Cross-Linking in Keratin-Based Films Enhances Cationic and Anionic Dye Adsorption

Area of Science:

• Materials Science
• Environmental Science
• Biotechnology

Background:

• Industrialization has led to increased dye usage and environmental pollution, necessitating sustainable dye removal solutions.
• Existing adsorbents often selectively remove either cationic or anionic dyes, limiting their practical application.
• Waste protein, specifically human hair keratin, presents an underutilized resource for developing novel materials.

Purpose of the Study:

• To develop chemically cross-linked keratin-based bioplastic films from waste human hair for efficient adsorption of both cationic and anionic dyes.
• To compare the properties and dye adsorption performance of cross-linked keratin films with pristine keratin films.
• To investigate the structural, mechanical, thermal, and biodegradability characteristics of the developed films.

Main Methods:

• Fabrication of chemically cross-linked and pristine keratin films from waste human hair.
• Characterization of film morphology, surface properties, and mechanical strength using techniques like FT-IR and XRD.
• Assessment of thermal stability and biodegradability.
• Batch adsorption studies using model cationic (methylene blue, rhodamine 6G) and anionic (bromophenol blue) dyes.
• Kinetic modeling and diffusion analysis (Weber-Morris model) to understand adsorption mechanisms.

Main Results:

• Cross-linked keratin films exhibited enhanced surface morphology and mechanical properties compared to pristine films.
• FT-IR and XRD analysis indicated a conformational change from α-helix to β-sheet structure upon cross-linking.
• The cross-linked films demonstrated good thermal stability (up to 200 °C) and biodegradability.
• Significantly higher adsorption capacities were observed for cross-linked films: ~10% for methylene blue, ~50% for rhodamine 6G, and ~70% for bromophenol blue.
• Intraparticle diffusion was identified as the rate-limiting step in the dye adsorption process.

Conclusions:

• Chemically cross-linked keratin films derived from waste human hair are effective and versatile materials for adsorbing both cationic and anionic dyes.
• The cross-linking process improves the material's structural integrity and adsorption efficiency.
• These keratin-based films represent a promising, sustainable approach to wastewater treatment and dye removal, contributing to environmental remediation efforts.