Abstract
The mixed collector can improve low rank coal flotation efficiency, but its synergistic mechanism needs to be further explored. In this paper, oleic acid-dodecane (OA-D), oleic acid (OA), and dodecane (D) were employed to treat the low rank coal for revealing new synergistic mechanism of the mixed collector. First the surface free energy of the coal, the surface free energy of coal-water and coal-water-coal were calculated. Then wetting heat measurement, X-ray Photoelectron Spectroscopy (XPS) and FTIR were used to analyze synergistic mechanism of the mixed collector in depth. The results showed that OA-D obtained a higher combustible recovery than using OA and D, respectively. The essence of synergetic mechanism of OA-D was that they formed a relatively ordered “supramolecular structure” on the low rank coal surface, especially there were hydrophobic and van der Waals forces between the oleic acid chain and the dodecane chain that can promote the formation of a continuous collector film.
Highlights
Coal, as a main energy source, makes an important contribution to the national economy with its consumption accounting for 58% of China’s total energy consumption in 2018 [1]
For α-bromonaphthalene, the contact angles for coal treated with D, oleic acid (OA), and oleic acid-dodecane (OA-D) were lower than untreated coal, and the contact angles decreased in the order of D > OA > OA-D
The polar head of OA was mainly absorbed on the C-O group of coal surface and the nonpolar head extended outward, which facilitated D to absorb on the hydrophobic area of coal surface or the area modified by OA
Summary
As a main energy source, makes an important contribution to the national economy with its consumption accounting for 58% of China’s total energy consumption in 2018 [1]. 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]. Large consumption of collector, and high cost are the main problems that restrict the efficient utilization of fine low rank coal
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