Sulfate-based ionic liquids as solvents for decomposition of lignocellulose materials from coconut husk fiber

This study investigates the use of sulfate-based ionic liquids (ILs) as solvents for decomposing lignocellulose materials derived from coconut husk fibers. Coconut husk, a commonly discarded biomass waste, has high lignin content, making its decomposition challenging using traditional methods. The objective of the research was to determine the efficiency of the decomposition process of lignocellulose from coconut husk fiber by using sulfate-based ionic liquids and assess their characteristics. Samples were subjected to two types of ILs and characterised using FTIR, NMR, and TGA analyses. FTIR analysis confirmed the presence of functional groups corresponding to sulfate and ammonium ions, with distinctive peaks representing NH stretching, C–N bonds, and S=O vibrations, indicating the successful synthesis of the ILs. NMR spectra further verified the molecular structures of diethylammonium sulfate (DEAS) and triethylammonium sulfate (TEAS), with chemical shifts consistent with the expected hydrogen and carbon environments of the ionic liquid components. TGA analysis demonstrated that both ILs possessed good thermal stability, with decomposition onset temperatures above 200°C, suitable for biomass decomposition processes. The untreated and treated coconut husk fibers were analysed via FTIR that showed reductions in lignin and hemicellulose peaks, confirming partial removal of these components. FESEM analysis revealed noticeable morphological changes on the fiber surface, from smooth and denser structure (untreated) to rough and fragmented (treated), and CHNS elemental analysis showed a reduction in post-treatment carbon content, supporting the conclusion that lignin-rich fractions were successfully removed during the decomposition process. Results showed that the optimal decomposition yields were about 75.33% for TEAS and 83.66% for DEAS at 130°C for 5 hours. These findings highlight the effectiveness of sulfate-based ionic liquids in decomposing the rigid structure of lignocellulose. The significant decomposition yields demonstrate that ILs can successfully break down biomass into simpler components, providing an eco-friendly alternative.