Magnetic amphiphilic hybrid carbon nanotubes containing N-doped and undoped sections: powerful tensioactive nanostructures.

In this work, unique amphiphilic magnetic hybrid carbon nanotubes (CNTs) are synthesized and used as tensioactive nanostructures in different applications. These CNTs interact very well with aqueous media due to the hydrophilic N-doped section, whereas the undoped hydrophobic one has strong affinity for organic molecules. The amphiphilic character combined with the magnetic properties of these CNTs opens the door to completely new and exciting applications in adsorption science and catalysis. These amphiphilic N-doped CNTs can also be used as powerful tensioactive emulsification structures. They can emulsify water/organic mixtures and by a simple magnetic separation the emulsion can be easily broken. We demonstrate the application of these CNTs in the efficient adsorption of various molecules, in addition to promoting biphasic processes in three different reactions, i.e. transesterification of soybean oil, quinoline extractive oxidation with H2O2 and a metal-catalyzed aqueous oxidation of heptanol with molecular oxygen.

Efficient and versatile fibrous adsorbent based on magnetic amphiphilic composites of chrysotile/carbon nanostructures for the removal of ethynilestradiol.

In this work, chrysotile was used as support to grow carbon nanotubes and nanofibers to produce fibrous amphiphilic magnetic nanostructured composites. Iron impregnated on the chrysotile surface at 1, 5 and 15 wt% was used as catalyst to grow carbon nanostructures by CVD (chemical vapor deposition) with ethanol at 800°C. Raman, TG/DTA, Mössbauer, XRD, BET, SEM, TEM, elemental analyses and contact angle measurements suggested the formation of a complex amphiphilic material containing up to 21% of nanostructured hydrophobic carbon supported on hydrophilic Mg silicate fibers with magnetic Fe cores protected by carbon coating. Adsorption tests for the hormone ethynilestradiol (EE), a hazardous water contaminant, showed remarkable adsorption capacities even compared to high surface area activated carbon and multiwall carbon nanotubes. These results are discussed in terms of the hydrophobic surface of the carbon nanotubes and nanofibers completely exposed and accessible for the adsorption of the EE molecules combined with the hydrophilic Mg silicate surface which allows good dispersion in water. The composites are magnetic and after adsorption the dispersed particles can be removed by a simple magnetic process. Moreover, the fibrous composites can be conformed as threads, screens and pellets to produce different filtering media.

Hybrid magnetic amphiphilic composites based on carbon nanotube/nanofibers and layered silicates fragments as efficient adsorbent for ethynilestradiol.

In this work, hybrid magnetic amphiphilic composites were prepared by the catalytic growth of carbon nanotubes (CNTs) and nanofibers CNF on layered silicates fragments. SEM, TEM, Raman, XRD, Mössbauer, TG/DTA showed that CVD with CH(4) at 800°C produced CNF and magnetic Fe cores fixed on the surface of microfragments of silicates layers. Due to the amphiphilic character, the composites can be easily dispersed in water and efficiently adsorb hydrophobic contaminant molecules. For example, the composites showed remarkable adsorption capacities for the hormone ethinylestradiol, e.g. 2-4 mg m(-2), compared to ca. 0.1 mg m(-2) obtained for high surface area activated carbon and multiwall CNT. These results are discussed in terms of a high hydrophobic exposed surface area of the CNT and CNF fixed on the layered silicates fragments surface. Moreover, the composites can be easily removed from water by a simple magnetic separation process.