Challenge to rapid separation of Rhodium from high-level liquid waste using superabsorbent material

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K15202
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 31010:Nuclear engineering-related
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: Ito Tatsuya 国立研究開発法人日本原子力研究開発機構, 福島研究開発部門 福島研究開発拠点 廃炉環境国際共同研究センター, 任期付研究員 (20757653)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 高レベル放射性廃液 / 廃棄物資源化 / ロジウム / ゲル / 吸着

Outline of Final Research Achievements

Useful metals such as rhodium (Rh) contained in high-level liquid waste were expected to be recycled by separation and recovery. Because rhodium is in high demand as a catalyst and is extremely expensive, there was the idea of using it as a semi-domestic resource after its radioactivity has decays. On the other hand, Rh is difficult to separate due to its inert ligand exchange. Therefore, considering that the water molecules bound to rhodium also transferred the interphase together with Rh, we focused on superabsorbent gel as a separation medium that can allow water molecules.
In this study, a gel monomer having a sulfur-containing diamide structure which has a high affinity for platinum group metals and a highly water-absorbing Rh-adsorbing gel using the monomer were synthesized. Then, it was found that the gel adsorbed Rh in nitric acid solution. And there was a possibility that the Rh adsorption rate of the gel is faster than that of sulfur-containing diamide-modified silica.

Free Research Field

原子力化学

Academic Significance and Societal Importance of the Research Achievements

原子力発電（核燃料サイクル）から排出される高レベル放射性廃棄物中には有用な希少元素であるロジウム（Rh）が含まれている。Rhは自動車用などの触媒材料として非常に重要であり、その供給を海外に依存している我が国にとって、国内の資源開発やリサイクルは重要な課題である。よって、高レベル放射性廃液からRhを回収することが可能ならば、廃棄物の資源化が達成され、資源セキュリティの向上に一役買うことができる。
また、これまでの抽出剤や吸着材で困難だったRhの迅速分離に対して、高吸水性ゲルという分離媒体の利用を検討し、その可能性を示すことができた。今後のゲルの改良によってRh吸着速度の向上が望める。