ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Efficient thorium (IV) removal from cerium-containing solution using hydrogels of polyacrylic acid and polyethylenimine as sustainable interpolymer system

Ainamgul Utesheva, Talkybek Jumadilov, Juozas Vidas Gražulevičius, Yelemessova Zhanerke, Khaidar Tassibekov, Khimersen Khuangul, and Aldan Imangazy

Laboratory of Polymer Synthesis and Physicochemistry, Bekturov Institute of Chemical Sciences, Almaty, Kazakhstan

E-mail: imangazy.aldan@gmail.com

Received: 25 May 2025  Accepted: 17 November 2025

Abstract:

The increasing demand for rare earth elements (REEs) necessitates sustainable methods for thorium (Th) removal from REE-containing solutions. This study introduces an interpolymer system of polyacrylic acid (hPAA) and polyethylenimine (hPEI) hydrogels for selective Th(IV) sorption from Ce(III)-containing solutions. The system (hPAA@hPEI, molar ratios X:Y of ionogenic groups) was activated via remote interaction in aqueous media. ICP-AES analysis showed 92% Th(IV) removal at pH 2.65 after 24 h from a Th/Ce mixture (initial [Th] = [Ce] = 5.0 mg/L), with Th uptake of 4.416 mg/g in hPEI (corresponding to a metal-to-ligand M/L ratio of 1:4) and negligible Ce sorption (0.014 mg/g). SEM–EDS confirmed 1.95 wt.% Th in hPEI, while FTIR revealed N–H shifts (from 3270 to 3250 cm⁻¹) indicating Th-N coordination. Sorption followed the Langmuir isotherm (q_max = 5.12 mg/g, K_L = 0.82 L/mg, R² = 0.99), indicative of monolayer chemisorption on homogeneous amine sites. The conditional stability constant (log K_c) was estimated at ~ 5.2, with a detection limit (LOD) of 0.1 mg/L. This eco-friendly system offers potential for immobilizing radioactive Th, enhancing REE purification sustainability.

Keywords: Hydrogels; Activation; Interpolymer system; Sorption; Cerium; Thorium

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04553-z

Chemical Papers 80 (3) 2803–2817 (2026)