Chitosan/Graphite/Polyvinyl Alcohol Magnetic Hydrogel Microspheres for Decontamination of Reactive Orange 16 Dye

Abstract

A rapid gelation method was used to fabricate magnetic chitosan/graphite/polyvinyl alcohol (m-CGPA) hydrogel beads crosslinked with glutaraldehyde. A thorough characterization was carried out by FTIR, SEM-EDX, XRD, VSM, and TGA. Studies with batch experiments indicated that m-CGPA removes more than 95% of reactive orange 16 (RO 16) dye with a Langmuir monolayer adsorption capacity of 196.3 mg/g at pH 4.0 in just 90 min of contact time. Langmuir isotherm model fitted well with the experimental data. Pseudo-second order kinetics was proposed for the adsorption process. Adsorption thermodynamics evidenced the fact that the process was spontaneous, exothermic, and enthalpy-driven in nature. The saturation magnetization of the material as obtained from VSM analysis was found to be 7.2 emu/g in comparison with that of pure Fe3O4 at 66.4 emu/g. In light of its excellent decontamination efficiency, low cost, and rapid adsorption, this material was found to be an excellent decontaminant for RO16. In addition to enhanced adsorption capacity, the magnetic behavior was an added advantage as it could be easily separated with the help of an external magnet. Fixed bed column studies revealed that the column method can be applied to large-volume treatment. Also, it was possible to regenerate m-CGPA using a 5% NaOH solution and reuse it in multiple cycles.