A comprehensive review of spinel ferrites and their magnetic composites as highly efficient adsorbents of rare earth elements

Rare earth elements (REEs), comprising 17 % of known elements, are pivotal in diverse industries. Despite their name, they are not geologically rare but dispersed, posing challenges for economically viable mining. This review explores the environmental and health implications of REEs, emphasizing their emerging status as contaminants in aquatic environments, raising health concerns through the food chain. The necessity to recover REEs from wastewater demands efficient methods, particularly focusing on adsorption. Spinel ferrites (SFs), characterized by superparamagnetism and thermal stability, are gaining prominence in this context. Utilizing metal cations like Fe, Co, Ni, Mn, Zn, and Cu, SF-based magnetic nanocomposites exhibit remarkable efficiency in adsorbing REEs. This article delves into adsorption mechanisms, including electrostatic interactions and ion exchange, highlighting the advantages of stability, biocompatibility, and cost-effectiveness associated with SFs. SF-based nanocomposites, offering scalability and effectiveness at low concentrations, emerge as a promising solution for addressing environmental concerns related to REEs while meeting the escalating demand for these essential elements.