## 3 Results and Discussion
### Analysis of Surface Morphological Changes in Coal Dust Samples after the Experiment  
3.1 Analysis of Coal Dust Surface Morphology after the Action of Non-Ionic Fluorine-Containing Solution  
Figure 8a shows the state of the FS-30 fluorinated solution after 48 h of action on coal dust. At a concentration of 0.001%, coal dust attached to the wall of the glass dish, but this did not occur at other concentrations. The surface of the experimental coal sample still had a lot of unwetted coal dust. At a concentration of 0.01%, the surface of the coal sample still had obvious particle sensation. With the increase in concentration, no obvious loose particles were observed on the surface of coal samples, which showed a dense and uniform morphology, and all appeared as fine small cracks. Figure 8b shows the state of the FS-31 fluorine solution after 48 h of action on coal dust. Loose coal dust particles still exist on the surface of coal dust at low concentrations, but this does not occur at other concentrations. A lot of unwetted coal dust was still present on the surface of the experimental coal sample. At a concentration of 0.01%, the surface of the coal sample also had a distinct granularity. With the increase in concentration, no obvious loose particles were observed on the surface of coal samples, which showed a dense and uniform morphology, and all appeared as fine small cracks. Figure 8c shows the state of the FS-34 fluorinated solution acting on coal dust after 48 h. As shown in Figure 9, at lower concentrations of 0.01%, 0.02%, and 0.03%, coal dust attached to the wall of the glass dish, but this did not occur at other concentrations. There is more loose granular coal dust on the surface of coal dust. This indicates that at lower concentrations, the surface energy of the solution is low, making the coal dust samples fail to be completely wetted. With the increase in concentration, at a concentration of 0.04%, the surface of the coal sample obviously became denser, but a small crack appeared on the surface. With the increase in concentration, no obvious loose particles were observed on the surface of the coal sample, which showed a dense and uniform morphology, and no small cracks appeared. Figure 8: Consolidation of coal dust surface with FS-30, FS-31, FS-34, FS-50 solution at different concentrations. Figure 9: Consolidation of coal dust surface after experiments with FS-60, FS-61, FS-63 solution at different concentrations. In Figure 8d, at concentrations of 0.01%, 0.02%, 0.03%, and 0.04%, coal dust attached to the wall of the glass dish, but this was not obvious at other concentrations. With the increase in concentration, the surface of the six experimental coal samples between 0.07% and 0.3% were dense and homogeneous, without obvious bulk particles, and without the appearance of cracked fine lines. Collectively, it seems that the wetting and water retention of the experimental coal sample surface increased significantly with the increase in solution concentration. 3.2 Analysis of Coal Dust Surface Morphology after the Action of Anionic Fluorine-Containing Solution  
Figure 9a shows the state of FS-60 fluorinated solution acting on coal dust after 48 h. As shown in Figure 9a, coal dust was attached to the walls of the glass dishes of the coal samples at each concentration. Compared with the coal samples of other concentrations, the surface of the experimental coal samples with a concentration of 0.3% was denser and uniform, without obvious particles and cracks, and the wetting effect was better. At concentrations of 0.02%, 0.03%, 0.04%, and 0.05%, there was also an obvious sense of granularity on the surface of the coal samples, and the amount of loose coal dust particles on the surface increased significantly at the concentration of 0.1%.