Molecular Dynamics Simulation For Carbon Nanotube Membrane Separating Li(Ⅰ)/Mg(Ⅱ)

Recent years, electronic products have constantly appeared,and applications of lithium resource have become more and more. How to separate Li+and Mg2+has become the focus of academic research.Many studies have found that carbon nanotubes’(CNTs) nanoscale pore is similar with biological ion channels,and has a special separation for different ions.In this paper,using molecular dynamics simulation,the conductance,potential mean force(PMF),radial and axial density distribution, and transporting trajectories for Li+and Mg2+in different diameter carbon nanotubes is explored."Armchair" carbon nanotube CNTs(7,7)、 CNTs(8,8)、 CNTs(9,9) CNTs(10,10、 CNTs(11,11) is used to establish continuous membranes of carbon nanotubes with3D periodic boundary conditions.The membranes are dissolved in solutions with250mmo1/L LiCl or MgCl2.Molecular dynamics simulation is used to research the conductivity of Li+and Mg2+in nanotube membrane.In the simulation,the permeability for Li+and Mg2+of different diameters is studied, and the potential mean force for both ions when they enter the nanotube is detected.The radial and axial density distribution of the two ions inside the carbon nanotube and the trajectory of the individual ions within the nanotube is explored. The results show that CNTs(9,9) can separate the two ions effectively;and both ions are not through CNTs(7,7) and CNTs(8,8); and both ions can pass through CNTs(10,10) and CNTs(11,11),but carbon nanotubes have different ion selectivity.What’s more,one end of CNTs(10,10) is modified different functional groups,and the influence of different groups for ions regarding permselective.CNTs(10,10) is choosed based on both ions selectivity and flux,and the conductivity of ions in CNTs(10,10) functioned by varying amounts of-COO-and-NH3+on one end is explored.The cases include:two-COO-,four-COO-,eight-COO-,two-NH3+,four -NH3+,one-COO-and one-NH3+.The influence on ion flux,PMF for ions entering nanotube,radial and axial density function,and ions transporting trajectories of different modified carbon nanotubes is investigated.The results show that ion selectivity of CNTs(10,10) is improved, and modified CNTs(10,10) can separate Li+and Mg2+effectively.Fluxes for both ions decrease when add charged groups on CNTs. Within the scope of the simulation, flux of Mg2+in modified nanotube is0,and the effect on Li+and Mg2+separation in nanotube modified by one-COO-and one-NH3+is the best.The fluxes of Li+in nanotubes with two-COO" and four-COO-have a little difference.Both the two ions can’t pass the nanotubes added eight-COO-groups and four-NH3+groups.In nanotubes with different charged groups,PMF, radial and axial density distributions and transporting trajectories of the two ions have their respective characteristics.The possibility of carbon nanotube membrane separating Li+and Mg2+is basically studied by molecular dynamics simulation.The results show that carbon nanotube is respected used as a membrane material for lithium extraction from salt lake brine.It’s expected to provide theoretical reference and technical support for effectively exploring lithium resource that studying different diameter carbon nanotube separating Li+and Mg2+,and different charged groups modified nanatube separating Li+and Mg2+...