Production of Silk Fibroin Membrane for Heavy Metal Removal in Water

Abstract

Silk fibroin (SF) membranes derived from Bombyx mori cocoons were fabricated using salt-induced phase separation and thermal annealing. A 5% silk fibroin solution was blended with sodium chloride (NaCl) and polyethylene glycol (PEG) to enhance porosity and structural integrity. Among the fabricated membranes, the SF/NaCl membrane exhibited superior surface porosity, enhanced hydrophilicity, and higher β-sheet crystallinity compared to both pure SF and SF/PEG membranes. These characteristics were confirmed through morphological and spectroscopic analyses. The SF/NaCl membrane was subsequently evaluated for its ability to remove cadmium (Cd²⁺), lead (Pb²⁺), and mercury (Hg²⁺) ions from contaminated water. Experimental results revealed that operational parameters such as pressure, pH, and temperature significantly influenced removal efficiency. Under optimal conditions, maximum removal efficiencies were 45.36% for Cd²⁺, 61.43% for Pb²⁺, and 86.87% for Hg²⁺. Corresponding maximum adsorption capacities reached 8.50 mg/g (Cd²⁺), 6.42 mg/g (Pb²⁺), and 41.14 mg/g (Hg²⁺), under optimal conditions. These findings highlight the potential of the SF/NaCl membrane as a sustainable and efficient material for mercury removal in water treatment, owing to its excellent biocompatibility, biodegradability, and mechanical stability.