Synthesis of Fe3O4 nanoparticles functionalized polyvinyl alcohol/chitosan magnetic composite hydrogel as an efficient adsorbent for chromium (VI) removal

Fe3O4 nanoparticles functionalized polyvinyl alcohol/chitosan magnetic composite hydrogel (Fe3O4-MCH) was successfully synthesized via crosslinking method. The Fe3O4-MCH was explored to be used as an adsorbent for removing chromium (VI) (Cr-VI) from aqueous solution and it exhibited encouraging adsorption performance for Cr-VI both under neutral and acidic conditions. In neutral condition, sharing electron may be one of the possible adsorption reasons, while in acidic condition, the electrostatic attraction was a possible adsorption mechanism. The pseudo-first-order rate model can be well described the adsorption and the equilibrium isotherm was better matched with the Langmuir model. In addition, the swelling ratio of the blank hydrogel was conspicuously higher than that of the hydrogel containing Fe3O4 nanoparticles (Fe3O4 NPs). The loading capacity of Cr-VI on the adsorbent remained at a high level even after five cycles, which showed that the as-prepared hydrogel can be widely used for repeated Cr-VI removal in wastewater in near future.