Synthesis of Schiff's base magnetic crosslinked chitosan-glyoxal/ZnO/Fe3O4 nanoparticles for enhanced adsorption of organic dye: Modeling and mechanism study

In this work, Schiff's base magnetic crosslinked chitosan-glyoxal/Fe₃O₄ composite (CS-G/Fe₃O₄) was synthesized and further developed by loading zinc oxide (ZnO) nanoparticles into its polymeric matrix. The final composite material of magnetic crosslinked chitosan-glyoxal/ZnO/Fe₃O₄ nanoparticles (CS-G/ZnO/Fe₃O₄ NPs) was tested for the removal of organic dye pollutant (reactive blue 19, RB19). The synthesized magnetic nanomaterials were characterized by several techniques such as CHN elemental analysis, Brunauer-Emmett-Teller analysis, vibrating-sample magnetometer, X–ray powder diffractometry, Fourier Transforms infrared, scanning electron microscope, energy dispersive X-Ray analysis, pH_pzc, and pH-potentiometric titrations. A statistical approach namely Box–Behnken design (BBD) was applied to optimize the synthesis conditions as well as adsorption key parameters (A: ZnO nanoparticles loading (0–50%), B: adsorbent dosage (0.02–0.1 g), C: pH (4–10), D: temperature (30–60 °C), and time E: (10–60 min)). The adsorption kinetic and equilibrium results were well described with pseudo-second order model and Freundlich isotherm model, respectively. The maximum adsorption capacity of CS-G/ZnO/Fe₃O₄ NPs for RB19 was 363.3 mg/g at 60 °C. The adsorption mechanism of RB19 onto CS-G/ZnO/Fe₃O₄ NPs can be ascribed to several types of interactions (e.g. electrostatic attractions, hydrogen bonding, and n-π interactions). This study provides a new and effective adsorbent for water remediation due to its recoverability and high efficiency in removing the organic dye pollutants.