Uranium removal by magnetic ZnFe2O4@g-C3N4 nanocomposites: characterization and mechanism

The highly efficient extraction of uranium from aquatic environments through adsorption method has emerged as a pivotal research focus, particularly within the domains of environmental protection and sustainable development. In this investigation, magnetically recyclable mesoporous ZnFe 2 O 4 @g-C 3 N 4 (ZFOCN) is synthesized by grafting ZnFe 2 O 4 (ZFO) nanospheres onto g-C 3 N 4 (CN) nanosheets through straightforward solution mixing followed by simple calcination, which addresses the challenge associated with the recovery of adsorbents. Characterization analyses and batch experiments reveal that the ZFOCN surface exhibits more negative zeta potential (∼−14.00 mV when pH = 5) alongside reduced contact angle with water (∼43.1° on average). Consequently, ZFOCN demonstrates superior adsorption capacity ( q max  = 36.3 mg·g − 1 ), accelerated reaction kinetics (reach equilibrium within approximately 8 h) and heightened selectivity compared with CN and ZFO at pH = 5, which is better fitted by Freundlich isotherm model and pseudo-second-order kinetic model. Notably, the cycle experiment results indicate that it retains high efficiency even after five cycles (∼80 %), showing remarkable recyclability. During the adsorption process, the underlying reaction mechanisms are identified as electrostatic interaction coupled with inner-sphere surface complexation predominantly attributed to Zn–O and Fe–O bonds. Thus, this study not only introduces an effective strategy for fabricating novel magnetic adsorbent but also offers fresh insights into eliminating U(VI), contributing significantly to environmental preservation and sustainable advancement.