Review on the environment friendly leaching of rare earth elements from the secondary resources using organic acids

ABSTRACT Essential for smartphones, computers, batteries of hybrid and electric cars, medical scanners and weaponry, rare earth elements (REEs) play a pivotal role in every sphere of life globally. The race is on to develop alternative ways to utilize secondary sources, open new mines, reduce waste and recycle more. From being entirely dependent on China’s REE resources, the researchers and entrepreneurs globally are working towards development of alternative strategies to explore their indigenous resources to be self-sufficient. However, the existing strategies to extract these valuables rely on usage of mineral acids/alkalis. Continued effort on development of sustainable leaching methodologies led to the exploration of organic acids as a potential alternative. Low-molecular-weight carboxylic acids and organosulphonic acids have emerged as highly potent class of lixiviants for REE extraction. The knowledge of their variation in chemical structure and their complex potency towards lanthanides is essential towards development of an industrially viable process. In this review, the efficiency of the different organic acids in leaching REEs from various primary and secondary sources, along with their respective structural relevance has been summarized. This is expected to ameliorate the existing momentum of advancing nature-friendly industrial processes.