New magnetic Schiff's base-chitosan-glyoxal/fly ash/Fe₃O₄ biocomposite for the removal of anionic azo dye: An...

In this study, a new magnetic Schiff's base-chitosan-glyoxal/fly ash/Fe₃O₄ biocomposite (Chi-Gly/FA/Fe₃O₄) was successfully synthesized by direct compositing of magnetic chitosan (Chi) with fly ash (FA) powder particles, and followed by Schiff's base formation via cross-linking reaction with glyoxal (Gly). Various techniques such as BET, XRD, FTIR, and SEM-EDX were utilized to characterize of Chi-Gly/FA/Fe₃O₄ biocomposite. The effectiveness of Chi-Gly/FA/Fe₃O₄ as an adsorbent was evaluated for the removal anionic azo dye such as reactive orange 16 (RO16) from aqueous environment. The effect of adsorption process parameters namely adsorbent dose (A: 0.02-0.1 g), solution pH (B: 4-10), temperature (C: 30-50 °C), and contact time (D: 5-20 min) were optimized via Box-Behnken design (BBD) in response surface methodology (RSM). The adsorption process followed the pseudo-second order (PSO) kinetic, and Freundlich isotherm models. The maximum adsorption capacity of Chi-Gly/FA/Fe₃O₄ biocomposite for RO16 dye was recorded to be 112.5 mg/g at 40 °C. The RO16 dye adsorption mechanism was attributed to various interactions such as electrostatic, n-π, H-bonding, and Yoshida H-bonding. Furthermore, the Chi-Gly/FA/Fe₃O₄ biocomposite exhibited a high ability to separate from the aqueous solution after adsorption process by external magnetic field.