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.
Highlights
Coal is China’s main energy source, and it occupies a dominant position in the energy consumption system
Since a large number of hydrophilic oxygen-containing functional groups and pores exist on the low-rank coal, a stable hydration layer can be formed on the surface during the flotation process [5,6,7,8,9]
The results showed that there were many oxygen atoms on the surface of low-rank coal, which could promote the formation of hydrogen bonds of water molecules in an aqueous solution
Summary
Coal is China’s main energy source, and it occupies a dominant position in the energy consumption system. After the separation of raw coal, much more fine slime is obtained. The most efficient method to separate coal slime is froth flotation. Since a large number of hydrophilic oxygen-containing functional groups and pores exist on the low-rank coal, a stable hydration layer can be formed on the surface during the flotation process [5,6,7,8,9]. The traditional oil flotation collector is difficult to adsorb on its surface, which leads to low flotation efficiency of low-rank coal [10,11,12,13,14,15,16]. With the increase in mining depth and mine service life, the raw coal quality is getting worse and worse, and the direct combustion of low-rank slime can no longer meet the current environmental protection situation and product quality requirements. The high-efficiency flotation and upgrading technology of low-rank coal slime has become a “stuck neck” problem that restricts clean and efficient production and utilization of low-rank coal
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