Functional porous protein nanofibrils/polysaccharides aerogel beads for efficient dyes removal from water

The rational design and fabrication of functional and feasible adsorbents with enhanced adsorption properties for pollutant removal remain challenging. Here, to achieve efficient adsorption of dyes, a radial-freezing technique was employed to develop freeze-dried bio-nanocomposites in the form of aerogel beads composed of cellulose nanofibers, protein nanofibers, and chitosan (CPCs). This strategy led to the formation of a spherical aerogel with a dandelion-like structure in the radial cross-section. FE-SEM micrographs of the aerogel beads revealed a highly porous morphology with a network of interconnected pores, allowing for the effective adsorption of liquids. The characterization results of the functional aerogel beads showed a remarkable ability to adsorb various cationic and anionic azo dyes. The maximum adsorption capacity of 1349.7 +/- 34.36 mg g-1 and removal efficiency of nearly 100% in the initial 1000 mg L-1 Congo Red (CR) solution were obtained for CPCs aerogel beads. The resulting adsorption experimental data were fit by the sip isotherm and pseudo-second-order models. The porous structure of the CPCs aerogel bead enhanced the diffusion of dye molecules into the pores and inner surface. Furthermore, combined with the analysis results of FT-IR spectroscopy and XPS, multiple adsorption mechanisms (strong electrostatic interactions, hydrogen bonds, CH-pi and pi-pi bonds) were ascribed between the CPCs composite and dye cations. It is believed that our CPCs aerogel beads can be regarded as a sustainable green bio-adsorbent for water remediation. The multiple transport paths provided by the linked pore channels in CPCs aerogel facilitate the effective separation and elimination of dye molecules. Furthermore, these channels' functional groups improve their performance when they interact with particular substances.