Research on the Effect of Carbon Defects on the Hydrophilicity of Coal Pyrite Surface from the Insight of Quantum Chemistry

Peng, Xi; Liu, Wenli

doi:10.3390/molecules24122285

Cited by 7 publications

(6 citation statements)

References 20 publications

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“…Furthermore, we optimized the carbon atoms and water molecules in a 20 × 20 × 20 Å cubic cell with Brillouin zone sampling restricted to the gamma point in the calculation process. The other parameters were consistent with those in Reference [17].…”

Section: Calculation Methods and Modelsupporting

confidence: 91%

“…As in the case of the ideal surface DOS in Figure 5a [17], the one-carbon-atom-covered surface with water adsorbing the adjacent to Fe site, Figure 5b, shows a strong hybridization between the Fe (surface) and O (water molecule) from about −8.2 eV to −1.6 eV. Furthermore, the antibonding state from approximately 0.4 eV to 2.5 eV is also quite weak, as shown in Figure 5c.…”

Section: Resultsmentioning

confidence: 99%

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DFT Study into the Influence of Carbon Material on the Hydrophobicity of a Coal Pyrite Surface

et al. 2019

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From the macroscopic point of view, the hydrophilicity of symbiotic carbon pyrite is weakened overall compared to that of pure pyrite. It is very important to explain the impact of elemental carbon accreted on a pyrite surface on the surface’s hydrophobicity from the perspective of quantum chemistry. To study the influence of adsorbed carbon atoms on the hydrophilicity of a coal pyrite surface versus a pyrite surface, the adsorption of a single water molecule at an adjacent Fe site of a one-carbon-atom-covered pyrite surface and a carbon atom monolayer were simulated and calculated with the first-principles method of density functional theory (DFT). The water molecules can be stably adsorbed at the adjacent Fe site of the carbon-atom-covered pyrite surface. The hybridization of the O 2p (H2O) and Fe 3d (pyrite surface) orbitals was the main interaction between the water molecule and the pyrite surface, forming a strong Fe–O covalent bond. The water molecule only slightly adsorbs above a C atom on the carbon-atom-covered pyrite and the carbon atom monolayer surfaces. The valence bond between the water molecule and the pyrite surface changed from an Fe–O bond to an Fe–C–O bond, in which the C–O bond is very weak, resulting in a weaker interaction between water and the surface.

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Section: Calculation Methods and Modelsupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

DFT Study into the Influence of Carbon Material on the Hydrophobicity of a Coal Pyrite Surface

et al. 2019

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“…The formation energy of carbon atom doping at the sulfur vacancy defect is significantly lower, indicating that it is a stable form of defect. Xi et al [16] and Qi et al [15] also reported that the formation energy of carbon doping at the sulfur vacancy is low and the structure is stable. Therefore, the influence of doping concentration and the location of carbon atoms at the vacancy defect is discussed in this paper.…”

Section: The Effect Of Different Carbon Impurity Defects On the Crystmentioning

confidence: 99%

“…Qi et al [15] analyzed the structure and properties of carbon-doped pyrite via the first-principles method based on DFT with the Hubbard U correction (DFT + U and found that carbon-doping can reduce the hardness of pyrite and enhance its oxidizability, leading to difficult coal-pyrite depression in coal flotation. Xi et al [16,17] studied the effect of carbon defects and surface carbon atom adsorption on the hydrophilicity of the whole surface of the coal-pyrite using DFT calculations. They found that the carbon defects reduced the hydrophilicity of the pyrite surface (the closer to the carbon defect center, the weaker the hydrophilicity) and that the adsorption of carbon atoms on the pyrite surface markedly enhanced its hydrophobicity.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Carbon Defects in the Coal–Pyrite Vacancy on the Electronic Structure and Optical Properties: A DFT + U Study

Wei

Cheng

2020

Minerals

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Pyrite is a mineral often associated with coal in coal seams and is a major source of sulfur in coal. Coal–pyrite is widely distributed, easily available, low-cost, and non-toxic, and has high light absorption coefficient. So, it shows potential for various applications. In this paper, the density-functional theory (DFT + U) is used to construct coal–pyrite with carbon doped in the sulfur and iron vacancies of pyrite. The effects of different carbon defects, different carbon doping concentrations, and different doping distributions in the same concentration on the electronic structure and optical properties of coal–pyrite were studied. The results show that the absorption coefficient and reflectivity of coal–pyrite, when its carbon atom substitutes the iron and sulfur atoms in the sulfur and iron vacancies, are significantly higher than those of the perfect pyrite, indicating that coal–pyrite has potential for application in the field of photovoltaic materials. When carbon is doped in the sulfur vacancy, this impurity state reduces the width of the forbidden band; with the increase in the doping concentration, the width of the forbidden band decreases and the visible-light absorption coefficient increases. The distribution of carbon impurities impacts the band gap but has almost no effect on the light absorption coefficient, complex dielectric function, and reflectivity, indicating that the application of coal–pyrite to photovoltaic materials should mainly consider the carbon doping concentration instead of the distribution of carbon impurities. The research results provide a theoretical reference for the application of coal–pyrite in the field of photoelectric materials.

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“…The surface properties of coal kaolinite are the key factors to determine its surface floatability [3] and the surface properties depend on the surface crystal structure [4]. The previous study found that the coal pyrite surface was substituted [5] and covered [6] by carbon atoms so that the structure and properties of coal pyrite were different from the non-coal pyrite [7]. Meanwhile, the formed sulfur after optimization enhanced the hydrophobicity of coal pyrite [8].…”

Section: Introductionmentioning

confidence: 99%

Study on the Crystal Structure of Coal Kaolinite and Non-Coal Kaolinite: Insights from Experiments and DFT Simulations

Peng

Liu

2020

Symmetry

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Coal is often coated by kaolinite in flotation, leading to a decrease in the quality of clean coal. The structure of the mineral determines its properties and flotation behavior. Therefore, to remove the kaolinite from coal efficiently, the difference in mineralogical characteristics between non-coal and coal kaolinite were analyzed using advanced instruments. The experiment results showed that, due to the substitution of the C atom for Si atom, the interplanar spacing of the kaolinite (001) surface became small with C-O-C, Al-O-C, and C-O-Si covalent bonds formed instead of Al-O-Si and Si-O-Si bond. Based on this, the models of monolayer and bilayer coal kaolinite (001) surfaces were built and the structure difference was compared through DFT calculation. The calculation results showed that the silicon atom of the kaolinite Si-O-(001) surface was easier to be doped by carbon atoms with external energy as the interplanar spacing of the kaolinite (001) surface decreased with the increase in doped carbon atoms (7.15440 Å→7.11859 Å→7.10902 Å→7.10105 Å). The structural difference between non-coal kaolinite and coal kaolinite were compared from the view of the experiment and quantum chemistry, which provides an important theory for subsequent research on the properties of coal kaolinite and its further processing and utilization.

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Research on the Effect of Carbon Defects on the Hydrophilicity of Coal Pyrite Surface from the Insight of Quantum Chemistry

Cited by 7 publications

References 20 publications

DFT Study into the Influence of Carbon Material on the Hydrophobicity of a Coal Pyrite Surface

DFT Study into the Influence of Carbon Material on the Hydrophobicity of a Coal Pyrite Surface

The Effect of Carbon Defects in the Coal–Pyrite Vacancy on the Electronic Structure and Optical Properties: A DFT + U Study

Study on the Crystal Structure of Coal Kaolinite and Non-Coal Kaolinite: Insights from Experiments and DFT Simulations

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