Carbon Nanotube-Chitosan Composite Beads with Radially Aligned Channels and Nanotube-Exposed Walls for Bilirubin Adsorption

Porous nanocomposite materials combine the advantages of a polymer matrix in forming a stable framework and the nanofillers that provide high surface area. Here, we use carbon nanotubes (CNTs) as nanofillers to fabricate chitosan beads with controlled porous structure. We synthesized spherical chitosan-CNT composite beads via freeze casting by dropping a mixed solution into liquid nitrogen, and the resulting highly porous composite beads contain radially oriented channels with hybrid chitosan-CNT channel walls. In particular, we observed localized regions of small CNT agglomerates embedded within the chitosan matrix at a lower CNT loading (40wt%), and predominately exposed CNTs distributed throughout the channel walls at a higher loading (80wt%). Owing to the hierarchical open-porous structure and mesopores provided by exposed CNTs, these composite beads showed much higher adsorption capacity (43.6mgg(-1) within 2h) to bilirubin than CNT-free chitosan beads. Our nanocomposite beads with tunable pore wall structure have potential applications in environmental and biomedical areas such as efficient adsorption materials.