Study on the Wettability of a Composite Solution Based on Surface Structures of Coal

[Image: see text] In order to research the influence of composite surfactant solutions on the wetting ability of coal, the wettability parameters, pore structure parameters, and surface microscopic morphology were determined in this study. The results show that the wettability of the surfactant can be improved by adding NaCl. As the concentration of NaCl increased, the spreading coefficient of the NaCl–SDS composite solution increases; the spreading coefficient increased from −10.838 to −3.7624 mN/m. The surface free energy decreased from −2.031 to 3.670 J/mol × 10(3), and the adhesion work decreased from 113.802 to 55.058 mJ/m(2). In terms of the pore structure and surface morphology of coal, the pore size will affect the wettability of coal. The contact angle reduces with pore size increase (R(2) = 0.955). The surface pores of coal treated with the NaCl–SDS composite solution increase and the fracture connectivity is improved, which facilitated the solution to penetrate coal for wetting. The results of this paper have great practical significance for mining at the face to reduce coal dust pollution.