Revisiting the enhanced performance in coal gasification fly ash coal flotation by combined grinding process and nano-mixed collectors

The coal gasification fly ash (CGFA) has low flotation efficiency and serious environmental pollution, due to the abundant oxygen-containing functional groups and developed pore structures. Herein, the grinding process and novel nano-mixed collectors were synergistically used on enhancing CGFA flotation, where the nano-mixed collectors were synthesized through nanoemulsifying and rapid-cooling method. The grinding time and nano-mixed collector compositions with different beeswax and kerosene contents were used to determine the optimum flotation process parameters. The results indicated that the removal rate of unburned carbon (RUC) for CGFA with optimum grinding process (12 min) and nano-mixed collector system (#4) exhibited significant higher value (92.48%) than that of raw CGFA samples (61.25%). The grinding process could obviously decrease the pore volumes and contents of oxygen-containing functional groups on CGFA surfaces, as well as reduce the average diameter of CGFA samples from 81.538 to 7.872 µm. Moreover, the application of novel nano-mixed collectors as flotation collectors could further improve the surface hydrophobicity, decrease the surface pore volumes, high wetting heat and low water adsorption capacity. Therefore, this study can provide a new approach for solving the problems of low flotation efficiency and improving the efficient utilization of CGFA.