Hydrothermal-Assisted Grafting of Schiff base Chitosan by Salicylaldehyde for Adsorptive Removal of Acidic Dye: Statistical Modeling and Adsorption Mechanism

The present study employed the hydrothermal technique to graft biopolymer chitosan (CHS) with an aromatic aldehyde (salicylaldehyde, SA) for the adsorption of an acidic azo dye (reactive orange 16, RO 16) from an aqueous environment. The obtained hydrothermally achieved Schiff’s base (chitosan-salicylaldehyde, CHS-SA) material was analyzed using BET, CHN-O, FTIR, SEM, XRD, and pH pzc . The impacts of A: CHS-SA dosage (0.02–0.08 g/100 mL), B: pH (4–10), and C: time (5–25 min) factors on the adsorption performance of CHS-SA towards RO16 dye were fully examined using Box-Behnken design (BBD). The pseudo-second-order model exhibited the greatest match for the adsorption of RO16 dye by CHS-SA, whilst the equilibrium isotherm observations matched the Freundlich model. The maximal adsorption capacity of CHS-SA as established by the Langmuir model was 143.4 mg/g. Several pathways, including electrostatic attraction, π-π stacking, n-π interaction, and H-bonding drive the RO16 adsorption by CHS-SA. This work supports the idea of a hydrothermal way to produce grafted CHS-SA capable of removing harmful contaminants from an aquatic environment.