Recent advances in functional materials for rare earth recovery: A review

Rare Earth elements (REEs) were considered as one of the 14 critical mineral raw materials that are a crucial part of high-tech and everyday consumer products. The demand for REEs has rapidly grown in recent years since they are used in high-tech and sustainable technologies such as high-performance magnets, rechargeable batteries, and low-energy fluorescent lamps. Due to the latest political tensions and low substitutability of REEs mining technology, the REEs world market is at risk. One of the crucial concepts of industrial strategy to reduce supply risks related to critical raw materials is to increase their recycling. Among others, end-of-life electronic equipment such as mobile phones, fluorescent lamps, and computer hard drives (e-waste) can be a promising source for REE recovery. Critical parameters for adsorptive recovery of REEs from e-wastes are selectivity that can be provided by functionalization of the adsorbent surface. The scope of this review is an insight into current achievements in the adsorptive recovery of REEs from solutions with a high content of transition and heavy metals. The review covers resent advances in the synthesis and application of metal chelating, ion imprinted and porous polymers; silica-based adsorbents with covalently and non-covalently attached ligands; magnetic and green adsorbents; metal-organic frameworks and carbon-based nanomaterials for REEs recuperation. Special attention was paid to emerging materials, such as green and hybrid adsorbents containing carbon nanoparticles. The adsorbents' efficiency, selectivity, and peculiarities of their application are revealed by critical analysis of the essential conditions of the rare earth elements recovery experiment. Different experimental parameters revealing adsorbents efficiency and selectivity, such as optimal pH working range, adsorption capacity, kinetic data, design of the REEs adsorption experiment, the effect of coexisting ions, and recovery degree, are presented in the review. Advances and drawbacks of each class of the adsorbent presented were highlighted in the review, as well as modern tendencies in developing adsorbents.