煤泥水中微细煤与高岭石颗粒间微观作用的密度泛函研究

Density Function Study on Microscopic Interactions Between Fine Particles of Coal and Kaolinite in Coal Slurry Water

煤和高岭石是高泥化煤泥水中的主要微细颗粒,对煤泥水沉降有着显著的影响。本工作构建了水分子及四种不同煤结构单元的结构模型,采用密度泛函理论(Density functional theory,DFT)分别对单一水分子/不同煤结构单元在高岭石表面吸附及煤结构单元与水分子在高岭石表面的竞争吸附进行模拟计算,并初步探讨了煤泥水中微细煤与高岭石颗粒间的微观作用机理。DFT计算结果表明:四种不同煤结构单元均能够通过氢键作用及静电引力作用稳定吸附在高岭石表面,且吸附能都低于单一水分子在高岭石相应表面的吸附能;当水分子参与竞争吸附时,会在一定程度上抑制煤结构单元在高岭石表面的吸附,同时煤结构单元能够排开周围水分子以摆脱其占位影响,并与高岭石表面发生稳定吸附;煤泥水中微细煤与高岭石颗粒间的微观作用主要是煤结构单元中含氧官能团与高岭石表面形成的氢键作用和煤结构单元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。

Fine particles of coal and kaolinite are primary fine particles in high muddied coal slurry water and have significant influence on the sedimentation of coal slurry water.The structural models of water molecule and four different coal structural units were constructed.The density functional theory(DFT)method was used to calculate the adsorption of single water molecule/different coal structural units on kaolinite surface and the competitive adsorption of coal structural units and water molecule on kaolinite surface,respectively.And the microscopic mechanism of micro-coal and kaolinite particles in coal slurry water was preliminarily discussed.The results of DFT calculation show that these four different coal structural units can be stably adsorbed on the kaolinite surface by hydrogen bonding and electrostatic attraction,and the adsorption energies are lower than that of single water molecule adsorption on the corresponding surface of kaolinite.In the case of competing adsorption with water molecule,the water molecule inhibit the adsorption of coal structural units on kaolinite surface to a certain extent,and the coal structural units are capable of flushing out the surrounding water molecule to get rid of its steric effect and stably adsorbing on kaolinite surfaces at the same time.The microcosmic mechanism of the interactions between fine particles of coal and kaolinite is mainly due to the hydrogen bonding between the oxygen-containing functional groups in the coal structural units and the kaolinite surfaces and the electrostatic attraction between the benzene rings in the coal structure units and kaolinite surfaces,in which the electrostatic attraction between the benzene rings and the kaolinite surfaces is dominant.