Flotation of lean coal using trisodium citrate dihydrate as a dispersant in the presence of sodium oleate

[Display omitted] •Flotation behavior of lean coal using TCD as a novel dispersant in NaOL system was studied.•With the addition 2000 g/t TCD at pH value of 5, flotation perfect index is greatly increased.•SEM-EDS and turbidimeter analysis reveal that the slime coating is reduced by using TCD.•The attachment energy barrier between low-ash coal and high-ash fine slimes is increased by using TCD.•TCD is an appropriate dispersant for the flotation of lean coal. Flotation is a highly efficient method for purifying low-ash coal particles from high-ash fine slimes. Herein, the dispersion effect of trisodium citrate dihydrate (TCD) on the reduction of slime coating on low-ash lean coal particle surface was studied using flotation tests, scanning electron microscope–energy Dispersive Spectroscopy (SEM–EDS) observation, turbidity measurements, and extended Derjaguin–Landau–Verwey–Overbeek (E-DLVO) calculations. Flotation tests revealed that after adding of 2000 g/t TCD, the yield of clean coal increased by 1.09 % and the ash content of clean coal decreased by 1.45 % with 1000 g/t NaOL at pH 7.0, thereby increasing the combustible recovery and flotation perfect index by 2.50 % and 6.42 %, respectively. The SEM–EDS observation and turbidity measurements indicated that the coating of the high-ash fine slimes on the low-ash coal particle surface was significantly weakened in the presence of 2000 g/t TCD. Furthermore, the E-DLVO calculations verified that the addition of 2000 g/t TCD increased the energy barrier between the low-ash coal particles and high-ash fine slimes, providing theoretical evidence for flotation tests and SEM–EDS observation. Therefore, TCD served as an effective dispersant for the high-ash fine slimes to improve the flotation performance of lean coal.