This study demonstrates a green and sustainable strategy for efficient single-step recovery of cerium through the rational design of core–shell Fe 3 O 4 @ZIF-8 nanocomposites. The material is comprehensively characterized in terms of morphology, magnetic properties, functional groups, and pore structure. Adsorption studies reveal pH-dependent recovery behavior, with optimal performance in the pH range of 3.9–7.2. Analysis of isotherms and thermodynamics confirms the endothermic nature of the recovery process, showing a monotonic increase in the maximum adsorption capacity from 110 mg g −1 to 185 mg g −1 as temperature rises from 283 K to 328 K. Notably, the effect of ionic strength (IS) suggests that NaCl significantly enhances Ce(III) recovery efficiency, while K 2 SO 4 exhibits marked suppression. Competitive adsorption experiments reveal stronger interference from heavy REEs (Ho 3+ /Tm 3+ ) compared to light REEs (La 3+ ). The fundamental mechanisms are elucidated through multiscale interaction analysis, revealing a synergistic process combining dual-phase transition dynamics and photoinduced redox reactions. The surface architecture of magnetic core evolves from initial ZnO-dominant nanocrystals to ZnO/CeO 2 heterostructures, and ultimately stabilizes as a CeO 2 -enriched framework with increasing Ce(III) concentrations. Moreover, across the time scale, the speciation of surface-adsorbed cerium underwent a gradual transition from Ce(III)-dominance to Ce(IV)-dominance, ultimately forming a regime where Ce(IV) (CeO 2 ) served as the primary species. This progressive transformation enables in situ immobilization and single-step recovery of Ce(III) under mild conditions, establishing a novel paradigm for REEs recovery technology.
Cerium is a critical element to modern technologies . Nowadays, its increased applications have led to elevated levels in the environment. Cerium recovery by microorganisms has gained a great deal of attention. Here, our research showed that Bacillus licheniformis could be used to recover Ce 3+ from aqueous solution. The adsorption capacity of cerium on this bacterial strain achieved 38.93 mg/g (dry weight) biomass. Adsorption kinetics followed a pseudo-second-order rate model, and adsorption isotherm was fitted well with the Freundlich model. Scanning electron microscope (SEM) observations coupled with X-ray energy dispersive spectroscopy (EDS) analysis revealed a spatial association of Ce with C, N, O, S, and P. Fourier transform infrared spectroscopy (FT-IR) analysis further suggested that the phosphate and carboxyl groups on the cell surface might be responsible for the adsorption of cerium. Furthermore, X-ray diffraction (XRD) and transmission electron microscopy (TEM) with electron energy loss spectroscopy (EELS) suggested that cerium initially occurred on the bacterial cell surface as Ce(OH) 3 , which was mainly converted to monazite (CePO 4 ) and a small amount of CeO 2 overtime. Hydrothermal treatment was used to accelerate the mineralization process of cerium by B. licheniformis . The hydrothermal treatment is conducted for comparative analysis of mineralization process in extreme geological condition.
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