Development of Recycling System for Rare Metals by High Performance Centrifugal Partition Chromatography

各种稀有金属被广泛用于制造电子设备和产品，如电视机、个人电脑、二次电池。在这些金属中，La和La、Y、Sm、Eu、Ni、Co等过渡金属具有代表性。这类稀有金属通常是从自然资源中生产出来的。这就是为什么我们应该从保护有价金属的角度，回收和发展工业技术，使其在使用后进行回收利用。在过去的两年里，我们对金属络合物的两相萃取平衡及其在高效离心色谱分离金属中的应用进行了基础研究。高效离心色谱原理上是基于多次萃取的方法，因此对于从废物中分离密切相关的金属离子非常有用。感兴趣的金属离子在STAT…之间被重复地分配更多的离子相和流动相将它们分开。选用双-2-乙基己基膦酸(BEHPA)和二-甲基-2-甲基壬基磷酸(DMNPA)作为络合剂，用于分离镧和过渡金属。以氯乙酸酯或三氯乙酸酯缓冲液为流动相，0.16M BEHPA/正庚烷为固定相，研究了高效毛细管电泳法分离金属镧。测定了轻、中级金属镧的半萃取pH(pH；lt；1/2&gt；)值，并对pH值的差异进行了评价，探讨了HPCPC分离的可行性。除Pr/ND和Tb/Dy分离外，其余金属离子采用两步洗脱法相互分离。影响HPCPC分离的主要因素是流动相的pH值和流速。对于目标金属离子浓度较高的水样，需要增加BEHPA的浓度。用DMNPA庚烷溶液作为固定相，也可用于HPCPC分离过渡金属离子。Fe(III)的萃取可以在很低的pH值下进行，因此可以用酒石酸盐来掩盖。用这种HPCPC方法发现镍(II)和钴(II)与其他过渡金属离子分离。这项技术对于从电子零件废料中回收钴和镍具有很好的前景，因为它们可以重复用于电池。较少

A variety of rare metals have widely been used for the manufacturing of electronic devices and products, e.g. television sets, personal computer, secondary batteries. Among the metals, such lanthanum and transition metals as La, Y, Sm, Eu, Ni and Co are representative ones. Such rare metals are generally produced from natural resources. This is the reason why we should recover and develop the industrial technique to recycle them after use, from the standpoint of conservation of valuable metals. In this research project, the fundamental studies on the two-phase extraction equilibrium of metal complexes and their applications to the metal separation by high performance centrifugal partition chromatography (HPCPC) have been undertaken for the last two years.The HPCPC method is in principle performed based on the multiple extraction, and therefore very useful for the separation of closely related metal ions from waste materials Metal ions of interest are partitioned repeatedly between stat … More ionary and mobile phases to separate them. Bis-2-ethylhexylphosphinic acid (BEHPA) and di-2-methylnonylhosphoric acid (DMNPA) were chosen as the chelating agents for the separation of lanthanum and transition metals, respectively. The mobile phase was made of chloroacetate or trichloroacetate buffer.The HPCPC separation of lanthanum metals was investigated using 0.16M BEHPA/heptane as a stationary phase. Half-extraction pH (pH_<1/2>) values were obtained for light and middle class lanthanum metals, and the differences in pH_<1/2> were evaluated for the feasibility of HPCPC separation. Except for Pr/Nd and Tb/Dy separation, the other lanthanum metal ions were separated mutually by the two-step elution method. The main factors governing HPCPC separation were found to be pH and flow rate of mobile phase used. Increased concentration of BEHPA is needed for aqueous samples containing higher concentrations of target metal ions.A DMNPA solution in heptane as the stationary phase was also used for the separation of transition metal ions by HPCPC. Fe(III) extraction can be carried out at very low pH values, and therefore was masked with addition of tartrate. Nickel(II) and cobalt(II) were found to separate from the other transition metal ions by this HPCPC method. This technique would be quite promising for the recovery of cobalt and nickel from waste materials of electrical parts, because of their reuse for batteries. Less