Interactions between Mg2+-doped kaolinite and coal: Insights from DFT calculation and flotation

Abstract

In order to explore the micro-influence mechanism of clay surface/interface property differences on coal slime flotation based on impurity defects, the influence mechanism of Mg2+ doping on the microscopic interactions between particles of kaolinite and coal is preliminarily discussed by using DFT (density functional theory) and flotation. DFT results showed that different coal structural units adsorption on Mg(II)_K (Mg2+-doped kaolinite) surface mainly through electrostatic attraction, and the coal structural units can be stably adsorbed on Mg(II)_K surface in the case of competitive adsorption with H2O. When coal structural units and H2O competed for adsorption on Mg(II)_K surface, H2O promoted the adsorption of coal structural units on Mg(II)_K surface. Flotation results showed that with the increase of kaolinite mass percentage in mixed minerals, the clean coal yield significantly decreased, and the clean coal ash firstly decreased and then increased. The influence mechanism of Mg2+ doping on the interaction between kaolinite and coal was that Mg2+ doping significantly enhanced the interaction between Mg(II)_K surface and coal structural unit. The results revealed the complex interaction between fine particles in coal slime, paving the way for its efficient selective separation.