The leather industry faces significant environmental challenges due to the potential risks associated with conventional chrome tanning. This study engineered oxidized lignin (OLG) via a H 2 O 2 –O 3 synergistic oxidation system specifically to serve as a bio-based ligand for aluminum–zirconium (AZ) salts, thereby constructing a sustainable chrome-free tanning system. The H 2 O 2 –O 3 system effectively generates hydroxyl radicals, which play a key role in disrupting aromatic rings as well as cleaving carbon-carbon (β-5’ and β-β’) and carbon-oxygen (β-O-4) linkages in the LG structure. This process results in synergistic decolorization (ΔE = 8.2), substantial depolymerization ( M w = 735), and a notable increase in carboxyl content (8.2 mmol/g). The resulting OLG coordinates with AZ salts through its carboxyl groups to form stable complexes. These complexes enable uniform OLG–AZ penetration into collagen fibrils, reducing the D -period to 64.0 nm. Beyond coordination bonds formed between AZ and the carboxyl and amino groups of collagen, OLG engages in hydrogen bonding and hydrophobic interactions with collagen via its Ph-OH groups and aromatic rings. Together, these interactions form a stable, rigid cross-linking network during tanning. Consequently, OLG–AZ tanned leather exhibits a high shrinkage temperature (86.8°C), refined grain surface (pore size 0.08 mm), improved fiber dispersion (52.6% porosity), and excellent physical properties. This work provides a sustainable and practical route for advanced leather manufacturing.
YOU et al. (Sat,) studied this question.