Mechanistic elucidation of platinum group metal separation by aluminum hexacyanoferrate in nitric acid systems

中瀬 正彦*; 中沢 亮太*; 三島 理愛  

Nakase, Masahiko*; Nakazawa, Ryota*; Mishima, Ria

The separation of Platinum Group Metals (PGMs) is critical across various fields, including industrial metal recovery and nuclear waste management. This study rigorously examines the separation mechanisms of PGMs using Aluminum Hexacyanoferrate (AlHCF) by employing some analytical techniques. The mechanism involves not only simple adsorption but also the dissolution of AlHCF, leading to PGM ion precipitation and elution of components, as well as adsorption onto the AlHCF surface. We conducted X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray absorption fine structure (XAFS), and pair distribution function (PDF) to thoroughly investigate the structural and chemical changes in AlHCF and FeHCF before and after PGM adsorption. Our findings reveal that Pd ions replace Fe in AlHCF, preserving the ferrocyanide framework and the adsorption of Ru and Rh. In contrast, Ru and Rh adsorption results in broadened XRD pattern without initial AlHCF structure, suggesting the formation of amorphous precipitates through complexation with dissolved ions. By detailing these mechanisms, this study highlights the efficacy of AlHCF as a PGM separation agent and offers valuable insights for the improvement of useful metal recovery processes.