Rationally designed dipicolinate-functionalized silica for highly efficient recovery of rare-earth elements from e-waste

Composition of the immobilized layer plays a crucial role in metal adsorption properties of complexing organomineral materials. Ignoring the specific features of chemical reactions on solid surface can lead to a significant deterioration in the target properties of the resulted materials. In this research we demonstrated that rationally designed surface-assembling synthesis of organo-silica with covalently immobilized fragments of dipicolinic acid (DPA) resulted in the adsorbent that is capable quantitively recover almost all Rare Earth elements (REEs) from multielement solution with pH > 1.7. In ten consecutive adsorption/desorption cycles no noticeable loss of its efficiency was found, with a mean value of REEs recovery larger than 97%. The adsorbent has been used to recover REEs from model solutions (22 metal ions in 0.5 mol L-1 NaCl) and real leaching solution of waste of fluorescent lamps. It was demonstrated that even 3200-fold excess of Fe and Cu ions only slightly reduces REEs recovery. The adsorbent is capable to recover above 80% of all (except La) REEs from acidic leaching solution from fluorescent lamps with enrichment factors above 600. After adsorption of Eu3+ and Tb3+, the resulting materials exhibited strong red and green luminescence, respectively, indicating chelating mechanism of REEs adsorption on SiO2-DPA.

Automated summary

The composition of the immobilized layer in organomineral materials is crucial for metal adsorption properties. A rationally designed surface-assembling synthesis of organo-silica with covalently immobilized DPA fragments has shown to be efficient in quantitatively recovering almost all Rare Earth elements from multielement solutions. The adsorbent demonstrated excellent performance with over 97% REEs recovery in consecutive adsorption/desorption cycles, making it a promising option for REEs recovery from acidic leaching solutions.