Exploring the wetting mechanism of surfactants for coals based on molecular simulations

Authors

TONG Yanjun, Coal Mining and Utilization Research Institute of Pingdingshan Tian’an Coal Industry Co., Pingdingshan 467000, ChinaFollow
YANG Zundong, College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, ChinaFollow
SONG Jie, School of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China
LI Yongcheng, School of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China
LIU Yiting, College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China

Abstract

With a gradual increase in the depth and mechanization degree of coal mining, secondary explosions of gas and coal dust have become increasingly severe. Chemical dust suppressants such as surfactants can reduce these explosions by effectively inhibiting the generation and diffusion of coal dust. To explore the inhibition mechanism of nonionic surfactants for hydrophobic coal dust, this study analyzed the basic physicochemical properties of typical hydrophobic coal dust at a depth of 1050 m using FT-IR, XRF, and XRD. This study built a molecular structure model of coal dust by combining test techniques such as EA, XPS, and ¹³C NMR. It also investigated the equilibrium adsorption configuration and molecular spatial distribution of the water-surfactant-coal wetting adsorption systems by establishing a molecular model. Then, this study designed an experiment to examine the compositions of the surface free energy of coal dust before and after surfactant adsorption, followed by verifying and discussing the wetting adsorption mechanism of surfactants on coal dust interfaces. The results show that surfactants can form an effective directional adsorption layer, which is tight and has a high coverage degree, on the surface of hydrophobic coal dust. The hydrophobic structure of the coal dust surface is covered by the hydrophobic tail chains of surfactants, with the hydrophilic head groups facing the aqueous phase, increasing the polar components of surface free energy of the coal dust. As a result, the hydrophobic coal dust surfaces become hydrophilic. The results of this study can provide theoretical guidance and a reference for efficient dust suppression in coal mining.

Keywords

coal dust, wettability, molecular simulation, nonionic surfactant, surface free energy

DOI

10.12363/issn.1001-1986.23.03.0110

Recommended Citation

TONG Yanjun, YANG Zundong, SONG Jie, et al. (2023) "Exploring the wetting mechanism of surfactants for coals based on molecular simulations," Coal Geology & Exploration: Vol. 51: Iss. 8, Article 15.
DOI: 10.12363/issn.1001-1986.23.03.0110
Available at: https://cge.researchcommons.org/journal/vol51/iss8/15

Reference

[1] GAO Mingzhong,ZHANG Zhilong,YIN Xiangang,et al. The location optimum and permeability−enhancing effect of a low–level shield rock roadway[J]. Rock Mechanics and Rock Engineering,2018,51(9):2935−2948.

[2] GAO Mingzhong，XIE Jing，GUO Jun，et al. Fractal evolution and connectivity characteristics of mining−induced crack networks in coal masses at different depths[J]. Geomechanics and Geophysics for Geo–Energy and Geo–Resources，2021，7(1)：1−15.

[3] GAO Mingzhong,ZHANG Jianguo,LI Shengwei,et al. Calculating changes in fractal dimension of surface cracks to quantify how the dynamic loading rate affects rock failure in deep mining[J]. Journal of Central South University,2020,27(10):3013−3024.

[4] GAO Mingzhong,XIE Jing,GAO Yanan,et al. Mechanical behavior of coal under different mining rates:A case study from laboratory experiments to field testing[J]. International Journal of Mining Science and Technology,2021,31(5):825−841.

[5] GAO Mingzhong,HAO Haichun,XUE Shouning,et al. Discing behavior and mechanism of cores extracted from Songke–2 well at depths below 4,500 m[J]. International Journal of Rock Mechanics and Mining Sciences,2022,149:104976.

[6] 周福宝,李建龙,李世航,等. 综掘工作面干式过滤除尘技术实验研究及实践[J]. 煤炭学报,2017,42(3):639−645.

ZHOU Fubao,LI Jianlong,LI Shihang,et al. Experimental investigation and application of dry–type filtering dust collection technology in fully mechanized excavation face[J]. Journal of China Coal Society,2017,42(3):639−645.

[7] 张建国,李红梅,刘依婷,等. 煤尘微细观润湿特性及抑尘剂研发初探:以平顶山矿区为例[J]. 煤炭学报,2021,46(3):812−825.

ZHANG Jianguo,LI Hongmei,LIU Yiting,et al. Micro–wetting characteristics of coal dust and preliminary study on the development of dust suppressant in Pingdingshan mining area[J]. Journal of China Coal Society,2021,46(3):812−825.

[8] 金龙哲. 我国作业场所粉尘职业危害现状与对策分析[J]. 安全,2020,41(1):1−6.

JIN Longzhe. The occupational hazards and strategy analysis of dust exposure in workplace in China[J]. Safety & Security,2020,41(1):1−6.

[9] 高明忠,王明耀,谢晶,等. 深部煤岩原位扰动力学行为研究[J]. 煤炭学报,2020,45(8):2691−2703.

GAO Mingzhong,WANG Mingyao,XIE Jing,et al. In–situ disturbed mechanical behavior of deep coal rock[J]. Journal of China Coal Society,2020,45(8):2691−2703.

[10] SINGH B P. The role of surfactant adsorption in the improved dewatering of fine coal[J]. Fuel,1999,78(4):501−506.

[11] CRAWFORD R J,MAINWARING D E. The influence of surfactant adsorption on the surface characterisation of Australian coals[J]. Fuel,2001,80(3):313−320.

[12] KILAU H W,PAHLMAN J E. Coal wetting ability of surfactant solutions and the effect of multivalent anion additions[J]. Colloids and Surfaces,1987,26:217−242.

[13] 阎杰. 基于表面特性的煤尘润湿性质研究[D]. 北京：中国矿业大学(北京)，2019.

YAN Jie. Study on wettability of coal dust based on its surface properties[D]. Beijing：China University of Mining & Technology (Beijing)，2019.

[14] 胡强. 表面活性离子液体影响煤尘润湿性的实验研究[D]. 徐州：中国矿业大学，2020.

HU Qiang. Experimental study on effect of surface active ionic liquids on coal dust wettability[D]. Xuzhou：China University of Mining & Technology，2020.

[15] GUTIERREZ–RODRIGUEZ J A,PURCELL R J,APLAN F F. Estimating the hydrophobicity of coal[J]. Colloids and Surfaces,1984,12:1−25.

[16] HU Yingying,ZHANG Qingtao,ZHOU Gang,et al. Influence mechanism of surfactants on wettability of coal with different metamorphic degrees based on infrared spectrum experiments[J]. ACS omega,2021,6(34):22248−22258.

[17] REN Xiaoyuan，YANG Zhiyuan，QU Shicun，et al. The effect of sodium dodecyl sulphate (SDS) on wettability of different coals[J]. Advanced Materials Research，2013，2482(734/735/736/737)：513–516.

[18] 杨兆中,韩金轩,张健,等. 泡沫压裂液添加剂对煤层甲烷扩散影响的分子模拟[J]. 煤田地质与勘探,2019,47(5):94−103.

YANG Zhaozhong,HAN Jinxuan,ZHANG Jian,et al. Molecular simulation of the influence of foam fracturing fluid additives on coalbed methane diffusion[J]. Coal Geology & Exploration,2019,47(5):94−103.

[19] 孙致学,闵成,张婉露,等. CO₂/N₂二元气体对甲烷在煤中吸附影响的分子模拟研究[J]. 煤田地质与勘探,2022,50(3):127−136.

SUN Zhixue,MIN Cheng,ZHANG Wanlu,et al. Molecular simulation of the effect of CO₂/N₂ binary gas on methane adsorption in coal[J]. Coal Geology & Exploration,2022,50(3):127−136.

[20] 孟筠青,张硕,曹子豪,等. 屯留矿煤分子孔隙重构及其表征与分析[J]. 煤炭学报,2022,47(增刊1):160−170.

MENG Junqing,ZHANG Shuo,CAO Zihao,et al. Insight on coal molecular–scale pore reconstruction of Tunliu mine and its characterization and analysis[J]. Journal of China Coal Society,2022,47(Sup.1):160−170.

[21] TANG Honghu,ZHAO Lihua,SUN Wei,et al. Surface characteristics and wettability enhancement of respirable sintering dust by nonionic surfactant[J]. Colloids and Surfaces A:Physicochemical and Engineering Aspects,2016,509:323−333.