Semi-crystalline Ce(III/IV)-chitosan architecture overcomes the oxidation-adsorption paradox in hazardous antimony treatment

Antimony (Sb) treatment presents a paradox: oxidizing toxic Sb(III) to Sb(V) for detoxification generates Sb(OH) 6 − species with a large hydration radius (7.36 Å) that hinders adsorption on conventional crystalline adsorbents due to limited accessible sites. We developed a Ce(III/IV)-chitosan semi-crystalline complex with mixed-valence coordination (Ce 3+ /Ce 4+  = 62.3:37.7) that addresses this challenge. Ce coordination constructs a semi-crystalline architecture where amorphous regions provide more accessible sites for large Sb(OH) 6 − while ordered domains maintain structural stability. The mixed-valence system sustained positive surface charge (+25 to +40 mV, pH 2–10) for electrostatic Sb(V) attraction, while Ce 3+ /Ce 4+ cycling catalyzed H 2 O 2 -mediated Sb(III) oxidation. At 2 mg/L Sb, a challenging concentration for industrial wastewater, the material achieved >98% removal within 90 min, reducing residual Sb to <0.04 mg/ L. maximum capacities reached 595.5 mg/g (Sb(V)) and 461.6 mg/g (Sb(III)), with excellent regenerability (>86% after five cycles). This work demonstrates how coordination-induced structural reorganization and mixed-valence chemistry overcome fundamental barriers in mixed-oxidation-state contaminant treatment.