Molecular dynamics simulation of surface structure-dependent pyrite wettability in coal flotation

Desulphurisation is very critical in coal flotation. Some liberated pyrite particles can float into the clean coal due to entrainment or its own floatability. Based on the wettability experiments, the floatability of (100), (210) and (111) crystal planes of pyrite was further investigated by molecular dynamics simulation in this work. The diethyl phthalate was selected as the oil phase. The adsorption configuration, water/collector concentration distribution and interaction energy were discussed. The results show that the hydrophilic difference between pyrite crystal surfaces and coal surface is large, but the lipophilic difference is small in two-phase system. Both water and oil droplets can be absorbed on pyrite surfaces. Pyrite (210) plane is more hydrophilic due to more active four coordinated iron atoms, while the (111) plane is more oleophilic due to two layers of sulphur atoms on the surface. In addition, oily collector droplet can spread on the pyrite (111) plane and coal surface in aqueous solution. This suggests that pyrite (111) plane has certain floatability in coal flotation. These findings shed light on the root cause of the adverse effect of pyrite on coal flotation and are expected to provide theoretical guidance for flotation desulphurisation.