| 研究実績の概要 |
The platinum group metal (PGM) reserves are depleting severely every year, and the demand to supply ratio is forecast to widen significantly by 2020. These factors induce the growing pressure on PGM recycling. High-level liquid waste (a spent nuclear fuel), spent automotive catalyst leachates are potential secondary sources for the urban mining of PGMs. The preparation of high acid tolerant and efficient functional materials is a challenging task in the solid phase recovery of noble metals. To overcome this issue, covalently functionalized graphene oxide (GO) materials were explored. The GO was covalently functionalized with 1-(3-aminopropyl)imidazole (ImGO), 2-methylthiophene (ThpGO), 2-aminoethanethiol (CysGO) through amide or amine formation at different reactive sites. Both ImGO and ThpGO were found efficient for the selective extraction of Pd from HLLW containing several metal ions. Both the materials could be recycled without a drop in efficiency for the studied five cycles.
CysGO was employed for the recovery of precious metals from the simulated spent catalyst leachates containing various PGMs (Pd, Pt and Rh), rare metals (Zr, Y, La and Ce), alkaline earth metals (Ba), and base metals (Cu, Fe, Zn, and Ni) at 1M acid concentration. CysGO could selectively extract precious metals from all three medium with Pd (87.7 mol%) as major component and Pt co-adsorbed in small amount. The regenerated materials were converted into PGM nanoparticle supported graphene materials, a well-known heterogeneous catalyst through simple pyrolysis under N2 atmosphere at 500oC.
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