Synthesis of Lignin/PAN Fibers from Sawdust

Abstract

Carbon nanofibers based on lignin from wood waste have a promising potential for the ability to produce electrodes that can modernize existing energy storage technology. The most important detail is that the low cost, as well as the availability of the initial products for the production of lignin, will reduce the cost of energy storage devices and contribute to improving the environment. In this study, pine sawdust and elm sawdust were used as raw materials for the production of lignin, which accumulate in large quantities in metal workshops in Almaty. Lignin extraction was carried out using an organosolvent method, which is environmentally friendly, low-cost, uses minimal amounts of strong acids and metal catalysts, does not pollute water, and does not emit sulfur dioxide (SO2). A comprehensive study of the characteristics of the obtained lignins from wood waste was carried out. Infrared spectroscopy (IR) revealed that the obtained lignin contains aromatic, phenolic, hydroxyl, methyl, and methoxyl groups. The results of nuclear magnetic resonance (NMR) spectroscopy showed the presence of a high number of syringyl (S) links compared to guaiacyl (G), which contribute to increased efficiency in the thermal processing of lignin. Also, this study investigated the use of the obtained lignins to produce continuous fibers by electrospinning. The effect of lignin mass on the viscosity of the lignin/polyacrylonitrile (PAN) solution and the effect of the carbonization temperature on the physico-chemical characteristics of the lignin/PAN solution were investigated. The following research methods were used for this purpose: Raman spectroscopy, thermogravimetric analysis (TGA), electron scanning microscopy, energy dispersion analysis, IR, NMR, and optical microscopy. The conditions for the production of lignin-containing carbon fibers at temperatures of 800, 900, and the carbonation heating rate, is an important parameter in the production of carbon fibers as it strongly affects the characteristics of the resulting carbon fibers. The heating rate affects were studied, and it was found that, at a heating rate of 5 °C/min and a carbonation temperature of 800 °C, porous carbon nanofibers with a diameter of 47 nm are formed in a nitrogen medium for 60 min.