Abstract

The leather industry faces mounting regulatory and environmental challenges due to the ecological risks of chromium-based tanning, particularly the generation of carcinogenic hexavalent chromium. To address this issue, we developed a novel metal-free tanning technology using triglycidylamine (TGA), a self-catalysed epoxy compound synthesized from ammonia and epichlorohydrin. TGA exhibits a high epoxy value of 1.54mol/100g, as confirmed by FTIR and 1H NMR characterisation, enabling efficient cross-linking with collagen. The optimal process conditions for TGA tanning were systematically investigated using pickled sheepskin as the raw material, and the mechanical properties of the tanned leather were analysed. The results demonstrated that the optimal tanning conditions for TGA are as follows: initial pH of 7–8, tanning duration of 18 hours, tanning temperature of 40°C, and TGA dosage of 6%. The shrinkage temperature of the tanned leather reached 81.7°C, and the yellowing resistance achieved a grade of 5. The mechanical properties of the TGA-tanned leather were comparable to those of commercially available chrome-free tanned leather. Moreover, the TGA-tanned leather exhibited a higher isoelectric point (pI = 5.4) and demonstrated better absorption rates for anionic dyes and fatliquors, effectively addressing the common issues of poor dyeability and fatliquor uptake associated with traditional organic tanning agents. Additionally, the TGA tanning effluent showed excellent biodegradability (BODs/CODCr=0.47), significantly reducing the burden of wastewater treatment. This novel approach provides new insights for developing eco-friendly leather and contributes to the complete elimination of hazardous chromium pollution.