•The trends of monomer and mixed solutions with varying concentrations were studied in binary and ternary systems.•A quaternary system was established to elucidate the micro wetting mechanism of ...composite agents on bituminous coal.•The mechanism of interaction between SDBS and XTG molecules was revealed.
To study the interaction process of sodium dodecyl benzene sulfonate (SDBS) and xanthan gum (XTG) molecules in a composite dust suppressant and its influence mechanisms on the wettability and agglomeration characteristics of bituminous coal dust, Material Studio software was used to establish water–XTG binary system models, water–SDBS–XTG ternary system models, and water–SDBS–XTG–coal quaternary system models. Then, molecular dynamics simulations were performed through angular distribution, relative concentration distribution, mean squared displacement (MSD), and interaction energy to study the interaction mechanism between SDBS and XTG and the change in wettability of coal dust. Results showed that the configuration in the binary system changed after stabilization, and SDBS transformed from a disordered state into a directional arrangement with the head group oriented toward the liquid phase and the tail group oriented toward the gas phase. In the ternary system, the head group of SDBS interacted with the XTG molecules, and the XTG wound into a helical structure, reducing the viscosity of the solution. With an increase in the number of SDBS molecules, the angle of the head group of SDBS and the tail chain of SDBS increased to 113.95°. The number of H bonds in the system increased from 1676 to 1697. In the quaternary system, the rate of change of the diffusion coefficient continuously increases. The absolute value of the interaction energy increased from 5920.48 kJ/mol to 9295.35 kJ/mol. The higher the concentration of SDBS, the better the adsorption effect, and the more stable the molecular configuration. The number of H bonds and the distribution area of the overlapping region between water and coal gradually increased, indicating that the larger the area where water molecules could penetrate into the coal molecules, the better the wetting effect on coal. This study reveals the intermolecular interaction process and the mechanisms of coal dust wetting and agglomeration in a composite dust suppressant. It provides theoretical support for the application of this composite dust suppressant.
•Growth characteristics of the mixed methanotrophic consortia are monitored in real time.•Methane oxidation characteristics of microorganisms are obtained.•The wetting characteristics of bacterial ...liquid on coal surface were studied.
In the process of coal mining, a large amount of methane is emitted into the atmosphere every year, which enhances the greenhouse effect of the atmosphere. Microbial methane oxidation technology provides a new idea for methane emission reduction and methane control in coal mines. To improve the environmental adaptability of microorganisms, mixed methanotrophic consortia were selected from the natural environment. During the growth process, microorganisms grew most vigorously in the 4th–10th days and peaked on the 7th day. Affected by microbial metabolism, the pH (potential of hydrogen) of the solution increased, and the ORP (oxidation–reduction potential) decreased, both of which were negatively correlated. The selected mixed methanotrophic consortia have extremely strong methane-oxidizing ability, the volume of methane gas decreased by 71.19 %. It is particularly important that the microorganisms still have a certain methane oxidation capacity, after which the oxygen in the device is exhausted. The results showed that the mixed methanotrophic consortia adjusted the population structure to adapt to the changes in the surrounding environment and continued to exert methane oxidation ability. The contact angle between the bacterial solution and coal sample surface was far lower than that of pure water and culture medium. Microorganisms adsorbed onto the surface of the coal sample through self-movement, greatly improving the contact ability between the bacterial solution and the coal sample. The retention of microorganisms in the coal sample was affected by the flow velocity and the particle size of the coal sample. A low flow velocity and large contact area can improve the contact efficiency of microorganisms on the coal surface. Mixed methanotrophic consortia have high application value and feasibility in coal mine methane emission reduction and underground methane treatment.
To improve the ability of water spray additives to wet coal dust, the compounding wetting characteristics of several nonionic and anionic surfactants on bituminous coal dust were studied, the surface ...tension, contact angle and the settling time of coal dust were measured. Results showed that the compounding of sodium dodecyl sulfate (SDS) and two other anionic surfactants exhibits an antagonism effect and reduces the wettability of water. The compounding of primary alcobol ethoxylate (JFC), ethylene glycol polyoxyethylene ether (PEG800) and the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) achieves the strongest synergistic effect at a mass ratio of 3:1:1. Furthermore, the infrared spectra of raw coal and coal treated with dust suppressant showed that the hydrophilicity of coal dust is improved after the treatment by dust suppressant. Finally, the synergistic effect mechanism of JFC, PEG800 and SDBS was explained from the perspective of molecular and hydrogen bond.
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•The wetting characteristics of noncationic surfactants on coal dust was studied.•A dust suppressant compounded by JFC, PEG800 and SDBS was proposed.•The hydrophilicity and hydrophobicity of coal dust before and after treatment with dust suppressant were analyzed.•The mechanism of synergistic wetting of coal dust by JFC, PEG800 and SDBS was analyzed.
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•The wettability of six types of the coal sample dust was evaluated.•With the metamorphic degree increase, the wettability shows a high-low-high trend.•Pore size is the main factor ...determining the wettability of coal dust (R2 = 0.96).•The wetting ability of anionic surfactant to coal dust is stronger than nonionic.
To select suitable surfactant as water-spray additive to improve dust suppression efficiency, six types of coal sample (lignite, long flame coal, non-caking coal, gas coal, coking coal, and anthracite) were selected from some typical mining areas in China, the influence of the physical chemistry characteristics of coal samples on the wetting ability of surfactants to the coals dust was investigated. Their proximate composition, ultimate content, chemical structure, surface morphology, pore structure parameters, and contact angle were determined. Three kinds of anionic surfactants – Sodium Alcohol Ether Sulphate (AES), Sodium Alpha-Olefin Sulfonate (AOS), Fatty Acid Methyl Esters Ethoxylate Sulfonate (FMES) – and one kind of nonionic surfactant – Coco Diethanolamide (CDEA) – were selected to carry out sedimentation experiments on the coal samples dust, to explore the main factors influencing the wettability of the coal samples dust. Among these factors, pore size is the main factor determining the wettability of coal dust, the contact angle decreases linearly (R2 = 0.96) with pore size increase. The experimental results demonstrate that the following factors produce correspondingly increased wettability: higher moisture content, lower carbon content, higher oxygen content, more oxygen-containing functional groups, and increased pore size. In addition, the wettability of the six types of the coal samples dust shows a high-low-high trend with metamorphic degree increase, lignite has the strongest wettability, and the coking coal with the highest degree of metamorphism in the selected bituminous coal sample has the weakest wettability. Moreover, compared with nonionic surfactants, anionic surfactants have stronger wetting ability, but the same anionic surfactants have different wetting abilities to coal dust with different metamorphic degrees. AOS has stronger wetting ability to the dust of long flame coal, non-caking coal, and anthracite; AES has stronger wetting ability to the dust of lignite and coking coal; and FMES has stronger wetting ability to the dust of gas coal. The research results provide a theoretical basis for different coal mines to select suitable surfactants as water-spray additives to improve dust suppression efficiency.
Micrometric foils of graphene oxide are prepared in the laboratory starting from water dispersed solution of graphene oxide at low concentration. Measurements on five physical properties have been ...performed in the foils of graphene oxide and reduced graphene oxide. The reduction is obtained thermally, using IR and UV laser irradiations and MeV helium ion beam irradiations at different fluence. The parameters such as the atomic composition, the mass density, the surface roughness, the wetting ability, and the electrical conductivity are investigated. This last parameter assumes different values for the pristine graphene oxide foils and for the reduced ones. Comparison of experimental measurements with the literature data and the results and discussion are presented.
The reduction of graphene oxide (GO) can be obtained using different techniques, such as thermal annealing, laser beam, and ionizing irradiations. Five important properties can modified by the GO reduction, such as the C/O atomic ratio, the mass density, the wetting ability, the surface roughness and the electrical conductibility, which increase depending on the level of obtained reduction.
Nowadays, Y2O3–Al2O3–SiO2 (YAS) glass joining is considered to be a promising scheme for nuclear-grade continuous silicon carbide (SiC) fiber reinforced SiC matrix composites (SiC/SiC). CaO has great ...potential for nuclear applications since it has low reactivity and low decay rate under nuclear irradiation. In this paper, the effect of CaO doping on the structure, thermophysical properties, and crystallization behavior of YAS glass was systematically studied. As the CaO doping content increased, the number of bridge oxygens and the viscosity at high temperatures reduced gradually. After heat treatment at 1400 °C, the main phases in YAS glass were β-Y2Si2O7, mullite, and SiO2 (coexistence of crystalline and glass phases), while that with 3.0% CaO doping turned into a single glassy phase under the same treatment conditions. Moreover, a structural model and the modification mechanism were proposed, which provided a theoretical basis for the subsequent component design and optimization.
Complex antioxidant enzyme inhibitor (SC), as an innovative technology was proposed, which mainly includes polyethylene glycol-Cu,Zn superoxide dismutase (PEG-SOD), Mn catalase (CAT) and sodium ...dodecyl sulfate (SDS). It exhibits excellent performance in inhibiting the low-temperature oxidation of coal. This study includes wettability of SC solution and the thermal characteristics of SC suppressing the self-heating of coal. For wettability of SC solution, it was found that the nuclei of the PEG polymer could adsorb hydrophilic groups of SDS to form an outer PEG polymer layer through chemical shift alterations, and the inner SDS tail groups were adsorbed at the hydrophobic coal sites, leading to an SC solution with excellent wetting ability on the coal surface. For the thermal characteristics analysis, the SOD and CAT contained in SC could quickly neutralize superoxide radicals through a disproportionation reaction below 90 °C; the PEG, with the thermoplastic properties of SC, could fuse to form a colloid that could wrap onto the coal surface to form a protective layer below 150 °C. Research results indicated, as for coal-SC, that chain propagation reactions were terminated, homolysis of chemical bonds to generate new free radicals was prevented, and the free radical concentration obviously decreased on the coal surface; the relative content of CO groups obviously decreased, that of CC/CH groups gradually increased, and those of CO/OCO and OCO groups remained almost constant with increasing temperature; oxygen adsorption was significantly reduced, leading to an obvious decrease in oxidation of active groups to form surface oxides.
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•Static-dynamic wetting characteristics of surfactant on coal dust was evaluated.•Adsorption mechanism of compound surfactant on coal dust surface was clarified.•Anionic-nonionic ...compound surfactants can show a significant synergism.
The compound surfactant has a synergistic effect on the wetting ability of coal dust. In the study, the wettability of compound surfactant on coal dust with different metamorphic degrees was studied from static wetting experiment, dynamic wetting experiment, and micro molecular simulation. The results showed that the contact angle of the anionic-nonionic compound surfactant solution on any coal sheet was significantly smaller than that of the single component, which was 14.04%～63.31% lower than that of the single component. The contact angle of the anionic-anionic compound surfactant on the six kinds of coal dust test pieces was not smaller than the contact angle of each single component, only a compromise of contact angle of single component. The dust suppression efficiency of the gas coal in 0.025 wt% fatty acid methyl esters ethoxylate sulfonate (FMES) and 0.025 wt% coconutt diethanolamide (CDEA) compound solution was the highest, which was 78.4%. Lignite coal, long flame coal, non-caking coal, coking coal, and anthracite all have the highest dust suppression efficiency when sprayed with 0.025 wt% sodium alcohol ether sulphate (AES) and 0.025 wt% CDEA, which were 91.53%, 88.24%, 85.7%, 73.25%, and 80.57%, respectively. For any metamorphic degree of coal sample dust, the anionic-nonionic compound surfactant shows obvious synergistic effect on improving the wettability of coal dust. Furthermore, when the surfactant is adsorbed on the surface of coal molecules, the concentration of water molecules on the surface of coal molecules is increased, the hydrophilicity of the solid–liquid interface is improved, and the water molecules are more intensely diffused on the surface of coal dust. And the absolute value of the adsorption energy of the surfactant on the surface of the coal dust is higher, and the more hydrogen bonds formed by the hydrophilic groups, the better the wettability of the coal dust surface.
