Preparation of Polypeptide Surfactants Using Chromium‐Containing Waste Leather: Effect of Hydrophilic and Lipophilic Groups

Abstract

AbstractPolypeptide surfactants with different lengths of hydrophilic groups and lipophilic groups were synthesized from collagen hydrolysate polypeptides by the Schotten‐Baumann reaction. Collagen hydrolysate polypeptides were prepared through alkaline hydrolysis of chromium‐containing leather wastes, followed by changing the molecular weight of the collagen hydrolysate and the carbon chain length of the acid chloride. Fourier transform infrared spectroscopy, confirmed the successful synthesis of the polypeptide surfactants. Furthermore, surface activities of surfactants were tested to reflect the influence of the length of hydrophilic and lipophilic groups on properties, such as surface tension, foamability, foam stability, wettability, and Hydrophile–Lipophile Balance value. The results indicated that for surfactants prepared from collagen hydrolysate, a shorter hydrophilic group length resulted in lower surface tension and better foamability, foam stability, and a wetting ability which indicates the surfactants can be used as wetting agents. In contrast, the surfactant with a greater lipophilic group length had lower surface tension and poorer foamability, foam stability, and wetting ability. The presence of the C=C bond of the oleoyl lipophilic group decreased surface tension. The polypeptide surfactants prepared from collagen hydrolysate not only can effectively utilize chromium‐containing leather solid waste produced, but also avoid environmental pollution and promote the sustainable development of the leather industry.