Heap leaching of ion adsorption rare earth ores and REEs recovery from leachate with lixiviant regeneration

In this work, semi-industrial scale heap leaching of 200 t ion adsorption rare earth ores (IRE-ore) and rare earth elements (REEs) recovery from lixivium was first conducted. Biosynthetic citrate/(Na)3Cit, a typical microbial metabolite, was chosen as the lixiviant to conduct heap leaching. Subsequently, an organic precipitation method was proposed, which used oxalic acid to effectively recover REEs and reduce the production cost by lixiviant regeneration. The results showed that the heap leaching efficiency of REEs reached 98 % with a lixiviant concentration of 50 mmol/L and a solid-liquid ratio of 1:2. The lixiviant can be regenerated during the precipitation process, with REE yields and impurity aluminum yields of 94.5 % and 7.4 %, respectively. The residual solution can then be cyclically used as a new lixiviant after simple adjustment. High-quality rare earth concentrates with a rare earth oxide (REO) content of 96 % can be finally obtained after roasting. This work provides an eco-friendly alternative for IRE-ore extraction to solve the environmental issues caused by traditional technology. The results proved feasibility and provided a foundation for in situ (bio)leaching processes in further industrial tests and production.

Automated summary

In this study, semi-industrial scale heap leaching of 200 t ion adsorption rare earth ores was conducted using biosynthetic citrate/(Na)3Cit as the lixiviant. An organic precipitation method using oxalic acid was proposed to effectively recover rare earth elements (REEs) and reduce production cost. The heap leaching efficiency of REEs reached 98% with a lixiviant concentration of 50 mmol/L and a solid-liquid ratio of 1:2. The lixiviant can be regenerated during the precipitation process, with REE yields of 94.5% and impurity aluminum yields of 7.4%. The work provides an eco-friendly alternative for IRE-ore extraction and proves feasibility for further industrial tests and production in situ (bio)leaching processes.