A Comparative Study of Sodium Sulfide and Sodium Hydroxide for Keratin Extraction from Waste Chicken Feathers Based on Response Surface Methodology (RSM)

Abstract

Keratin extraction from poultry feathers represents an environmentally sustainable approach for converting bio-waste into materials used in cosmetic and personal care applications, including shampoos, hair care formulations, skin creams, and related products. This study presents a comparative evaluation of sodium hydroxide (NaOH) and sodium sulfide (Na2S) as extraction agents, with Response Surface Methodology (RSM) employed to optimize the operational parameters. The results demonstrated that NaOH was more effective in preserving peptide chain integrity and maintaining the structural stability of keratin, particularly under optimized conditions of 0.75 M concentration, 80 °C, and a 4 h, R² = 0.9285 extraction period. In contrast, the Na2S achieved higher extraction yields and recovered mass; however, this advantage was accompanied by an increased tendency toward partial protein degradation. Structural characterization using FT-IR and SEM analyses confirmed that keratin extracted with NaOH retained its characteristic β-sheet fibrous morphology, supporting its suitability for cosmetic and personal care applications that require high structural integrity.