Synergistic collaboration of stirred mill and saline water to improve flotation decarburization efficiency of coal gasification fly ash

The presence of unburned carbon seriously restricts the reasonable disposal and utilization of coal gasification fly ash (CGFA), leading to resources waste and environmental pollution. Due to the abundant micropores and hydrophilic structures on the surface of unburned carbon, the conventional flotation decarburization efficiency of CGFA is low. In this study, the stirred mill and saline water were synergistically applied to enhance the flotation decarburization efficiency. The synergistic mechanism between stirred mill and saline water was revealed through comprehensive characterization of surface morphologies, particle size distribution, pore structure evaluation, contact angle measurement, and surface property assessment. The results demonstrated that CGFA achieved a decarburization efficiency of 87.85 % by stirring mill grinding at 600 rpm for 10 min. There are three key reasons: preferential exposure of carbonaceous components, median particle size reduction to 8.11 µm with specific surface area decrease to 21.277 m²/g, and an increase in contact angle of 29.73°. Subsequent saline water treatment further improved efficiency to 94.41 % (0.8 mol/L Na⁺) and 96.16 % (0.4 mol/L Mg²⁺). This is caused by three complementary mechanisms: surface tension reduction, foam stabilization, and Zeta potential modulation. Consequently, the synergistic collaboration of stirred mill and saline water exhibit remarkable performances and can be used as an ideal candidate for flotation decarburization of CGFA.