Tannic acid‐zinc crosslinked chitosan hydrogels: High‐performance adsorbent for titan yellow removal from wastewater

Abstract Designing hybrid materials with tunable properties offers efficient solutions for wastewater purification. This work aims to develop chitosan‐based hydrogels capable of effectively removing titan yellow (TY) dye from wastewater. A chitosan–zinc hydrogel (ChZn) adsorbent was prepared using a simple non‐cumbersome wet‐chemical method, and showed swift and effective removal of TY dye. A 22.1 mg dose of ChZn removed 68.2% of TY dye from its 10.0 mL solution of concentration 500 mg L −1 at optimum pH ~ 6 within 25 min, demonstrating a capacity of 384.45 mg g −1 . By crosslinking ChZn with tannic acid, a new adsorbent (ChZnTA) was obtained. At optimized conditions of time (25 min) and strength (10.0 mL solution of 500 mg L −1 TY dye), ChZnTA removed 97.5% of TY dye at pH ~ 7, offering a much higher capacity of 505.05 mg g −1 . The experimental data demonstrated that the adsorption process conformed to pseudo‐second‐order kinetics and was best described by the Freundlich isotherm, suggesting multilayer adsorption on a heterogeneous surface. The combined effect of hydrogen bonding, π‐π stacking, van der Waals, and electrostatic interactions is suggestive of high adsorption capacities of the hydrogels. The desorption and regeneration tests confirmed the reusability of the materials, even after five consecutive cycles. ChZnTA and ChZn retained removal efficiencies of 59.9% and 35.3%, respectively. These findings underscore the potential of ChZnTA as a practical and highly effective adsorbent for sustainable water purification applications.