Efficient recovery of europium by biosorption and desorption using beads developed from sericin residues from silk yarns processing, sodium alginate and poly(ethylene glycol) diglycidyl ether.

The removal and recovery of critical rare-earth elements (REEs) are important from an environmental and economic perspective. The recovery of critical metals from secondary sources has received considerable attention. This work aims to evaluate the beads produced from sericin, alginate, and poly(ethylene glycol) diglycidyl ether (SA@PEGDGE) to recover Eu³⁺. The pH effect showed that pH 5.0 had the highest uptake of Eu³⁺ (0.289 ± 0.006 mmol/g) with stoichiometric cationic exchange with Ca²⁺ (0.425 ± 0.023 mmol/g) by SA@PEGDGE. The kinetic (pseudo-first order, pseudo-second order, and external diffusion) and equilibrium (Langmuir) models adequately represented the adsorption results. The particles had an increase in adsorptive capacity from 0.555 mmol/g at 25 °C to 0.633 mmol/g at 55 °C. Hydrochloric acid (0.1 mol/L) showed the highest recovery rate of Eu³⁺ (96.50 ± 0.84%) from SA@PEGDGE. Eu³⁺ recovery was highly successful for five cycles. The recovery was greater than 95% and the reuse of the eluent in the adsorption cycles enriched the Eu³⁺ concentration 10-fold, from 1.07 mmol/L to 9.96 mmol/L. The SA@PEGDGE also showed better performance for biosorption of Eu³⁺ with other competing ions. The characterization analyzes showed that the SA@PEGDGE beads produced by the ionotropic gelation technique have a spherical shape, surface with low roughness, and amorphous character. The mechanisms of Eu³⁺ biosorption involved interactions with the functional groups present on the SA@PEGDGE surface, cation exchange, and electrostatic interactions. Thus, the crosslinked sericin/alginate particles can be a sustainable alternative for the recovery of critical REEs from wastewater, resulting in social and economic benefits from a circular economy. [Display omitted] • PEGDGE- crosslinked sericin/alginate blend by is effective in recovering europium. • Cationic exchange mechanisms between Eu³⁺ and Ca²⁺ are involved in biosorption. • The maximum capacities are: 0.555 (25 °C), 0.608 (40 °C) and 0.633 mmol/g (55 °C). • Regeneration: Reuse of eluent-enriched europium (up to 10-fold) after 5 cycles. • Selectivity: Eu³⁺ was preferentially removed from multicomponent systems. [ABSTRACT FROM AUTHOR]