Synthesis and characterization of carbonaceous materials for lead adsorption

• Cocoon was considered as a source for silk fibroin-based protein fiber for hydrogel formation. • Silk fibroin, collagen and hyaluronic acid-based hydrogel composite was successfully prepared. • Calcium chloride was employed as a crosslinking agent for hydrogel composite formation. • The hydrogel exhibited the excellent adsorption properties for lead ions. Protein fibers derived from silk fibroin (SF) were chemically extracted and purified from cocoons. It was used as a reinforced fiber for hydrogel formation with collagen (Col) and hyaluronic acid (HA). Calcium chloride (8 wt. %) was employed as a crosslinking reagent to synthesize the SF/Col/HA-based hydrogel composite. FTIR spectroscopy confirmed the presence of N–H stretching due to the plane bending of amide II in the β-sheet structure. XRD analysis confirmed the crystallinity of the SF/Col/HA-based hydrogel composite. Scanning electron microscopy revealed three-dimensional porous structures with interconnected pores. These porous structures can serve as reservoirs for storing adsorbent media. The hydrogel composite was thermally stable at 250 °C. The low-boiling bound solvent evaporation temperature, glass transition temperature, and degradation temperature were 102 °C–105 °C, 298 °C–300 °C, and 524 °C–545 °C, respectively. The ranges of porosity and gel fraction were 60 %–80 % and 90 %–95 %, respectively. The hydrogel composite was rapidly swollen within 1 h, reaching a plateau afterward. The compressive strength was 4–6 MPa. As absorbent media, hydrogels can easily adhere to lead ions via electrostatic interactions. They can be used as reservoirs for the adsorption of heavy metals.