Studies on the Effects of Hydrophilic Groups and Hydrolyzed Cations of Anionic Surfactants on Solution Improvement of Surface Properties of Bituminous Coal

To investigate how the hydrolysis unit of anionic surfactants affects the surface properties of coal dust, combining macroscopic experiments (surface tension, dynamic contact angle, wettability settling, and conductivity) with microscopic simulations (molecular dynamics and quantum chemistry), the effects of head groups and cations on the hydrophilicity and hydrophobicity of bituminous coal were jointly studied. The experimental results show that the head groups and cations can synergistically enhance the hydrophilicity of coal powder, and the two sulfonate groups carrying benzene rings and the corresponding cations synergistically worked best. The interaction intensity between surfactants and coal dust is mainly influenced by the quantity, type, and charge of the head groups and hydrolyzed cations. The simulation findings indicate that the surfactant coverage of coal dust is spontaneous. The head groups form more H-bonds with H2O by the promotion of cations. However, the cation's ability to diffuse and bind H2O is limited by the head group. The relative concentration, coordination number, and diffusion coefficient verified this view. The head group and cation form the first H2O layer by van der Waals and electrostatic forces, respectively. Furthermore, the electrostatic potential and molecular orbital energy demonstrate that the head groups and cations are extremely hydrophilic and highly reactive. A comprehensive comparison reveals that the anionic surfactants promote the wetting ability in the order of SLDED > PDS > SDBS > SDS > SDSN. The research results can provide theoretical references for the efficient screening of the dust suppressant.