Expanded vermiculite as an alternative adsorbent for the dysprosium recovery

Background: Dysprosium (Dy) is a critical resource for developing high-tech green energies, and its growing demand implying the need to recover it from secondary sources. Due to the known stability, availability, and high cation exchange capacity, adsorption on vermiculite can be promisor for this purpose. Methods: This work evaluated the dysprosium adsorption and desorption on expanded vermiculite through experiments of equilibrium, thermodynamic, and reuse cycles. Also, the regenerated material was characterized regarding morphological, compositional, thermal, superficial aspects. Significant findings: The equilibrium data achieved high adsorption capacities (0.9 mmol/g), and the sigmoidal isotherms indicated a first layer saturation and progressive surface precipitation, which may favor a Dy selective sorption. The process is feasible and spontaneous, endothermic, and classified as physisorption, advantageous for facilitating dysprosium desorption. From the reusability experiments, high efficiencies of adsorption (99%) and desorption (94%) were reached during five cycles, indicating the effective regeneration of the adsorbent and recovery of the adsorbate using a source of magnesium as eluent (magnesium nitrate hexahydrate solution). The characterization analyzes corroborated the stability and the renewability of the adsorbent. Thus, the material shows a high adsorption capacity and an easy regeneration compared to other complex adsorbents, giving the vermiculite an expressive potential for future applications in rare earth metals recovery. (c) 2021 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

The study evaluated dysprosium adsorption and desorption on expanded vermiculite, finding it to possess good adsorption capacity and renewability, with high efficiency of recovery using magnesium as an eluent.