Effect of SDBS solution on the surface potential properties of the Zhaozhuang coal

It is of great significance to study the effect of surfactants on the coal surface potential for effective dust suppression in mining faces. The effect of different concentrations of sodium dodecyl benzene sulfonate (SDBS) solution on the surface potential of the Zhaozhuang coal was measured by atomic force microscopy (AFM). The experimental results show that the SDBS solution has significant influence on the surface potential of the Zhaozhuang coal. The electrical characteristics of the coal surface at the nanometer scale are different from those of macroscopic or the mesoscopic level. The surface potential of coal is basically a normal distribution, showing certain electrical characteristics. The mean value of the surface potential of the Zhaozhuang coal is increased with the increase in concentration of the SDBS solution; when the concentration of the SDBS solution is 0.3%, the mean value of surface potential is 5.59 mv, which is about two times of the mean value of the surface potential without SDBS solution added. With the increase of the concentration of the SDBS solution, the maximum value of the surface potential of the Zhaozhuang coal increases, and the minimum value decreases. It shows that the SDBS solution has a significant effect on the potential distribution law and the magnitude of the coal surface. Subsequently, on the basis of the constructed Zhaozhuang coal macromolecule model, xtb and Multiwfn simulation software were used to calculate the molecular surface electrostatic potential value and electron density value of the Zhaozhuang coal molecules after adding water molecules. The variation law for the electrostatic potential surface of the molecule was obtained after adding numbers of water molecules to the surface of the coal molecule. The simulation results show that the area proportion of absolute molecular surface electrostatic potential greater than 10 kcal/mol is increased with the growth in the number of water molecules, while the area proportion of absolute molecular surface electrostatic potential less than 10 kcal/mol is decreased. Because of the free state O─H bond polarity of water molecules, the charges on the molecular surface are rearranged in order to change the electron density on the surface of coal molecules, which affects the overall electrostatic potential of the configuration.