture was improved by an decrease in the flow rate and an increase in pH of the soltition. The experimental data agreed reasonably with the theoretical breakthrough curves predicted on the basis of the proposed rate expression.