Novel magnetic chitosan/poly(vinyl alcohol) hydrogel beads: Preparation, characterization and application for adsorption of dye from aqueous solution

Novel magnetic chitosan/poly(vinyl alcohol) hydrogel beads (m-CS/PVA HBs) were prepared by an instantaneous gelation method and characterized by X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and thermogravimetric analysis (TGA). Results of characterization indicated that m-CS/PVA HBs have been prepared successfully without damaging the crystal structure of Fe3O4 and their saturation magnetization were about 21.96 emu g−1. The adsorption capacity of Congo Red on the m-CS/PVA HBs was 470.1 mg g−1. The adsorption was well described by pseudo-second-order kinetics and Langmuir equation. Positive value of enthalpy change (ΔH∘)(ΔH∘) (13.32 kJ mol−1) showed that the adsorption was endothermic and physical in nature. The values of Gibbs free energy change (ΔG∘)(ΔG∘) were found to be −3.321 kJ mol−1 at 298 K for m-CS/PVA HBs, indicating the spontaneity of Congo Red adsorption. Therefore, the m-CS/PVA HBs could be employed as a low-cost alternative to other adsorbents in the removal of dyes from aqueous solution.

► The m-CS/PVA HBs were prepared with inter- and intra-hydrogen bonds between chitosan and PVA.
► The adsorption capacity of Congo Red on the m-CS/PVA HBs was 470.1 mg g−1.
► The adsorption was endothermic in nature.
► The m-CS/PVA HBs could be employed as a low-cost alternative to other adsorbents.
► The m-CS/PVA HBs could be easily removed with an addition of a permanent magnet.