New magnetic Schiff's base-chitosan-glyoxal/fly ash/Fe 3 O 4 biocomposite for the removal of anionic azo dye: An optimized process.

In this study, a new magnetic Schiff's base-chitosan-glyoxal/fly ash/FeO biocomposite (Chi-Gly/FA/FeO) 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/FeO biocomposite. The effectiveness of Chi-Gly/FA/FeO 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/FeO 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/FeO biocomposite exhibited a high ability to separate from the aqueous solution after adsorption process by external magnetic field.