## 3 Results and Discussion
### MS of Coal Processed with VESFFs
When exposed to anionic VESs, the -CH-, -CH2-, and -CH3 groups of the TS coal were oxidized to carboxyl, alcohol hydroxyl, ketone, and aldehyde groups, and even further oxidized to generate CO, CO2, and H2O, reducing the side chain length, leading to a relative increase in the proportion of aromatic carbon atoms, aromatic rings, and aromatic C=C bond content, and an increase in the peak position difference (G-D1) in the coal. The G peak position of the NC samples that had been processed with VESFFs B, B2, C, and D exhibited a shift to a lower wavenumber range, which is indicative of a decline in the orderliness of the macromolecular structure within the coal. The effect of VESFF D was the most pronounced. This phenomenon can be attributed to the adsorption of water and VES molecules onto the coal surface. The adsorption capacity of VES molecules on the coal surface is superior to that of methane molecules, leading to alterations in the aromatic size and order of the original microscale crystalline structure of the coal. The NC coal samples were a lean coal that had undergone significant metamorphism and exhibited a reduced number of side chains and oxygen-containing functional groups. Consequently, the oxidation of the VESs in VESFF D by anions was not readily apparent. The MS of coal  
Figure 9: Raman spectra showing peak fitting of coal samples processed with VESFF B: (**a**) TS coal samples; (**b**) NC coal samples. is primarily affected by the adsorption of VESs, which impairs the ordered arrangement of the macromolecular structure of coal. The area of the G peak (A\({}_{\rm G}\)) in the Raman spectrum of coal can be considered to be an indicator of the number of aromatic rings present in the macro-molecular structure. The area of peak D\({}_{1}\) (A\({}_{\rm D1}\)) is indicative of the degree of molecular order and the number of structural unit defects present in the macro-molecules of coal. The ratio of the peak areas between the D\({}_{1}\) and G peaks (A\({}_{\rm D1}\)/A\({}_{\rm G}\)) demonstrated an inverse proportional relationship with the size of the macromolecular planar MS of the coal samples [46; 47]. As illustrated in Figure 11, the peak area ratio of the D\({}_{1}\) and G peaks (A\({}_{\rm D1}\)/A\({}_{\rm G}\)) in the TS coal processed with VESFF D was lower (approximately 0.35) than that of the TS coal processed with \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Coal Sample**} & \multicolumn{2}{c}{**Peak Position/cm\({}^{-1}\)**} & \multicolumn{2}{c}{**G-D\({}_{1}\)/cm\({}^{-1}\)**} & \multicolumn{2}{c}{**D\({}_{1}\) Peak**} & \multicolumn{2}{c}{**G Peak**} & \multicolumn{2}{c}{**A\({}_{\rm DI}\)/A\({}_{\rm G}\)**} & \multicolumn{2}{c}{**R\({}^{2}\)**} \\ \cline{3-8} \multicolumn{1}{c}{} & **D\({}_{1}\) Peak** & **G Peak** & **FWMM** & **FWM** & **A\({}_{\rm DI}\)** & **A\({}_{\rm G}\)** & **R\({}^{2}\)** \\ \hline \multirow{4}{*}{TS} & A & 1327.1 & 1582.9 & 255.8 & 138.82 & 98.92 & 0.96 & 0.9941 \\  & B & 1324.8 & 1582.6 & 257.8 & 144.09 & 96.71 & 1.06 & 0.9947 \\  & B\({}_{2}\) & 1324.7 & 1583.0 & 258.3 & 142.21 & 95.70 & 1.17 & 0.9973 \\  & C & 1322.7 & 1583.9 & 261.2 & 129.34 & 90.76 & 1.12 & 0.9941 \\  & D & 1322.7 & 1596.7 & 274.0 & 86.93 & 70.00 & 0.61 & 0.9946 \\ \hline \multirow{4}{*}{NC} & A & 1323.6 & 1588.2 & 264.6 & 127.35 & 79.73 & 1.27 & 0.9955 \\  & B & 1324.9 & 1585.9 & 261 & 144.51 & 76.80 & 1.57 & 0.9962 \\ \cline{1-1}  & B\({}_{2}\) & 1325.6 & 1582.1 & 256.5 & 140.77 & 90.15 & 1.37 & 0.9959 \\ \cline{1-1}  & C & 1326.0 & 1583.6 & 257.6 & 122.96 & 84.60 & 1.17 & 0.9962 \\ \cline{1-1}  & D & 1326.5 & 1572.9 & 246.4 & 110.49 & 49.56 & 0.95 & 0.9977 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Raman structure parameters of coal samples treated with FFs. Figure 10: Peak position difference of coal samples treated by FFs: (**a**) TS coal samples; (**b**) NC coal samples. deionized water, indicating that the aromatic layer extension in the aromatic crystal nucleus of the TS coal processed with VESFF D and the micropore volume both increased.