Modification of Zhaotong Lignite by Steam Explosion Treatment: Pore Structure and Oxygen-Containing Functional Groups

Abstract

The pore structure and oxygen-containing functional groups of lignite play an important role in drying behavior, spontaneous combustion characteristics, and other applications of lignite. In this paper, Zhaotong lignite was modified by steam explosion (SE) technology. The changes in pore structure and fractal characteristics were analyzed by mercury intrusion porosimetry (MIP). The effect of SE modification on surface oxygen-containing functional groups was studied by Fourier transform infrared spectroscopy. Finally, the relationships between the water adsorption capacity of modified lignite and pore structure or oxygen-containing functional groups were investigated. The results indicated that the macroporous and mesoporous pore volumes of modified lignite can be increased to the greatest extent by SE modification at 130 °C. For transition pores and micropores, the maximum pore volume can be obtained by SE modification at 230 °C. The irregularity of the pore structure surface of modified lignite can be increased by SE modification. In particular, the surface of all porous structures can be destroyed to the greatest extent by SE modification at 230 °C. Oxygen-containing functional groups in Zhaotong lignite can be effectively removed by SE modification, and the removal amount is positively correlated with the temperature of SE modification. Moreover, the decrease in monolayer water adsorbed on the modified lignite surface is due to the reduction in the number of oxygen-containing functional groups on the surface after SE modification. The pore volume of modified lignite is increased by SE modification, which clearly increases the amount of capillary water adsorbed by the modified lignite.

Characterization and adsorption applications of composite biochars of clay minerals and biomass

“…Figure 5 The mechanisms involved in MB adsorption onto mineral-biochar composites oxygen and hydrogen content were the controlling properties of mineral-biochar composites to adsorb MB. To increase the adsorption capacity of MB, it may be necessary to apply pore reaming and surface modification coupled methods (such as physical activation-steaming exploration (Miao et al, 2019), chemical activation-KOH activation (Qu et al, 2021)) to produce a composite with higher pore volume and increase the oxygen and hydrogen content. Further research will explore the relationship between adsorbent properties and coexistence of multiple pollutants with different nature, then developing and designing the upgraded biochar to removal pollutants with maximum capacity.…”

Characterization and Adsorption Applications of Composite Biochars of Clay Minerals and Biomass

“…T-test results (Table 3) From this multiparameter linear regression model, we see that pore volume and oxygen and hydrogen content were the controlling properties of mineral-biochar composites to adsorb MB. To increase the adsorption capacity of MB, it may be necessary to apply pore reaming and surface modification coupled methods (such as physical activation-steaming exploration (Miao et al, 2019), chemical activation-KOH activation (Qu et al, 2021)) to produce a composite with higher pore volume and increase the oxygen and hydrogen content. Further research will explore the relationship between adsorbent properties and coexistence of multiple pollutants with different nature, then developing and designing the upgraded biochar to removal pollutants with maximum capacity.…”

Molecular Characterization of Soluble Components in the Lignite by Sequential Solvent Extraction via Continuously Reducing Particle Size

“…Lignite plays a very important role in fossil fuels, accounting for 12.68% of total coal reserves in China . It provides an alternative way to produce liquid fuels and chemicals because of its high oxygen content, high volatility, and low price. − However, most of lignite has been used for power generation, which is far from fully utilized and producing severe environmental pollution. The study of coal molecular structure and composition is considered important to develop processing techniques for producing clean coal and high value-added products. − However, the achievements are not satisfactory because of the complexity of coal itself and the limitation of analytical techniques.…”