Effect of Hydration Layer on the Adsorption of Dodecane Collector on Low-Rank Coal: A Molecular Dynamics Simulation Study

Abstract

The hydration layer has a significant effect on the adsorption behavior of reagents during the flotation process of low-rank coal. Understanding the effect of hydration layer on the adsorption of common collectors on low-rank coal is a prerequisite for proposing a new enhanced coal floatation method. In this study, a smooth low-rank coal surface model with a density of 1.2 g/cm3 was constructed and compared with the XPS results. Three different systems, coal-water, coal-collector, and coal-water-collector, were constructed. Molecular dynamics method was applied to study the adsorption behaviors of water and dodecane molecules. Simulation results revealed that a stable hydration layer with a thickness of about 5 Å was formed due to the strong attraction of coal surface. The negative value of interaction energy (IE) indicated that dodecane molecules could spontaneously adsorb on the coal surface. Dodecane molecules were successfully adsorbed on the coal surface when it was located inside the hydration layer. While the dodecane molecule was outside the hydration layer, it could not pass through the hydration layer on the surface of low-rank coal.

Improving Low Rank Coal Flotation Using a Mixture of Oleic Acid and Dodecane as Collector: A New Perspective on Synergetic Effect

“…Introducing Equations (7) and (8) into Equation (6), the change in the total Gibbs free energy of the solid-water adhesion is as follows:…”

“…The high oxygen content, especially the abundance of polar groups (phenolic/alcoholic hydroxyl, carbonyl, carboxyl, ether, and methoxyl), results in the poor floatability of coal [4][5][6][7]. These hydrophilic functional groups weaken the surface hydrophobicity of low rank coal via absorbing water molecules to form hydration film [8]. Moreover, some weakly acidic groups (phenolic OH and COOH) ionize in solution making the coal surface negatively charged [9].…”

Emerging Trends of Computational Chemistry and Molecular Modeling in Froth Flotation: A Review

“…The electronic properties and reactivity of minerals’ surfaces can readily be altered in an aqueous environment, leading to different adsorption properties compared to dry surfaces. ,− ,,− ,− For instance, DFT calculations showed that the water hydration layer on the smithsonite weakens the hybridization of s and p orbitals and lowers the electrophilicity of Zn atoms on the outermost mineral layer, subsequently reducing the interaction levels of smithsonite with carboxyl collectors . As further confirmed by DFT, hydration of sphalerite significantly alters the mineral surface properties through localization of Zn 3 d , 4 s , and 4 p orbitals, resulting in a reduction in the reactivity of Zn atoms and, ultimately, the Zn-xanthate collector interactions .…”

Study on the Wetting Mechanisms of Different Coal Ranks Based on Molecular Dynamics

“…With the continuous development of computer technology, molecular simulation is increasingly applied to study the micromechanism of coal surface wettability. This approach has gradually become an important method in the field of coal flotation [20][21][22][23]. Zhao [24] revealed the significant effects of carbon and oxygen elements in coal on the wettability of coal dust.…”