New crosslinked-chitosan graft poly(N-vinyl-2-pyrrolidone) for the removal of Cu(II) ions from aqueous solutions

Abstract

Crosslinked chitosan beads were grafted with N-vinyl-2-pyrrolidone (NVP) using ammonium persulfate (APS) as free radical initiator. Important variables on graft copolymerization such as temperature, reaction time, concentration of initiator and concentration of monomer were optimized. The results revealed optimum conditions for maximum grafting of NVP on 1 g crosslinked chitosan as follows: reaction temperature, 60 °C; reaction time, 2 h and concentrations of APS and NVP of 2.63 × 10−1 M and 26.99 × 10−1 M, respectively. The modified chitosan beads were characterized by FTIR spectroscopy, 13C NMR, SEM and BET to provide evidence of successful crosslinking and grafting reactions. The resulting material (cts(x)-g-PNVP) was evaluated as adsorbent for the removal of Cu(II) ions from aqueous solutions in a batch experiment. The Langmuir and Freundlich adsorption models were also applied to describe the equilibrium isotherms. The results showed that the adsorption of the copper ions onto the beads agreed well with Langmuir model with the maximum capacity (qmax) of 122 mg g−1.