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

1.天然聚合物（海藻酸）的凝胶颗粒可以收集镧、钕、钐、镝和镱等稀土离子。凝胶收集的稀土元素用稀盐酸溶液完全洗脱.测定了各稀土元素在凝胶相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。当乳酸作为络合剂存在于溶液中时，分离因子通过增加溶液中的同向酸浓度和pH而增强。就重稀土的分离因子而言，本系统可与25 ℃下HEDTA洗脱的离子交换树脂系统或TBP溶剂萃取系统相媲美。此外，凝胶颗粒的结合能力与合成的离子交换树脂的结合能力相当.使用分批操作的搅拌容器测量凝胶颗粒对稀土的吸收速率，并且得出结论，总体吸收速率由稀土离子与海藻酸的离子交换反应控制。然后分析数据以确定动力学方程中的反应速率常数.柱分离实验表明，用乳酸溶液可以实现钕镱二元混合物的完全分离。通过降低流速和提高溶液pH值，可改善Nd-Yb混合物的分离。实验数据与理论预测的突破曲线的基础上提出的速率表达式合理地同意。

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.