One-Step Functionalization of Chitosan Using Aromatic Groups via Hydrothermal Assisted Grafting for Removal of Reactive Orange 16 Dye: Optimization and Adsorption Mechanism

Herein, the biopolymer chitosan (CHI) was functionalized by grafting aromatic groups (benzaldehyde, BZA) onto its backbone using a hydrothermal technique to create an efficient hydrothermally chitosan-benzaldehyde adsorbent (CHI-BZA). The characterization results revealed a mesoporous and crystalline structural features of the CHI-BZA, further supporting that the aromatic ring of BZA was successfully grafted onto CHI. The resulting CHI-BZA product was applied as a promising adsorbent to remove a model of acidic dye (reactive orange 16, RO16) from simulated wastewater. Optimizing the major adsorption factors (A: CHI-BZA dose (0.02-0.08 g); B: pH (4-10); C: time (5-25)) was accomplished by the Box-Behnken design (BBD). The Freundlich isotherm and pseudo-second-order kinetic models match the adsorption profile of RO16 species. The hydrothermally prepared CHI-BZA was found to possess a maximum adsorption capacity (q(max)) of 228.9 mg/g for the RO16 dye. The adsorption of RO16 species onto the CHI-BZA surface is controlled by several types of interactions: electrostatic, n-pi, pi-pi, and H-bonding. This work highlights that hydrothermally prepared CHI-BZA may serve as an efficient and promising adsorbent for the removal of acidic dyes from contaminated water.