From adsorption to reduction: Crosslinking-grafting strategy to construct chitosan-based adsorbent for Cr(VI) removal...

This study developed a novel chitosan-based adsorbent (CS-PN) through a two-step synthesis method for efficient Cr(VI) removal from wastewater. Comprehensive characterization (SEM-EDS, XRD, XPS, FT-IR, BET, TGA) confirmed successful synthesis, revealing a mesoporous structure (90 m²/g) with excellent thermal stability. Batch adsorption experiments demonstrated that the maximum adsorption of Cr(VI) by CS-PN was 311.72 mg/g at pH 3 and 318 K. This process follows spontaneous adsorption and endothermic chemisorption, primarily exhibiting monolayer adsorption behaviour, jointly regulated by internal and external diffusion. CS-PN exhibited outstanding selectivity for Cr(VI) amid competing ions, showing partition coefficients of 1.145 (simulated) and 3.96 (actual wastewater). After five adsorption-desorption cycles, adsorption capacity was only decreased from 202.51 to 188.10 mg/g, and desorption amount was decreased from 201.86 to 178.51 mg/g, DFT calculations revealed binding energies of -13 to -14.13 eV, while zeta potential analysis indicated electrostatic attraction as the primary mechanism, supplemented by chemical coordination and reduction. This study provides a new method to evaluate the performance of modified chitosan for Cr(VI) removal in complex aqueous environments, and provides a theoretical basis and technical reference for its application in practical wastewater treatment.