Analysis of SO₂ Physisorption by Edge-Functionalized Nanoporous Carbons Using Grand Canonical Monte Carlo Methods and Density Functional Theory: Implications for SO₂ Removal

Abstract

Nanoporous carbons (NPCs) are ideal materials for the dry process of flue gas desulfurization (FGD) due to their rich pore structure and high specific surface area. To study the effect of edge-functionalized NPCs on the physisorption mechanism of sulfur dioxide, different functional groups were embedded at the edge of NPCs, and the physisorption behavior was simulated using the grand canonical Monte Carlo method (GCMC) combined with density functional theory (DFT). The results indicated that the insertion of acidic oxygenous groups or basic nitrogenous groups into NPCs could enhance the physisorption of SO 2 . The influence of edge functionalization on the pore structure of NPCs is also analyzed. To further explore the interaction in the adsorption process, the van der Waals (vdW) interaction and electrostatic interaction between the SO 2 molecule and the basic structural unit (BSU) were investigated. Simulated results showed that edge functionalization had limited influence on vdW interaction and did not significantly change the distribution characteristics of vdW interaction. According to the study on electrostatic interaction, edge functionalization was found to promote inhomogeneity of the surface charge of the adsorbent, enhance the polarity of the adsorbent, and thus enhance the physisorption capacity of SO 2 . More importantly, we provide an idea for studying the difference in adsorption capacity caused by different functional groups connected to carbon adsorbents.

Effects of Structure and Composition of Adsorbents on Competitive Adsorption of Gaseous Emissions: Experiment and Modeling

“…However, other modeling studies performed using more computationally demanding DFT methods have led to similar results for interactions between AC and NO/SO 2 [ 32 , 34 ]. Wang et al [ 34 ] reported the same behavior of NO on AC—the strongest interactions were observed on AC basal plane (compare with “side” in Figure 13 a), weaker interactions with -OH group (compare with “bottom_OH” in Figure 13 a), and the weakest with -H (compare with “bottom” in Figure 13 a).…”

“…Wang et al [ 34 ] reported the same behavior of NO on AC—the strongest interactions were observed on AC basal plane (compare with “side” in Figure 13 a), weaker interactions with -OH group (compare with “bottom_OH” in Figure 13 a), and the weakest with -H (compare with “bottom” in Figure 13 a). Zhao et al [ 32 ] found the same E int trend for SO 2 on AC, where the molecule interacted most strongly with -COOH groups (compare with “bottom_COOH” in Figure 13 a), more weakly with -OH (compare with “bottom_OH” in Figure 13 a), and the weakest with -H (compare with “bottom” in Figure 13 a).…”

“…The comparison demonstrates the usefulness of computationally less demanding force field-based molecular modeling in adsorption research. It also reveals that there is no need to take into account the partial amorphousness of AC, e.g., by a large amount of polyaromatic hydrocarbons [ 32 ]. Approximation of AC using graphite, which additionally enables the preparation of pores of the required size, is sufficient for the given purpose.…”

“…Therefore, in this work, the process of competitive adsorption of emission gases on different materials with different physical and chemical properties was studied both experimentally and via force field-based molecular modeling. Activated carbon is extensively researched and modeled in connection with adsorption [ 31 , 32 , 33 , 34 ]. Therefore, it was used for comparing the obtained data and verifying the modeling strategy.…”

Computational Chemistry as Applied in Environmental Research: Opportunities and Challenges

“…The capture of gaseous pollutants, such as SO 2 , CO, and CO 2 , , by graphitic and nanoporous materials, has been studied and modeled with QM/MM methods. Grand Canonical Monte Carlo methods were combined with DFT to study adsorption isotherms on edge-functionalized nanoporous carbon (NPC) at the macroscopic and microscopic levels .…”