Preparation of poly-dopamine-silk fibroin sponge and its dye molecular adsorption

This paper proposes a process for fabricating a poly-dopamine-silk fibroin sponge (PDA-SF) by using dopamine self-assembly and coating the skeleton of a silk fibroin sponge. The PDA-SF sponge was characterized by SEM, TEM, XPS, XRD and FT-IR. It was found that the sponge exhibits sheet structures with a pore size of 60 ± 20 μm and poly-dopamine adhered to the surface of pure silk fibroin through noncovalent bond forces. With a hierarchical porous structure, the derived sponge provides fast flow channels and abundant active sites, which will benefit the diffusion and removal of cationic dyes. Batch adsorption and dynamic adsorption of crystal violet (CV) were studied. The batch adsorption capacity of the PDA-SF sponge for CV increased with its PDA content. Under a dynamic adsorption mode, the adsorption efficiency of the PDA-SF sponge for CV (5 mg/L, 200 mL) can reach up to 98.2% after 12 min, whereas it is only 90.2% under stationary mode after 72 h. Furthermore, the sponge shows an outstanding smart adsorption performance. More importantly, the composite sponge still keeps high separation and adsorption efficiencies after 20 cycles, and the appearance remains good.