The investigation of wetting and agglomerating mechanism of short-chain fluorocarbon surfactant suppressing coal dust from macro and molecular scales

•FS-50 is more effective in suppressing bituminous coal dust than FS-3100.•FS-50 achieves more efficient wettability and agglomeration than FS-3100.•FS-3100 achieved higher diffusion coefficient and lesser absolute wetting area.•The electrostatic potential energy and hydrogen bonds are key influencing factors.•The higher LUMO value and band gap energy deteriorates the performance of FS-3100. This paper carried out a multi-scale investigation on the wetting and agglomerating mechanism of short-chain fluorocarbon surfactant suppressing coal dust. As investigated, FS-50 achieves higher dedusting rate and shorter suppression time than FS-3100, which is attributed to its better wettability and more sufficient agglomeration on coal particles. Simulation indicates that FS-3100 with longer chain length is easier to generate chemical bond rotation, which results in a distorted spatial structure, higher steric hindrance, and poorer ability of FS-3100 in retaining H2O molecules and adsorbing surround the coal particles. The hydrophilic group of FS-50 is dominated by the induced effect and presenting larger charge density and electron-absorbing nature. Higher electrostatic potential difference with coal molecules, more hydrogen bonds, shorter bond length and larger bond angle are key factors to endorse FS-50 a better wetting and agglomerating performance. The C atom connected with the fluorocarbon tail chain of FS-3100 is linked to a carboxyl group with lone pair electrons. This carboxyl group enlarges the LUMO value of FS-3100 and weaken its ability to attract the electrons of coal particles. On the contrary, the lower LUMO value, lower band gap energy, and smoother spatial configuration jointly bring FS-50 better wetting and agglomerating ability.