Technological advancements in rare earth elements recovery from ionic clays: A comprehensive review

The growing demand for rare earth elements, pivotal for modern technologies, has necessitated the development of efficient and sustainable extraction methods from ionic clays. This review provides a comprehensive analysis of the advancements in rare earth recovery from ionic clays, focusing on the geological, geochemical, and technological aspects of the extraction processes. Historically, traditional methods of extracting rare earths from mineral ores have been environmentally detrimental and economically intensive due to their complex multi-step procedures and the handling of radioactive materials. In contrast, ionic clays, primarily found in weathered crusts of granite and volcanic rocks, offer a more accessible source of rare earths, particularly heavy rare earth elements (HREEs), through simpler ion exchange processes. The necessity to discuss this topic arises from the increasing environmental and economic pressures to find greener and more sustainable methods of rare earth extraction. The review highlights the transition towards environmentally friendly leaching agents, such as non-ammonium salts, and the integration of advanced techniques like microbial adsorption and solvent extraction. These innovations aim to enhance extraction efficiency while reducing ecological footprints. Additionally, the review highlights the importance of understanding the geological conditions that favor the formation of ionic rare earth deposits, such as climate, topography, and geological history, which are critical for efficient prospecting and exploitation. Moreover, the paper presents a life cycle analysis of in-situ leaching of rare earths from ionic clays, a method that minimizes surface disruption and environmental impact compared with conventional mining. The efficacy of this method is evaluated through case studies and field implementations, demonstrating significant improvements in efficiencies of recovery and operational sustainability. In conclusion, this review emphasizes the strategic importance of rare earth extraction from ionic clays, not only to meet the rising global demand but also to support the advancement of green technologies essential for a sustainable future. It calls for continued research into alternative extraction technologies and methods that balance economic feasibility with environmental responsibility, ensuring the sustainable exploitation of these critical resources.