Rare earth elements (REEs) are critical to renewable energy, electronics, and imaging technologies, but extraction currently relies heavily on primary mining. Australia holds ~3110 kilotonnes of rare earth oxide (REO) reserves (2021),1 with production of only 38.3 kilotonnes (2021).2 The recovery of REEs from mine tailings represents a sustainable pathway to diversify supply chains and remediate legacy waste, and ion exchange has shown to be a promising approach for the leaching of REEs from clays and ores.3 Water has also been used for in-situ leaching of tailings (Mary Kathleen - Qld), mobilising approximately 5% of total REE content.4 Herein, we investigate the leaching of REEs from uranium mine tailings (Radium Hill - SA) using simple, aqueous salt solutions.
Leaching using deionised water alone led to extraction of 10-30% of certain REEs, while addition of (NH4)2SO4 significantly enhanced recovery (>50%), particularly for light REEs. Additional factors such as salt concentration and type, stirring, extended leaching duration, temperature variation, and pulp density were also investigated, to achieve optimal leaching conditions. These findings demonstrate the potential of ion exchange approaches, in this case utilising ammonium salt additives, for the aqueous leaching of REEs from legacy uranium mine tailings. Future work will extend this ion exchange strategy toward selective REE recovery using alternative counter-ions and designing specific supramolecular hosts. This approach will enable study of the mechanism of REE mobilisation and binding and allow selective capture of high value elements from complex tailings matrices based on size, charge, and coordination preference.