Chitosan/ nanofibrillated cellulose aerogel with highly oriented microchannel structure for rapid removal of Pb (II) ions from aqueous solution.

Among the heavy metal ions, Pb (II) can cause serious diseases in the nervous and cardiovascular systems even at an ultralow concentration. Nowadays, various materials with high adsorption capacity have been developed for heavy metal ions adsorption. However, most of them have a low adsorption rate and may take a long time to achieve adsorption equilibrium. In this work, chitosan (CS)/ nanofibrillated cellulose (NFC) aerogel with oriented microchannel structure was developed via a directional freeze-drying approach. The structure of the CS/NFC aerogel was characterized and its adsorption performance for Pb (II) was also investigated. The results reveal that the maximum adsorption capacity for Pb (II) is 252.6 mg g-1, much higher than most chitosan-based adsorbents reported in the literature. More impressively, the developed aerogel takes only 5 min to achieve 85% of equilibrium adsorption capacity for Pb (II) due to its highly oriented microchannel structure. Furthermore, the aerogel maintains a high removal efficiency (>85%) after 5 adsorption-desorption cycles. The obtained results demonstrate that the as-prepared CS/NFC aerogel can be used as an effective adsorbent for Pb (II) removal from aqueous solution.