Absorption of methane by clay minerals in coal gangue

Clay minerals are the most important minerals in coal seams,and the compound of clay minerals and organic matter can improve the adsorption capacity of clay minerals on CH4 ,so the adsorption of clay minerals cannot be ig- nored. The coal gangue with the high content of clay minerals and pure clay samples were characterized by X-ray dif- fraction,infrared spectroscopy and scanning electron microscope,and also total organic carbon ( TOC),the type and maturity of organic matter were analyzed. Meanwhile,the results of the pore diameter,pore volume and specific surface area were combined to analyze the main factors influencing the clay minerals adsorption capacity by comparing the CH4 adsorption of the pure clay minerals with the clay mineral from coal gangue. The results show that the adsorption capacity of different clay minerals is as following:ammonium illite > kaolinite > illite > phlogopite. Moreover,the sur- face area cannot fully reflect the characteristics of CH4 adsorption,and the interlayer and other factors of clay minerals should also be taken into consideration. Meanwhile,the clay mineral samples from coal gangue with high TOC have more micro pores than the pure clay minerals samples. The micro pores,especially those less than 6 nm,play a key role in the increase of the specific surface area,furthermore enhance the CH4 adsorption capacity. By analyzing the contri- bution rate of CH4 adsorption by clay minerals,it was found that clay minerals and their complexes have high CH4 ad- sorption capacity and contributions ratio,especially in the coal gangue.