Fractionation of AquaSolv Omni Biorefinery Lignins and Their Application in Antioxidant and Ultraviolet‐Protective Films

Lignin and lignin-carbohydrate complexes (LCCs) were isolated using AquaSolv Omni (AqSO). The process involves hydrothermal treatment of wood followed by organic solvent extraction, using a sequential fractionation approach with water-based alkaline (1 wt%), ethanol, and acetone solutions. This strategy allowed for isolating different lignin/LCCs fractions with varying structure and properties. The sequential fractionation approach provided fractions with wide variability of glass transition temperatures ranging from 94°C to 153°C, while demonstrating excellent antioxidant activity with a normalized radical scavenging index up to 13.2 mmol g^-1. The incorporation of different lignin/LCCs with high antioxidant activity into lignocellulosic film formulation at 1.5 wt%, in which lignin and cellulose were the sole components, demonstrated superior effectiveness in blocking over 90% of ultraviolet (UV) rays (sun protection factor = 6-12), yet maintaining a high transparency of the resulting film. This study underscores the versatility of lignin and its high potential for integration into applications where strong UV and antioxidant protection are concerned without posing any environmental concern.