Enhanced recovery of rare earth elements from mine wastewater using microbial-derived ferrous sulfide

The recovery of rare earth elements (REEs) from mine wastewater has become increasingly critical due to the high demand for REEs in advanced technologies and their limited availability. Here, this study explored the use of biologically synthesized ferrous sulfide nanoparticles (bio-FeS) produced by Shewanella oneidensis MR-1 (FeS@MR-1) for the efficient and selective adsorption of REEs from mine wastewater. Our results demonstrated that FeS@MR-1 achieved high adsorption efficiencies of 50.3-98.8 % for REEs while showing minimal affinity for non-REEs (1.20-6.37 %), outperforming its two main components bio-FeS and Shewanella oneidensis MR-1. Physicochemical factors revealed by several characterizations indicated that the enhanced performance of FeS@MR-1 stemmed from synergistic effects between bio-FeS nanoparticles and bacterial cells, which improved dispersion, provided more active sites, and facilitated electron transfer. Adsorption kinetics, isotherm studies, and thermodynamic analysis suggested chemisorption, monolayer adsorption, and spontaneous and exothermic adsorption, respectively. Additionally, REEs were effectively desorbed (78.9-92.8 %) using acetic acid, enabling REEs' recovery. Overall, this study highlighted FeS@MR-1 as a practical and promising biomaterial for REE recovery from real mine wastewater.