| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2006: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2005: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
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
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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
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