High Adsorption Performance of a Porous Chitosan Scaffold With a Multilayer Structure for Congo Red Removal From Aqueous Media

ABSTRACT Chitosan (CS) is a natural polysaccharide that has been extensively investigated for removing dyes from aqueous media owing to its environmentally friendly nature and cost‐effective production. CS can be used in various forms, such as flakes, beads, particles, and thin films. In this work, our objective was to develop a green material for high‐performance removal of Congo red (CR) from aqueous media. A porous CS scaffold with a multilayer structure was fabricated via solvent casting followed by freeze‐drying for this purpose. The fabricated CS scaffold was characterized by FTIR, XRD, and scanning electron microscopy (SEM). The CR adsorption behavior of the CS scaffold was dependent on three main factors (i.e., contact time, adsorbent dosage, and pH). A high adsorption performance for the CR removal by the CS scaffold was achieved over a wide pH range of 4–10 with an optimal contact time of 120 min. The CR adsorption on the CS scaffold is best described by the Langmuir model. The maximum adsorption capacities of the CS scaffold increased with increasing temperature, being 344.83, 526.32, and 555.56 mg·g −1 at 296, 306, and 311 K, respectively, which were higher than those of other CS adsorbents. This indicated endothermic nature and favorability of the CR adsorption (∆ H ° = 27.41 kJ·mol −1 , ∆ S ° = 182.73 J·K −1 ·mol −1 , and ∆ G ° = −26.67 to –29.42 kJ·mol −1 ) in a range of 296–311 K. The CR adsorption obeyed a pseudo‐second‐order kinetic model. Moreover, it maintained a high CR removal efficiency of 80% after five cycles of reuse, with a 2% hydrogen peroxide solution as the most effective eluent. This work highlights the potential of eco‐friendly CS adsorbents for wastewater treatment toward sustainable development, offering a green alternative to conventional dye‐treatment methods.