Biosilica/Silk Fibroin/Polyurethane biocomposite for toxic heavy metals removal from aqueous streams

Abstract

Development of green, eco-friendly, and efficient adsorbents for wastewater treatment is highly researched to mitigate the alarming rate of water pollution. In this work, a novel biocomposite of biosilica (BS)/silk fibroin (SF)/polyurethane foam (PUF) was prepared and studied for the adsorptive recovery of toxic copper (Cu 2 + ) and chromium (Cr 6＋ ) ions from synthetic wastewater. XRD and FTIR studies confirmed the formation of biocomposite with amorphous structure and –OH, –NH, C=O surface functionalities. SEM results confirmed the successful incorporation of SF and PUF into BS. The biocomposite possessed a specific surface area of 751.9 m 2 /g and a mean pore size of 7.21 nm. Further, effects of pH, adsorbent dose, contact time, and initial metal ion concentration on the adsorptive removal of Cu 2 + and Cr 6＋ metal ions by the BS/SF/PUF biocomposite were studied in detail. Equilibrium and kinetic analysis showed that the metal ions sequestration by the BS/SF/PUF biocomposite followed the Freundlich isotherm and Elovich model, respectively. Maximum adsorption capacities of 331.69 mg/g and 201.56 mg/g were estimated for the Cu 2 + and Cr 6＋ ions, respectively. A plausible mechanism for the adsorption of the metal ions onto BS/SF/PUF biocomposite is postulated. Reusability studies of the biocomposite using EDTA eluent showed that the biocomposite could be efficiently reused up to four consecutive adsorption/desorption cycles. Thus, this study provides comprehensive data for applying the BS/SF/PUF biocomposite to treat Cu 2 + and Cr 6＋ metal ions polluted wastewater streams. • Amorphous BS/SF/PUF biocomposite was prepared through polymer blending. • Specific surface area and pore size of BS/SF/PUF were 751.9 m 2 /g and 7.21 nm. • High adsorptive removal efficiency of >80% for Cu 2+ and Cr 6+ heavy metal ions. • Freundlich isotherm & Elovich kinetic model best described adsorption operation. • BS/SF/PUF biocomposite was successfully reused up to 4 cycles through EDTA washing.