| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2003: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
The fundamental studies on chemical treatment and recycling of metals have been undeftaken by solvent extraction and high performance centrifugal partition chromatography (HPCPC). The aim of this investigation is to establish the procedure that the waste materials can be reduced and be promoted to reuse for manufacturing of products. Furthermore, it is considered that environmental protection and efficient use of natural resources can be performed through our investigations.
First, we have investigated the mutual separation of alkaline earth metal ions by HPCPC using 0.16 M bis-2-ethylhexylphosphinic acid in heptane (BEHPA) as a stationary phase. Two-step elution of the four metal ions loaded was accomplished with aqueous chloroacctic acid mobile phase (pH 6.5 and 5.3). Ethanol (5%) was added to the pH 6.5 mobile phase for the separation of Sr(II) and Ba(II). The chromatographic conditions were 2,136 partition channels, 800 rpm rotation speed, and 1.5 ml/min flow rate. The elution curve
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was obtained by monitoring the absorbance of each metal complex post-tabled with a chromogenetic agent.
The separation of such metal ions as Cu(II), Mn(II), Co(II) and Ni(II) has been investigated by HPCPC employing di-2-methylnonylphosphoric acid/heptane as a stationary phase. The four transition metal ions have mutually been separated by the two-step elution method, changing the pH of the chloroacetic acid acid mobile phase. The flow rate was 2.0 ml/min.
Such transition metal ions as Fe(III), Zn(II), Mn(II), Co(II) and Ni(II) can be separated by the two-step HPCPC method using 0.16 M BEHPA/heptane as a stationary phase. Acetate, chloroacetate and tartrate buffers were used as mobile phases. The coexisting Co(II) in a mixed Co(II)-Ni(II) solution was found to be selectively retained when the sample solution was continuously delivered into the stationary phase by a pump. Thus, the purification of Ni(II) solution by the present HPCPC method would be applied in the field of nickel battery industry.
The light and middle rare earth metal ions were attempted for HPCPC separation. It can be expected from extraction studies with BEHPA that the HPCPC separation of these metals is rather difficult at a conventional flow rate. We have tried to separate them at a slower flow rate of 0.2 ml/min. La(III)-Ce(III)-Pr(III), Eu(III)-Sm(III) and Gd(III)-Tb(III)-Dy(III) mixtures were mutually separated at pH 2.95, 2.30 and 1.55, respectively.
From the above results, it was found that the HPCPC method was very useful for the separation of metal ions investigated at a laboratory scale. Precipitation, ion exchange, membrane filter separation can be combined with HPCPC for actual and chemical treatments for recovery and recycling process of metals as the next step of investigation. Further studies are in progress to construct the system of recovery and recycling of metals in waste materials and waters. Less
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