One‐Pot Synthesis of Amine‐Rich Starch‐ PVA Composite Hydrogel Microspheres for Simultaneous Cr( VI ) Removal and In‐Situ Reduction

A one‐pot radical polymerization strategy was developed to directly copolymerize polyethyleneimine (PEI) into a starch‐poly(vinyl alcohol) hydrogel network, circumventing the multistep procedures, network heterogeneity, and poor product recovery inherent to conventional grafting. Suppressing the chain‐transfer activity of PEI through controlled monomer feeding and rapid initiation yielded uniform microspheres with homogeneously distributed amine sites, which achieved an adsorption capacity of 780.0 mg g −1 at pH 3.0 and 298 K, ranking among the highest values reported for starch‐based adsorbents. Kinetic and isotherm analyses showed that adsorption followed a pseudo‐second‐order rate law and the Freundlich model, consistent with a spontaneous, endothermic, entropy‐driven, chemisorption‐dominated multilayer process. Spectroscopic evidence revealed a synergistic adsorption–reduction–immobilization pathway whereby protonated amine groups electrostatically capture HCrO 4 − , neutral amines donate electrons to reduce Cr(VI) to Cr(III) in situ, and the reduced chromium is subsequently chelated and immobilized by carboxyl and residual amine groups within the hydrogel network. The material maintained over 69% removal efficiency in real water matrices and retained 90.6% of its initial capacity after five regeneration cycles with sodium hydroxide. This strategy integrates network construction, amine functionalization, and microsphere formation in a single step, establishing a new paradigm for high‐performance starch‐based adsorbents combining exceptional capacity, structural robustness, and practical separability.