A porous chitosan nanofiber-poly(ethylene glycol) diacrylate hydrogel for metal adsorption from aqueous solutions

Porous hydrogels for the adsorption of metals from aqueous solutions were prepared from chitosan nanofibers (CNFs) and poly(ethylene glycol) diacrylate (PEGDA). These hydrogels exhibited high swelling rates and porosities, which were evaluated by a gravimetric method and scanning electron microscopy, respectively. Both factors were influenced by the CNF/PEGDA ratio. The prepared hydrogels adsorbed both transition metals (e.g., copper) and post-transition metals (e.g., tin). The adsorption capacity increased with increasing CNF/PEGDA ratio, indicating synergism between chelation and the enlarged surface area of the porous structure during adsorption. The kinetic data indicated that metal adsorption could be fit to a pseudo-second-order kinetic model, whereas the equilibrium data were fit to the Langmuir isotherm model. Overall, the results revealed that CNF-PEG hydrogels are promising adsorbent materials for metal recovery in environmental applications.