Effects of Organic Ligands on Tanning Performance and Envi-ronmental Benefits of Aluminum-Zirconium Complexes
Oxidized sodium lignosulfonate(OSL),tartaric acid(TA),and oxidized starch(OST)were used as the ligands of aluminum-zirconium salt(AZ)for leather tanning.These complex tanning systems were compared with conventional chrome(Cr)tanning system in terms of the performance of tanned leather,the performance of crust leather,and the environmental benefits.OSL-AZ combines with collagen mainly by forming coordination bonds.Meanwhile,OSL forms ionic,hydrogen,and hydrophobic bond interactions with collagen through its sulfonic acid group,carboxyl group,phenolic hydroxyl group,and hydrophobic benzene ring.Thus,OSL-AZ forms a rigid macromolecule crosslinking network among collagen fibers.The OSL-AZ tanned leather has a shrinkage temperature high up to 88.4 ℃,an isoelectric point up to 7.54,and an uptake rate for post-tanning chemicals over 84％,thereby resulting in excellent physical properties of OSL-AZ crust leather,which is second only to Cr crust leather.TA and OST without sulfonic acid group,phenolic hydroxyl group and rigid benzene ring exhibit relatively weak interaction with leather collagen.As a result,the tanning performance of TA-AZ and OST-AZ is worse than that of OSL-AZ.The biodegradability of OSL-AZ tanned leather and wastewater is obviously better than that of traditional Cr tanned leather and wastewater.Therefore,OSL-AZ tanning technology is a practical and environmentally friendly leather manufacturing technology.
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