Facile fabrication of silk fibroin microparticles: their characterization and potential adsorption study

Silk fibroin (SF) microparticles were fabricated by blending of SF solution with hydroxyl propyl methyl cellulose (HPMC), and the SF/HPMC blend films were prepared using simple solvent evaporation technique. The SF/HPMC blends were dissolved in ultrapure water, and SF microparticles were generated with and without sonication. Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA)/derivative thermogravimetric (DTG) measurements were used for the characterization of blend films and microparticles. The microparticles obtained sonicated consist of nanosized pores on the surface. The size of the pores was nano, but the diameter of particles was around 10 µm. Further, SF microparticles were evaluated as a novel biosorbent for the methylene blue (MB), a cationic dye. The influential factors (pH, contact time) to the adsorption of the dye by the microparticles were investigated. The SF microparticles showed a very good adsorption capacity of about 490 (nonsonicated) and of about 512 (sonicated) mg/g of the dye without any surfactants. The adsorption kinetics validates the practicality of using the pseudo-second-order kinetics. Langmuir and Freundlich isothermal models were used, and the results showed that the adsorption behavior of the samples best fits (R2=0.998) the Langmuir model. The easy preparation and obtained results suggest that the SF microparticles can be used as effective adsorbent for MB dye removal.