Integration of lignin microcapsulated pesticide production into lignocellulose biorefineries through FeCl3-mediated deep eutectic solvent pretreatment

Abstract

The integration of nanotechnology into lignocellulose biorefineries with multi-product outcomes is appealing but technically challenging due to lignin's random chemical structure. In this work, FeCl₃-mediated deep eutectic solvents (DESs) were proposed to integrate microcapsulated pesticide production into current lignocellulose biorefineries to overcome this technical barrier. The addition of FeCl₃ to choline chloride/lactic acid DES significantly enhanced hemicellulose removal (by nearly 100%) and lignin yield (62.1%). A high delignification ratio (70.8%) was obtained by FeCl₃-mediated neutral DES (choline chloride/glycerol) pretreatment, which also significantly contributed to cellulose saccharification (81.6%). Moreover, an acid-catalyzed condensation reaction and the cleavage of β-O-4 linkages of lignin occurred during the FeCl₃-mediated DES pretreatment. The condensation structure and abundant phenolic-OH content produced its special aromatic structure and enhanced the amphiphilic properties for the preparation of lignin nanospheres (LNSs), and further improved the anti-photolysis performance of LNS-encapsulated avermectin (AVM@LNS) pesticide. A strong positive correlation (R² = 0.86) between the phenolic-OH content and the half-life was also found. The tailored chemical structure of lignin also provided for its strong π–π stacking to promote nonradiative migration and trigger photothermal conversion. Unlike the bare AVM solution, AVM@LNS presented controlled release performance and temperature response behaviors for sustained pest control. This study achieved technical integration using the tailored lignin to realize the targeted downstream products, and also improved the high-value utilization of lignin by-products for green agriculture.