Phosphorylated calix[4]arene/balsa wood copolymers for selective uranyl extraction from wastewater and seawater

Hyper-crosslinked polymers are frequently used to recover specific guest molecules due to their high porosities, excellent chemical properties, and structural stability. However, the recovery of powder adsorbents poses a significant challenge in the extraction of uranyl from aqueous solutions, which limits their practical application. A phosphorylated calix[4]arene/balsa wood copolymer (C4-W-P) was successfully synthesized and utilized for the extraction of uranyl from radioactive wastewater and seawater. Compared to previously reported adsorbents, C4-W-P demonstrated rapid uranyl capture kinetics, with adsorption equilibrium achieved within 150 min. The material exhibited a monolayer saturation adsorption capacity of 473.9 mg·g −1 at pH 5. Thermodynamic studies confirmed the spontaneous and endothermic nature of the adsorption process. Furthermore, C4-W-P exhibited exceptional structural stability, with only a 9.7 % reduction in adsorption capacity after six adsorption–desorption cycles. Additionally, C4-W-P demonstrated excellent selectivity in simulated wastewater containing 16 rare metal ions and simulated seawater containing an additional five metal ions. The K d U values were recorded to be 1817.2 and 33,265.3 mL·g −1, respectively, for these conditions. These results demonstrate the high-efficiency uranium removal capabilities of C4-W-P under realistic conditions. The abundant phosphate groups (∼1.69 mmol·g −1 ) on the material surface were identified as the primary adsorption contributors. Overall, this study provides a promising strategy for uranyl extraction with high selectivity and ease of preparation, contributing to environmental protection and economic development.