Constructing biodegradable nanochitin-contained chitosan hydrogel beads for fast and efficient removal of Cu(II) from aqueous solution

In this study, Fe3O4-nanoparticles-contained polyamide 6 (PA 6) microparticles (FP) were developed by a first dispersion of Fe3O4-nanoparticles in e-caprolactam (CL) monomer in the presence of polystyrene (PS) and a subsequent in situ CL open polymerization into PA 6, followed by PS removal. The FP microparticles (as magnetic separation material) and nanochitin (n-CT, as an effective metal-cation natural adsorbent) were then in situ encapsulated into poly(vinyl alcohol)-enhanced chitosan hybrids (PVA/CTS) to form biodegradable nanocomposite hydrogels (FPCC) with magnetic separation ability. The FPCC hybridized hydrogels enabled about 1.7-fold Cu(II) adsorption capacity as compared to the pure PVA/CTS hydrogels with a Cu(II) adsorption value of 38.7 mg/g. More attractively, the adsorption equilibrium could be achieved within 10 min, which is quicker than many previous adsorbents. Furthermore, simulation results indicated that Cu(II) adsorption behaviors of the hybrid hydrogels conform to a pseudo-second-order kinetic model and a Langmuir isotherm model.