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

Abstract

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.