P507体系反萃取条件对平衡负载稀土量的研究

Effect of Cycling Loaded Rare Earths on Stripping Process in P507 Extraction System

P507-盐酸体系是目前应用最为广泛的稀土萃取分离体系。在用P507-盐酸体系分离含中重稀土的原料时,由于重稀土元素(Tm,Yb,Lu)难于完全反萃,使得长期使用后的空白萃取剂中仍负载一定量的重稀土(称为平衡负载)。在重稀土元素分离时,平衡负载甚至高达有机相正常负载的10%以上,严重影响了相关分离工艺的运行和实际分离效果。根据多组分萃取分离体系的萃取-反萃平衡和物料平衡关系,将平衡负载引入反萃取参数计算的物料平衡模型,对反萃过程进行了计算机仿真模拟,研究了反萃酸的相对流量、反萃级数等工艺条件对平衡负载量的影响。模拟结果表明,平衡负载随反萃级数和反萃酸流量的增大而减小;消除重稀土平衡负载、保证反萃完全需要较高的反萃酸耗和较长的反萃级数。在工业生产中,可根据实际分离需要选择相对经济的工艺条件,将平衡负载控制在合理的范围内。

P507 （ HEH [ EHP ] ） is an important extractant for the separation of rare earth and is widely used in industry. Since the complexes of heavy rare earth ions with saponified P507 are so stable that the rare earth ions are difficult to be exchanged and stripped by H^＋ ions. Thus, the cycled extractant loads certain amount of heavy rare earth ion after stripped by acid. This amount of rare earth ions loaded in blank organic phase is named as the ＂cycling loaded rare earth ions （CLREs）＂. In the separation process of Tm^3＋, Yb^3＋, and Lu^3＋ , the amount of CLREs can be more than 10% of the normal capacity of saponified organic phase. In fact, CLREs affect the separation efficiency and decrease the purity of the products. Based on the extracting-stripping equilibrium and mass balance, the influence of different process parameters on the amount of CLREs was studied by computer simulation. The results indicate that higher acid consumption and more stripping stages are required to eliminate CLREs. For an industrial practice, however, the acid consumption and the number of stripping stage can be designed by choosing an economic process and controlling CLREs at a reasonable level.