Preparation and application of a novel sucrose-based amphoteric retanning agent for sustainable leather making

Abstract The reliance on fossil-derived compounds in most conventional retanning agents faces a challenge to the sustainable development of the leather industry. Consequently, the development of environmentally friendly biomass-based retanning agents is urgently needed. In this research, a novel sucrose-based amphoteric retanning agent (GLS) was synthesized with a weight-average molecular weight of 3.48 × 104 g/mol. The molecular structure of GLS was determined using FT-IR, 13C-NMR, XPS, and EA. The GLS exhibited a favorable isoelectric point (pI = 4.68) as a retanning agent. At a 10% dosage, GLS retanning of wet-blue resulted in a 14.42% thickness increase, substantially greater than that achieved with commercial amino resin (CML, 6.77%) and acrylic resin (LP, 10.8%) retanning agents. GLS also exhibited superior absorption (87.13%) compared to CML (75.27%) and absorption comparable to LP (89.2%). Notably, GLS improved the uptake of subsequent anionic fatliquoring agents compared to CML and LP. Moreover, GLS-retanned leather displayed good thermal stability and commendable physical and mechanical properties. The BOD₅/COD value of the GLS retanning wastewater was 0.48, indicating its excellent biodegradability. Life cycle assessment further highlighted the environmental benefits of GLS compared to LP and CML. These findings position GLS as a promising biomass-derived amphoteric retanning agent with the potential to displace conventional fossil-derived alternatives. Graphical Abstract