Effect of the surface oxygen groups on methane adsorption on coals

► We modified one coal with H2O2, (NH4)2S2O8 and HNO3 respectively, to prepare coal samples with different surface properties. ► The oxygen groups on coal surface were characterized by XPS. ► The textures of the coal samples were investigated by N2 adsorption at 77 K. ► The adsorption behaviors were measured by volumetric method. ► There was a negative correlation between methane saturated adsorption capacity and the Ototal/Ctotal.