Rapid extraction of lignin from bamboo with high yield by microwave-assisted choline chloride-formic acid method

Abstract Efficient extraction of lignin from lignocellulose by low-cost and eco-friendly way has been a key focus in the lignin-first biorefinery strategy. The bamboo lignocellulose consists of three major components, in which the complex crosslinking structure greatly hindering the rapid and large-scale extraction of lignin. To address this issue, an innovative method of microwave-assisted deep eutectic solvent (MA-DES) was developed to extract lignin from bamboo. The DES emerging as promising alternatives to conventional solvents, offers outstanding selective extraction capabilities. The effect of DES types on the lignin yield was investigated. The DES containing choline chloride-formic acid (1:6 Molar ratio), and the 1:40 solid–liquid ratio of bamboo powder to solution were selected as optimal conditions for the high lignin yield. Under the microwave radiation, the optimum lignin yield (89.5 %) was achieved in 10 min. The bamboo fibers and extracted lignin were analyzed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermos gravimetric (TG) techniques. The extracted lignin was granular and irregular cluster morphology. The crystallinity index of bamboo fibers increased by 20.4 % after treatment, thus offering a new strategy for optimizing extraction procedures for producing lignin.