Investigation into the physicochemical properties of three types of biomass-derived soot

This study experimentally examined the morphological characteristics, nanostructure, oxidation reactivity, and functional group composition of soot generated during biomass combustion. Three soot samples were collected from the combustion flames of pine (sample #1), straw (sample #2), and bamboo (sample #3). The samples were further analyzed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR) to characterize their physicochemical properties. The SEM results reveal that the soot produced from straw and bamboo exhibit a higher degree of agglomeration compared to that from pine. Specifically, straw-derived soot forms chain-like aggregates, whereas bamboo-derived soot forms clump-like aggregates. XPS analysis reveals that these samples contain substantial amounts of carbon (C), notable amounts of oxygen (O), sodium (Na), potassium (K), and magnesium (Mg), as well as trace amounts of other elements. Among these samples, the one produced by sample #2 has the highest sp3/sp2 ratio and volatile organic fraction, as well as the lowest fixed carbon content. Consequently, the oxidation reaction constant derived from TGA analysis for the soot produced by sample #2 is the highest, followed by that from sample #3 and sample #1. In these samples, C=O vibration peaks of conjugated aldehydes and carboxylic acids are observed at 1702 cm−1, while those of aromatic rings are observed at 1580 cm−1. Furthermore, the FTIR spectra in the ranges of 1400–1000 cm−1 and 925–720 cm−1 reveals the presence of vibration modes associated with C-C skeletal defects as well as out-of-plane (OPLA) C-H bending vibrations of aromatic structures.