Using Recyclable Deep Eutectic Solvents with Wheat Straw to Produce Lignin-Based Nanocomposites

Abstract

This study presents an integrated “deep eutectic solvent (DES)-assisted directed depolymerization and in situ nanoparticle synthesis” strategy for wheat straw refining. A recyclable DES composed of choline chloride/lactic acid (ChCl /LA, 1:2) was employed to fractionate lignocellulose while maintaining solvent activity through in situ pH regulation. Dropwise addition of 5 to 10 fresh DES droplets effectively reconstructed the hydrogen-bond network, reducing lignin retention from 18.4% to 13.6% and extending DES recyclability from two to four cycles. The extracted lignin was directly used for the in situ synthesis of lignin-derived silver nanoparticles (LigAg NPs) through reduction of [Ag(NH₃)₂]⁺ , yielding uniform particles (320 ± 15 nm) with 67% higher surface area (18.7 m²/g) than those from alkali lignin. The LigAg NPs formed a strong hydrogen-bonded interface with poly(vinyl alcohol) (PVA), enhancing composite modulus and reducing energy dissipation (21%). This work establishes a mechanistically guided, recyclable DES route for hierarchical utilization–material creation–circular regeneration of lignocellulosic biomass.