Treatment of Coffee Husk with Ammonium-Based Ionic Liquids: Lignin Extraction, Degradation, and Characterization.

Four ammonium-based ionic liquids were synthesized for the selective extraction and degradation of lignin from coffee husk. The extracted lignin samples were characterized by Fourier transform infrared, gel permeation chromatography, gas chromatography-mass spectrometry, UV-vis, H and C NMR, heteronuclear single-quantum coherence-NMR, thermogravimetric analysis, X-ray diffraction, and field emission scanning electron microscopy analyses. The analyzed results confirmed that these ionic liquids are able to effectively extract and decompose the lignin to smaller molecules from the biomass. Experimental results show that a significantly high yield, 71.2% of the original lignin, has been achieved. This processing method is an efficient, economical, and environmentally friendly green route for producing high-added-value lignin from wasted coffee husk.