Treatment of Furfural Residue by Solvent Extraction for Enzymatic Hydrolysis: Effect of Delignification on the Structure and Digestibility

The effect of different treatments on the enzymatic hydrolysis of furfural residue (FR) was investigated in delignification and structural features. In this case, hot water, ethanol, sodium hydroxide, alkali ethanol, and alkaline hydrogen peroxide solution (AHP) were selected as the delignification solvents. The structure and morphology of the original and treated samples were comparatively studied by diffuse reflectance infrared Fourier transform spectrometry (DRIFT), XRD, SEM, and CP/MAS ¹³C NMR. After AHP treatment, the ratio of total lignin to cellulose content in FR and the absorbance ratio of lignin to cellulose (A ₁₅₀₈/A ₁₀₅₇) on the sample surface in the DRIFT spectra was reduced from 0.99 to 0.13 and from 0.40 to 0.04, respectively, which resulted in the highest conversion of cellulose to glucose (99.3 %). It was found that the crystallinity index of FR linearly increased with the decrease of total lignin to cellulose ratio. DRIFT analysis indicated that the high lignin content on the sample surface resulted in a low enzymatic hydrolysis efficiency.