Magnetic grafted chitosan-salicylaldehyde via hydrothermal synthesis for acid red 88 dye removal: a statistical optimization

Herein, an aromatic ring aldehyde (salicylaldehyde, SL) was grafted onto the biopolymer matrix of the magnetic chitosan (CS/Fe₃O₄) to yield a recoverable promising adsorbent for the removal of acid red 88 (AR88 dye) from aqueous media. Various characterization methods such as VSM, pH_pzc, CHNS, XRD, SEM–EDX, FTIR, and BET were used to determine the physicochemical properties of CS-SL/Fe₃O₄. A Box-Behnken design (BBD) was adopted to optimize the experimental parameters of A: CS-SL/Fe₃O₄ dose (0.02–0.1 g), B: [AR88] concentration (10–50 mg/L), C: pH (4–10), and D: contact time (10–90 min) on the adsorption performance of CS-SL/Fe₃O₄ with the AR88 dye. The Freundlich isotherm and pseudo-second-order kinetic models were applicable to describe the dye adsorption rate of AR888. The maximum dye adsorption capacity (q_max) of the hydrothermally grafted CS-SL/Fe₃O₄ with AR88 was 137.3 mg/g at a fixed adsorbent dosage (0.09 g) and pH (4.16). Various intermolecular interactions such as electrostatic, π-π stacking, n-π interactions, and H-bonding contribute to AR88 adsorption by CS-SL/Fe₃O₄. This study introduces a recoverable and a promising magnetic grafted chitosan adsorbent for the removal of an anionic dye from aqueous media. Moreover, this adsorbent can be further applied to the removal of other types of water contaminants in aquatic environmental media.