Production of cationic bio-hydrogels from lignin oligomer via click chemistry for efficient gold recovery.

The transformation of alkaline lignin into bio-hydrogels for efficient Au(III) absorption is achieved through a successive oxidation-amination strategy. Alkaline lignin was initially oxidized with NaIO4, a process that disrupts its highly condensed three-dimensional structure, yielding ring-opened lignin oligomers carrying dicarboxyl groups. The oligomers were then subjected to a process of amination, resulting in the production of water-soluble, nitrogen-rich derivatives containing up to 22.0 wt% nitrogen. Finally, the resulting aminated oligomers were assembled into hydrogels containing 30 wt% lignin-derived material, thereby achieving a maximum gold adsorption capacity of 1687.4 mg g-1.