摘要
黏土矿物是一类具有层状结构的硅酸盐矿物。土水相互作用对土体许多宏观力学响应、物质运移和传导起重要影响。现有的实验技术和手段即很难在物理上微观探测黏土从绝对干燥至含微量水分子的吸附过程,也很难实现黏土对放射性核素吸附过程的跟踪。使用分子动力学模拟对黏土矿物的水化性质及对放射性污染物吸附性能进行研究。以蛭石、高岭土及蒙脱土三种黏土矿物为研究对象,通过晶层间距、自扩散系数、径向分布函数、吸附复合物结构等模拟测试结果对蛭石的水化性能和黏土对放射性核素的吸附行为阐述。最后,对分子动力学模拟技术在岩土工程的应用发展进行了展望。
The aim of the present paper is to investigate the application of molecular dynamics simulation methods on the micro properties of clay minerals. The evolution of the basal spacing of vermiculite with the increasing water content under the influence of temperature is illustrated. The diffusion behavior of water is much faster than that of Na+at the same hydrated state.Moreover, the evolution of diffusion of water and cations shows a great increase in the thresholds of each hydrated state and then a decrease till the next hydrated state. The adsorption mechanisms of radionuclide species onto defected kaolinite and substituted montmorillonite(001) surface in the presence of different counterions are studied. The thermodynamic behaviors of adhesion between the complexes and the MMT surface are calculated to evaluate the adsorption interaction. The complexes with the carbonate and covalent cations components exhibit a relative higher adhesion with the buffer material surface.
引文
[1]UDDIN M K.A review on the adsorption of heavy metals by clay minerals,with special focus on the past decade[J].Chemical Engineering Journal,2017,308:438-462.
[2]YILDIZ B,ERTEN H N,KIS M.The sorption behavior of C s+ion on clay minerals and zeolite in radioactive waste management:sorption kinetics and thermodynamics[J].Journal of Radioanalytical&Nuclear Chemistry,2011,288(2):475-483.
[3]LI Yu-xiang,QIAN Guang-ren YI Fa-cheng,et al.Study on rich alumina alkali activated slag clay minerals cementitious materials for immobilization of radioactive waste[J].Chinese Journal of Nuclearence&Engineering,1999,19(4):379-384.
[4]DAI Q.Application of clay minerals in waste water treatment and the development prospect.Express Information of Mining Industry,2005.
[5]ANASTáCIO A S.Characterization of a redox-modified clay mineral with respect to its suitability as a barrier in radioactive waste confinement[J].Applied Clay Science,2008.39(3/4):172-179.
[6]BOTAN A.How electrostatics influences hydrodynamic boundary conditions:poiseuille and electro-osmostic flows in clay nanopores[J].Physica B Condensed Matter,2017,117(2):193-198.
[7]KERISIT S,LIU C.Molecular dynamics simulations of uranyl and uranyl carbonate adsorption at aluminosilicate surface[J].Enviromeutal Science&Technology,2014,48:3899.
[8]ZHANG L.Hydration and mobility of interlayer ions of(Nax,Cay)-montmorillonite:a molecular dynamics study[J].Journal of Physical Chemistry C,2014,118(51):29811-29821.
[9]BRICE F N W,ANDREY G,KALINICHEV A G.Structural arrangements of isomorphic substitutions in smectites:molecular simulation of the swelling properties,interlayer structure,and dynamics of hydrated Cs-montmorillonite revisited with new clay models[J].J Phys Chem C,2014,118(24):12758-12773.
[10]VIRGINIE M.Water dynamics in hectorite clays:influence of temperature studied by coupling neutron spin echo and molecular dynamics[J].Environmental Science&Technology,2011,45(7):2850-2855.
[11]HOLMBOE M,BOURG I C.Molecular dynamics simulations of water and sodium diffusion in smectite interlayer nanopores as a function of pore size and temperature[J].Chemical Society Reviews,2014,42(8):3628-3646.
[12]GREATHOUSE J A,CYGAN R T.Water structure and aqueous uranyl(VI)adsorption equilibria onto external surfaces of beidellite,montmorillonite,and pyrophyllite:?results from molecular simulations[J].Environmental Science&Technology,2006,40(12):3865-3870.
[13]TAMBACH T J,BOEK E S,BEREND S.Molecular order and disorder of surfactants in clay nanocomposites[J].Physical Chemistry Chemical Physics Pccp,2006,8(23):2700-2702.
[14]CYGAN R T,LIANG J J,KALINICHEV A G.Molecular models of hydroxide,oxyhydroxide,and clay phases and the development of a general force field[J].Journal of Physical Chemistry B,2004,108(4):1255-1266.
[15]ZHENG Y,ZAOUI A,SHAHROUR I.A theoretical study of swelling and shrinking of hydrated Wyoming montmorillonite[J].Applied Clay Science,2011,51(1/2):177-181.
[16]PLIMPTON S.Fast parallel algorithms for short-range molecular dynamics[J].J Comp Phys,1995,117:1-19.
