scholarly journals Adsorption Behavior of Methyl Laurate and Dodecane on the Sub-Bituminous Coal Surface: Molecular Dynamics Simulation and Experimental Study

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 30 ◽  
Author(s):  
He Zhang ◽  
Wenli Liu ◽  
Hongxiang Xu ◽  
Qiming Zhuo ◽  
Xiaopeng Sun
Keyword(s):  
Molecular Dynamics ◽  
Bituminous Coal ◽  
Ester Group ◽  
Adsorption Behavior ◽  
Dynamics Simulation ◽  
Low Rank ◽  
Methyl Laurate ◽  
Head Group ◽  
Coal Surface ◽  
Liquid Environment

Biodiesel was found to be a more effective collector on low-rank coal flotation than the common oily collectors (diesel and kerosene) in previous research. However, the micro-adsorption behavior of these collectors on the coal surface remains to be further explored. In the present work, the adsorption behavior of methyl laurate and dodecane, representing biodiesel and common oily collectors, was investigated using experimental and molecular dynamics (MD) simulation methods. The results of MD simulations showed that dodecane was difficult to diffuse on the surface of sub-bituminous coal and formed a spherical structure on the surface of sub-bituminous coal. Methyl laurate was adsorbed on the surface of coal via the head group (ester group), while the tail group (alkyl chain) was exposed to a liquid environment, forming a wider network structure on the coal surface. The above results, mainly attributed to methyl laurate, had a higher interaction with the sub-bituminous surface compared to dodecane. The self-diffusion coefficient results showed that the aggregate configurations of methyl laurate cause higher water mobility, which was more conducive to enhancing the hydrophobicity of the coal surface. The adhesion efficiency measurement and X-ray photoelectron spectrometer (XPS) analysis confirmed that methyl laurate could cover more oxygen-containing functional groups on the coal surface than dodecane, thus enhancing the hydrophobicity of coal. The results of simulations conformed to the experimental results.

scholarly journals Construction of Molecular Model and Adsorption of Collectors on Bulianta Coal

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 4030
Author(s):  
He Zhang ◽  
Peng Xi ◽  
Qiming Zhuo ◽  
Wenli Liu
Keyword(s):  
Molecular Dynamics ◽  
Adsorption Capacity ◽  
Functional Groups ◽  
Molecular Model ◽  
Proximate Analysis ◽  
Dynamics Simulation ◽  
Low Rank ◽  
Methyl Laurate ◽  
Hydroxyl Groups ◽  
Coal Surface

To study the effects of different oxygen functional groups on the quality of flotation clean low-rank coal, two kinds of collectors with different oxygen-containing functional groups, methyl laurate, and dodecanol, were selected and their flotation behaviors were investigated. The Bulianta coal was the typical sub-bituminous coal in China, and the coal molecular model of which was constructed based on proximate analysis, ultimate analysis, 13C-NMR, and XPS. The chemical structure model of the coal molecule was optimized, and the periodic boundary condition was added via the method of molecular dynamics methods. The different combined systems formed by collectors, water, and a model surface of Bulianta coal have been studied using molecular dynamics simulation. The simulation results of dodecanol and methyl laurate on the surface of Bulianta coal show that dodecanol molecules are not evenly adsorbed on the surface of coal, and have higher adsorption capacity near carboxyl and hydroxyl groups, but less adsorption capacity near carbonyl and ether bonds. Methyl laurate can completely cover the oxygen-containing functional groups on the coal surface. Compared with dodecanol, methyl laurate can effectively improve the hydrophobicity of the Bulianta coal surface, which is consistent with the results of the XPS test and the flotation test.

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

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1207
Author(s):  
Lingyun Liu ◽  
Erle Qiao ◽  
Liang Shen ◽  
Fanfei Min ◽  
Changguo Xue
Keyword(s):  
Molecular Dynamics ◽  
Dynamics Simulation ◽  
Low Rank ◽  
Surface Model ◽  
Coal Surface ◽  
Low Rank Coal ◽  
Hydration Layer ◽  
Flotation Process ◽  
Pass Through ◽  
Water Collector

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.

Self-diffusion of lignite/water under different temperatures and pressure: A molecular dynamics study

2016 ◽  
Vol 30 (01) ◽  
pp. 1550253 ◽  
Author(s):  
Xinjian Liu ◽  
Yu Jin ◽  
Congliang Huang ◽  
Jingfeng He ◽  
Zhonghao Rao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Water System ◽  
Simulation Method ◽  
The Self ◽  
Dynamics Simulation ◽  
Low Rank ◽  
Self Diffusion ◽  
Change Mechanism ◽  
Different Temperatures ◽  
Temperature And Pressure

Temperature and pressure have direct and remarkable implications for drying and dewatering effect of low rank coals such as lignite. To understand the microenergy change mechanism of lignite, the molecular dynamics simulation method was performed to study the self-diffusion of lignite/water under different temperatures and pressure. The results showed that high temperature and high pressure can promote the diffusion of lignite/water system, which facilitates the drying and dewatering of lignite. The volume and density of lignite/water system will increase and decrease with temperature increasing, respectively. Though the pressure within simulation range can make lignite density increase, the increasing pressure showed a weak impact on variation of density.

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