Direct amidoximation of pan fibers for high-performance uranium adsorption: Batch and fixed-bed column studies

Amidoxime-functionalized polyacrylonitrile (PAN-AO) fibers were synthesized via a two-step chemical modification and evaluated for uranium(VI) adsorption performance in both batch and fixed-bed column systems. The adsorption capacity was highly dependent on pH, with optimal uptake observed in the range of pH 5.0–7.5. PAN-AO fibers exhibited strong selectivity for uranium even in the presence of competing ions such as those in seawater. Kinetic studies revealed that the adsorption followed a pseudo-second-order model, indicating chemisorption as the predominant mechanism, while intraparticle diffusion analysis confirmed a two-step process. Equilibrium data fit well with the Langmuir isotherm, yielding a maximum monolayer adsorption capacity of 83.3 mg/g. Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic. Fixed-bed column studies showed that the Bohart – Adams and BDST models effectively described the breakthrough behavior. Despite low packing density, PAN-AO fibers exhibited a short mass transfer zone ( < 3 mm), enabling efficient uranium capture. Desorption with 0.1 M HCl demonstrated high regeneration efficiency (~95% after 10 bed volumes), highlighting the potential of PAN-AO fibers for practical uranium recovery from complex aqueous environments, including seawater.