Polyethyleneimine Functionalized Rice Straw‐Based Cationic Adsorbent With High Efficiency for Phosphate Adsorption

ABSTRACT Phosphorus enrichment in water bodies represents a significant global environmental challenge, driven by increasing water scarcity and pollution issues. This study aims to enhance the phosphate adsorption capacity of polycationic adsorbents through functionalization with polyethyleneimine (PEI). A PEI‐modified rice straw‐based cationic adsorbent was successfully developed through three steps: rice straw activation with LiCl, introduction of aldehyde groups via NaIO4 oxidation, and cationization with PEI. The results demonstrated that rice straw was effectively activated by LiCl, and the adsorbent possesses a nitrogen content of 15.3% after PEI grafting. Batch adsorption experiments demonstrated that the PEI‐modified dialdehyde rice straw exhibited exceptional phosphate adsorption capacity (117.71 mg/g), even under acidic conditions. Furthermore, the pseudo‐second‐order kinetic model fitted to the experimental data exhibited a correlation coefficient ( R 2 ) exceeding 0.99, indicating that phosphate adsorption occurs predominantly on the monolayer surface of the adsorbent. This study indicates that PEI‐DARS could serve as a promising new phosphate adsorbent for wastewater treatment applications.