Effects of hydrodynamic cavitation treatment on flotation of coal gasification fine slag

Coal gasification fine slag (CGFS) is a significant source of solid waste, consisting of residual carbon (RUC) and ash particles. This study investigates the mechanism of hydrodynamic cavitation (HC) treatment for enhancing CGFS flotation and improving decarbonization efficiency. HC treatment increased the flotation efficiency of CGFS, achieving a removal rate of RUC of 67.14% and a concentrate loss on ignition (LOI) of 61.92%. Scanning electron microscopy (SEM) and particle size analysis revealed that the high-speed jet generated by HC treatment effectively cleaned the surface and pores of CGFS, while reducing the D50 of collector droplets from 42.38 μm to 5.06 μm. Particle–bubble attachment experiments demonstrated that the nanobubbles produced by the HC treatment increased the attachment angle from 35.1° to 41.6° and reduced the induction time from 52 ms to 17.5 ms, thereby enhancing hydrophobicity. Additionally, focused beam reflectance measurement (FBRM) and dynamic foam analyzer results indicated that HC treatment promoted fine particle flocculation and improved froth stability, ultimately enhancing flotation recovery efficiency. These findings highlight the effectiveness of HC treatment in improving CGFS flotation performance through enhanced particle–bubble interactions, surface cleaning, and froth stability.