SYNTHESIS OF BIO-BASED ORGANIC TANNING AGENT AND INVESTIGATION OF ITS USAGE IN SUSTAINABLE LEATHER PRODUCTION

Project no. 32487 · Status: Kapanmış (Yayın bekleniyor) · 2024

Summary

Sustainability and environmental benignity in the leather industry are promising initiatives that are becoming increasingly important, emphasizing the imperative to reduce harmful chemical consumption. In the tannery industry, nearly 90% of the leather is still processed using basic chromium sulfate (BCS), resulting in chromium-containing solid waste and wastewater that require extra care for their management. To identify alternatives to Chromium in leather processing and adopt eco-friendly tanning practices, bio-based organic Chrome-free tanning agents offer a promising pathway toward a sustainable future for the leather industry. Due to some constraints in the preparation, availability, and application stages, organic tanning agents have found to be limited usage in the industry, as most have failed to match the commercial viability and performance of inorganic tanning materials such as Chrome tanning agents. In this study, Chrome-free tanning material based on bio-derived organic compounds, referred to as Sustainable Organic Tanning Agent (SOTA), was synthesized using natural precursors such as collagen hydrolysate (CH) and bio-based dicarboxylic organic acid. The synthesized SOTA was characterized and applied in the leather tanning process to evaluate its tanning properties. Optimization was conducted by assessing the tanning performance and structural interactions of SOTA with skin collagen through various analytical and instrumental techniques. The FTIR, 1H NMR, particle size, and SDS-PAGE analysis collectively indicated that SOTA possesses the characteristics of an ideal tanning agent. To examine the tanning performance, a practical process recipe was formulated based on the hypothesized reactivity of the SOTA tanning agent. In the tanning trials, 4 - 12% SOTA was applied without pickling, while a vegetable tanning agent (Acacia nilotica L.) was used during the retanning stage for the experimental leathers. In parallel, commercial wet-white and conventional Cr-tanning processes were conducted to enable comparative assessment with the developed SOTA tanned leather. The application results indicated that a 10% SOTA dose at 25 °C and pH 6.5 exhibited a shrinkage temperature (Ts) of 88 °C, representing the optimum tanning parameters. The SOTA tanned leather demonstrated excellent organoleptic qualities, including fullness, smooth touch, roundness, and softness. Scanning electron microscopy (SEM) revealed a uniform dispersion of collagen fiber bundles, indicative of the adequate tanning capacity of the developed tanning material. The tensile and tear strength, DSC, and TGA analyses of tanned leather confirmed SOTA as a successful organic tanning agent, imparting characteristic structural and performance properties of quality leather. Environmental assessments were conducted to validate the eco-friendliness of SOTA, revealing it to be a highly promising, biodegradable tanning agent with minimal ecological footprint. Compared to conventional Chromium tanning, SOTA application resulted in a 47% reduction in Chemical oxygen demand (COD), underscoring its potential for significantly reducing the pollution load associated with leather processing. Although SOTA alone achieved excellent tanning effects, the synergistic combination of SOTA with Acacia nilotica vegetable tannin further enhanced leather quality, producing fuller, firmer, and more resilient material. This approach aligns with sustainability goals by minimizing environmental impact. Therefore, this study represents a successful step toward the development of fully organic, eco-friendly, and renewable tanning materials for leather production.

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