%0 Journal Article
%T The Separation Power of Nanotubes in Membranes: A Review
%A Bart Van der Bruggen
%J ISRN Nanotechnology
%D 2012
%R 10.5402/2012/693485
%X Research on mixed matrix membranes in which nanoparticles are used to enhance the membrane's performance in terms of flux, separation, and fouling resistance has boomed in the last years. This review probes on the specific features and benefits of one specific type of nanoparticles with a well-defined cylindrical structure, known as nanotubes. Nanotube structures for potential use in membranes are reviewed. These comprise mainly single-wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs), but also other structures and materials, which are less studied for membrane applications, can be used. Important issues related to polymer-nanotube interactions such as dispersion and alignment are outlined, and a categorization is made of the resultant membranes. Applications are reviewed in four different areas, that is, gas separation, water filtration, drug delivery, and fuel cells. 1. Introduction The use of nanoparticles has a long history. Nanoparticles were used by artisans as far back as the 9th century in Mesopotamia for generating a glittering effect on the surface of pots. This was denoted as ¡°luster art,¡± which refers to a metallic film applied to the transparent surface of a glazing, consisting of Cu or Ag nanoparticles. In this way, beautiful iridescent reflections of different colours (in particular gold and ruby-red) are obtained [1]. This was of interest in Muslim art, where no gold was to be used for decoration. The first scientific description of nanoparticles, however, was given in 1857 by Michael Faraday, who studied the size-dependent optical properties of gold and silver colloids or nanoparticles [2]. In the modern era, and in de last decade in particular, insights and discoveries in the field of nanostructures are booming. This stems generally from the fact that nanoparticles form a bridge between bulk materials and atomic or molecular structures; a bulk material should have constant physical properties regardless of its size, whereas a molecular structure may show discrete differences [3]. Nanoscience is the study of phenomena and the manipulation of materials at the atomic or molecular level. Nanotechnology involves the design, production and use of structures through control of the size and shape of the materials at the nanometer scale [4]. There is, however, some ambiguity with respect to what exactly should be considered as nanomaterials. Especially when nanomaterials are used in macroscopic structures, this might be somewhat unclear. This is the case for membranes used for separations; even though there is evidence for
%U http://www.hindawi.com/journals/isrn.nanotechnology/2012/693485/