直径大于2nm的(15,15)碳纳米管的仿生生物改性及其脱盐行为的分子模拟

Biomimetic Modification and Desalination Behavior of (15,15) Carbon Nanotubes with a Diameter Larger than 2 nm

模仿水通道蛋白结构在直径大于2 nm的(15,15)的碳纳米管内壁添加不同数量的―NH_3^+和―COO^-,并结合端口改性建立连续的碳纳米管膜模型,利用分子动力学模拟方法研究了水以及Na+和Cl-在碳纳米管中的通量、密度分布和离子进入碳纳米管的平均力势。结果表明,在200 MPa压力下,对碳纳米管进行内壁和端口改性可以在保持较高水通量基础上显著提高碳纳米管的截盐作用。当在(15,15)碳纳米管内壁添加5对―COO^-和―NH_3^+基团或内壁添加4对―COO^-和―NH_3^+且端口添加1对时,Cl^-截盐率可达到100%,Na^+的截盐率达到88%。改性(15,15)碳纳米管的最小水通量仍是未改性(8,8)碳纳米管的4.6倍。

Different charged functional groups including ―COO^- and ―NH3^＋were added to the interior and entrance of（15,15） armchair carbon nanotubes（CNTs） with a diameter larger than 2 nm to construct membranes that imitated the structure of the protein aquaporin-4. The potential of mean force, conductance, and density distributions of ions in the CNTs were calculated. The results showed that under 200 MPa, CNTs modified with oppositely charged groups in their interior and at their entrance could greatly improve salt desalination on the basis of high water flux. When five pairs of ―COO^- and ―NH3^＋functional groups were added to the interior of a CNT or four pairs of ―COO^- and ―NH3^＋functional groups were added to the interior of a CNT with another pair at the entrance, 100% Cl^- rejection and 88% Na^＋rejection were achieved. The lowest water conductivity of the functionalized CNTs was 4.6 times that of（8,8） unfunctionalized CNTs, and even slightly lower than that of unfunctionalized（15,15） CNTs.