Molecular simulation investigation of pore structure impact on the wettability and flotation efficiency of coal gasification fine slag

Coal gasification slag is a kind of solid waste that exhibits suboptimal resource utilization and contributes to environmental pollution. Flotation is a common method of sorting coal gasification fine slag. However, the adverse influence of the well-developed pores structure of residual carbon on wettability and flotation efficiency is not adequately addressed in the literature. In this research, the adsorption characteristics of water molecules in the residual carbon model with different pore structures were investigated by Grand Canonical Monte Carlo simulation. We employed molecular dynamics simulations and mathematical models to investigate the mechanism of pore water movement. Additionally, the influence of pore structure on the flotation effect of coal gasification fine slag was explored for molecular dynamics simulations and flotation experiments. The results indicated that water molecules were adsorbed and aggregated in the residual carbon pores in the form of clusters. The cluster size decreased as the porosity decreased. Moreover, the same pore model showed an equivalent adsorption of water molecules. The binding effect of residual carbon on water molecules was stronger for smaller pore sizes. However, the simulation and experimental findings demonstrated that the more developed the pore structure of coal gasification fine slag, the lower its flotation efficiency. Finally, various methods of strengthening the flotation of coal gasification fine slag are theoretically verified. The findings of this research elucidate the underlying microscopic mechanism responsible for the adsorption of water molecules by residual carbon pores. Moreover, we explicate the principle of weakening the pore wetting effect and lay a theoretical foundation for developing advanced flotation techniques for coal gasification fine slag. It provides some theoretical guidance and technical support for realizing high-value utilization of coal gasification slag with specific environmental and resource benefits.