Experimental and molecular dynamics investigations of the effects of ionic surfactants on the wettability of low-rank coal

Gan, Jian; Wang, Deming; Xiao, Zhongmin; Wang, Yanan; Zhang, Kang; Zhu, Xiaolong; Li, Shuailong

doi:10.1016/j.energy.2023.127012

Cited by 23 publications

(5 citation statements)

References 47 publications

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“…The ability of surfactants to modify the interfacial properties of coal dust is an element in dust elimination, and the influence of anionic, nonionic, and cationic surfactants on the microstructure and water injection efficiency is widely described. – However, chemical surfactants are harmful to its environment, which is not the original intention of green dust removal, , although they can effectively ameliorate the wettability of coal. Therefore, more scholars turn their attention to green and environmentally friendly surfactants. , Biosurfactants have the advantages of lower critical micelle concentration, nontoxic, biodegradable, and environmentally compatible characteristics. , Singh and Tripathi used rhamnolipids to degrade the coal components, converting the coal components in situ into methane .…”

Section: Introductionmentioning

confidence: 99%

Effect of Sophorolipid Adsorption on the Coal Microstructure: Experimental and Wettability Mathematical Model Discussion

Wang,

Zheng,

Jiang

et al. 2023

Langmuir

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Green biosurfactants are emerging as a promising area of research. However, there is a limited focus on the adsorption and wetting characteristics of biosurfactants on coal dust. This study explores the effects of sophorolipid (SL) biosurfactants on the microstructure and wettability of different coalification degree coal. The microstructure parameters of SL adsorbed on coal dust were measured using a surface tensiometer, contact angle analyzer, and particle size analyzer. The results indicate that SL has the lowest critical surface tension, leading to a 9.25°decrease in the contact angle for low-rank bituminous coal (YZ-LRBC). Furthermore, SL significantly altered the particle size distribution of lignite (NM-LC) and YZ-LRBC. The pore size structure of SL-infiltrated coal dust was quantified using a specific surface area analyzer, revealing a decrease in the specific surface area and an increase in the average pore size. The infrared analysis demonstrated that SL permeation significantly increased the percentage of hydrophilic functional groups (hydroxyl structures) while reducing the hydrophobic functional groups (aliphatic hydrocarbon and aromatic structure). Based on the measured microstructure parameters, a regression equation for contact angle was established: [contact angle (°)] = 73.800 − 0.860 × [D10 (nm)] + 4.280 × [specific surface area (m 2 /g)]. Notably, the characteristic particle size D10 had a significant negative effect on the contact angle, while the specific surface area had a significant positive effect. These findings provide a theoretical foundation for the application of biosurfactants in water injection to reduce dust and improve the wetting efficiency.

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Section: Introductionmentioning

confidence: 99%

Effect of Sophorolipid Adsorption on the Coal Microstructure: Experimental and Wettability Mathematical Model Discussion

Wang,

Zheng,

Jiang

et al. 2023

Langmuir

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“…In summary, the contact angle always increases with increasing pressure, and the most significant increase was in the CO 2 environment, while the contact angle changed the least in the He environment. The increase in contact angle implies a weakening of coal wettability. , Preliminary analysis suggests that in CO 2 and N 2 environments, the coal-water contact angle is affected by both gas adsorption and gas pressure and therefore changes more significantly compared to He because coal adsorbs CO 2 and N 2 . Additionally, the contact angle increase differs due to the difference in coal’s ability to adsorb the two gases.…”

Section: Results and Analysismentioning

confidence: 99%

“…The increase in contact angle implies a weakening of coal wettability. 16 , 17 Preliminary analysis suggests that in CO 2 and N 2 environments, the coal-water contact angle is affected by both gas adsorption and gas pressure and therefore changes more significantly compared to He because coal adsorbs CO 2 and N 2 . Additionally, the contact angle increase differs due to the difference in coal’s ability to adsorb the two gases.…”

Section: Results and Analysismentioning

confidence: 99%

Study on Coal Wettability under Different Gas Environments Based on the Adsorption Energy

Ding

Wei

et al. 2023

ACS Omega

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Coal seam water injection is a kind of comprehensive prevention and control measure to avoid gas outburst and coal dust disasters. However, the gas adsorbed in the coal seriously influence the coal-water wetting effect. With the deepening of coal seam mining, the gas pressure also gradually increases, but there is still a lack of in-depth understanding of the coal-water wetting characteristics under the high-pressure adsorbed gas environment. Therefore, the mechanism of coal-water contact angle under different gas environments was experimentally investigated. The coal-water adsorption mechanism in pre-absorbed gas environment was analyzed by molecular dynamics simulation combined with FTIR, XRD, and 13C NMR. The results showed that the contact angle in the CO2 environment increased most significantly, with the contact angle increasing by 17.62° from 63.29° to 80.91°, followed by the contact angle increasing by 10.21° in the N2 environment. The increase of coal-water contact angle in the He environment is the smallest, which is 8.89°. At the same time, the adsorption capacity of water molecules decreases gradually with increasing gas pressure, and the total system energy decreases after the coal adsorbs gas molecules, leading to a decrease in the coal surface free energy. Therefore, the coal surface structure tends to be stable with rising gas pressure. With the increase in environmental pressure, the interaction between coal and gas molecules enhances. In addition, the adsorptive gas will be adsorbed in the pores of coal in advance, occupying the primary adsorption sites and thus competing with the subsequent water molecules, resulting in a decline of coal wettability. Moreover, the stronger the adsorption capacity of gas, the more obvious the competitive adsorption of gas and liquid, which further weakens the wetting capacity of coal. The research results can provide a theoretical support for improving the wetting effect in coal seam water injection.

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“…In the meantime, surface tension is also one of the important factors that affect the wettability of solutions. It is generally acknowledged that the lower the surface tension is, the better the wettability of solutions . Therefore, variation of the surface tension of SiO 2 –H 2 O nanofluids was tested to quantitatively analyze the time-varying characteristics of the stability and wettability of the SiO 2 –H 2 O nanofluids.…”

Section: Methodsmentioning

confidence: 99%

“…It is generally acknowledged that the lower the surface tension is, the better the wettability of solutions. 53 Therefore, variation of the surface tension of SiO 2 −H 2 O nanofluids was tested to quantitatively analyze the time-varying characteristics of the stability and wettability of the SiO 2 −H 2 O nanofluids. An SKW-200A surface tension meter was adopted in the tests, the measurement range of which was 0.1−199.9 mN/m.…”

Section: Ph Testsmentioning

confidence: 99%

Study of Time-Varying Laws of Stability and Wettability of SiO₂–H₂O Nanofluids with Different Particle Sizes

Zhao,

Tian,

Xie

et al. 2023

Ind. Eng. Chem. Res.

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It has been proven that SiO2–H2O nanofluids have great application potential for water injection in coal seams. To explore the influences of the particle size on the stability and wettability of SiO2–H2O nanofluids, sedimentation observation of nanoparticles (NPs), viscosity tests, pH tests, surface tension tests, and contact angle tests were performed for SiO2–H2O nanofluids with different particle sizes. The research shows that the larger the particle size of SiO2 NPs, the more obvious the aggregation and sedimentation of NPs. The smaller the particle size of SiO2 NPs is, the lower the surface tension and contact angle of the SiO2–H2O nanofluids. As time goes on, SiO2–H2O nanofluids successively show time-varying characteristics in the low stability stage, moderate stability stage, and high stability stage. Therein, the low stability stage is the optimal period for enhancing the water injection in coal seams by nanofluids. The research provides theoretical support for using SiO2–H2O nanofluids to enhance water injection in coal seams.

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Experimental and molecular dynamics investigations of the effects of ionic surfactants on the wettability of low-rank coal

Cited by 23 publications

References 47 publications

Effect of Sophorolipid Adsorption on the Coal Microstructure: Experimental and Wettability Mathematical Model Discussion

Effect of Sophorolipid Adsorption on the Coal Microstructure: Experimental and Wettability Mathematical Model Discussion

Study on Coal Wettability under Different Gas Environments Based on the Adsorption Energy

Study of Time-Varying Laws of Stability and Wettability of SiO₂–H₂O Nanofluids with Different Particle Sizes

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Experimental and molecular dynamics investigations of the effects of ionic surfactants on the wettability of low-rank coal

Cited by 23 publications

References 47 publications

Effect of Sophorolipid Adsorption on the Coal Microstructure: Experimental and Wettability Mathematical Model Discussion

Effect of Sophorolipid Adsorption on the Coal Microstructure: Experimental and Wettability Mathematical Model Discussion

Study on Coal Wettability under Different Gas Environments Based on the Adsorption Energy

Study of Time-Varying Laws of Stability and Wettability of SiO2–H2O Nanofluids with Different Particle Sizes

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Study of Time-Varying Laws of Stability and Wettability of SiO₂–H₂O Nanofluids with Different Particle Sizes