碳纳米管（CNTs）由于其独特的结构和优异的物理、化学、热学、力学等性质，在分子分离方面存在潜在的应用价值。目前，CNTs在分离方面的研究热点是将其作为分离膜的无机填充物，尤其是用于应用广泛的高分子膜。CNTs作为新型无机填充组分，一方面对气体和液体分子表现出良好的传输能力，另一方面可极大地改善高分子膜的结构和性能。本文回顾了近年来CNTs-高分子混合膜的主要研究工作，概括了CNTs在气体分离膜和液体分离膜的研究进展，并分析了CNTs在聚合物膜中的定向排列。然而，目前尚无理论能完整地解释CNTs对分离膜性质的影响，而CNTs在膜中的良好分散和定向排列也不易实现。

Carbon nanotubes (CNTs) is a novel allotrope of carbon with a unique tubular structure. In recent years, CNTs has been finding more and more applications in the preparation of functional composite materials due to its unique physical, chemical, and thermal properties. Its applications in separation membranes have also drawn much attention recently. These studies mainly focused on using CNT as an inorganic filler of polymeric membranes, It has been shown that CNTs display an excellent transport ability for gas and liquid molecules when used as membrane filler. In this paper, the recently reported work on CNTs-polymer hybrid membranes was reviewed. Subsequently, the alignment of CNTs in polymeric membrane matrix is  introduced in brief. However, so far there is no suitable theory to explain the influence of CNTs on separation membrane structures and properties. Also, good dispersion and ordered alignment of CNTs in polymer matrix is still difficult to realize.

[1] Robeson LM. Correlation of separation factor versus permeability for polymeric membranes [J]. J. Membr Sci, 1991, 62: 165-185.
[2] Ajayan PM, Zhou OZ. Applications of carbon nanotubes [J]. Carbon Nanotubes, 2001, 80: 391-425.
[3] Saito S. Carbon nanotubes for next-generation electronics devices [J]. Science, 1997, 278: 77-78.
[4] Collins PG, Zettle A, Bando H, et al. Nanotube anodevice [J]. Science, 1997, 278: 100-103.
[5] Liu Y, Gao L. A study of electrical properties of nanotube–NiFe2O4 composites: effect of surface treatment of carbon nanotubes [J]. Carbon, 2005, 43: 47–52.
[6] Schadler LS, Giannaris SC, Ajayan PM. Load transfer in carbon nanotube epoxy composites [J]. Appl Phys Lett, 1998, 73: 3842–3844.
[7] Peigney A, Laurent C, Rousset A. Synthesis and characterization of alumina matrix nanocomposites containing carbon nanotubes [J]. Key Eng Mat, 1997, 132–136: 743–746.
[8] Kuzumaki T, Miyazawa K, Ichinose H, et al. Processing of carbon nanotube reinforced aluminum composite [J]. J Mater Res, 1998, 13: 2445–2449.
[9] Mitchell DT,Lee SB,Trofin L,et al. Smart nanotubes for bioseparations and biocatalysis [J]. J Am Chem Soc, 2002, 124: 11864–11865.
[10] Holt JK, Noy A, Huser T, et al. Fabrication of a carbon nanotube-embedded silicon nitride membrane for studies of nanometer-scale mass transport [J]. Nano Lett, 2004, 4: 2245- 2250.
[11] Mao ZG, Sinnott SB. A computational study of molecular diffusion and dynamic flow through carbon nanotubes [J]. J Phys Chem B, 2000, 104: 4618-4624.
[12] Mao ZG, Sinnott SB. Separation of organic molecular mixtures in carbon nanotubes and     bundles: molecular dynamics simulations [J]. J Phys Chem B, 2001, 105: 6916-6924.
[13] Hummer G, Rasaiah JC, Noworyta JP. Water conduction through the hydrophobic channel of a carbon nanotube [J]. Nature, 2001, 414: 188-190.
[14] Kalra A, Garde S, Hummer G. Osmotic water transport through carbon nanotube membranes [J]. Proc Natl Acad Sci U.S.A., 2003, 100: 10175-10180.
[15] Shoulidas AI, Ackerman DM, Johnson JK, et al. Rapid transport of gases in carbon nanotubes [J].Phys Rev Lett, 2002, 89: 185901(1) -185901(4).
[16] Chen HB, Johnson JK, Sholl DS. Transport diffusion of gases is rapid in flexible carbon nanotubes [J]. J Phys Chem B, 2006, 110: 1971-1975.
[17] Majumder M, Chopra N, Andrews R, et al. Enhanced flow in carbon nanotubes [J]. Nature, 2005, 438: 44-44.
[18] Holt JK, Park HG, Wang Y, et al. Fast mass transport through sub-2-nanometer carbon nanotubes [J]. Science, 2006, 312: 1034-1037.
[19] Zheng J, Lennon EM, Tsao HK, et al. Transport of a liquid water and methanol mixture through carbon nanotubes under a chemical potential gradient [J]. J Chem Phys, 2005, 122: 1–7.
[20] Koga K,Gao GT, Tanaka H, et al. Formation of ordered ice nanotubes inside carbon nanotubes [J]. Nature, 2001, 412: 802–805.
[21] Peigney A, Laurent C, Flahaut E, et al. Carbon nanotubes in novel ceramic matrix nanocomposites [J].Ceram Int, 2000, 26: 677–683.
[22] Ismail AF, Goh PS, Tee JC, et al. A review of purification techniques for carbon nanotubes [J]. Nano, 2008, 3: 127–143.
[23] Hinds BJ, Chopra N, Rantell T, et al. Aligned multi-walled carbon nanotube membranes [J]. Science, 2004, 303: 62–65.
[24] Ismail AF, Goh PS, Sanip SM, et al. Transport and separation properties of carbon nanotube-mixed matrix membrane [J]. Sep Purif Technol, 2009, 70: 12-26.
[25] Cong H, Zhang JM, Radosz M, et al. Carbon nanotube composite membranes of brominated poly(2,6-diphenyl-1,4-phenylene oxide) for gas separation [J]. J Membr Sci, 2007, 294: 178–185.
[26] Kim S, Pechar TW, Marand E. Poly(imide siloxane) and carbon nanotube mixed matrix membranes for gas separation [J]. Desalination, 2006, 192: 330–339.
[27] Kim S, Chen L, Johnson JK, et al. Polysulfone and functionalized carbon nanotube mixed matrix membranes for gas separation:theory and experiment [J]. J Membr Sci, 2007, 294: 147-158.
[28] Qiu S, Wu LG, Pan XJ, et al. Preparation and properties of functionalized carbon nanotube /PSF blend ultrafiltration membranes [J]. J Membr Sci, 2009, 342: 165-172.
[29] Choi JH, Jegal J, Kim WN. Modification of performances of various membranes using MWNTs as a modifier [J]. Macromol Symp 2007, 249–250: 610–617.
[30] Peng F, Hu C, Jiang Z, et al. Novel ploy(vinyl alcohol)/carbon nanotube hybrid membranes for pervaporation separation of benzene/cyclohexane mixtures [J]. J Membr Sci, 2007, 297: 236–242.
[31] Zhao Q, Qian J, Zhu M, et al. Facile fabrication of polyelectrolyte complex/carbon nanotube nanocomposites with improved mechanical properties and ultra-high separation performance [J]. J Mater Chem, 2009, 19: 8732–8740.
[32] Chen W, Tao X. Self-organizing alignment of carbon nanotubes in thermoplastic polyurethane [J]. Macromol Rapid Commun, 2005, 26: 1763–1767.
[33] Sung JH, Kim HS, Jin HJ, et al. Nanofibrous membranes prepared by multiwalled carbon nanotube/poly(methyl methacrylate) composites [J]. Macromolecules, 2004, 37: 9899-9902.
[34] Kamat PV, Thomas KG, Barazzouk S, et al. Self-assembled linear bundles of single wall carbon nanotubes and their alignment and deposition as a film in a dc field [J]. J Am Chem  Soc, 2004, 126: 10757-10762.
[35] Kimura T, Ago H, Tobita M, et al. Polymer composites of carbon nanotubes aligned by a magnetic field [J]. Adv Mater, 2002, 14: 1380-1383.
[36] Tian Y, Park JG, Cheng QF, et al. The fabrication of single-walled carbon nanotube/ polyelectrolyte multilayer composites by layer-by-layer assembly and magnetic field assisted alignment [J]. Nanotechnology, 2009, 20: 335601-335607.