Carbon Nanotube Bucky Papers with Tailored Porosity for Filtration Applications A.M. K. Esawi * , A. R. Ramadan ** and R. ElNur *** * Department of Mechanical Engineering, The American University in Cairo, AUC Avenue, New Cairo 11835, Egypt, a_esawi@aucegypt.edu ** Department of Chemistry, The American University in Cairo, AUC Avenue, New Cairo 11835, Egypt, aramadan@aucegypt.edu *** Nanotechnology Graduate Program, The American University in Cairo, AUC Avenue, New Cairo 11835, Egypt, ruaa@aucegypt.edu ABSTRACT In this work, Carbon Nanotube Buckypapers (CNT- BPs) were prepared using vacuum filtration. Morphology and pore size distribution were investigated using scanning electron microscopy (SEM), and nitrogen gas adsorption. The prepared BPs were subsequently exposed to four different boiling solvents (acetone, IPA, THF and DMF) for 40 min and the morphology and pore size were re- evaluated. Results indicated that the type of solvent affects the pore size distribution with DMF giving more pores in the smaller pore size ranges. The findings confirm the potential of the solvent evaporation technique in tailoring the porosity of BP membranes for filtration applications. Keywords: CNT buckypaper, filtration, porosity 1 INTRODUCTION The steady development of membranes as filtration media has been helping in providing low cost membranes with enhanced properties to the water filtration industry. Conventional membranes made from polymeric materials have suffered problems in meeting good permeability and selectivity, poor chemical and heat resistance, and are also vulnerable to fouling [1]. Membranes based on nano-scale materials have been given mounting interest due to their unique properties that are superior to their bulk counterparts, and which could overcome some of these challenges [2]. At present, carbon nanotubes (CNTs) are considered to be one of the most promising nanomaterials, as they exhibit outstanding mechanical, electrical, thermal conductivity and adsorption properties [2-5]. The concept of using nanotubes in the separation and filtration industry has been put forward, but constructing macroscopic structures with controlled density, porosity, and morphology is still a challenge [2, 4]. Bucky paper (BP) is a material composed of randomly oriented CNTs in a woven or paper-like structure. The arrangement helps to provide a large specific area with a highly porous 3D network structure, which is useful for water filtration applications [2, 6]. The preparation of BPs basically entails the purification of CNTs, dispersion in suitable solvent, and their precipitation on a porous support [1]. The properties of BPs can be determined by several parameters during preparation such as the vacuum pressure, concentration and dispersion of CNTs, solvents used, surface functionalization of CNTs as well as their physio- chemical properties [7]. The use of CNT-BPs as filtration membranes is being investigated. For example, Yang et al. [8] investigated the use of buckypaper prepared from purified CNTs in removing humic acid (HA) from water and reported (>93%) removal rates. In order to widen their potential in filtration applications, control of the pore size is critical. Among the factors which affect the pore size are the CNT type, aspect ratio, purity as well as the substrate pore size. Some researchers demonstrated that forests of CNTs can be densified by a process known as capillary forming which entails subjecting the CNT forests to the vapours of a boiling solvent [9-12]. Recently, Dumee et al. [10] investigated the effect of solvent evaporation on the densification of vertically aligned CNT forests using different solvents and confirmed that the type of solvent affects the CNT-CNT interactions. As far as the current authors are aware, solvent evaporation was never used to control the porosity of CNT-BPs. In this work, CNT-BPs were prepared using vacuum filtration. Morphology and pore size distribution were investigated using scanning electron microscopy (SEM) and nitrogen gas adsorption. The prepared CNT-BPs were subsequently exposed to four different boiling solvents for 40 minutes and the morphology and pore size were re- evaluated. 2 MATERIALS AND METHODS 2.1 Reagents All CNTs in this paper are Elicarb multi-wall CNTs produced by Thomas Swan (England) with a diameter of 10-12 nm, tens of microns in length and a density of 1.7- 1.9 g/cm 3 . Triton X-100 (Sigma Aldrich) was used as a dispersant. Deionized water was used from MilliPore-Q. Acetone (Sigma Aldrich), Isopropanol (IPA; Aldrich), Dimethylformamide (DMF; Sigma Adlrich) and Tetrahydrofuran (THF; Carlo Erba) were used for densifying the CNT-BPs. 472 TechConnect Briefs 2015, TechConnect.org, ISBN 978-1-4987-4727-1