微细煤与高岭石颗粒间的分子动力学模拟研究

Molecular dynamics simulation on interactions between fine particles of coal and kaolinite

掌握煤泥水中多组分微细颗粒间复杂的相互作用机制是解决煤泥聚团沉降、选择性分选及脱水困难的重要基础。为了探寻煤泥水中微细颗粒界面间微观作用机制,以煤泥水中主要微细颗粒煤和高岭石为研究对象,采用分子动力学(MD,Molecular Dynamics)方法对水溶液中微细煤与高岭石颗粒间相互作用进行了模拟研究,模拟计算了高岭石颗粒界面处煤大分子空间平衡构型、原子浓度分布曲线及水分子自扩散系数、原子间径向分布函数的影响。MD模拟结果表明:煤大分子在高岭石(001)面及(001)面吸附动力学平衡后,能够排开周围水分子与高岭石表面发生了稳定吸附作用,同时煤大分子中的部分苯环结构近似平行于高岭石表面,即苯环结构与高岭石不同表面间都存在较强的静电引力作用;煤大分子中的含氧官能团能够与高岭石不同表面形成氢键,但氢键在煤大分子与高岭石表面间相互作用中所提供的贡献非常小;存在水分子竞争吸附的情况下,煤大分子更容易与高岭石(001)面发生稳定吸附。为验证分子动力学模拟结果的正确性,采用扫描电子显微镜(SEM)对不同粒度级的煤与高岭石颗粒间微观作用进行观测分析,结果表明:在水溶液环境中,微细煤与高岭石颗粒间能够发生相互吸引作用,使得两者吸附在一起难以分开。水溶液中微细煤与高岭石颗粒间的微观作用机理主要是煤中含氧官能团与高岭石表面形成的氢键作用及煤中苯环与高岭石表面间的静电引力作用,其中以苯环与高岭石表面间的静电引力作用为主导。

A good understanding of the complex interaction mechanism between multi-component fine particles in coal slurry is an important foundation for solving the problem on the agglomeration settlement,selective sorting and dewatering of coal slurry.In order to explore the microscopic interaction mechanism between fine particles in coal slurry,the main fine particles of coal and kaolinite in coal slurry were taken as the research objects,and the interactions between fine particles of coal and kaolinite in aqueous were investigated using molecular dynamics(MD)simulations.The effects of spatial equilibrium configuration of coal macromolecule,atomic concentration profiles,self-diffusion coefficient of water molecules,and atomic radial distribution function on kaolinite/water interface were simulated and analyzed.The results of MD simulation show that the coal macromolecule can push out the water molecules surrounding and stably adsorb on kaolinite surface,at the same time,some of the benzene ring structures in coal macromolecule are approximately parallel to kaolinite surfaces,namely that there is a strong electrostatic attraction between the benzene ring structures and different kaolinite surfaces.The oxygen-containing functional groups in coal macromolecule can form hydrogen bonds with different kaolinite surfaces,but the hydrogen bonds provide little contribution in the interaction between coal macromolecule and kaolinite surface.In the presence of competing adsorption with water molecules,coal macromolecule is more susceptible to stable adsorption on kaolinite(001)surface.In order to verify the accuracy of the molecular dynamic simulation results,the microscopic interactions between fine particles of coal and kaolinite with different sizes were observed by the scanning electron microscopy(SEM).The results indicate that the attraction interaction between fine kaolinite and coal particles can occur in the aqueous,which makes them adsorption together and difficult to be separated.The microscopic mechanism between the fine particles of coal and kaolinite in aqueous is mainly the hydrogen-bond interaction between oxygen-containing functional groups in coal and kaolinite surface and the electrostatic attraction between the benzene rings in coal and kaolinite surface,wherein the electrostatic attraction between the benzene rings and kaolinite surface is dominant.