The application of sulfonated tetraphenyl calix[4] resorcinarene as a novel, multi-functional and eco-friendly ligand in zirconium tanning system

The complex of resorcinarene and zirconium was used in the tanning process of goat skin with the optimal dosage of 5% resorcinarene and 4% zirconium. The shrinkage temperature of combination tanned leather kept at 88.9 °C although the additive amount of zirconium decreased by 8%. Meanwhile, the tear strength and tensile strength of tanned leather increased by 77% and 141%, respectively. The function of resorcinarene and its interaction with zirconium were studied by SEM-EDX and FT-IR technologies. The results indicated that resorcinarene can act as a ligand of zirconium, promoting the permeation of zirconium as well as decreasing the usage amount of zirconium. Furthermore, the tanning mechanism was explored by FT-IR and XRD methods. It showed that the three helix structures of collagen fiber were remained and the tanning agent had not enter the micro fibrils of the collagen. Moreover, the introduction of resorcinarene increased the biodegradability of wastewater remained after tanning process. This paper gives a new strategy for chrome-free tanning and provides a strong support for the wide application of zirconium tanning agent.