Influence of particle size on particle-bubble adhesion/desorption behavior during lignite flotation and the enhancing effect of mixed collector

Lignite has poor hydrophobicity and is difficult to adhere to bubbles. Particle size and collectors play critical roles in lignite flotation. This study conducted flotation kinetics test with lignite particle size of 0.50–0.25, 0.25–0.125, 0.125–0.074, 0.074–0.045, −0.045 mm (D50 = 21.79 μm), and −0.045 mm (D50 = 11.32 μm), and used tetradecane and mixed collector SYS as collector. Adhesion/desorption behavior between lignite and bubbles was investigated via induction time tests, oscillatory desorption tests, and adhesion/desorption force tests. Results showed particle size and collectors significantly affect flotation recovery. Optimal particle size facilitates flotation: the −0.045 mm (D50 = 21.79 μm) lignite achieved the highest combustible recovery (72.36% combined with SYS), accompanied by an induction time of only 10 ms and the highest critical desorption frequency. The particle size is much smaller than the optimal particle size for high-rank coal flotation. Coarse particles experienced 1–2 orders of magnitude higher vibration forces than fine particles, making it more prone to detachment from bubbles with same flotation conditions. SYS significantly increased interaction forces between coal particles and bubbles, enabling stable particle attachment to bubbles and float. This study systematically investigated adhesion/desorption behavior between lignite and bubbles from particle size and collectors two key aspects, enriching the theoretical basis of lignite flotation.