Exploring Deep Eutectic Solvents for the Extraction of Lignocellulosic Materials (3) : Study on Precipitation Solvents for Lignin Recovery from the Black Liquors of Sawtooth Oak Pulping

Abstract

This study evaluated whether lignin can be recovered in three different deep eutectic solvent (DES) black liquors by adding various precipitation solvents. Three DES black liquors prepared by cooking the oak wood chip with carboxylic acid-based DES, phenol-based DES, and alkaline organic compound-based DES were used in this study. Six solvents were used as precipitation solvents, including distilled water, ethanol, acetone, 5% sodium hydroxide, 5% sulfuric acid, and 20% acetic acid.BRThe solvent causing precipitation in each black liquor differed depending on the types of DES used to extract the wood chips. The precipitation efficiency of each solvent was also varied. In the case of the carboxylic acid-based DES black liquor, distilled water had the best precipitation characteristics. In contrast, it was found that acetone for the phenol-based DES black liquor, and 20% acetic acid solution for the alkaline organic compound- based DES black liquor were the most suitable precipitation solvents. It is expected that lignin recovery in the DES black liquor is relatively simple by various solvent treatments.