Speaker
Description
Palladium (Pd), ruthenium (Ru), and rhodium (Rh) are platinum group metals (PGM) present in spent nuclear fuel. These elements play important and irreplaceable roles in many industrial applications in modern society, including catalysis, electronics, and pharmaceuticals. However, their extremely low abundance in the Earth’s crust, combined with their high demand and cost, has intensified the search for new sources of these elements [1]. In addition, the European Critical Raw Materials initiative identifies PGMs as essential materials with a high supply risk and strategic importance for the economy and key technologies [2]. Spent nuclear fuel may therefore represent a rich, non-conventional source of these critical elements, in which they are formed as fission products. It has been estimated that 2.4 tonnes of Pd, 3.7 tonnes of Ru, and 0.7 tonnes of Rh could be recovered from the nuclear fuel spent annually in France. Thus, significant amounts of PGMs can potentially be recovered from spent nuclear fuel in comparison with the current global production, particularly in the case of Ru [3].
In this work, hexacyanoferrate structures, namely Cu2[Fe(CN)6] and Co2[Fe(CN)6], were prepared and applied for the recovery of Pd, Ru, and Rh. The synthesized materials were characterized by X-ray diffraction and thermogravimetric analysis. Mass distribution coefficients (Kd) were determined over a wide range of nitric acid concentrations (0.01, 1, 3.2, 5, and 7 mol L-1) using the batch equilibrium method at room temperature. The effects of key adsorption parameters, including adsorbent dosage and contact time, were investigated. Adsorption isotherms and kinetic models were also evaluated. Excellent Pd adsorption performance was observed for both materials, particularly for Cu2[Fe(CN)6], which achieved nearly 100% Pd removal from 3.2 mol L-1HNO3 even at the lowest tested adsorbent mass, while the adsorption of Ru and Rh remained low. Furthermore, Pd uptake was rapid and followed a pseudo-second-order kinetic model. Both hexacyanoferrate structures showed good stability in 3.2 mol L-1HNO3, with no detectable release of Cu or Co during the tested period of 14 days.
References:
[1] H. Weng, Y. Wang, F. Li, Y. Muroya, S. Yamsahati, and S. Cheng, “Recovery of platinum group metal resources from high-level radioactive liquid wastes by non-contact photoreduction,” Journal of Hazardous Materials, vol. 485, 2023, Art. no. 131852.
[2] Study on the Review of the List of Critical Raw Materials: Final Report, European Commission, 2017.
[3] S. Bourg and Ch. Poinssot, “Could spent nuclear fuel be considered as a non-conventional mine of critical raw materials?” Progress in Nuclear Energy, vol. 94, 2017, pp. 222–228.
Acknowledgement: We gratefully acknowledge the EU and Czech MEYS funded project CROP (CZ.02.01.01/00/22_011/0008569) and the HORIZON-EURATOM-2021-funded FREDMANS project (GA No. 101060800) for supporting this research.