Abstract
Lignin is a sub-product from lignocellulose apart from cellulose and hemicellulose that produced from empty fruit bunch fiber (EFB). Lignin has low solubility and reactivity due to its bulky macromolecule structre. Being one of the wastes that being generated in massive amount, many alternatives has been taken to transform lignin into valuable products. To do so, many reactions are needed for the lignin to go through. In this study, lignin will be extracted from empty fruit bunch (EFB) with the aid of acid hydrotrope concentration of 30 % and microwave assisted with various extraction heating time and temperature. Characterization of lignin is done using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and Nuclear magnetic resonance (NMR) while Scanning Electron Microscopy (SEM) and X-ray Powder Diffraction (XRD) used to characterize residues. The highest percentage of lignin yield and its purity obtained are 19.47 % and 96.63 % with the reaction time and temperature of the microwave is 30 minutes and 90 °C. From Fourier Transform Infrared Spectroscopy (FTIR), a wide band at 3430.09 cm-1 and 3413.45 cm-1 are observed due to O-H stretching vibration. As for peak at 1123.17 cm-1 and 1051.26 cm-1, it correspond to syringyl and guaicyl unit in both lignin and raw EFB. As for Thermogravimetric analysis (TGA), it shows that lignin decomposes slowly compared to raw EFB due to the aromatic structure of lignin that is very stable, therefore leading to difficulty of decomposing while from Differential Scanning Calorimetry (DSC), after removing cellulose and hemicellulose, glass transition temperature (Tg) obtained from lignin DSC spectroscopy is 193.05 °C at heat flow of 1.15 mW/mg. Next, from Nuclear magnetic resonance (NMR) spectroscopy, the signals observed around 6.5 – 8.0 ppm indicate aromatic H in syringyl and guaiacyl unit only at lignin spectra while at 3.3 – 4.0 ppm, raw EFB has an intense peak compared to lignin which attribute to methoxyl group. When the residue of the lignin as well as the raw EFB powder is characterized using X-ray Powder Diffraction (XRD), the crystallinity index of the lignin with reaction time and temperature of the microwave 30 minutes and 90 °C is the highest, 69.28 %. As a conclusion, an admissible percent of lignin yield and purity is able to be obtained with addition of acid hydrotrope depending on the variables. From the spectroscopies characterization, it is proved that lignin characteristics and properties are compatible for the production of new and value added products.
Highlights
Biomass sources are abundant, as they can be found almost everywhere on earth
Since empty fruit bunch fiber (EFB) is a type of renewable energy resource, many research and development efforts are put to enhance the expansion of the renewable energy plant in Malaysia and support Malaysia's Small Renewable Energy Power Plant Program at the same time
Insoluble lignin was obtained from the weight of lignin after filtered and dried on a PTFE membrane, while soluble lignin was measured from the UV absorbance at 320 nm
Summary
As they can be found almost everywhere on earth. Since empty fruit bunch fiber (EFB) is a type of renewable energy resource, many research and development efforts are put to enhance the expansion of the renewable energy plant in Malaysia and support Malaysia's Small Renewable Energy Power Plant Program at the same time. Lignin is acquired and dried from the plant precisely, empty fruit bunch (EFB) formed during the palm oil milling process It has high potential application in the pulp and paper industry [3]. Lignin is generally isolated from the biomass into phenolic compounds compared to its native state. Hydrotropy solution does not occur in a linear fashion but with the increase in hydrotrope concentration [8] Hydrotropic acid such as p-TsOH can depolymerize lignin through ether bond cleavage and isolate carbohydrate-free lignin from the empty fruit bunch (EFB) [10]. The objective of this research is to optimize the extraction of lignin from EFB fiber using acid hydrotrope with microwave-assisted heating. This study's main scope is to extract lignin from EFB using acid hydrotrope as a solvent with microwave-assisted heating. No lignin removal occurs for the treatment with ionic liquid (IL) [10]
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