Preparation and characterization of porous chitosan microspheres and adsorption performance for hexavalent chromium.

Porous chitosan microspheres were successfully developed by the simple procedure of freezing chitosan hydrogel beads and subsequently lyophilizing the frozen structure in present study. The characterization of porous chitosan microspheres was subjected to detailed analysis of scanning electron microscopy (SEM), porosity and Fourier transform infrared spectra (FTIR), and their adsorption performance for hexavalent chromium (Cr(VI)) was investigated. Results showed that when the chitosan solution concentration ranged from 2.5% to 3.5% (w/v), porous spherical structures with uniform size distribution and good sphericity formed, and the pore size and porosity could decrease significantly by increasing the concentration of chitosan solution or reducing the freezing temperature. The porous chitosan microsphere prepared with 3% chitosan solution at -40 °C for 200 min experienced the highest Cr(VI) adsorption due to its higher porosity. FTIR result suggested that porous chitosan microspheres provided adsorption sites of the amino and hydroxyl groups for the removal of Cr(VI).