Preparation of chitosan/SiO2-loaded graphene composite beads for efficient removal of bilirubin

Porous nanocomposite materials possess enhanced adsorption properties, but uniformly dispersing nanofillers in polymer matrices is still a challenging technical difficulty. In this study, modification through loading with SiO2 successfully improved the dispersibility of graphene in chitosan suspensions. By employing a phase-inversion method, cross-linked chitosan/SiO2-loaded graphene (CS/graphene-SiO2) composite beads were prepared. The resulting CS/graphene-SiO2 beads were characterized by scanning electron microscopy and Raman spectroscopy, which clearly showed that graphene was well-dispersed in the chitosan matrix. Adsorption results demonstrated that CS/graphene-SiO2 beads possessed much better adsorption capacity for bilirubin (77.87%) compared to pure chitosan (CS) beads (22.47%), mainly due to the synergistic effect between the hydrophobic forces of graphene and the electrostatic interactions provided by the amino groups of CS. The adsorption of bilirubin was found to match a monolayer model, as well as a pseudo-first-order kinetic model. The mechanical strength of composite beads was significantly improved as compared to CS beads, due to the incorporation of graphene. The effects on hemolytic activity and the components of blood were negligible, which indicate an excellent compatibility of the obtained composite beads with blood. Overall, the proposed CS/graphene-SiO2 beads as an efficient adsorbent for bilirubin have high potential in blood purification applications.