Molecular dynamics simulation of flotation of difficult-to-float oxidized coal slime enhanced by polar and non-polar mixed collectors

Abstract

Aiming at the problem of poor flotation effect of oxidized coal slime, this study used a composite flotation collector compounded with diesel oil (DO) and an alcohol polar collector reagent (KD) in order to improve the flotation effect. Through the flotation test, combined with the molecular dynamics simulation method, the effect of the mixed collector on the flotation of oxidized coal was investigated, and the adsorption characteristics of the mixed collector with different ratios in the oxidized coal/water/reagent system were explored, including the parameters of the relative concentration distribution, the contact surface area and the interaction energy. The compatibility of six different components of DO with KD reagent was also investigated. The results showed that compared with the use of diesel fuel only, using the mixed collector with a DO:KD ratio of 4:1, the ash content of the cleaned coal did not change much, the cleaned coal yield could be increased by 20.07%, and the combustible matter recovery could be increased by 25.29%. The KD molecules in the mixed collector can adsorb with the hydrophilic parts on the surface of oxidized coal and cover the hydrophilic sites on the surface of oxidized coal, so that the DO/KD molecules can adsorb together on the surface of oxidized coal and enhance the hydrophobicity of the surface of oxidized coal. When the proportion of KD in the mixed collector exceeds 20%, some KD molecules undergo self-polymerization, forming semi-micellar adsorption through hydrophobic binding, which will reduce the effect of the mixed collector. In addition, carbazole and dibenzothiophene among the DO components have the closest Chi values to 0 and smaller ΔE values, which have the best compatibility with the polar reagent KD and better chemical reaction activity, and can better enhance the flotation effect of oxidized coal slime.