Hydrotropic Extraction for Process Intensification in Delignification of Dried Jackfruit (Artocarpus heterophyllus) Leaves

Background: The extraction of lignin is costliest, challenging process and is significant for production of various starting material useful in chemical synthesis, fuel production, weakening of cell wall to assists the extraction of natural active constituents from plants, in solid waste management and delignification assists in breaking of strong bonds of lignin and hemicellulose which entraps the fermentable cellulose. There is huge dried leaf waste, which has lignin component suitable for various applications. Further, the available lignin extraction methods affect the quality of lignin. Aim: The present study aimed to investigate the delignification of dried jackfruit tree foliage using aqueous hydrotropic solutions. Methods: The parameters studied for the delignification of dried jackfruit tree foliage include temperature, hydrotrope concentration dried leaves loading and delignification time. The obtained lignin is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, and the ethanol extract of lignin is characterized by Gas chromatography-mass spectroscopy (GC-MS), gel permeation chromatography (GPC) correspondingly to understand in factors including the surface functionality, nature and morphology, molecular weight, phenolic compounds, thermal stability. Results: The hydrotrope NaXS at 30 % w/w concentration, extraction temperature of 100 0C, 5 % w/w foliage loading concentration were optimum. The process enabled 81 % of lignin extraction and 95 % of hydrotrope recovery. The lignins recovered from different aqueous hydrotrope solutions of Na-XS, and Na-CS, were apparently similar indicating similar nature of the lignin extracted by different hydrotropes. Sodium xylene sulfonate was most satisfactory amongst different hydrotropes for the delignification, the lignin could be recovered simply by water dilution and no solvent was used in any step. Reusability of hydrotrope was around 95 % for foliage delignification. Conclusion: The obtained lignin is free of organic solvents. The method selectively extracts lignin and keeps the cellulosic material intact as observed in conventional delignification processes.