Effective removal of dyes from aqueous solution using ultrafine silk fibroin powder

Ultrafine silk fibroin powder was successfully produced using our developed machine and used as low-cost adsorbent to remove dyes in the printing and dyeing wastewater. The silk powder thus prepared was characterized by scanning electronic microscopy (SEM), laser particle analyzer and Fourier transform infrared (FTIR) spectrum. It showed that the silk powder with an average diameter of 3.8 μm was dominant in β-sheet structure. Dye adsorption experiments demonstrated that silk powder could effectively remove model dyes including direct orange (DO), disperse blue (DB) and methylene blue (MB) in particular. Factors influencing the adsorption of MB, e.g., solution pH, contact time, adsorption concentration and ionic strength were systematically investigated. Isotherm equilibrium studies demonstrated that MB adsorption process followed Langmuir model. The maximum adsorption capacity for MB dye was estimated to be 20.58 mg/g and the decoloration percentage could reach up to 95%. The batch experimental results suggested that silk fibroin powder could be used as an efficient sorbent to remove dyes in textile effluents.