Highly recyclable EDTA-crosslinked chitosan-gelatin biopolymer adsorbent for separation and recovery of rare earth elements from aqueous solution

Highlights

	● Chitosan gelatin crosslinked biopolymer was used for REEs separation and recovery.
	● Rate constant ( k 2) was obtained as (9.60–10.30) × 10−4 g/(mg·min) for used REEs.
	● Monolayer adsorption capacities were 76.70–86.20 mg/g for used REEs.
	● β for Eu(III) separation was 1.383 and 1.322 for Eu/Sc and Eu/Yb.
	● Adsorption and separation were due to electrostatics and complexation with REEs.

Abstract

A biopolymer adsorbent was prepared by crosslinking chitosan (CS) and gelatin (GL) with ethylenediaminetetraacetic acid (EDTA) for the separation and recovery of three famous rare earth elements (REEs), i.e., lanthanum (La(III)), cerium (Ce(III)), and europium (Eu(III)), from water. In this adsorbent, the EDTA moiety acts as a crosslinking agent, in addition to aiding in REE adsorption via coordination sites. Various parameters, including contact time, pH, initial REE concentration, reusability, and selectivity, were investigated during the REE recovery from water. The kinetic results fit better with the pseudo-second-order (PSO) kinetics model, confirming the involvement of chemisorption and external film diffusion in the rate-determining step. The isotherm data fit the Langmuir model, indicating a homogeneous surface for REE adsorption. The rate constant (k₂) values for PSO kinetics were (9.60 ± 0.05) × 10⁻⁴, (8.67 ± 0.04) × 10⁻⁴, and (10.30 ± 0.04) × 10⁻⁴ g/(mg·min), while the maximum adsorption capacities were 76.70 ± 5.70, 79.10 ± 6.80, and 86.20 ± 5.10 mg/g for La(III), Ce(III), and Eu(III), respectively. The CS-EDTA-GL adsorbent provided a good separation factor (β) in 16 REE mixtures; among them, an optimal β was observed for Eu(III) with values of 1.3838, 1.322, 1.284, 1.351, 1.4896, and 1.2792 for Eu/Sc, Eu/Yb, Eu/Tm, Eu/Y, Eu/La, and Eu/Er, respectively. Adsorption mechanism confirms the electrostatic interactions and coordination complexation role in the REE adsorption. Finally, the adsorbent was used in pure water, tap water, and two industrial wastewater samples collected at real environmental concentrations to determine its suitability for practical applications.

Graphical abstract

Keywords

Adsorption recovery / Rare earth elements / Separation factor / Industrial wastewater / Recovery mechanism

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CRediT Authorship Contribution Statement

M. Verma: Conceptualization, experiments, writing original draft; D. Sachan: experiments; V. Kumar, W. Ahmad, N. Sharma: Editing, H. Kim: investigation and review.

Conflict of Interests

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgements

Monu Verma would like to thank the National Research Foundation of Korea (NRF) for funding provided by the Ministry of Science and ICT through the Brain Pool Program (RS-2024-00406513). This study was supported by the Green Venture R&D program (S3051540) funded by the Ministry of SMEs and Startups (MSS, Republic of Korea). This study was supported by the Strategic Academic Leadership Program of RUDN University, Russia.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11783-025-1971-1 and is accessible for authorized users.

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