端基改性碳纳米管膜分离Li^+/Mg^(2+)的分子动力学模拟

Molecular Dynamics Simulation of Tip Functionalized Carbon Nanotube Membrane for Li^+/ Mg^(2+) Separation

通过向"扶手椅"型(10,10)碳纳米管一端添加不同数量的COO-和NH+3修饰基团建立连续的碳纳米管膜模型,利用分子动力学模拟的方法研究了80 MPa水压力下Li+和Mg2+在膜中的通量和密度分布并计算了两种离子进入修饰碳纳米管的平均力势。结果表明,恰当的修饰基团添加使(10,10)碳纳米管能够有效分离Li+和Mg2+。带电基团与离子间静电作用力所产生的束缚和排斥作用使离子在纳米管内通量下降,Mg2+在修饰纳米管中的通量均为0,添加8个COO-以及4个NH+3基团均能完全阻挡两离子通过,在添加1个COO-和1个NH+3基团的情况下,Li+通量达到最大,具有最佳分离效果。因此,添加特定带电修饰基团可有效改善较大直径碳纳米管膜对Li+和Mg2+的分离性能,修饰基团电荷性质和数量对分离效果影响很大。

Using molecular dynamics simulations, membrane formed from armchair type （10,10） carbon different charged functional groups including COO- we studied the transport of Li~ and Mg2＋ through nanotubes whose top rims were modified with a range of and NH3＋ under 80 MPa hydrostatic pressure, and investigated the potential of mean force, conductance and density distributions of ions in the carbon nanotubes. The results show that appropriately modified （10,10） carbon nanotubes can effectively extract Li＋. The bound and rejection effects produced by electrostatic interaction between charged groups and ions reduce the conductance of ions in the tubes. Mg2＋ can permeate the functionalized carbon nanotubes and Li are also completely blocked with the addition of 8C00- and 4NH3. The maximum conductance of Li＋ are found in carbon nanotubes modified with 1 COO- and 1 NH3 functional groups which can most effectively separate Li ＋ and Mg2＋. Therefore, through addition of specific charged modified groups, the separation performance of large diameter carbon nanotube to Li＋ and Mg2＋ can be effectively improved. Charge properties and the quantity of modification groups greatly affect the separation effects.