Harnessing the reversible reaction principle: A novel Zr-based halide Perovskite tanning system for effective Zr4+ penetration in the leather collagen.

The development of green chromium-free tanning agents continues to be actively researched as a prominent topic in the leather industry. Zirconium tanning agents have good tanning performance, but their permeability is poor. Halide perovskites, composed of metal ions and organic ligands, are metal-tunable nanomaterials. In order to improve the permeability of zirconium, Cs2ZrCl6 was synthesized using zirconium ions and combined with Zr(SO4)2 for collagen modification application in this study. Based on the principle of reversible reactions, the introduction of Zr(SO4)2 effectively alleviated the rapid hydrolysis of Cs2ZrCl6, ensuring the preservation of its nanostructure and enabling continuous penetration during the tanning process. The EDS analysis confirmed the uniform distribution of zirconium in leather collagen tanned with Cs2ZrCl6/Zr(SO4)2. Compared with Zr(SO4)2 tanned leather (73.1 °C), the shrinkage temperatures of Cs2ZrCl6/Zr(SO4)2 tanned leather collagen (83.7 °C) is better. Additionally, the BOD5/CODcr ratio of the tannery wastewater in this system is 0.65, indicating excellent biodegradability. The development of the Cs2ZrCl6/Zr(SO4)2 tanning system provides a new approach for creating chromium-free tanning agents.