Interaction between Protocatechuic Acid and Zirconium Ions and their Tanning Properties

The interaction between protocatechuic acid (PCA) and zirconium ions has been studied via UV-Vis, FTIR and 1H-NMR spectra. The results show that the phenolic hydroxyl and carboxyl groups of PCA can coordinate with zirconium ions. The tanning performance of the protocatechuic acid combined with zirconium ions has been studied. The results show that the shrinkage temperature of the leather can reach 86-87 degrees C in both Zr- PCA combined tanning and PCA-Zr combined tanning. Different tanning orders will lead to different pH values being required to achieve the best tanning effect, which is probably caused by the different interactions among PCA, zirconium ions and collagen fibres during the tanning process.