Abstract
In order to investigate the effect of deep burial metamorphism on the wettability of coal during deep burial metamorphism, a superficial coal sample (∼90 m) and a deep coal sample (∼490 m) collected from two main mining seams were selected to simulate the deep burial metamorphism process. The wettability of two coal samples during deep burial metamorphism was investigated by X-ray photoelectron spectroscopy (XPS), FTIR, zeta potential, and contact angle measurements. Besides, comprehensive DLVO interaction analyses between two coal samples from different mining depths were carried out through the zeta potentials measurements under different pH values. The XPS results demonstrate that the content of surface oxygen atom and oxygen-containing functional group for superficial coal tends to be higher than that of deep coal. The FTIR results indicate that the peak intensity of oxygen-containing functional groups for the superficial is higher than that of deep coal, implying the stronger surface hydrophobicity of deep coal compared to superficial coal. The contact angle of superficial coal is lower than that of deep coal. The zeta potential and DLVO theory analyses of superficial particles and deep coal particles indicate that deep burial metamorphism process might be favorable for bubble-particle collision and attachment, while might be unfavorable for the wetting process oppositely. Based on the surface chemistry characterization and theory analyses, this study is expected to give a theoretical insight into the efficient processing or dedusting process of coals experiencing different deep burial metamorphism processes in the future.
Highlights
It is well known that coals experienced successive plate tectonic movements during the coal-forming periods. ese plate tectonic movements and orogeny caused collision, uplift, depression, extrusion, tension, faulting, magmatic activity, and other geological movements, making the coal seams to deform, slip, and shear, and the coal thickness, coal structure, and the degree of coal metamorphism changed [1]. erefore, the degree of coal metamorphism varies in different mining depths, resulting in a different wettability of the coal dust [2]
X-ray photoelectron spectroscopy (XPS) Peak fit software is employed to split and fit the XPS spectrogram at 1 s. e spectra were fitted with four Gaussian-shaped peaks that occur at 284.6, 285.3, 286.3, and 289.0 eV. e peak at 284.6 eV is corresponding to C-C or C-H bond. e peak at 285.3 eV represents the contribution from chemical groups of C-O-C and C-OH
The superficial and deep coal samples were selected to simulate the deep burial metamorphism process. e surface properties of two coal samples were comparatively studied by X-ray photoelectron spectroscopy (XPS), FTIR, zeta potential, contact angle measurements, and DLVO theory
Summary
It is well known that coals experienced successive plate tectonic movements during the coal-forming periods. ese plate tectonic movements and orogeny caused collision, uplift, depression, extrusion, tension, faulting, magmatic activity, and other geological movements, making the coal seams to deform, slip, and shear, and the coal thickness, coal structure, and the degree of coal metamorphism changed [1]. erefore, the degree of coal metamorphism varies in different mining depths, resulting in a different wettability of the coal dust [2]. Erefore, the degree of coal metamorphism varies in different mining depths, resulting in a different wettability of the coal dust [2]. For this reason, it is necessary to study the effects of the physical chemistry characteristics of coal dust with different metamorphic degrees on wetting behavior. Wettability of the coal surface has been widely used in modern coal processing, e.g., the flotation and dedusting process [3,4,5,6,7,8,9]. Due to the poor wettability of the coal dust, the insignificant dedusting effect of the wet dust removal method was observed in the underground workplace
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