Flotation is a crucial technique for separating coal gasification fine slag. However, in practical flotation processes, circulating water often contains a high concentration of metal ions. This study investigates the flotation performance of coal gasification fine slag in the presence of metal ions with different valences. The effects of metal ions on the wettability of coal gasification fine slag were examined through single bubble loading experiments. Additionally, scanning electron microscopy, zeta potential measurements, FT-IR spectroscopy, and laser diffraction were used to analyze the impact of metal ions on the surface topography, zeta potential, functional group, and particle size distribution of coal gasification fine slag. The results demonstrated that K⁺, Ca²⁺, Mg²⁺, and Al³⁺ all have a positive effect on the flotation of coal gasification fine slag, with Al³⁺ being particularly effective. At a concentration of 0.2 mol/L, Al³⁺ increased the recovery of combustible matter in coal gasification fine slag from 66.70% to 91.05% compared to deionized water. Single bubble loading experiments and zeta potential measurements revealed that metal ions reduce the absolute value of the gasification fine slag potential while increasing surface hydrophobicity. The higher the ion concentration, the closer the potential approaches zero and the stronger the hydrophobicity. FT-IR test results indicated that Al³⁺ promote diesel adsorption onto coal gasification fine slag. Therefore, the introduction of metal ions into coal gasification fine slag can enhance its surface hydrophobicity, compress its double layer, and promote diesel adsorption on its surface. This work explains the effects of metal ions on coal gasification fine slag flotation.

 

Metal ions,Coal gasification fine slag,Single bubble loading,Flotation,ζ potential