Effect of SDS modified coal microstructure on wettability and methane adsorption

Adding ionic solution can improve the microstructure of coal, inhibit the gas absorption capacity and effectively reduce the outburst risk. In this paper, the high-quality anthracite in Jincheng, Shanxi Province is selected as the research object, and sodium dodecyl sulfate (SDS) ion solutions with different concentrations are configured. Combined with infrared spectroscopy, mercury intrusion test, the change features of coal microstructure after soak by SDS solutions with different concentrations are studied, and the variations of the contact angle and adsorption constant of samples before and after modification are tested. The paper further discusses the influence of changing coal microstructure on the wettability and gas adsorption. The experimental results show that SDS can modify the microstructure of coal to some extent: –OH, -CO, and COC increase obviously, macropores and mesopores increase, micropores and ascospores decrease. After SDS modification, the contact angle and the maximum gas adsorption a decrease linearly as oxygen groups and vtotal increase. In addition, the hydrophilic groups in the coal body increase significantly, which makes it easier to attract water molecules, and strengthen the pore connectivity and coal wettability. The polar oxygen-containing functional group molecules of coal also increase, occupying the adsorption site of non-polar molecular methane, and the adsorption site (micropore) decreases. The conclusion of this paper establishes theoretical foundation for the exploitation of coal seam gas resources. Adding SDS can directionally ameliorate coal microstructure, and then regulate the coal wettability and its ability to adsorb methane, to utilize coal resources safely and efficiently.