Different anionic MIL structure optimization and molecular dynamics simulation of adsorption on coal surface

Surfactants can regulate the surface wettability of low-rank coal (LRC), resulting in highly efficient coal usage. Magnetic ionic liquids (MILs), a novel form of surfactants, provide environmental protection, excellent designability, and recyclability. In this study, quantum chemical simulations were performed to optimize the structures of [C12mim]FeCl4, [C12mim]2CoCl4, and [C12mim]2NiCl4 and the structural parameters were verified. The effect of MILs on the surface wettability of LRC was investigated by measuring the critical micelle concentration (CMC) using a conductivity technique and computing the adhesion work; thus, the micro-control mechanism of wettability was clarified. The wettability investigation revealed that the three different types of MILs had higher critical micelle concentrations as the temperature increased. Molecular dynamics modeling was utilized to calculate the adsorption process simultaneously, and the results demonstrated that the three different MILs may spontaneously complete adsorption on the surface of the LRC. Thermogravimetric and X-ray photoelectron spectroscopy analyses demonstrated that after the addition of the three different types of MILs, the oxygen-containing functional groups in the LRC were covered, the LRC surface became more hydrophobic, the water content of the LRC decreased, and the wettability of the LRC was effectively controlled.