Degradation of mechanical and microporous properties of coal subjected to long-term sorption

• Long-term sorption significantly degraded the mechanical and microporous properties of coal. • Long-term CO 2 sorption can pulverize and destroy coal samples without loading. • The changes in pore structure induced by long-term sorption are primarily in the micropore and macropore ranges. Both coal-gas outburst (hereafter abbreviated as ‘outburst’) and CO 2 sequestration are subjected to and significantly affected by a long-term sorption process. In the present paper, to explore the influence of long-term sorption on the mechanical and porous characteristics of coal, long-term sorption tests were performed using coal samples from the Panzhihua coalmine. The changes in mechanical properties after sorption were examined. Furthermore, the pore-structure characteristics were analyzed through low-temperature nitrogen isothermal adsorption (LT-N 2 IA), scanning electron microscopy (SEM), and fractal theory. The results indicated that the long-term sorption significantly degraded the mechanical and microporous properties of coal. The adsorptive property of coal was degraded with the reductions in specific surface area (SSA) and pore volume and the loss of micropores, which was attributed to pores collapse and necks blocking. After long-term sorption, the surface roughness of the pores ( D 1 ) was increased, and their structural complexity ( D 2 ) was reduced. Additionally, long-term CO 2 adsorption had a more significant degradation effect than CH 4 , even destroying and pulverizing the coal samples. The findings of this study enhance our understanding of the mechanism underlying the fragmentation of the coal mass during outbursts, while may present challenges for CO 2 sequestration in coal seam.