Purification of single-walled carbon nanotubes (SWNTs) by froth flotation : effects of oxidative treatment and surfactant type

Abstract

Single-Walled Carbon Nanotubes (SWNTs) are of great interest because of their many superb properties. However, the great potential of SWNTs is restrained by impurities derived from the production. Therefore, the objective of this study was to develop an effective method for purifying of SWNTs. As-prepared SWNTs. synthesized from the dissproportionation of CO over Co-Mo/SiO2 catalyst were used in this study. The proposed method for the purification consisted of four sequential steps: oxidative pretreatment; acid treatment; silica dissolution; and froth flotation. The as-prepared SWNTs were first oxidized at 250C to convert the metal catalysts into metal oxides, resulting in increasing the exposure surface. After that, the oxidized sample was treated with HCl in which 90% removal of the catalysts was achieved as compared to 10% removal for non-pretreatment. For the silica dissolution step. NaOH was applied to increase the carbonpurity to 35% from the original carbon purity of 2.55%. Finally, froth flotation was used to separate the SWNTs from silica by using two types of surfactants: sodium dodecyl benzene sulfonate (SDBS) and alcohol ethoxylate surfonic L24-7. From the results, SDBS provided the highest carbon purity, up to 69.3% at 0.5 CMC and 5 pH, as compared to the 64.82% at 0.75 CMC and pH 7 for the Surfonic L24-7.