Surface structure-dependent hydrophobicity/oleophilicity of pyrite and its influence on coal flotation

Flotation is an important method to remove the inorganic sulfur from coal. Its effect depends on the difference in adhesion between coal and pyrite to air bubbles and flotation reagents. In this study, the interface properties of coal powder/plate and pyrite powder/crystals were investigated using a comprehensive approach combining wetting process, induction time, contact angle, and X-ray photoelectron spectroscopy. The experimental results show that the spreading and adsorption speed of diethyl phthalate on pyrite crystals and powder is close to that on coal surface in the air. However, the adsorption rate of pyrite to water is much higher than that of coal. In aqueous environment, it is difficult for diethyl phthalate to spread on pyrite crystals, especially in alkaline solution. The difference of hydrophobicity between coal and pyrite at air-water interface is smaller than that at oil-water interface. The adhesion of air bubble and reagent droplet on three pyrite facets is also different. The oxidation of pyrite {100} is faster and greater than that of {210} and {111} facets in alkaline solution, which is beneficial to the coal desulfurization. These findings disclose the hydrophobicity/oleophilicity and structure-reactivity dependence of pyrite in the flotation. (C) 2020 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.