Physical protection of lignin by organic matter and clay minerals from chemical oxidation

► Coating with dodecanoic acid protected lignin phenols from chemical oxidation. ► Lignin in humic acid-clay complexes is more protected at pH 7 than at pH 4. ► Relative resistance of lignin phenol to chemical oxidation is related to lignin structure. ► Organic matter interaction, composition, conformation influence its protection in soil.