Preparation of Amidoxime Polyacrylonitrile and Sodium Alginate Composite Membrane with Superior Regeneration Performance for Efficient Uranium Adsorption

Amidoxime-based materials are widely used for uranium adsorption due to their selective capacity. However, current preparation methods, such as homogeneous modification in organic solvents or heterogeneous modification in aqueous solutions, pose environmental challenges. In this study, an amidoxime polyacrylonitrile–sodium alginate composite membrane (PAO-SA) was synthesized via simple blending and nonsolvent phase separation using sodium thiocyanate as the solvent. SEM-EDS analysis confirmed the uniform distribution of U(VI) adsorbed onto the PAO-SA membrane surface. The optimal adsorption performance was achieved at pH 6.0 and a temperature of 298 K, with a maximum adsorption capacity of 326.1 mg/g. The membrane demonstrated excellent selectivity toward U(VI) in the presence of competing ions, exhibiting a high distribution coefficient (Kd = 3.0 × 104). Adsorption–desorption experiments identified 0.5 mol/L NaHCO3 as the most effective eluent, achieving a desorption efficiency of 93.2% after six cycles while maintaining an adsorption capacity of 309.0 mg/g. Kinetic and thermodynamic evaluations revealed that the adsorption process followed a pseudo-second-order kinetic model and conformed to the Langmuir isotherm, indicating chemisorption governed by a spontaneous, endothermic mechanism. The PAO-SA composite membrane is environmentally friendly and easy to prepare and demonstrates strong selective adsorption and recyclability, making it commercially viable for uranium removal.