Application and implementation of chitosan as a potential and sustainable adsorbent for rare earth metal recovery: A review

Owing to their wide range of applications, limited availability, and high cost, the removal and recovery of REE have become an essential and attractive process. Among the divergent conventional method employed for removing and recovering REE from wastewater streams, adsorption, ascribed to its feasibility, low energy consumption, economic adaptability, and low cost, have received persistent attention. Among different biopolymers, chitosan, the second most abundant, emerged as a preferential adsorbent owing to its characteristics which include non-toxicity, biodegradability, antimicrobial, and excellent physiochemical properties, which imparts high adsorption capacity (∼85–100%), selectivity, excellent surface area, porosity volume, high chelating power, and high hydrophilicity. This review provides a comprehensive overview of the most recent literature on the adsorption of rare earth elements (REE) by chitosan. The documented findings are elucidated with respect to (1) the toxic effects of different REE, (2) the efficacy of chitosan in the elimination and retrieval of diverse REE, (3) the utilization of functionalized chitosan in adsorption processes, and (4) the methods for regenerating, reusing, and scaling up chitosan adsorbents in industrial applications.