Tailoring the adsorption rate of porous chitosan and chitosan–carbon nanotube core–shell beads

Porous chitosan beads are widely used as adsorption media in environmental and biomedical areas. We present two simple methods to tailor the adsorption behavior of chitosan beads by dynamic adsorption and structural modification. Compressing the chitosan beads repeatedly in solutions containing dye molecules or nanoparticles leads to significant improvement in adsorption rate by enhancing internal molecular diffusion, compared with statically placed beads. We also create a hierarchical core-shell structure consisting of a single-walled carbon nanotube network uniformly wrapped around each chitosan bead, in which the outside nanotube network can block or slow down the diffusion of larger size nanoparticles without influencing adsorption of small sized molecules and nanoparticles. Our strategy involving dynamic adsorption and fabrication of hierarchical porous structures might be applied to many other porous materials to tailor their adsorption properties.